Review on the Aerogel-Type Oil Sorbents Derived from Nanocellulose

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A review on the aerogel-type oil sorbents derived from nanocellulose Hongzhi Liu, Biyao Geng, Yufei Chen, and Haiying Wang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b02301 • Publication Date (Web): 18 Nov 2016 Downloaded from http://pubs.acs.org on November 22, 2016

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ACS Sustainable Chemistry & Engineering 1

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A review on the aerogel-type oil sorbents derived

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from nanocellulose

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Hongzhi Liua,b*, Biyao Genga,b, Yufei Chena,b, Haiying Wangc

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a

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Hangzhou 31130, China;

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b

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Comprehensive Utilization, Lin’an, Hangzhou 311300, China;

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c

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University, Lin’an, Hangzhou 311300, China

School of Engineering, Zhejiang Agriculture & Forestry University, Lin’an,

National Engineering and Technology Research Center of Wood-based Resources

School of Environmental and Resource Sciences, Zhejiang Agriculture & Forestry

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∗ To whom the correspondence should be addressed; E-mail: [email protected] (Prof.

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Hongzhi Liu) & Tel: +8-571-63746552 (o)

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ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering

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Abstract：：Due to severe risk of oil pollution and increasing concerns about the

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sustainability of sorbent materials, there are currently considerable interests across the

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world to develop cost-effective, reusable, and and environmentally friendly

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oil-sorbents derived from renewable resources. Nanocellulose is a new family of

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promising cellulosic materials with a cellulose fibril width in the order of nanometer

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range (i.e. 2~100 nm). As a class of newly developed cellulose aerogels,

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nanocellulose-derived ones combine intriguing interconnected three-dimensional

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porous characteristics of aerogel-type materialssuch as high porosity, large surface

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area, and low density with fascinating advantages related to naturally occurring

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nanocellulose: impressive

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renewability, excellent biodegradability, and ease to surface modification. Therefore,

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nanocellulose-based aerogels are very ideal “green” oil-sorbents after either

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appropriate hydrophobic modifications or carbonization. This present review

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summarizes the state-of-the-art in the aerogel-type oil sorbents derived from

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nanocellulose, including hydrophobized nanofibrillated cellulose (NFC)-based

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aerogels, hydrophobized bacterial cellulose (BC)-based ones, and the carbon ones

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prepared through the pyrolysis NFC or BC aerogels. Their respective preparation

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methods, structure as well as oil-absorption performance were summarized. And the

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existing problems in the current research and the future development perspectives

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were also presented.

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Keywords

mechanical properties,

abundant sources,

Oil-sorbents; Nanocellulose; Aerogel; Hydrophobization; Carbon

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2


natural

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Contents

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1

Background ........................................................................................................ 3

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2

Conventional oil-sorbents materials .................................................................... 4

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3

Aerogel-type oil sorbents .................................................................................... 7

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3.1 Non-cellulose aerogel-type oil sorbents......................................................... 8

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3.2 Cellulose aerogel-type oil sorbents ................................................................ 8

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Nanocellulose-based aerogel type oil-sorbents .................................................. 12

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4.1 NFC-based aerogels oil-sorbents ................................................................. 15

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4.2 BC-based aerogel oil-sorbents..................................................................... 25

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4.3 Nanocellulose-derived carbon aerogels ....................................................... 30

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Conclusions and Future Perspectives ................................................................ 33

48 49

1 Background

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The hazard of oil pollution has been becoming one of the most serious global

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concerns due to its harmful impacts on the environmental and ecological system. It has

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been estimated that 224,000 tons of oil from the spillage of oil tankers were globally

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released into the marine environment from 2000 to 20111. In the explosion and sinking

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of the Deepwater Horizon oil rig in the Gulf of Mexico in 2010, the BP pipe was

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leaking oil and gas on the ocean floor about 42 miles off the coast of Louisiana. By

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the time the well was capped 87 days later, an estimated 3.19 million barrels of oil

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had leaked into the Gulf—making the oil spill the largest accidental ocean spill in

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history. Apart from spilled oil pollutants, the industrial oily effluent still remains

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another severe risk to the ecosystem and even human health.

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The potential magnitude of environmental threat of oil pollutants can be gauged

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by the fact that one liter benzene can effectively render several million gallons of water 3



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unfit for human drinking2. Moreover, oil-contaminated water has a disastrous effect on

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aquatic and terrestrial life forms, and also threatens human health and the economy,

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particularly tourism, due to its coating properties, unsightliness, and offensive odor3.

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Thus, there is an urgent demand across the world to develop a variety of technologies

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for the removal of oil pollutants from contaminated water sources.

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2 Conventional oil-sorbents materials

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To address the environmental issues arising from oil spills, organic pollutants

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and industrial oily wastewater, a variety of oil cleanup methods or techniques have

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been developed towards the treatment of oil pollution4. Generally, the strategies are

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classified into several categories: in-situ burning, mechanical methods, chemical

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treatments, bioremediation, and adsorption5. In practice, they can be used either

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separately or in combination with each other. Among these alternatives, the adsorption

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by the use of oil-sorbents is generally considered to be the optimal technology

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because of its relatively low cost, high efficiency, and less secondary pollution1.

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Furthermore, these materials can, in some cases, be recycled. The detail advantages

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and limitations of each method above are listed in Table 1.

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It has been suggested that conventional oil-sorbent materials can be grouped into

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three major classes: inorganic mineral sorbents, synthetic polymer sorbents, and

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natural organic sorbents6.

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Inorganic mineral sorbents, also known as sinking sorbents, are highly dense,

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fine-grained mineral or inorganic materialsnatural or processedused to sink

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floating oil. Examples include fly ash7, zeolites8, exfoliated graphite9, activated

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carbon10, organoclay11, silica nanoparticles12, amorphous silica13, and silica aerogels14.

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But these mineral sorbents are less preferred due to their low oil-sorption capacities

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(typically less than 20 times by weight), poor oil/water selectivity, and low buoyancy 4


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that is inconvenient to recycle.

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Synthetic polymer oil-sorbents, such as polypropylene fibers15, polyurethane

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foam16, nanoporous polystyrene fibers17, polypropylene nonwoven web18, and

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macroporous rubber gels19, are the most commonly used commercial sorbents in the

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oil-spill cleanup due to their inherent oleophilic and hydrophobic characteristics.

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Despite excellent oil-sorption capacities, one major drawback of these sorbents lies in

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the fact that they degrade very slowly in comparison to mineral or natural products9, 20.

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And their environmental and ecological impact remains less optimistic.

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Natural organic sorbents are among the eco-friendly alternatives for the oil

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removal from wastewater. Unlike synthetic organic sorbents, natural sorbents are

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derived either from various abundant and cheap plants or animal residues28. The most

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common natural oil-sorbents are kapok fiber22, sugarcane bagasse23, cotton24, rice

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straw25, wood ships26, barley straw27 and so on. These sorbents are either used as

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received29 or formed into sheets, booms, pads30-31, filter32, and fiber assemblies33. Raw

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natural sorbents have moderate oil-sorption capacity (i.e. 3~50 times that their own

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weight), comparable or sometimes lower density than inorganic and synthetic

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sorbents, and excellent biodegradability34. Other advantages include their possibility

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of recycling, higher oil recovery, and relatively easy disposal compared to other types

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of conventional sorbents. Despite the above advantages, the majority of traditional

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natural sorbents also exhibit many drawbacks, such as poor buoyancy and selectivity

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of oil sorption which is associated with high water uptake of these sorbents. Low

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water repelling ability also reduces the effectiveness of their microporous structure to

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absorb oil23, 35. For clarity, the advantages and limitations of each oil-sorbents above

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are listed in Table 2.

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Table 1. Comparison of various oil clean-up methods in the literature6, 21 Classification

Examples

Advantages

Limitations

Environmental impact

Cost

Formation of large

In-situ burning

Combustion

Effectively quickly removing

Environment and safety

quantities of oil

concerns

quantities of harmful smokes and viscous

Cheapest

residues after combustion

Mechanical methods

Chemical treatments

Bioremediation

Adsorption

Skimmers; booms

Use of dispersants or solidifiers

Microorganism degradation

Use of oil-sorbents (fly ash, sand, exfoliated graphite)

Labor-intensive,

Efficient

time-consuming

Simple operation, suitable to treat a large polluted area

Little effect on very viscous oil, ineffective in calm water, high initial and/or running costs

Good oil-removal efficiency, low

Ineffective in spill with large

operation cost

coherent mass

secondary pollution

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Being harmful to aquatic organisms

Friendly

Very expensive

Expensive

Cheap

Friendly, its

Good oil-removal efficiency, simple operation, practically feasible, less

Friendly

Labor intensive

biodegradation depends on the used sorbents

Cheap

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Table 2. Performance comparison of three kinds of conventional oil-sorbents Classification

Examples

Advantages

Limitations Difficult recovery (e.g. fly ash, zeolites, activated carbon, silica nanoparticles,

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Zeolites ;

Inorganic mineral sorbents

amorphous silica), low oil-sorption (e.g.

fly ash7;

zeolites ~170 mg/g, activated carbon

exfoliated graphite9;

~340 mg/g, organoclay ~7.5 g/g, silica

activated carbon10;

Abundant

nanoparticles ~15 g/g, silica aerogel

sources

~15.1 g/g), eco-unfriendly (e.g.

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organoclay ; silica nanoparticles12;

exfoliated graphite), expensive

amorphous silica13;

(organoclay, exfoliated graphite), low

silica aerogel14;

absorption selectivity and rate (e.g. activated carbon), poor biodegradability (e.g. fly ash, organoclay) Low capacity (e.g. polyurethane foams

Polypropylene fiber cut 15; Synthetic

polyurethane foams16；

polymer

nanoporous polystyrene fibers17;

sorbents

polypropylene nonwoven web18; macroporous rubber gels19;

7~9 g/g), poor biodegradability (e.g. Moderate

polypropylene fibers, nanoporous

adsorption

polystyrene fibers),

capacity, good

difficult recovery (e.g. nanoprous

reusability

polystyrene fibers, polypropylene nonwoven web, macroporous rubber gels)

Kapok fiber22; Natural organic sorbents

sugarcane bagasse23; cotton24; 25

rice straw ; wood chips26; barley straw27;

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Abundant resources, low cost, excellent biodegradability and environmental-

Low capacity (e.g. sugarcane bagasse ~10.51 g/g, wood chips ~343 mg/g, barley straw 584.2~613.3 mg/g), poor hydrophobicity and reusability (e.g. kapok fiber, cotton, rice straw, wood

friendliness

chips)

3 Aerogel-type oil sorbents

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For effective collection oil from water, it is vital to choose an appropriate

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material as an oil-sorbent. Typically, an ideal oil-sorbent material is characterized of

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ahigh sorption capacity and oil/water selectivity, a high porosity, a fast oil sorption

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rate, a high floatability (i.e. hence a low density), low cost, environmentally

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friendliness, and recyclability36. Aerogels refer to one class of highly interconnected

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porous and lightweight solid materials formed by replacing the liquid in a gel by air37.

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Due to the large specific surface area, high porosity, and low density, they display

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promising potentials as an ideal oil-sorbent candidate to rapidly absorb a large amount

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of oil and to float on water. 7



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3.1 Non-cellulose aerogel-type oil sorbents To date, various kinds of aerogel-type oil sorbents, e.g. silica12-13, 38, carbon 39-41

, and graphene aerogels42-44, have been developed. Pure silica

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nanotube (CNT)

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aerogels can absorb oils but are difficult to separate the sorbent with oil from the

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water because their inherent mechanical brittleness could not endure the capillary

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force and crack seriously when oils are absorbed inside the mesopores of the aerogels.

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Although the newly developed nanostructured carbon-based aerogels (e.g. CNT,

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graphene, carbon nanofibers) exhibit superior sorption capacities (i.e. 100~913 g/g)

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and reusability, the complicated synthesis methods as well as high cost and

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non-renewability of precursors largely hamper their practical applications. Hence,

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considerable efforts have been devoted to developing a novel and sustainable aerogel

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material, which possesses excellent sorption properties and low cost for the oil/water

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separation.

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3.2 Cellulose aerogel-type oil sorbents

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As a ‘young’ third generation of aerogel materials succeeding silica and synthetic

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polymer-based ones, cellulose aerogels or sponges combine the intriguing features of

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aerogel-type materials with additional advantages of naturally occurring cellulose,

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such as abundant sources, natural renewability, biodegradability, and ease to surface

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modification. Therefore, cellulose aerogels seem to be one of the most fascinating

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natural oil-sorbents after appropriate modifications45-48. Depending on the nature of

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cellulosic materials, cellulose aerogels include cellulose derivative-based ones49-51,

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regenerated cellulose (RC)-based ones52-61, and nanocellulose-based ones.

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Prior to the formation of cellulose aerogels by drying process, the gelation is a

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key step. During the gelation, the three-dimensional cellulose network (3D) is formed.

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Depending on whether the reaction is involved or not during the formation of gels, the 8


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gelation mechanism can be classified into the physical cross-linking and chemical

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cross-linking. For the former mechanism, the intramolecular and/or intermolecular

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hydrogen bonds and physical entanglement between cellulose molecules are mainly

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responsible for the gelation. The physical crosslinking mechanism is involved in the

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case of both RC aerogels and nanocelulose ones.62,

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mechanism, an additional crosslinking agent, such as paper-strengthening resin64, 65

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needs to be added to induce the formation of the cross-linked cellulose network.

63

For the chemical gelation

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The initially developed cellulose aerogel-type oil-sorbents are based on

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regenerated cellulose (RC). Generally, RC-based aerogels are prepared through the

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following steps: (i) fully dissolving the cellulose in an appropriate solvent; (ii)

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regeneration of cellulose by replacing the solvent by a non-solvent (i.e. gelation); (iii)

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drying of the obtained lyogels. Nevertheless, the dissolution, gelation, and

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solvent-exchange steps are very time-consuming in the preparation of RC aerogels

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and also the used solvents are usually very harmful. During the regeneration step, the

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gelation mechanism mostly belongs to physical crosslinking. Moreover, unlike

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nanocellulose (e.g. NFC) aerogels, the favorable cellulose-I crystalline structure is

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converted to cellulose-II one during the preparation of RC aerogels, yielding the

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aerogels with relatively inferior mechanical properties (e.g. fragility) and lower aspect

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ratio of the fibrils with respect to NFC47, 66.

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It is well-known that the oil-sorption performance of cellulose aerogels depends

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not only on the density and viscosity of oily liquid, but also largely on the capillary

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effect, van der Waals forces, hydrophobic interaction between the oils and absorbents,

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and morphological parameters of the aerogels63, 67 (e.g. surface wettability, total pore

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volume, and pore structure). The oil density would contribute to the saturated

161

absorption capacity in aerogel-type sorbents with same pore size distribution and 3D 9



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network structure.65 And a lower oil viscosity facilitates their penetration into the

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porous network of aerogels, and thus results in a higher adsorption capacity40,68,69,

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while highly porous aerogels usually tend to show higher oil-sorption capacities

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because they provide more internal free volume for oil sorption.

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The pore structure of cellulose aerogels critically depends on the choice of

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drying processes. In practice, freeze and supercritical dryings are the most commonly

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used methods for the preparation of cellulose aerogels. Since a low surface tension

169

effect (i.e. capillary effect) occurs during the drying stage, the supercritical carbon

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dioxide (sc-CO2) drying can effectively avoid the collapse of 3D porous structure and

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result in cellulose aerogels with a low density and a high specific surface area49-50, 70-72.

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But the operation of supercritical drying is expensive and dangerous, which to some

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extent limits the practical feasibility of its industrial applications.

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Comparatively, the freeze-drying technique (also known as lyophilization) in

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which the solvent in the frozen gel is sublimated without entering a liquid state, is

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relatively safer and more economical. Thus, it is an eco-friendly alternative to replace

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traditional supercritical drying from a practical point of view. However, effects of

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large ice crystals during the freezing step and sublimation stages of the freeze-drying

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process can cause the aggregation of NFC nanofibrils, and thus the specific surface

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area of as-obtained cellulose aerogels is dramatically decreased, usually in the range

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of 10~70 m2/g63,

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self-assembly”, can be ameliorated by the freeze-drying after the solvent-exchange of

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aqueous NFC suspensions into tert-butanol66, 77-79. Due to the nature of tert-butanol

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having less hydrophilic character, a lower extent of surface tension effects is displayed

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during the drying process. As a result, the aerogels with a higher specific surface area

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are obtained due to less significantly aggregated microfibrils in this case79-81.

73-76

. This phenomenon, also known as “ice segregation

10


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In addition, increased hydrophobicity and oleophilicty in the aerogels would

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contribute to the improvement of their oil/water selectivity. Owing to the presence of

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abundant hydroxyl groups, native cellulose aerogels display the amphiphilicity (i.e.

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poor oil/water selective adsorption)63, 82. Consequently, they have to be tailored to

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convert the inherent hydrophilicity of the skeleton to hydrophobicity and oleophilicity.

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The hydrophobicity of the surfaces can be created by introducing roughness (i.e.

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micro- or nanoscale asperities) and low surface-energy substances. Usually, the

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surface wettability is evaluated by measuring the water contact angle (CA).

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Depending on the CA values, the surface wettability is classified into hydrophilic,

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hydrophobic, and superhydrophobic. If the CA is less than 90o, the surface is

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described as hydrophilic; if the CA lies between 90o and 150o, then hydrophobic; if

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the CA is more than 150o, the surface is superhydrophobic83.

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At present, the commonly used hydrophobization processes of cellulose-based

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aerogels include chemical vapor deposition (CVD), atom layer deposition (ALD),

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cold plasma treatment84, sol-gel85,

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examples of hydrophobizing agents include TiO2, SiO2, alkoxysilanes, chlorosilanes,

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alkyl

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1H,1H,2H,2H-perfluorodecyltrichlorosilane89, stearoyl chloride51, and palmitoyl

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chloride73.

ketene

dimer87,

86,

esterification51, and fluorination. And the

(tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane88,

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Several previous studies have utilized kinetic models to describe the adsorption

207

behaviors of sorbent materials90-92. Among these models, the pseudo-first order and

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pseudo-second order models40,

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solvent sorption of cellulose aerogel-type oil sorbents. The relative coefficients of the

210

models are calculated using linear least-square fitting. The pseudo-first-order model

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represents the sorption process controlled by physisorption, while the pseudo

93-95

are commonly used ones for the oil/organic

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second-order model is used to describe the sorption process controlled by

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chemisorptions. The pseudo-first-order equation is described as follows: ln( − ) = ln −

214

(1)

215

where and , are the adsorption capacities (mg/g) at the equilibrium and time t,

216

respectively, is the rate constant for pseudo-first order adsorption. From the plots

217

of ln( − ) versus t, the values of and can be determined.

218 219 220

Meanwhile, the pseudo-second order equation can be converted into a linear form：

=

+

(2)

221

where is the rate constant for the second-order adsorption (g⋅mg−1⋅min−1) and is

222

determined from the linear plot of t/ versus t.

223

In the case of hydrophobized cellulose aerogels, the driving force for the

224

oil-sorption mainly arises from hydrophobic interactions between modified cellulose

225

and oils (or organic solvents) as well as the capillary effect of the pores 62. Thus, their

226

adsorption process mostly belongs to the physisorption.

227

4 Nanocellulose-based aerogel type oil-sorbents

228

To overcome the drawbacks of RC aerogels, the aerogels based on nanocellulose,

229

has been recently developed. Nanocellulose refers to a family of novel cellulosic

230

materials with the lateral dimension in the order of nano-sized range (2~60 nm)96-98.

231

Depending on cellulose source, functions as well as preparation methods, which in

232

turn depend mainly on the cellulose sources,

233

three main sub-categories: nanocrystalline cellulose (NCC), nanofibrillated cellulose

234

(NFC), and bacterial nanocellulose (BC or BNC)96, 99. Typical characteristics of three

235

kinds of nanocelluloses are outlined in Table 3. Compared to RC, nanocellulose shows

236

favorable cellulose-I crystalline structure with a higher strength/stiffness, and also

nanocelluloses may be grouped into

12


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displays larger specific surface area. As compared to RC aerogels, the resultant

238

aerogels based on nanocellulose exhibit superior mechanical integrity after

239

freeze-drying76. Besides, because nanocellulose aerogels are usually obtained by

240

directly drying its frozen aqueous suspension without the use of organic solvents to

241

dissolve cellulose, the preparation process is thus more facile and environmentally

242

friendly than that of RC ones.

243

Nanocrystalline cellulos (NCC), also known as cellulose nanowhiskers (CNW),

244

consist of rod-like cellulose crystals with widths and lengths of 5~70 nm and between

245

100 nm and several microns, respectively. They are generated by the removal of

246

amorphous region of partially crystalline cellulose by acid hydrolysis. In comparison

247

to NFC and BC having three-dimensional (3D) cellulose nanofibers network, NCC

248

owns a higher degree of crystallinity and a shorter aspect ratio (100 µm; different types of nanofiber networks

High

Low

High

14


Cost

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4.1 NFC-based aerogels oil-sorbents

259

NFCsalso called as cellulose nanofibers (CNF)are isolated from native

260

cellulose fiber suspensions with or without the pretreatment by mechanical

261

disintegration99. It is characterized of long, flexible and entangled network of

262

cellulose nanofibers (i.e. 2~60 nm in diameter and several micrometers in length),

263

which consist of both individual and aggregated nanofibrils made of alternating

264

crystalline and amorphous cellulose domains. Such unique morphologies render

265

NFC-based aerogels superior flexibility and hierarchically porous structure than

266

regenerated cellulose aerogels. However, the sole mechanical disintegration of

267

cellulose fibers normally suffers from intensive energy consumption for fiber

268

delamination, i.e. even up to 27000 kWh per ton of NFC100. For this purpose, the pulp

269

fibers have been subjected to various pre-treatments, such as beating (or refining),

270

acid, enzyme, and/or chemical modifications. It has been demonstrated that the

271

introduction of charged groups onto the surfaces of fibers through chemical

272

pre-treatments is able to remarkably enhance the individualization of the fiber due to

273

the charge repulsion, and also the energy consumption for subsequent mechanical

274

treatment

275

charge-functionalized

276

2,2,6,6-tetramethyl-1-piperidinyloxy

277

carboxymethylation, sequential periodate-chlorite oxidation, and trimethylammonium

278

modification, have been developed in the literature101-103. Compared to RC aerogels,

279

NFC-based ones are prepared from the direct drying of frozen aqueous NFC

280

suspensions and no complicated regeneration steps and harmful solvents are involved.

281

Thus, the latter cellulose aerogels appear more facile and environmentally friendly.

282

is

dramatically

reduced.

For

pre-treatment

this

purpose,

different

surface

strategies,

including

(TEMPO)-mediated

oxidation,

Recently, the novel cellulose aerogels (also designated as cellulosic sponges or 15



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Page 16 of 47 16

283

foam in the literature) based on NFC have aroused considerable research interests due

284

to their renewability, good mechanical properties, low density, high porosity, natural

285

biodegradability, and environmental friendliness. These fascinating properties make it

286

possible to use them as oil sorbents.

287 288

Fig. 1 Reusability of aerogel sorbents. (a) Mass-based absorption capacity (m/m0) of toluene in

289

TiO2-coated aerogel, where m0 is aerogel dry mass and m is total mass; (b) Aerogel immersed in

290

toluene is translucent with air bubbles trapped inside; (c) Plot of mass-based absorption capacity

291

of different organic solvents and oils as a function of liquid density. Upper dashed lines represent

292

theoretical volume-based absorption capacity (vol/vol) corresponding to a case where aerogel is,

293

ostensibly, completely filled with liquid. Lower lines represent a case where aerogel is 80%

294

filled104. Reprinted with permission. Copyright 2011 American Chemical Society

295

Korhonen et al.104 prepared hydrophobic but oleophilic nanocellulose aerogels by

296

freeze-drying

NFC

hydrogels

and

subsequently

functionalizing

297

low-surface-energy TiO2 coating through an ALD technique. The resultant highly

298

porous (porosity>98%) and low-density (20~30 mg/cm3) aerogels exhibited highly

299

water-repellent properties and the oils do not drain out when the aerogel was floating

300

on water or taken out from water. Depending on the density of the absorbed oils (e.g.

301

30 g/g for mineral oil, 37.5 g/g for paraffin oil) or non-polar liquids (e.g. 40 g/g for

302

chloroform), their volume-based and mass-based sorption capacities were able to

303

reach 80~90% of total volume of the aerogel and 20~40 g/g, respectively. (Fig. 1c) 16


with

a

Page 17 of 47

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304

The absorbed organic liquids were readily removed by drying or washing out with an

305

appropriate solvent. Its absorption capacity of toluene was not deteriorated even after

306

10 sorption-drying-resorption cycles, indicating good reusability (Fig. 1a). This

307

feature made them an attractive bio-sorbents for oil spillage cleanup.

308 309

Fig. 2 A treated aerogel is able to float on water and simultaneously absorb a non-polar liquid

310

(hexadecane, coloured red) distributed on top of the water phase. The aerogel used in these

311

experiments had been prepared from a 1 wt% NFC dispersion and it could be removed after the

312

absorption without losing its integrity105. Reprinted with permission. Copyright 2011 Springer

313

Among various hydrophobization techniques of NFC-based aerogels, chemical

314

vapor deposition (CVD) is the most widely used. CVD involves flowing a precursor

315

gas of hydrophobizing agents into a chamber containing one or more heated solid

316

samples to be coated. And chemical reactions occur on and near the hot surfaces,

317

resulting in the deposition of thin films on the surfaces of the samples106. Cervin et al.

318

105

319

nanocellulose aerogels by freeze-drying an aqueous carboxymethylated nanocellulose

320

dispersions with varying solid contents. In order to make the hydrophilic NFC

321

aerogels hydrophobic, the resultant aerogels were then subjected to the treatment with

322

octyltrichlorosilane (OTCS) via CVD. The water contact angle of silanized aerogel

323

reached approximately 150o (i.e. superhydrophobicity). The hydrophobic aerogel was

324

almost instantly filled with the oil phase while selectively absorbing n-hexadecane

325

from water, (Fig.2) with a sorption capacity 45 times its own weight. The formed

326

aerogels at higher solids contents showed insignificant change in volume upon

fabricated a series of highly porous (99.1~99.8%) and light-weight (4~14 mg/cm3)

17



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Page 18 of 47 18

327

sorption/desorption and can be reused for three times. This was related to their high

328

mechanical strength. It was also found that the octyltrichlorosilane (OTCS) treatment

329

had only a minor negative effect on the absorption capacity of the aerogels towards

330

heptane. However, XPS analysis showed that the distribution of grafted Si element

331

throughout the whole aerogel was inhomogeneous with a higher content on the

332

surfaces.

333

In another work by Xiao and coworkers107, natural pine needles were used to

334

extract cellulose, which was then used to isolate aqueous NFC suspensions by

335

combining acid-pretreatment with high-intensity ultrasonic treatment. After freeze

336

drying, trimethylchlorosilane (TMCS) was used to treat the as-obtained ultra-light

337

NFC aerogel (3.12 mg/cm3) using CVD. The hydrophobic aerogel showed a water

338

contact angle of 135o, and can absorb 52 times oil than its own weight without any

339

structural collapse in oil.

340

To further improve oil-sorption capacities of NFC-based aerogels, Jiang et al.63

341

fabricated ultra-light (1.7~8.1 mg/cm3) and ultra-porous (99.5~99.9%) aerogels

342

through lyophilization-induced assembling of TEMPO-oxidized cellulose nanofibrils

343

(TO-NFC) that were defibrillated from rice straw cellulose. The resultant NFC

344

aerogels exhibited the characteristics of amphiphilic super-sorbents towards both

345

polar and non-polar liquids. Depending on density of the aerogels, they can absorb

346

116~210 and 128~375 times their own weight of water and chloroform, respectively.

347

To gain absorption selectivity for non-polar liquids from highly polar water, the

348

TO-NFC aerogel with a density of 2.7 mg/cm3 was modified by the exposure to

349

triethoxyl(octyl)silane (OTES) vapor treatment using a CVD technique to reduce its

350

surface hydrophilicity. The silane-modified aerogel exhibited excellent absorbency for

351

non-polar hydrocarbons, polar aprotic solvents, and oils. Depending on density of the 18


Page 19 of 47

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352

liquids, its absorption capacities ranged from 139 to 356 g/g, (Fig. 3a, b) which was

353

far surpassing the sorbents derived from natural organic, inorganic or synthetic

354

polymers. Noteworthy, its oil-water selectivity was significantly enhanced and the

355

capacities to absorb water, chloroform, decane, pump oil, and soybean oil amounted

356

to 11.4, 356, 219, 240, and 250 g/g, respectively. The absorbed liquids could be easily

357

distilled for the collection and recovery. Upon six absorption-distillation cycles, the

358

hydrophobic aerogels appeared slightly smaller in the dimension but its adsorption

359

capacity for toluene decreased from ca. 250 to 120 g/g. (Fig. 3d)

360

361 362

Fig. 3 Absorption capacity of silane-modified 0.2 CNF aerogels. (a) Mass-based (g liquid per g

363

aerogel); (b) Volume-based (mL liquid per g aerogel) with dashed lines representing 100%, 76%,

364

and 64% absorption capacities calculated as (porosity ×ρliquid/ρaerogel) in (a) And (porosity/ρaerogel)

365

in (b). (c) Chloroform absorption capacity in comparison with graphene aerogel, CNT–graphene

366

aerogel, carbonized bacterial cellulose (BC) aerogel, graphene-coated melamine sponge, CNT

367

sponge, graphene sponge, activated carbon (AC)-coated sponge, and nanocellulose aerogel; and (d)

368

Cyclic absorption and distillation of toluene63. Copyright 2014 Royal Society of Chemistry

369

Despite the encouraging oil-sorption results obtained previously, the recovery

370

methods for these hydrophobic sponges or aerogels made from NFC (i.e. solvent

371

extraction and distillation) still remain arduous and low-efficient due to the

372

unfavorable shape recovery properties in these cases. To overcome the above

373

limitations, Wang and coworkers67 produced a series of highly porous, elastic and 19



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Page 20 of 47 20

374

highly recyclable oil supersorbents from commercial hardwood pulp via beating

375

treatment in the papermaking, freeze-drying, and subsequent CVD treatment. The

376

microfibrillation degrees of hierarchical fibers were adjusted by varying beating

377

revolutions (i.e. 0, 3000, and 6000r). It was found that the beating treatment was

378

favorable to produce NFC sponges with a higher porosity. And irrespective of the

379

microfibrillation degree, the porosity of original NFC sponges was reversely

380

proportional to the concentration of NFC slurry, which was in coincidence with the

381

result reported by Jiang et al.63 (a)

382 (b)

383 384

Fig. 4 (a) Oil absorption capacity of hydrophobic MCF materials as functions of fiber

385

concentration and the microfibrillation degree; (b) Recyclability and WCA of hydrophobic MCF

386

material67. Reprinted with permission. Copyright 2015 Royal Society of Chemistry

387

After hydrophobic modification, the water contact angle of these sponges was

388

larger than 150o, indicative of their superhydrophobic feature. Because of high

389

porosity and hydrophobicity, these sponges exhibited the oil-sorption capacities up to

390

197 g/g for pump oil, 178 g/g for white oil, and 228 g/g for silicone oil, respectively.

391

(Fig. 4a) With increasing fiber concentration from 0.2 wt% to 2.0 wt%, the absorption

392

capacities for pump oil and motor oil were significantly decreased. (Fig. 4a) At lower 20


Page 21 of 47

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393

concentrations of pulp fiber slurry (i.e. 0.2 wt% and 0.5 wt%), the beating treatment

394

contributed to a remarkable increase in oil sorption capacity of hydrophobic sponges.

395

At a higher fiber concentration (i.e. 1.0 wt% or 2.0 wt%), however, the influence of

396

beating treatment on their oil-sorption capacity became insignificant. Interestingly, the

397

oil sorbents displayed excellent flexibility and elasticity. The absorbed oil could be

398

readily and rapidly recovered by simple mechanical squeezing, while the sorbents

399

could be reused at once without any other treatment. In addition, they showed

400

excellent recyclability and could be reused for at least 30 cycles while still

401

maintaining high oil absorption capacity (e.g. 137 g/g for pump oil).(Fig. 4b) These

402

advantages made them a very ideal alternative for oil spillage cleaning.

403 404

Fig. 5 (a) Absorption capacities of the PVA/CNF and (b) PVA aerogels for various organic

405

solvents and oils as indicated by weight gain108. Reprinted with permission. Copyright 2014 Royal

406

Society of Chemistry

407

Apart from pure NFCs, NFCs are also able to be utilized to mix with other

408

polymers to fabricate hybrid aerogels for the use of oil sorbents. Using glutaraldehyde

409

as a crosslinking agent, Zheng et al.108 prepared crosslinked PVA/TO-NFC aerogels

410

through a freeze-drying process. And the resulting cross-linked hybrid aerogel

411

exhibited both superhydrophobic and superoleophilic characteristics after being

412

treated with methyltrichlorosilane (MTCS) by CVD. The MTCS-coated aerogels

413

displayed excellent absorption capacities (i.e. ranging from 44~96 times their own dry 21



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Page 22 of 47 22

414

weight) for a variety of oils (e.g. 55.6 g/g for diesel, 45 g/g for gasoline, 63.5 g/g for

415

crude oil, 62.6 g/g for corn oil) and organic solvents (e.g. 95.2 g/g for chloroform),

416

(Fig. 5) but strongly repelled water with a water CA of 150.3o. Furthermore, these

417

hydrophobic aerogels demonstrated excellent elasticity and mechanical durability

418

after the MTCS-treatment, as evidenced by 10 times cyclic compression tests. Thus,

419

these hybrid aerogels had excellent potentials for cleaning up oil spills.

420

421 422

Fig. 6 General scheme for synthesis of silylated NFC sponges. (a) SEM micrograph of NFC (scale

423

bar of 10 µm); (b) Preparation of polysiloxane sol; (c) Image of a silylated NFC sponge; and (d)

424

Possible interactions between polysiloxane sol and NFC surface74. Reprinted with permission.

425

Copyright 2014 American Chemical Society

426 427

Fig. 7 Demonstration of the reusability of the silylated sponge(18.9 wt% Si) as an oil sorbent. The

428

absorption capacity (Cm) with regard to dodecane was evaluated after up to 10 rinsing−absorption

429

cycles74. Reprinted with permission. Copyright 2014 American Chemical Society

430

The aforesaid aerogel-type oil sorbents based on NFC are mostly prepared 22


Page 23 of 47

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431

through freeze-drying of NFC suspensions followed by gas phase depositions of

432

silanes or coating with TiO2. Although excellent oil-sorption capacities are observed

433

for resultant hydrophobic aerogels, the preparation procedure of the aerogels and their

434

hydrophobization process are in separated steps and are thus lengthy for practical

435

applications. Furthermore, the grafting distribution of hydrophobic groups formed by

436

CVD, tends to be non-uniform throughout the aerogels. To integrate both steps above

437

into a single one, Zhang et al.74 reported a facile synthetic process to prepare

438

hydrophobic, flexible, and lightweight (i.e. density≤17.3 mg/cm3) sponges by directly

439

freeze-drying aqueous NFC suspensions in the presence of acid-hydrolyzed

440

methyltrimethoxysilane(MTMS) sols. (Fig.6) The resultant silylated sponges were

441

composed of a three-dimensional cellulosic network of thin sheets and nanofilaments

442

covered by polysiloxanes.

443

Compared with conventional inorganic porous materials, the ultra-porous

444

sponges displayed an excellent flexibility with a maximal shape recovery

445

corresponding to 96% of the original thickness after 50% compression strain. Also,

446

they combined both hydrophobic and oleophilic properties and proved to be very

447

efficient in removing dodecane spills from a water surface with an excellent

448

selectivity and recyclability. The absorption capacity with oil (e.g. 49 g/g for motor

449

oil, 63 g/g for mineral oil), and nonpolar solvents (e.g. 102 g/g for chloroform) ranged

450

from 49~102 g/g. Compared to unmodified aerogels, the hydrophobic aerogels

451

maintained their original morphology and oil absorption capacity of n-dodecane after

452

10 absorption-extraction-drying cycles. (Fig.7)

23



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Page 24 of 47 24

453 454

Fig. 8 Absorption capacities of various oils for hydrophobic CNF aerogels and their theoretical

455

pore volume capacities109. Reprinted with permission. Copyright 2016 American Chemical

456

Society

457 458

Fig. 9 Absorbent reusability of hydrophobic CNF aerogels over five cycles109. Reprinted with

459

permission. Copyright 2016 American Chemical Society

460

In another work by reported Mulyadi and coworkers109, to avoid the use of

461

relatively expensive and toxic fluorine chemicals or silanes during the surface

462

hydrophobization of NFC aerogels, the surfaces of cellulose nanofibrils were

463

hydrophobized using styrene-acrylic monomer through chemical grafting methods in

464

the aqueous medium. The as-obtained hydrophobic aerogels exhibited a low density

465

(23.2 mg/cm3), a high porosity (98.5%), an apparent contact angle of 149o, and

466

solvent-induced recovery properties. The hydrophobicity of the aerogels was

467

attributed to the low-surface-energy styrene-acrylic copolymers that in-situ covered

468

on the surfaces of NFC. But the hydrophobicity prevailed throughout the whole 24


Page 25 of 47

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469

aerogel and not just for outermost layer, which was quite different from those

470

hydrophobic NFC analogues prepared by CVD. Depending the density of absorbed oil

471

liquids, the absorption capacity of the hydrophobic NFC aerogel ranged from 20 to

472

46.6g/g, and approximately 73~84% of theoretical pore volume in the aerogel could

473

be filled. (Fig. 8) The result of the aerogel reusability after successive

474

absorption-evaporation of toluene revealed that a 60% decrease in the absorption

475

capacity due to the structural collapse of pores was noted after the first cycle, but no

476

significant change occurred during the subsequent multiple cycles. (Fig. 9)

477

4.2 BC-based aerogel oil-sorbents

478

As another class of nanocellulose materials, bacterial (nano)cellulose (BC or

479

BNC), also known as microbial cellulose, has a higher degree of crystallinity,

480

polymerization, mechanical stability and water-retention properties with respect to

481

NFC. BC is biosynthesized through a bottom-up method from low-molecular weight

482

carbon sources (such as glucose) in the culture medium by a family of acetic acid

483

bacteria, referred to as gluconoacetobacter xylinus96. The resulting cellulosic

484

nanofiber network structure is in the form of a pellicle of randomly assembled ribbon

485

shaped fibrils 20~100 nm in width that are in turn composed of a bundle of much

486

finer nanofibrils (i.e. 2~4 nm in diameter). These bundles are relatively straight,

487

continuous and dimensionally uniform110. Therefore, BC was also utilized to fabricate

488

aerogel-type oil sorbents in the literature.

489 25



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Page 26 of 47 26

490

Fig. 10 Schematic illustration of the trimethylsilylation of BCAs. (a) The image and contact angle

491

test of BCA. (b) The image and contact angle test of HBCA. (c) The schematic chemical structure

492

of modified bacterial cellulose111. Reprinted with permission. Copyright 2015 American Chemical

493

Society

494

To overcome the drawback of inhomogeneous silylation during the gas phase

495

deposition of aerogels, Sai et al.111 attempted to modify the 3D web-like skeleton of

496

bacterial cellulose aerogels in the dichloromethane (CH2Cl2) phase containing

497

trimethylchlorosilane (TMCS) and triethylamine, followed by the solvent-exchange

498

into a water/tert-butanol mixture and subsequent freeze-drying to obtain the intact

499

hydrophobic bacterial cellulose aerogels (HBCAs), as shown in Fig. 10. Compared

500

with CVD method, the modifiers which have uniformly dispersed in the liquid phase

501

could diffuse into the pore more rapidly in this case. Meanwhile, this modification

502

was free from the heterogeneity in the hydrophobic aerogels obtained by CVD. Since

503

the hydrophobization only occurred on the surfaces of BC nanofibers, both shape and

504

microstructure of BCA were well preserved before and after trimethylsilylation owing

505

to the low degrees of substitution (≤0.132). This observation was different from that

506

of sol-gel modification reported by Zhang et al.,74 in which the silylation altered the

507

microstructure of NFC aerogels markedly. The obtained HBCAs exhibited low

508

density (≤6.77 mg/cm3), high BET specific surface area (≥169.1 m2/g), and high

509

porosity (ca. 99.6%). Because of excellent hydrophobic and oleophilic properties

510

(water contact angle as high as 146.5o), the HBCAs displayed a high selectivity for oil

511

absorption from water. The HBCAs were able to collect a wide range of oils (e.g. 100

512

g/g for gasoline, 120 g/g for diesel, 113 g/g for plant oil) and organic solvents (e.g. 97

513

g/g for acetone, 142 g/g for chlorobenzene) and showed the sorption capacities of up

514

to 185 times their own weight, depending on the density of the liquids. (Fig. 11a)

515

Furthermore, the maximum absorption capacity (Cm) with regard to diesel nearly 26


Page 27 of 47

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516

maintained constant even after 10 compression-rinsing-drying-absorption cycles,

517

demonstrating good reusability as an oil sorbent. (Fig. 11b)

518

519 520

Fig. 11 (a) Plot of mass-based absorption capacity of different organic solvents and oils as a

521

function of liquid density. Upper dashed line represents theoretical volume-based absorption

522

capacity (v/v) corresponding to a case where aerogel is completely filled with oils or organic

523

liquids, lower dashed line represents a case where it is 80% filled. (b) Reusability of HBCA-3 as

524

oil sorbent. Absorption capacity (Cm) of diesel evaluated after up to 10 rinsing-absorption cycles111.

525

Reprinted with permission. Copyright 2015 American Chemical Society

526

Graphene aerogels have shown good absorption capacities and reusability

527

because of their low density, high aspect ratio, good elasticity and excellent

528

mechanical properties42-44. Hence, the oil-sorption capacity of BC aerogels can be

529

endowed by preparing a hybrid structure containing graphene. By incorporating

530

graphene oxide (GO) in the BC suspension, Wang and coworkers82 produced

531

ultra-light and highly porous BC/reduced GO (rGO) hybrid aerogels by the

532

freeze-drying process and subsequent thermal reduction in H2. It was demonstrated

533

that porous morphologies of the composite aerogels did not change significantly after

534

the reduction of GO. Compared to amphiphilic nature of pure BC aerogels and

535

BC/GO aerogels, BC/rGO composite aerogels could selectively absorb organic liquids

536

from water and its absorption capacity for the organic liquids (i.e. DMF and

537

cyclohexane) reached as high as 135~150 g/g, even at a high BC content up to 80% in

538

the nanocomposite aerogels. This was mainly attributed to the hydrophobic rGO 27



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Page 28 of 47 28

539

nanosheets that totally decorated or surrounded the surfaces of nanoscale BC fibrils.

540

541 542

Fig. 12 (a) SEM image and photograph of the BC matrix; (b) SEM image and photograph of

543

BC–silica CAs (SiO2 about 90% w/w); (c–f) Schematic illustrations of CA formation85. Reprinted

544

with permission. Copyright 2013 Royal Society of Chemistry

545

In another report by Sai et al.85, flexible and robust BC–silica hybrid aerogels

546

(CAs) were prepared through a sol–gel process followed by freeze drying. The

547

interpenetrating network (IPN) structure was constructed by diffusing as-prepared

548

tetraethoxysilane (TEOS) alcosols as a precursor into a three-dimensional BC matrix

549

followed by permeating the catalyst into the BC network gradually to promote the

550

in-situ condensation of precursor to form a silica gel skeleton from outside to inside.

551

Schematic formation mechanism of the CAs is illustrated in Fig. 12. After further

552

hydrophobic modification using methyltrimethoxysilane (MTMS) sol, the hybrid

553

aerogels could float on the surface of water and have a water contact angle of about

554

133o and specific surface area as high as 507.8 m2/g. Moreover, the hydrophobic CAs

555

was able to retain their integrity after absorbing the oil and can be removed from the

556

water surface easily. In case of this process, however, the gel time of organic silica

557

precursor (TEOS) was quite long and often took several minutes or even a few hours 28


Page 29 of 47

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558

to complete the sol-gel process. And the freeze-drying was also needed twice to

559

construct dried BC matrix and CAs, respectively, and thus time-consuming during the

560

practical operation.

561 562

Fig. 13 Schematic illustration of the formation mechanism of CAs. (a) SEM (scanning electron

563

microscopy) image and photograph of BC hydrogels 3D network (matrix). (b) SEM image and

564

photograph of BC–silica CAs (SiO2 about 95.9% w/w). Firstly, the Na2SiO3 diffused into the BC

565

hydrogel 3D network. Then, the (SiO3)2- converted into SiO2 nanoparticles (represented by blue

566

balls) as H+ diffused into the BC 3D network, and these nanoparticles assembled with the silica gel

567

skeleton to form the IPN structure with the BC network. Lastly, the wet gels were dried with a

568

freeze drying method to obtain the CAs86. Reprinted with permission. Copyright 2014 Royal

569

Society of Chemistry

570

To resolve these problems, in the subsequent work, Sai and coworkers86 used

571

water-soluble sodium silicate (Na2SiO3) to replace traditional TEOS as a silica

572

precursor and also simplified the aforesaid synthesis procedure of CAs by using

573

freeze drying only once, as illustrated in Fig. 13. In the modified process, the hybrid

574

aerogels were prepared from diffusing the precursor into the wet matrix (i.e. BC

575

hydrogel) rather than freeze-dried one, followed by catalyzing the condensation of the

576

precursor (SO32-) through the immersion of 2M diluted sulfuric acid. It was thus

577

different from the previous work, in which the silica alcosols diffused into the dried

578

BC matrix (i.e. BC aerogel) to continue the sol–gel process inside of the BC matrix.

579

Furthermore, as compared to un-modified CAs, the hydrophobization modified CAs 29



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Page 30 of 47 30

580

exhibited smaller specific surface area (324.5 vs. 507.8 m2/g), a higher water contact

581

angle (145 vs. 133o), and a lower density (11 vs. 121 mg/cm3). The outstanding

582

hydrophobicity in conjunction with large specific surface area also endowed the

583

hydrophobic CAs with excellent oil absorption capability from the water surface with

584

retaining the integrity after absorbing oils. Strikingly, it was found that the

585

hydrophobic CAs with oil could be conveniently washed by immersing them in an

586

organic solvent (e.g. alcohol), and the washed hydrophobic CAs were reusable after

587

freeze drying. Consequently, the materials showed attractive potentials as a recyclable

588

oil adsorbent to clean oil spills in a marine environment.

589

4.3 Nanocellulose-derived carbon aerogels

590

Carbon aerogels have been widely reported to act as oil-sorbent materials owing

591

to the outstanding sorption capability, intrinsic hydrophobic and oleophilic nature, and

592

excellent chemical and thermal stability. Traditionally, to fabricate carbon aerogels,

593

resorcinol-formaldehyde organic aerogels were pyrolyzed in an inert atmosphere to

594

form a highly cross-linked carbon structure112-113. These carbon aerogels always have

595

a high density (100~800 mg/cm3)114-115 and tend to fracture under compression.

596

Alternatively, the carbonization of biomass materials has been considered as a facile,

597

less expensive and chemical-free preparation process. Likewise, nanocellulose

598

aerogels can also be converted into carbon aerogels through the same process. Apart

599

from commonly environmentally friendly and sustainable benefits associated with

600

biomass-derived carbon aerogels, the nanostructured ones derived from nanocellulose

601

are expected to possess a larger specific surface area, higher porosity as well as

602

superior mechanical properties. The precursors of these nanostructured carbon

603

aerogels can be either from NFC or BC. During the pyrolysis process, hydrophilic

604

functional groups, such as C=O, C–O, C–H, and O–H in the nanocellulose molecules, 30


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605

were removed while retaining the oleophilic properties.

606

Very recently, few efforts have been devoted to transforming nanocellulose-based

607

aerogels into their carbonaceous equivalents. Wu et al.116 prepared ultralight, flexible,

608

and fire-resistant carbon aerogels from BC pellicles by through freeze-drying process

609

followed by the pyrolysis under argon atmosphere. After the pyrolysis, the porous 3D

610

and interconnected network structure of BC aerogels was maintained, and the

611

diameter of the nanofibers decreased to 10~20 nm. After the pyrolysis treatment of

612

BC aerogels, the volume of resultant carbon nanofiber aerogels was shrunk to 15%

613

that of their original precursors and the density decreased from 9~10 mg/cm3 to 4~6

614

mg/cm3. It was found that pyrolysis temperature had a great influence on crystalline

615

structure and surface wettability of the obtained carbon aerogels. When increasing

616

pyrolysis temperature to 1300 C, the graphite structure began to appear. And a

617

significant change occurred in the surface wettability after pyrolysis treatment of BC

618

aerogels and the water contact angle was increased from 90% volume

623

reduction and almost recover its original volume after release of the load.

o

o

624

When used as sorbents, the carbon aerogels were able to absorb a broad spectrum

625

of organic solvents and oils with excellent recyclability and selectivity. And the

626

absorption capacity was as high as 106~312 times its own weight (e.g. 140 g/g for

627

pump oil, 180 g/g for gasoline, 170 g/g for diesel oil, 155 g/g for sesame oil, 165 g/g

628

for soybean oil), which were higher than that of other typical carbon-based sorbents in

629

the literature. Furthermore, such carbon aerogels can be regenerated by distillation 31



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 47 32

630

and direct combustion in air. Thus, they were considered to be an ideal candidate for

631

highly efficient separation/extraction of specific substances, such as organic pollutants

632

and oils.

633 634

Fig. 14 Sorption kinetics of different oils absorbed by carbonized MFC aerogel: (a) Canola oil, (b)

635

Pump oil, (c) Diesel oil, (d) Paraffin oil, (e) Normalized saturated sorption capacities of different

636

oils by oil density, (f) Absorption reusability of carbon aerogel65. Reprinted with permission.

637

Copyright 2015 Springer

638

Instead of BC aerogels as a carbonaceous precursor, Meng et al.65 also prepared

639

sponge-like carbon aerogels by freeze-drying a mixture of NFC and commercial

640

crosslinker (Kymene resin) to create 3D porous aerogels and subsequent

641

carbonization under nitrogen to render both hydrophobic and oleophilic properties. It

642

was found that heating rate had a considerable impact on the char yield. After 32


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643

carbonization, the bulk density was decreased from 25 g/cm3 for MFC aerogel to

644

10 mg/cm3, while the porosity was increased from 97.8% to 99%. Similar to the

645

previous report by Wu and coworkers, the fiber diameter of NFC aerogel was found to

646

dramatically decrease from 50~200 nm to 10~20 nm after the pyrolysis. Both BET

647

surface area (521 vs. 145 m2/g) and total pore volume (0.55 vs. 0.28 cm3/g) of the

648

sample prepared at 700oC were significantly higher than that of the one prepared at

649

950oC. And the graphite-like structure was observed at the carbon aerogel sample

650

prepared at 950oC. The removal of hydrophilic function groups during carbonization

651

caused carbon aerogel to achieve good hydrophobic properties (149o for a water CA)

652

and fast absorption rate. In addition, carbon aerogel pyrolyzed at 700oC was found to

653

possess higher oil absorption capacity of various types of oils (e.g. 55.8 g/g for pump

654

oil, 72.8 g/g for diesel oil, 73.6 g/g canola oil), (Fig. 14a-e) which were correlated

655

with its higher BET surface area, as compared to the one pyrolyzed at 950oC. More

656

importantly, the carbon aerogel was able to retain the same absorption capacity after

657

10 absorption/extraction (rinsing with alcohol) cycles, demonstrating excellent

658

multiple reusability.(Fig. 14f) For clarity, the comparison of preparation processes,

659

properties as well as costs of these above nanocellulose-based aerogel-type oil

660

sorbents, are summarized in Table 4.

661

5 Conclusions and Future Perspectives

662

In summary, the aerogel-type sorbents derived from nanocellulose precursors

663

(including NFC and BC) have exhibited superior oil-absorption performance,

664

mechanical strength, and reusability because of their highly porous 3D network

665

structure with interconnected microfibrils. The unique properties of these natural

666

oil-sorbents, along with the advantages of environmental friendliness, low-cost raw

667

materials, and mechanical durability, make them superior to other sorbent materials in 33



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Page 34 of 47 34

668

a wide range of oil-spill cleanup applications. To replace traditional oil sorbents in

669

practice, however, there are still several challenges to be addressed in the future

670

development of the NFC-based aerogel sorbents:

671

(1) The existing hydrophobization process of nanocellulose-based aerogels are

672

usually complex and energy-consuming. As one of the most widely used strategies,

673

the gas phase deposition (e.g. CVD and ALD) of silanes tends to suffer from the

674

drawback of inhomogeneous silylation with a higher Si content on the aerogel

675

surfaces. Thus, one of the concerns is to how to make the process more industrially

676

feasible and effective.

677

(2) Many existing recovery methods for oil-sorbents, such as distillation, rinsing

678

(i.e. solvent extraction), vacuum distillation, and burning, are usually complicated,

679

time-consuming, and have high-energy output and low efficiency, especially for

680

carbon aerogels. Comparatively, mechanical squeezing appears more facile to recover

681

oil and to reuse sorbent materials from the viewpoint of practical applications. But the

682

majority of the reported oil-sorbents derived from nanocellulose are still lack of

683

sufficient compression robustness. After multiple compression-absorption cycles, they

684

tends to exhibit an decrease in the oil-sorption capacity.

685

(3) It has been demonstrated that the aerogel-type sorbents derived from BC

686

exhibited superior mechanical and extraordinary oil-absorption properties. But in

687

comparison to BC produced by bacteria such as Acetobacter G. xylinus species, NFC

688

is generally extracted by a combination of pre-treatment and mechanical

689

disintegration of various native cellulose sources. Therefore, the latter sub-category of

690

nanocellulose has a relatively lower cost with respect to BC, and thus appears more

691

competitive and favorable precursor to prepare the aerogel-type oil sorbents. But how

692

to make isolation process of NFC more highly efficient and inexpensive on an 34


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693

industrial scale is very crucial for nanocellulose oil-sorbents to be implemented in the

694

practical oil-cleaning treatments.

695 696

Acknowledgments: The authors are grateful for the financial supports from the

697

Public Welfare Projects of Zhejiang Province (No. 2016C33029), Scientific Research

698

Foundation of Zhejiang Agriculture & Forestry University (No.2013FR088),

699

New-shoot Talents Program of Zhejiang Province (No.2015R412046)

35


Nanocellulose disintegration Mechanical, homogenization

1 2 3 Carboxymethylation pre-treatment, 4 high-pressure 5 homogenization 6 HCl pre-treatment, 7 ultrasonic disintegration 8 9 TEMPO oxidation, mechanical 10 disintegration 11 12 13 Mechanical beating 14 15 Mechanical 16 disintegration 17 18 Mechanical 19 disintegration 20 21 22 23 TEMPO oxidation, mechanical 24 disintegration 25 26 27 28 29 Commercial BC 30 31 32 n.a 33 34 Commercial BC 35 36 Commercial BC 37 38 39 40 n.a 41 42 43 44 45 46 47 48 Commercial sources;

Hydrophobic treatments

Density Porosity BET specific Contact Oil-sorption 2 （mg/cm3） ACS (%) area (m /g) angle&(oEngineering ) capacity(g/g) Sustainable Chemistry

Cost Raw materials

Synthesis methods

Ref

Cheap

Expensive

104

Coated with TiO2 via ALD

20~30 (before)

>98 (before)

n.a

>90

20~40 (e.g. 30 for mineral oil, 37.5 for paraffin oil)

Modified with OTCS via CVD

4~14 (before)

99.1~99.8 (before)

11~42 (before)

~150

~45

Cheap

Expensive

105

Modified with TMCS via CVD

3.12 (before)

n.a

20.09 (before)

135

~52

Very expensive

Expensive

107

Modified with OTES via CVD

2.7 (before)

99.5~99.6 (before)

10.9 (before)

n.a

Very expensive

Expensive

63

Modified with MTMS via CVD

2.4 (before)

98.4~99.8 4 (before)

n.a

>150

Cheap

Cheap

67

Modified with MTMS-hydrolyzed poysilxane

6.7 (before) 5.07-17.3 (after)

99.6 (before), 99.0~99.7 (after)

24 (before), 3~25 (after)

110~150

Cheap

Cheap

74

Chemical grafting with hydrophobic styrene-acrylic monomer

23.2 (after)

98.5 (after)

18.4 (after)

~149

Cheap

Expensive

109

Cheap

Expensive

108

Expensive

Expensive

111

139~356 (e.g. 240 for pump oil, 250 for soybean oil) 88~228 (e.g. 197for pump oil) 49~102 (e.g. 49 for motor oil, 63 for mineral oil) 20~46.4 45~96 (e.g. 55.6 for diesel , 45 for gasoline, 63.5 for crude oil, 62.6 for corn oil) 90~185 (e.g. 100 for gasoline, 120 for diesel, 113 for plant oil)

Modified with MTCS via CVD

10.6 (before), 13 (after)

>98 (after)

195 (before), 172 (after)

150.3

Modified with TMCS/TEA in CH2Cl2

6.74 (before), 6.69~6.77 (after)

99.6% (after)

160.2 (before), 169.1~180.7 (after)

90

Reduction in H2 at 200oC

n.a

99.84~99. 86

n.a

n.a

~150

Expensive

Expensive

82

121 (after)

n.a

507.8 (after)

133

n.a

Expensive

Expensive

85

11 (before)

n.a

324.5 (after)

145

n.a

Less expensive

Less expensive

Expensive

Expensive

116

Cheap

Expensive

65

Modified with pre-hydrolyzed MTMS alcosols Modified with pre-hydrolyzed MTMS alcosols

Carbonization under argon atmosphere

4~6 (before)

Carbonization under nitrogen

10 (after carbonizatio n)

106~312 (e.g. 140 for pump oil, 180 for gasoline, 170 99.7 n.a 113~128 for diesel oil, (before) 155 for sesame oil, 165 for soybean oil) 55.8~86.6 ACS Paragon Plus Environment (e.g. 55.8 for 99 (after 145~521 pump oil, carbonizat (after 149 72.8 for diesel ion) carbonization)

86

Page 36 of 47

Page 37 of 47

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References (1) Sabir, S., Approach of cost-effective adsorbents for oil removal from oily water. Crit. Rev. Env. Sci.Tec. 2015, 45, 1916-1945. (2) Syed, S.; Alhazzaa, M. I.; Asif, M., Treatment of oily water using hydrophobic nano-silica. Chem. Eng. J. 2011, 167 (1), 99-103. (3) Santander, M.; Rodrigues, R. T.; Rubio, J., Modified jet flotation in oil (petroleum) emulsion/water separations. Colloid. Surface. A. 2011, 375 (s 1–3), 237-244. (4) Cambiella, Á.; Ortea, E.; Ríos, G.; Benito, J. M.; Pazos, C.; Coca, J., Treatment of oil-in-water emulsions: Performance of a sawdust bed filter. J. Hazard. Mater. 2006, 131 (1-3), 195–199. (5) Angelova, D.; Uzunov, I.; Uzunova, S.; Gigova, A.; Minchev, L., Kinetics of oil and oil products adsorption by carbonized rice husks. Chem. Eng. J. 2011, 172 (1), 306-311. (6) Al-Majed, A. A.; Adebayo, A. R.; Hossain, M. E., A sustainable approach to controlling oil spills. J. Environ. Manage. 2012, 113 (1), 213–227. (7) Banerjee, S. S.; Joshi, M. V.; Jayaram, R. V., Treatment of oil spills using organo-fly ash. Desalination. 2006, 195 (1), 32-39. (8) Rajaković-Ognjanović, V.; Aleksić, G.; Rajaković, L., Governing factors for motor oil removal from water with different sorption materials. J. Hazard. Mater. 2008, 154 (1), 558-563. (9) Toyoda, M.; Aizawa, J.; Inagaki, M., Sorption and recovery of heavy oil by using exfoliated graphite. Desalination. 1998, 115 (2), 199-201. (10) Okiel, K.; El-Sayed, M.; El-Kady, M. Y., Treatment of oil–water emulsions by adsorption onto activated carbon, bentonite and deposited carbon. Egypt. J. Petrol. 2011, 20 (2), 9-15. (11) Carmody, O.; Frost, R.; Xi, Y.; Kokot, S., Adsorption of hydrocarbons on organo-clays—Implications for oil spill remediation. J. Colloid. Interf. Sci. 2007, 305 (1), 17-24. (12) Cho, Y. K.; Park, E. J.; Kim, Y. D., Removal of oil by gelation using hydrophobic silica nanoparticles. J. Ind. Eng. Chem. 2014, 20 (4), 1231-1235. (13) Nishi, S.; Tokunaga, T., Highly oil absorbing amorphous silica particles. Google Patents: 2009. (14) Wang, D.; McLaughlin, E.; Pfeffer, R.; Lin, Y., Adsorption of oils from pure liquid and oil–water emulsion on hydrophobic silica aerogels. Sep. Purif. Technol. 2012, 99, 28-35. (15) Lin, C.; Hong, Y. J.; Hu, A. H., Using a composite material containing waste tire powder and polypropylene fiber cut end to recover spilled oil. Waste. Manage. 2010, 30 (2), 263-267. (16) Oh, Y. S.; Maeng, J.; Kim, S. J., Use of microorganism-immobilized polyurethane foams to absorb and degrade oil on water surface. Appl. Microbiol. Biot. 2000, 54 (3), 418-423. (17) Lin, J.; Shang, Y.; Ding, B.; Yang, J.; Yu, J.; Al-Deyab, S. S., Nanoporous polystyrene fibers for oil spill cleanup. Mar. Pollut. Bull. 2012, 64 (2), 347-352. (18) Wei, Q.; Mather, R.; Fotheringham, A.; Yang, R., Evaluation of nonwoven polypropylene oil sorbents in marine oil-spill recovery. Mar. Pollut. Bull. 2003, 46 (6), 780-783. (19) Karakutuk, I.; Okay, O., Macroporous rubber gels as reusable sorbents for the removal of oil from surface waters. React. Funct. Polym. 2010, 70 (9), 585-595. (20) Teas, C.; Kalligeros, S.; Zanikos, F.; Stournas, S.; Lois, E.; Anastopoulos, G., Investigation of the effectiveness of absorbent materials in oil spills clean up. Desalination. 2001, 140 (3), 259-264. (21) Adebajo, M. O.; Frost, R. L.; Kloprogge, J. T.; Carmody, O.; Kokot, S., Porous materials for oil spill cleanup: a review of synthesis and absorbing properties. J. Porous. Mat. 2003, 10 (3), 159-170. (22) Wang, J.; Zheng, Y.; Wang, A., Effect of kapok fiber treated with various solvents on oil absorbency. Ind. Crop. Prod. 2012, 40, 178-184. (23) Ali, N.; El-Harbawi, M.; Jabal, A. A.; Yin, C.-Y., Characteristics and oil sorption effectiveness of kapok fibre, sugarcane bagasse and rice husks: oil removal suitability matrix. Environ. Technol. 2012, 33 (4), 481-486. (24) Hussein, M.; Amer, A. A.; Sawsan, I. I., Heavy oil spill cleanup using law grade raw cotton fibers: Trial for practical application. J. Petrol. Technol. Altern. Fuel. 2011, 2 (8), 132-140. (25) Sun, X. F.; Sun, R.; Sun, J. X., Acetylation of rice straw with or without catalysts and its characterization as a natural sorbent in oil spill cleanup. J. Agr. Food. Chem. 2002, 50 (22), 6428-6433. (26) Khan, E.; Virojnagud, W.; Ratpukdi, T., Use of biomass sorbents for oil removal from gas station runoff. Chemosphere. 2004, 57 (7), 681-689. (27) Ibrahim, S.; Ang, H. M.; Wang, S., Removal of emulsified food and mineral oils from wastewater using surfactant modified barley straw. Bioresource. Technol. 2009, 100 (23), 5744–5749. (28) Singh, V.; Jinka, S.; Hake, K.; Parameswaran, S.; Kendall, R. J.; Ramkumar, S., Novel natural sorbent for oil spill cleanup. Ind. Eng. Chem. Res. 2014, 53 (30), 11954-11961. 37



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 47 38

(29) Lim, T.-T.; Huang, X., In situ oil/water separation using hydrophobic–oleophilic fibrous wall: a lab-scale feasibility study for groundwater cleanup. J. Hazard. Mater. 2006, 137 (2), 820-826. (30) Li, F.; Wu, X.; Wu, J.; Xu, X.; Ma, S. In Kinetic study of adsorption of oil from oilfield produced water using modified porous ceramics filtration media in column mode, 2008 2nd International Conference on Bioinformatics and Biomedical Engineering. IEEE: 2008, 2745-2748. (31) Tansel, B.; Sevimoglu, O., Coalescence and Size Distribution Characteristics of Oil Droplets Attached on Flocs After Coagulation. Water. Air. Soil. Poll. 2005, 169 (1), 293-302. (32) Pasila, A., A biological oil adsorption filter. Mar. Pollut. Bull. 2004, 49 (11), 1006-1012. (33) Rengasamy, R.; Das, D.; Karan, C. P., Study of oil sorption behavior of filled and structured fiber assemblies made from polypropylene, kapok and milkweed fibers. J. Hazard. Mater. 2011, 186 (1), 526-532. (34) Annunciado, T.; Sydenstricker, T.; Amico, S., Experimental investigation of various vegetable fibers as sorbent materials for oil spills. Mar. Pollut. Bull. 2005, 50 (11), 1340-1346. (35) Likon, M.; Remškar, M.; Ducman, V.; Švegl, F., Populus seed fibers as a natural source for production of oil super absorbents. J. Environ. Manage. 2013, 114, 158-167. (36) Wahi, R.; Chuah, L. A.; Choong, T. S. Y.; Ngaini, Z.; Nourouzi, M. M., Oil removal from aqueous state by natural fibrous sorbent: an overview. Sep. Purif. Technol. 2013, 113, 51-63. (37) Nakagaito, A.; Kondo, H.; Takagi, H., Cellulose nanofiber aerogel production and applications. J. Reinf. Plast. Com. 2013, 32 (20), 1547-1552. (38) Yun, S.; Luo, H.; Gao, Y., Ambient-pressure drying synthesis of large resorcinol–formaldehyde-reinforced silica aerogels with enhanced mechanical strength and superhydrophobicity. J. Mater. Chem. A. 2014, 2 (35), 14542-14549. (39) Gui, X.; Wei, J.; Wang, K.; Cao, A.; Zhu, H.; Jia, Y.; Shu, Q.; Wu, D., Carbon nanotube sponges. Adv. Mater. 2010, 22 (5), 617-621. (40) Gui, X.; Li, H.; Wang, K.; Wei, J.; Jia, Y.; Li, Z.; Fan, L.; Cao, A.; Zhu, H.; Wu, D., Recyclable carbon nanotube sponges for oil absorption. Acta. Mater. 2011, 59 (12), 4798-4804. (41) Gui, X.; Zeng, Z.; Lin, Z.; Gan, Q.; Xiang, R.; Zhu, Y.; Cao, A.; Tang, Z., Magnetic and highly recyclable macroporous carbon nanotubes for spilled oil sorption and separation. ACS. Appl. Mater. Inter. 2013, 5 (12), 5845-5850. (42) Zhao, Y.; Hu, C.; Hu, Y.; Cheng, H.; Shi, G.; Qu, L., A versatile, ultralight, nitrogen-doped graphene framework †. Angew. Chem. Int. Edit. 2012, 51 (45), 11371-11375. (43) Bi, H.; Xie, X.; Yin, K.; Zhou, Y.; Wan, S.; He, L.; Xu, F.; Banhart, F.; Sun, L.; Ruoff, R. S., Spongy graphene as a highly efficient and recyclable sorbent for oils and organic solvents. Adv. Funct. Mater. 2012, 22 (21), 4421-4425. (44) Nguyen, D. D.; Tai, N.-H.; Lee, S.-B.; Kuo, W.-S., Superhydrophobic and superoleophilic properties of graphene-based sponges fabricated using a facile dip coating method. Energ. Environ. Sci. 2012, 5 (7), 7908-7912. (45) Innerlohinger, J.; Weber, H. K.; Kraft, G. In Aerocellulose: aerogels and aerogel‐like materials made from cellulose, Macromol. Symp., 2006; pp 126-135. (46) Cai, J.; Kimura, S.; Wada, M.; Kuga, S.; Zhang, L., Cellulose aerogels from aqueous alkali hydroxide–urea solution. Chemsuschem. 2008, 1 (1-2), 149-154. (47) Roxane, G.; Tatiana, B., Aerocellulose: new highly porous cellulose prepared from cellulose-NaOH aqueous solutions. Biomacromolecules. 2008, 9 (1), 269-277. (48) Pinnow, M.; Fink, H. P.; Fanter, C.; Kunze, J. In Characterization of highly porous materials from cellulose carbamate. Macromol. Symp. Wiley Online Library: 2008, 129-139. (49) Tan, C.; Fung, B. M.; Newman, J. K.; Vu, C., Organic Aerogels with Very High Impact Strength. Adv. Mater. 2001, 13 (9), 644-646. (50) Fischer, F.; Rigacci, A.; Pirard, R.; Berthon-Fabry, S.; Achard, P., Cellulose-based aerogels. Polymer. 2006, 47 (22), 7636-7645. (51) Granström, M., Highly water repellent aerogels based on cellulose stearoyl esters. Polym. Chem-UK. 2011, 2 (8), 1789-1796. (52) Jie, C.; Shilin, L.; Jiao, F.; Satoshi, K.; Masahisa, W.; Shigenori, K.; Lina, Z., Cellulose-silica nanocomposite aerogels by in situ formation of silica in cellulose gel. Angew. Chem. Int. Edit. 2012, 51 (9), 2076-2079. (53) Liu, S.; Yan, Q.; Tao, D.; Yu, T.; Liu, X., Highly flexible magnetic composite aerogels prepared by using cellulose nanofibril networks as templates. Carbohyd. Polym. 2012, 89 (2), 551-557. (54) Zhang, J.; Cao, Y.; Feng, J.; Wu, P., Graphene-oxide-sheet-induced gelation of cellulose and 38


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promoted mechanical properties of composite aerogels. J. Phys. Chem. C. 2012, 116 (14), 8063-8068. (55) Sescousse, R.; Gavillon, R.; Budtova, T., Aerocellulose from cellulose–ionic liquid solutions: Preparation, properties and comparison with cellulose–NaOH and cellulose–NMMO routes. Carbohyd. Polym. 2011, 83 (4), 1766-1774. (56) Aaltonen, O.; Jauhiainen, O., The preparation of lignocellulosic aerogels from ionic liquid solutions. Carbohyd. Polym. 2009, 75 (1), 125-129. (57) Hoepfner, S.; Ratke, L.; Milow, B., Synthesis and characterisation of nanofibrillar cellulose aerogels. Cellulose. 2008, 15 (1), 121-129. (58) Duchemin, B. J. C.; Staiger, M. P.; Tucker, N.; Newman, R. H., Aerocellulose based on all‐cellulose composites. J. Appl. Polym. Sci. 2010, 115 (1), 216-221. (59) Nguyen, S. T.; Feng, J.; Shao, K. N.; Wong, J. P. W.; Tan, V. B. C.; Hai, M. D., Advanced thermal insulation and absorption properties of recycled cellulose aerogels. Colloid. Surface. A. 2014, 445 (6), 128-134. (60) Wan, C.; Lu, Y.; Cao, J.; Sun, Q.; Li, J., Preparation, Characterization and Oil Adsorption Properties of Cellulose Aerogels from Four Kinds of Plant Materials via a NaOH/PEG Aqueous Solution. Fiber. Polym. 2015, 16 (2), 302-307. (61) Tsioptsias, C.; Stefopoulos, A.; Kokkinomalis, I.; Papadopoulou, L.; Panayiotou, C., Development of micro- and nano-porous composite materials by processing cellulose with ionic liquids and supercritical CO2. Green. Chem. 2008, 10 (9), 965-971. (62) Nguyen, S. T.; Feng, J.; Le, N. T.; Le, A. T.; Hoang, N.; Tan, V. B.; Duong, H. M., Cellulose aerogel from paper waste for crude oil spill cleaning. Ind. Eng. Chem. Res. 2013, 52 (51), 18386-18391. (63) Feng, J.; Hsieh, Y. L., Amphiphilic superabsorbent cellulose nanofibril aerogels. J. Mater. Chem. A. 2014, 2 (18), 6337-6342. (64) Feng, J.; Nguyen, S. T.; Fan, Z.; Duong, H. M., Advanced fabrication and oil absorption properties of super-hydrophobic recycled cellulose aerogels. Chem. Eng. J. 2015, 270, 168-175. (65) Meng, Y.; Young, T. M.; Liu, P.; Contescu, C. I.; Huang, B.; Wang, S., Ultralight carbon aerogel from nanocellulose as a highly selective oil absorption material. Cellulose. 2015, 22 (1), 435-447. (66) Jin, H.; Nishiyama, Y.; Wada, M.; Kuga, S., Nanofibrillar cellulose aerogels. Colloid. Surface. A. 2004, 240 (1–3), 63-67. (67) Wang, S.; Peng, X.; Zhong, L.; Tan, J.; Jing, S.; Cao, X.; Chen, W.; Liu, C.; Sun, R., An ultralight, elastic, cost-effective, and highly recyclable superabsorbent from microfibrillated cellulose fibers for oil spillage cleanup. J. Mater. Chem. A. 2015, 3 (16), 8772-8781. (68) Wang, J.; Zheng, Y.; Wang, A., Coated kapok fiber for removal of spilled oil. Mar. Pollut. Bull. 2013, 69 (1), 91-96. (69) Choi, H. M.; Cloud, R. M., Natural sorbents in oil spill cleanup. Environ. Sci. Technol. 1992, 26 (4), 772-776. (70) Kobayashi, Y.; Saito, T.; Isogai, A., Aerogels with 3D ordered nanofiber skeletons of liquid‐ crystalline nanocellulose derivatives as tough and transparent insulators. Angew. Chem. Int. Edit. 2014, 53 (39), 10394-10397. (71) Sehaqui, H.; Zhou, Q.; Ikkala, O.; Berglund, L. A., Strong and tough cellulose nanopaper with high specific surface area and porosity. Biomacromolecules. 2011, 12 (10), 3638-3644. (72) Heath, L.; Thielemans, W., Cellulose nanowhisker aerogels. Green. Chem. 2010, 12 (8), 1448-1453. (73) Matthieu, F.; Djamila, O.; Sonia Molina, B.; Laurent, H., Versatile gas-phase reactions for surface to bulk esterification of cellulose microfibrils aerogels. Biomacromolecules. 2013, 14 (9), 3246-3255. (74) Zhang, Z.; Sèbe, G.; Rentsch, D.; Zimmermann, T.; Tingaut, P., Ultralightweight and flexible silylated nanocellulose sponges for the selective removal of oil from water. Chem. Mater. 2014, 26 (8), 2659-2668. (75) Feng, J.; Hsieh, Y. L., Super water absorbing and shape memory nanocellulose aerogels from TEMPO-oxidized cellulose nanofibrils via cyclic freezing–thawing. J. Mater. Chem. A. 2013, 2 (2), 350-359. (76) Pääkkö, M.; Vapaavuori, J.; Silvennoinen, R.; Kosonen, H.; Ankerfors, M.; Lindström, T.; Berglund, L. A.; Ikkala, O., Long and entangled native cellulose I nanofibers allow flexible aerogels and hierarchically porous templates for functionalities. Soft. Matter. 2008, 4 (12), 2492-2499. (77) Inoué, T., .; Osatake, H., . A new drying method of biological specimens for scanning electron microscopy: the t-butyl alcohol freeze-drying method. Arch. Histol. Cytol. 1988, 51 (1), 53-59. (78) Ishida, O.; Kim, D. Y.; Kuga, S.; Nishiyama, Y.; Brown, R. M., Microfibrillar carbon from native 39



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 47 40

cellulose. Cellulose. 2004, 11 (11), 475-480. (79) Sehaqui, H.; Zhou, Q.; Berglund, L. A., High-porosity aerogels of high specific surface area prepared from nanofibrillated cellulose (NFC). Compos. Sci. Technol. 2011, 71 (13), 1593-1599. (80) Feng, J.; Hsieh, Y. L., Assembling and redispersibility of rice straw nanocellulose: effect of tert-butanol. ACS. Appl. Mater. Inter. 2014, 6 (22), 20075-20084. (81) Nemoto, J.; Saito, T.; Isogai, A., A simple freeze-drying procedure for producing nanocellulose aerogel-containing, high- performance air filters. ACS. Appl. Mater. Inter. 2015, 7 (35), 19809-19815. (82) Wang, Y.; Yadav, S.; Heinlein, T.; Konjik, V.; Breitzke, H.; Buntkowsky, G.; Schneider, J. J.; Zhang, K., Ultra-light nanocomposite aerogels of bacterial cellulose and reduced graphene oxide for specific absorption and separation of organic liquids. Rsc. Adv. 2014, 4 (41), 21553-21558. (83) Gupta, S.; Tai, N. H., Carbon materials as oil sorbents: a review on the synthesis and performance. J. Mater. Chem. A. 2015, 4 (5), 1550-1565. (84) Shi, J.; Lu, L.; Guo, W.; Sun, Y.; Yang, C., An environment-friendly thermal insulation material from cellulose and plasma modification. J. Appl. Polym. Sci. 2013, 130 (5), 3652–3658. (85) Sai, H.; Xing, L.; Xiang, J.; Cui, L.; Jiao, J.; Zhao, C.; Li, Z.; Li, F., Flexible aerogels based on an interpenetrating network of bacterial cellulose and silica by a non-supercritical drying process. J. of Mater. Chem. A. 2013, 1 (27), 7963-7970. (86) Sai, H.; Xing, L.; Xiang, J.; Cui, L.; Jiao, J.; Zhao, C.; Li, Z.; Li, F.; Zhang, T., Flexible aerogels with interpenetrating network structure of bacterial cellulose–silica composite from sodium silicate precursor via freeze drying process. RSC. Adv. 2014, 4 (57), 30453-30461. (87) Russler, A.; Wieland, M.; Bacher, M.; Henniges, U.; Miethe, P.; Liebner, F.; Potthast, A.; Rosenau, T., AKD-modification of bacterial cellulose aerogels in supercritical CO2. Cellulose. 2012, 19 (4), 1337-1349. (88) Hua, J.; Marjo, K.; Ari, L.; Hanna, P. N.; Jouni, P.; Abraham, M.; Olli, I.; Ras, R. H. A., Superhydrophobic and superoleophobic nanocellulose aerogel membranes as bioinspired cargo carriers on water and oil. Langmuir. 2011, 27 (5), 1930-1934. (89) Aulin, C.; Netrval, J.; Wågberg, L.; Lindström, T., Aerogels from nanofibrillated cellulose with tunable oleophobicity. Soft. Matter. 2010, 6 (14), 3298-3305. (90) Sharma, P.; Saikia, B. K.; Das, M. R., Removal of methyl green dye molecule from aqueous system using reduced graphene oxide as an efficient adsorbent: kinetics, isotherm and thermodynamic parameters. Colloid. Surface. A. 2014, 457, 125-133. (91) Vargas, A. M.; Cazetta, A. L.; Kunita, M. H.; Silva, T. L.; Almeida, V. C., Adsorption of methylene blue on activated carbon produced from flamboyant pods (Delonix regia): Study of adsorption isotherms and kinetic models. Chem. Eng. J. 2011, 168 (2), 722-730. (92) Chen, Y.; Zhang, D., Adsorption kinetics, isotherm and thermodynamics studies of flavones from Vaccinium Bracteatum Thunb leaves on NKA-2 resin. Chem. Eng. J. 2014, 254, 579-585. (93) Wu, B.; Zhou, M., Recycling of waste tyre rubber into oil absorbent. Waste. Manage. 2009, 29 (1), 355-359. (94) Bastani, D.; Safekordi, A.; Alihosseini, A.; Taghikhani, V., Study of oil sorption by expanded perlite at 298.15 K. Sep. Purif. Technol. 2006, 52 (2), 295-300. (95) Sokker, H.; El-Sawy, N. M.; Hassan, M.; El-Anadouli, B. E., Adsorption of crude oil from aqueous solution by hydrogel of chitosan based polyacrylamide prepared by radiation induced graft polymerization. J. Hazard. Mater. 2011, 190 (1), 359-365. (96) Dieter, K.; Friederike, K.; Sebastian, M.; Tom, L. M.; Mikael, A.; Derek, G.; Annie, D., Nanocelluloses: a new family of nature-based materials. Angew. Chem. Int. Edit. 2011, 50 (24), 5438-5466. (97) Dufresne, A., Nanocellulose: a new ageless bionanomaterial. Mater. Today. 2013, 16 (6), 220-227. (98) Isogai, A.; Saito, T.; Fukuzumi, H., TEMPO-oxidized cellulose nanofibers. Nanoscale. 2011, 3 (1), 71-85. (99) Siró, I.; Plackett, D., Microfibrillated cellulose and new nanocomposite materials: a review. Cellulose. 2010, 17. (100) Lindström, T.; Winter, L., Mikrofibrillär cellulosa som komponent vid papperstillverkning. Internal STFI report C 1988, 159. (101) Tsuguyuki, S.; Yoshiharu, N.; Jean-Luc, P.; Michel, V.; Akira, I., Homogeneous suspensions of individualized microfibrils from TEMPO-catalyzed oxidation of native cellulose. Biomacromolecules. 2006, 7 (6), 1687-1691. (102) Yusuke, O.; Tsuguyuki, S.; Akira, I., Entire surface oxidation of various cellulose microfibrils by 40


Page 41 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TEMPO-mediated oxidation. Biomacromolecules. 2010, 11 (6), 1696-1700. (103) Besbes, I.; Alila, S.; Boufi, S., Nanofibrillated cellulose from TEMPO-oxidized eucalyptus fibres: effect of the carboxyl content. Carbohyd. Polym. 2011, 84 (3), 975-983. (104) Korhonen, J. T.; Kettunen, M.; Ras, R. H.; Ikkala, O., Hydrophobic nanocellulose aerogels as floating, sustainable, reusable, and recyclable oil absorbents. ACS. Appl. Mater. Inter. 2011, 3 (6), 1813-1816. (105) Cervin, N. T.; Aulin, C.; Larsson, P. T.; W02gberg, L., Ultra porous nanocellulose aerogels as separation medium for mixtures of oil/water liquids. Cellulose. 2011, 19 (2), 401-410. (106) Creighton, J.; Ho, P., Introduction to chemical vapor deposition (CVD). Chem. Vapor. Depos. 2001, 2, 1-22. (107) Xiao, S.; Gao, R.; Lu, Y.; Li, J.; Sun, Q., Fabrication and characterization of nanofibrillated cellulose and its aerogels from natural pine needles. Carbohyd. Polym. 2015, 119, 202-209. (108) Zheng, Q. C., Z.; Gong, S., Green synthesis of polyvinyl alcohol (PVA)–cellulose nanofibril (CNF) hybrid aerogels and their use as superabsorbents. J. Mater. Chem. A. 2014, 2 (9), 3110-3118. (109) Mulyadi, A.; Zhang, Z.; Deng, Y., Fluorine-free oil absorbents made from cellulose nanofibril aerogels. ACS. Appl. Mater. Inter. 2016, (8), 2732- 2740. (110) Habibi, Y., Key advances in the chemical modification of nanocelluloses. Chem. Soc. Rev. 2014, 43 (5), 1519-1542. (111) Sai, H.; Fu, R.; Xing, L.; Xiang, J.; Li, Z.; Li, F.; Zhang, T., Surface modification of bacterial cellulose aerogels’ web-like skeleton for oil/water separation. ACS. Appl. Mater. Inter. 2015, 7 (13), 7373-7381. (112) Wu, D.; Fu, R., Requirements of organic gels for a successful ambient pressure drying preparation of carbon aerogels. J. Porous. Mat. 2008, 15 (1), 29-34. (113) Pekala, R., Organic aerogels from the polycondensation of resorcinol with formaldehyde. J. Mater. Sci. 1989, 24 (9), 3221-3227. (114) Wu, D.; Fu, R.; Zhang, S.; Dresselhaus, M. S.; Dresselhaus, G., Preparation of low-density carbon aerogels by ambient pressure drying. Carbon. 2004, 42 (10), 2033-2039. (115) Fu, R.; Zheng, B.; Liu, J.; Dresselhaus, M. S.; Dresselhaus, G.; Satcher, J. H.; Baumann, T. F., The fabrication and characterization of carbon aerogels by gelation and supercritical drying in isopropanol. Adv. Funct. Mater. 2003, 13 (7), 558-562. (116) Wu, Z. Y.; Li, C.; Liang, H. W.; Chen, J. F.; Yu, S. H., Ultralight, flexible, and fire‐resistant carbon nanofiber aerogels from bacterial cellulose. Angew. Chem. Int. Edit. 2013, 52 (10), 2925-2929.

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Table of Contents

A review on the aerogel-type oil sorbents derived from nanocellulos Hongzhi Liua,b*, Biyao Genga,b, Yufei Chena,b, Haiying Wangc a

School of Engineering, Zhejiang Agriculture & Forestry University, Lin’an,

Hangzhou 31130, China; b

National Engineering and Technology Research Center of Wood-based Resources

Comprehensive Utilization, Lin’an, Hangzhou 311300, China; c

School of Environmental and Resource Sciences, Zhejiang Agriculture & Forestry

University, Lin’an, Hangzhou 311300, China

∗ To whom the correspondence should be addressed; E-mail: [email protected] (Prof.. Hongzhi Liu) & Tel: +8-571-63746552 (o)

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Synopsis: Nanocellulose-derived aerogels combine the advantages of both aerogels and “green” cellulose materials, and thus is very promising “green” oil-sorbents with excellent reusability and absorption performance. In this review, recent research advances and future development perspectives in the nanofibrillated cellulose (NFC)-based

aerogel-type

oil

sorbents,

bacterial

nanocellulose

(BC)-based

aerogel-type oil sorbents as well as their carbonous equivalent prepared through the pyrolysis, were presented.

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Dr. Hongzhi Liu, received his PhD with the major of polymer chemistry & physics from Institute of Chemistry (ICCAS), Chinese Academy of Sciences in July 2005. From Feb 2006 to July 2013, he worked at Seoul National University, Louisiana State University, and Washington State University, respectively as a postdoc. After that, he joined Zhejiang Agriculture & Forestry University in Oct 2013 as a distinguished professor. In Nov 2016, he was successfully awarded to the “Zhejiang Thousand Talents Initiative” title (i.e. Introduction Program of Overseas Chinese High-leveled Talents). To date, he has published more than 75 scientific papers in the peer-reviewed journals, book chapters, and conference, and issued 2 international patents. His current research interests focus on developing novel or high-performance biomass-based materials.

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Biyao Geng was born in China in 1992. He achieved his B.S. degree with the major of polymer science and engineering from Zhejiang Agriculture & Forestry University in China in July 2015. Now he is pursuing his M.S. degree at the school of engineering under the supervision of Prof. Hongzhi Liu at the same university. His current research topic is the development of nanocellulose-based functional materials for the removal of various pollutants from water.

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Yufei Chen was born in China in 1992. He successfully completed B.S. degree of Polymer Materials and Engineering at the Zhejiang Agriculture & Forestry University in 2014. He is pursuing a M.S. degree at the school of engineering under the supervision of Prof. Hongzhi Liu at the same university. His research topic is to develop novel nanocellulose-based aerogels for the elimination of dye pollutants.

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Haiying Wang completed her B.S. program in 2004. She is currently a M.S. candidate with the major of agricultural resource utilization at the Zhejiang Agriculture & Forestry University. Her research topic deals with the development of novel bio-sorbent materials for the capture of heavy metal ions.

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Review on the Aerogel-Type Oil Sorbents Derived from Nanocellulose

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