Water Separation

28 Apr 2017 - E-mail: [email protected] (H.W.)., *Phone: +86 10 58802736. ... apparatus was designed to make MCC-CH3 a further practical application...
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Preparation of MCC/MC Silica Sponge and Its Oil/Water Separation Apparatus Application Bitao Liu,† Lu Zhang,† Hui Wang,*,† and Zhaoyong Bian*,‡ †

College of Environmental Science and Engineering, Beijing Forestry University, P.O. Box 60, No. 35 Qinghua East Road, Haidian District, Beijing 100083, PR China ‡ College of Water Sciences, Beijing Normal University, Beijing 100875, PR China ABSTRACT: A novel superoleophilic sponge, which has been prepared by a simple sol−gel process using microcrystalline cellulose (MCC) and methyl cellulose (MC), and its oil/water separation apparatus application are presented here. The samples were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectra (FTIR), and so on. The results indicated that MCC/ MC silica sponge (MCC-CH3) had been successfully introduced CO and methyl groups and exhibits better mechanical properties, absorption capacity, and high oil selectivity. Besides, a novel oil−water separation apparatus was designed to make MCC-CH3 a further practical application. Based on this simple but flexible and intelligent design, oil collection, sorption materials regeneration, and free navigation can be simultaneously achieved in the remediation of oil spills. The results showed the discharge flow of n-hexane was about 11700 g·h−1·g−1, and the oil ratio of the discharge mixture reached 99% under a continuous operation.

1. INTRODUCTION Frequently occurring oil and chemical spills/leaks have caused severe damage to water resources and ecosystems and also can lead to accidental fires and severely harm human beings. Up to now, different kinds of technologies to treat oily wastewater can be applied in different situations, including in situ burning, sorption materials, solidifiers, dispersants, and bioremediation.1−5 Generally, sorption materials have been considered as one of the most effective ways for separation of water/oil and spilled oil collection.6 Among the various sorption materials, cellulose deprived sponges show great potential for oily wastewater treatment because of their attractive features, such as good mechanical properties, low cost, environmentally friendly, biodegradability, biocompatibility, and so on.7 Recently, as a kind of biodegradable and biocompatible polymer, microcrystalline cellulose (MCC) and methyl cellulose (MC), which could be easily prepared from cellulose, have been widely studied.8 Comparing to the original cellulose, MCC exhibits a lower degree of polymerization of the cellulose chains [level-off degree of polymerization (LODP)].9 Besides, MC is a kind of cellulose ether consisting of at least one methyl group on each anhydroglucose unit.10 Both MCC and MC present numbers of hydroxyl groups on their anhydroglucose monomer which can be utilized for a further covalent binding with other functional polymers.11 Research of polymer matrices introducing MCC or MC has been investigated and reported. For example, Sun et al. used waste-derived MCC to prepare PVA/MCC composites. The testing results had proved the interfacial interaction of hydrogen bonding between MCC and © 2017 American Chemical Society

plasticized PVA could have good effect on the crystallization of PVA. Compare with the unfilled PVA, the melting temperature of PVA/MCC composites decreased, while the tensile strength remarkably improved.12 Liu et al. successfully synthesized a kind of pure crystalline zeolite Rho polymer using MC as the space-confinement additive.13 Their research showed that the MC gel network could work well for the space-confinement, thus helping to form a uniform particle size distribution with a particle size of zeolite Rho within 1 mm.13 However, MCC or MC is highly hydrophilic due to the multiple hydroxyl groups.14 It is a major challenge for us to modify their hydrophilic surface into a hydrophobic one physically or chemically. Hence, we introduce methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) as two kinds of polymer matrix. Both MTMS and DMDMS are expected to obtain large amounts of hydroxyl groups on their surface, leading to desirable interfacial interactions through hydrogen bonding among MCC/MC and MTMS/DMDMS matrix.15,16 After the completion of condensation reactions, the surface of the composite would mostly be covered by −CH3 groups, a kind of typical hydrophobic functional group. However, most research focuses excessively on the modification of sorption materials, ignoring their practical application issues when facing a complicated and multiple oil Received: Revised: Accepted: Published: 5795

January 15, 2017 April 25, 2017 April 28, 2017 April 28, 2017 DOI: 10.1021/acs.iecr.6b04854 Ind. Eng. Chem. Res. 2017, 56, 5795−5801

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Industrial & Engineering Chemistry Research

2.3. Synthesis of MCC/MC Silica Sponge. Different amounts of MTMS, DMDMS, and urea were added into the cellulose suspension, and the mixture was stirred for 2 h with magnetic stirring at room temperature. After that, these mixtures were sealed in an oven for gelation at 80 °C over several hours. Then the samples were washed with the methanol/water mixture after they were cooled to room temperature. After natural drying under ambient conditions, MCC/MC silica sponges were finally prepared, as shown in Figure 1.

spill environment. There are many reports about the method of oil spill remediation, such as electromagnetohydrodynamic (EMHD) marine oil film recovery technology.17 The flume tests showed that the device was very sensitive to the inlet’s water level. If the inlet’s water level is too high, the fluid absorbed into the MHD channel will be only seawater. Therefore, the process of the EMHD thin oil/oil film recovery method must be operated under random waves conditions. Ge et al. had applied an external pumping to the porous hydrophobic/oleophilic materials in order to spontaneously regulate the suction power. Although this oil collection system could save sorption materials cost, the problems of regeneration and free navigation remain unmentioned.18 To our best knowledge, few research has been reported concerning both MCC and MC into a silica matrix to synthesize a superhydrophobic sponge. Besides, its related practical application in water/oil separation is seldom investigated. In order to improve the compatibility among MC, MCC, and the hydrophobic polymer matrices, a cationic surfactant n-hexadecyltrimethylammonium chloride (CTAC) was used to promote MCC to form a uniform dispersed solution in the new solvent mixture. Considering MCC as a sort of anionic colloform, it would be well combined with CTAC, a cationic surfactant, under the charge effect. Besides, MC was used as a dispersant since it was well suitable in sol− gel processing.19 The aim of this work was to evaluate the physical and chemical effect of MCC-CH3 and its apparatus application. Besides, a novel kind of oil−water separation apparatus was designed to make MCC-CH3 a further practical application. Interestingly, based on this simple but flexible and intelligent design, oil collection, sorption materials regeneration, and free navigation by long-range control can be simultaneously achieved in the remediation of oil spills. This novel technique showed potential practical application in oil and chemical spill remediation.

Figure 1. MCC/MC silica sponges.

2.4. Characterization. 2.4.1. SEM Studies. The morphology of MCC/MC silica sponge was investigated by a scanning electron microscope (X-4800, Hitachi ltd., Japan). SEM images were taken at an accelerating voltage of 10 kV at various magnifications. The samples were previously sputter coated with gold to prevent charging on the surface. 2.4.2. XRD Studies. The XRD measurements were performed with a X-diffractometer (X′ Pert Pro MPD, PANalitical B.V., Holland) at an accelerating voltage of 40 kV and the current of 40 mA (Cu Ka radiation, k = 1.54184 Å). The data were collected from 2θ = 10−80° with a step width of Δ2θ = 0.015° at a speed of 5°·min−1. 2.4.3. Fourier Transform Infrared (FT-IR) Spectroscopy. The Fourier Transform Infrared spectra (FTIR) was obtained with a FT-IR spectrometer (Nicolet, NEXUS 670, USA). The analyses were performed on the Fourier transform mid-infrared region with wave numbers ranging from 4,000 to 400 cm−1. All the samples were dried in vacuum oven at 60 °C for 24 h before testing. 2.4.4. Contact Angles Measurement. Contact angles were measured with Drop Master (OCA20, DataPhysics Co., Ltd., German). The volume of water droplet was fixed at 2.0 μL, and a contact angle was determined at 12 s after the attachment to the sample surface. 2.4.5. Thermal Property Analysis. Thermo-oxidative degradation was monitored via thermogravimetric analysis (Q50, TAInstrument, American) under a flowing N2. All the samples were ground into fine powder and heated from 25 to 800 °C at a heating rate of 10 °C·min−1. 2.4.6. Mechanical Properties. For mechanical tests, aerogels were measured by a material tester (WDW3020, Kexin Changchun Corp., China). Samples were compressed-decompressed using a load cell of 5 kN with a rate of 1 mm·min−1. The diameter and height of each sample were recorded with vernier caliper. 2.4.7. Oil Absorption Performance. Various oils and organics, including n-hexane, toluene, petroleum, chloroform, gasoline, and diesel, were used to measure the work flux and oil separation efficiency of the apparatus using MCC-CH3 as sorption materials. The outside surface of the crawler belt on the running roller wheels is covered by 18−20 pieces of MCCCH3 (each piece is 3.5 cm in diameter and 1.0 cm in thickness, about 1.0 g of weight). Oil/water (oil 10 wt %; water 90 wt %)

2. EXPERIMENTAL SECTION 2.1. Materials. Microcrystalline cellulose (MCC) and methyl cellulose (MC) were used as purchased. Methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) were provided by Shandong Linyi Chemical Ind., Ltd. (China). Acetic acid, urea, surfactant n-hexadecyltrimethylammonium chloride (CTAC), and methyl alcohol were purchased from Guoyao Chemical Ind. Co., Ltd. (China). 2.2. Preparation of MCC/MC Suspension. A defined concentration of acetic acid was first introduced into a beaker, and then CTAC was added into it. Subsequently different amounts of MCC and MC were added gradually into the solution under a stirring condition. The resulting mixture was stirred for 30 min and transferred into ultrasonic treatment for 10 min. After that, the cellulose suspension was obtained. Different amounts of MCC and MC were used depending on the sample (see Table 1). Table 1. MCC and MC Mass Ratio in Samples sample

MCC/%

MC/%

MCC-5 MCC-10 MCC-15 MCC-CH3

5 10 15 5

10 5796

DOI: 10.1021/acs.iecr.6b04854 Ind. Eng. Chem. Res. 2017, 56, 5795−5801

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Industrial & Engineering Chemistry Research

Figure 2. SEM images of MCC-CH3 (a) ×1000, (b) ×5000, and (c) ×10000.

mixtures were filled in a transparent PVC container (450 mm × 300 mm × 80 mm) and prepared in a continuous supply to meet the demand for apparatus work simulating an opening ocean or river environment. The flux of the apparatus was calculated according to eq 1. Flux =

M1 M0 × T

(1)

Here, M0 is the weight of MCC-CH3 before separation (g); M1 is the weight of the collected oils and organics after separation (g); and T is the time duration of the separation (h). The separation efficiency was calculated according to eq 2. η% =

M1 × 100 M2

(2)

Figure 3. XRD patterns of MCC-5, MCC-10, MCC-15, and MCCCH3.

Here, M1 is the weight of the collected oils and organics after separation (g); and M2 is the weight of the collected oils (organics)/water emulsion after separation (g).

decreases, while the intensity of the cellulose peak increases to some extent. 3.3. FTIR Analysis. The IR spectra images of MCC/MC silica sponge and silica aerogel are presented in Figure 4. The

3. RESULTS AND DISCUSSION 3.1. Morphological Analysis. Figure 2 shows SEM images of the MCC-CH3 sponges. As shown in Figure 2, MCC-CH3 exhibits a well-defined bicontinuous macroporous structure. It is composed of a number of hemispherical microparticles, and these microparticles connect to each other to form a 3D crosslinked network structure. Under higher magnification, the surface of these microparticles is rather rough with some micrometer-scale protuberances. These protuberances would increase its surface area to some extent. This phenomenon is probably ascribed to the help of MC. Mohammad et al. had proved that the surface of composites with MC is much rougher than those without MC.20 As shown in the SEM images, some crystalline particles randomly distribute on the MCC-CH3 surface. These particles are most likely to be MC and MCC. The mechanism that MCC and MC crystalline particles tightly adhere to the MCC-CH3 can be explained through the chemical bond interaction among the hydroxyl groups from MCC, MC, and hydrolyzed silanes. 3.2. XRD Analysis. The X-ray diffractograms of MCC/MC silica sponges are shown in Figure 3. Both samples display three crystallinity peaks localized at 45°, 65°, and 77°, which are assigned to Si diffraction planes of 200, 220, and 311, respectively.21 The peaks identified at 2θ = 22.5° are characteristic of cellulose and are in agreement with those observed by Reis et al.22 Obviously, the intensity of Si diffraction peak increases with the incorporation of MC into the MCC/MTMS/DMDMS matrix. This is probably because the presence of MC could increase the crystallinity of materials due to the crystalline nature of cellulose.23 However, combining with MC and MCC, the intensity of Si diffraction peak

Figure 4. FT-IR spectra of the MCC/MC silica sponge.

bands at approximately 1600 cm−1 characterize the stretching of the CO in the carbonyl group of the ester bond, which is present in the MCC and MC structure.24,25 Besides, the intensity of the CO peak increases along with MC increasing. Therefore, the above results show that MCC/MC silica sponges have successfully introduced the CO group belonging to cellulose. The absorption peaks at around 2964, 1262, and 854 cm−1 are ascribed to the stretching vibration of C−H (methyl groups) rocking in Si-CH3 and Si-(CH3)2, suggesting that the composite structure has been modified by combining with a hydrophobic group, C−H (methyl groups). A quite strong peak corresponding to Si−O−Si bonding is 5797

DOI: 10.1021/acs.iecr.6b04854 Ind. Eng. Chem. Res. 2017, 56, 5795−5801

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Industrial & Engineering Chemistry Research observed at around 1000 and 750 cm−1, indicating its main chemical composition presents. 3.4. Contact Angles Measurement. As shown in Figure 5, MCC/MC silica sponges present a character of super-

of the thermal stability of the composites. The temperature of maximum weight loss rate (Tp) is in accordance with the following order: MCC-CH3 < MCC-5 < MCC-10 < MCC-15, while the weight of the residue (Rm) is MCC-15 < MCC-10 < MCC-5 < MCC-CH3. The results demonstrate that an increase of the MCC ratio leads to a gradual increase of the thermal stability of the composites. Although MCC-CH3 shows a decrease in the major degradation peak temperature, its char residue is approximately 50% more than any other, indicating a better flame retardancy property. This may be attributed to the incorporation of MC, making MCC-CH3 more durable to thermal degradation.13,20 3.6. Mechanical Properties. As shown in Figure 7, after 20 loading−unloading cycles, MCC-CH3 endures up to ca. 70%

Figure 5. Contact angle of the MCC/MC silica sponges.

hydrophobic, on which the water droplet maintained its initial contact angle as well as its round shape. The contact angle of the water droplet reached 159.4°−167.5°, showing superhydrophobicity. The in situ attachment of these hydrolytically stable −CH3 groups to the siloxane backbone during sol−gel polymerization leads to very low solid−liquid interfacial energies, which in turn results in a hydrophobic aerogel. This might be attributed to the surface roughness of the cellulose sponge. It evidently confirms that this method has led to a major enhancement of hydrophobicity.26 3.5. Thermal Gravimetric Analysis. As shown in Figure 6, the degradation of MCC/MC silica sponges goes through two

Figure 7. Compressive stress−strain curves of MCC-CH3 compressed to 70% strain under 20 circles.

linear compression and springs back to more than 95% of their original size. The compressive stress−strain curves do not change significantly demonstrating the tested sample has no obvious structural changes after removal of stress. The maximal stress at 70% strain was found to be 0.08 MPa. The compressibility capacity is comparable with those of many reported sorption materials such as polyaniline coated melamine sponge and CNF aerogels,27 thus confirming its good mechanical properties which is very important for its practical application as an oil absorbent. 3.7. Sorption Capacity. During 20 times repeated absorption-squeezing cycles, MCC-CH3 could absorb a broad spectrum of oil and organics at capacities of up to 13 times its own weight (see Figure 8, use chloroform as oil). Besides, in addition to the other oils, such as n-hexane, petroleum ether, methylbenzene, and so on, MCC-CH3 also exhibits a good and sustainable adsorption capacity. In the case of high-density oils, such as chloroform, MCC-CH3 reaches the highest sorption capacity, while it gets a lowest sorption capacity when treating petroleum ether. The reasons for this phenomenon are mainly due to the density of the oil and organics. 3.8. Oil/Water Separation Model Apparent. An oil/ water separation model apparent is shown in Figure 9. It mainly consists of a compressive roller wheel, a running roller wheel, a propeller, and so on. The sorption material (MCC/MC silica sponges) fixed on the crawler belt could absorb oil and other organic solvents when it is running at the bottom. And the oil absorbed sponge is compressed to release the oil when it is transmitted to the top. As MCC/MC silica sponges have good elasticity and mechanical properties, it is easy to release the oil

Figure 6. TG and DTG curves of MCC/MC silica sponges (MCC-5, MCC-10, MCC-15, and MCC-CH3).

stages: the first phase appears at a temperature of 20−400 °C. This part is due to the loss of water molecules, residue solvents, and some other unreacted substances. The second phase appears at a temperature of 400−600 °C. During this phase, some functional groups such as Si−O−Si, Si-CH3 groups, and long chain molecules begin to be cracked. Comparing to MCC5 and MCC-10, the major degradation peak temperature of MCC-15 shifts toward higher temperature alone demonstrating that an increase of the MCC ratio results in a gradual increase 5798

DOI: 10.1021/acs.iecr.6b04854 Ind. Eng. Chem. Res. 2017, 56, 5795−5801

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Industrial & Engineering Chemistry Research

Figure 8. Absorption capacities of MCC-CH3 for various oils and organics.

Figure 10. Work procedure of apparatus.

Figure 9. Physical model of apparatus.

and other organic solvents being absorbed under compression. Interestingly, it can be imagined that the oil−water separation apparatus can achieve free navigation and make a route planning in the oil and chemical spills/leaks area with the help of GPS and the wireless control system (GPS and the wireless control system are not exhibited in our model). The work procedure of the apparatus is shown in Figures 10 and 11. After running for 0.5 h, the discharge flow of n-hexane is about 11700 g·h−1·g−1, and the oil ratio of the discharge mixture reaches 99% (see Figure 12). Then during the following 1 h, 2 h, 3 h, and up to 6 h, the apparatus discharge flow and the oil ratio of the discharge mixture both stay at a small fluctuation which illustrates that the continuous work stability of the apparatus remains excellent. Figure 13 shows the oil mass flux and oil separation efficiency with different kinds of oils (n-hexane, toluene, petroleum, chloroform, gasoline, and diesel). When combined with MCCCH3, the apparatus could deal with a broad spectrum of oil and organic emulsion at a mass flux about 11700−27000 g·h−1·g−1, depending on the density as well as the viscosity of absorbed oils and organics. The mass flux of chloroform is higher than the others due to the high viscosity. While this result is quite contrary to what had been observed by Peng et al.,26 they had made a small-scale oil−water separation device using a kind of superhydrophobic magnetic cellulose sponge (SMCE). They pointed out that the higher viscosity of absorbed oils and organics would get a lower mass flux since SMCE was used to work as a filtering membrane in its separation device.26 Hence, there is no restriction on the viscosity in our apparatus system. Besides, the separation efficiency of each tested oil and organic

Figure 11. Magnification of apparatus detail.

Figure 12. Plot of the flux under a circulatory apparatus system.

remains steadily above 90%, indicating the apparatus system could work at a high efficiency.

4. CONCLUSION A simple method for the fabrication of a superhydrophobic and superoleophilic MCC/MC silica sponge (MCC-CH3) and a novel kind of oil−water separation apparatus have been presented in this article. When the mass ratio of MCC and MC reaches 1:2, MCC-CH3 gets a good surface integrity, and the CO stretching appears to be strongest. The tested 5799

DOI: 10.1021/acs.iecr.6b04854 Ind. Eng. Chem. Res. 2017, 56, 5795−5801

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Industrial & Engineering Chemistry Research

for Pseawater Sampled after an Oil-spill in Taranto Gulf (Italy): A comparison of Biostimulation, Bioaugmentation and Use of a Washing Agent in Microcosm Studies. Mar. Pollut. Bull. 2016, 106, 119−126. (6) Wang, J.; Geng, G. Highly Recyclable Superhydrophobic Sponge Suitable for the Selective Sorption of High Viscosity Oil from Water. Mar. Pollut. Bull. 2015, 97, 118−124. (7) Yang, X.; Cranston, E. D. Chemically Cross-Linked Cellulose Nanocrystal Aerogels with Shape Recovery and Superabsorbent Properties. Chem. Mater. 2014, 26, 6016−6025. (8) Thummanukitcharoen, P.; Limpanart, S.; Srikulkit, K. Preparation of Organosilane Treated Microcrystalline Cellulose (SiMCC) and the Polypropylene/SiMCC Composite, Proceedings of the ICCM International Conferences on Composite Materials, Jeju Island, South Korea, 21−26 Aug, 2011. (9) Cataldi, A.; Dorigato, F.; Deflorian, A. P. Thermo-mechanical Properties of Innovative Microcrystalline Cellulose Filled Composites for Art Protection and Restoration. J. Mater. Sci. 2014, 49, 2035−2044. (10) Bayer, R.; Knarr, M. Thermal Precipitation or Gelling Behaviour of Dissolved Methylcellulose (MC) Derivatives-Behaviour in Water and Influence on the Extrusion of Ceramic Pastes. Part 1: Fundamentals of MC-derivatives. J. Eur. Ceram. Soc. 2012, 32, 1007−1018. (11) Gunathilake, C.; Dassanayake, R. S.; Abidi, N.; Jaroniec, M. Amidoxime-functionalized Microcrystalline Cellulose-mesoporous Silica Composites for Carbon Dioxide Sorption at Elevated Temperatures. J. Mater. Chem. A 2016, 4, 4808−4819. (12) Sun, X.; Lu, C.; Liu, Y.; Zhang, W.; Zhang, X. Melt-processed Poly(Vinyl Alcohol) Composites Filled with Microcrystalline Cellulose from Waste Cotton Fabrics. Carbohydr. Polym. 2014, 101, 642−649. (13) Liu, X.; Zhang, X.; Chen, Z.; Tan, X. Hydrothermal Synthesis of Zeolite Rho using Methylcellulose as the Space-confinement Additive. Ceram. Int. 2013, 39, 5453−5458. (14) Miao, C.; Hamad, W. Y. Cellulose Reinforced Polymer Composites and Nanocomposites: a Critical Review. Cellulose 2013, 20, 2221−2262. (15) Venkateswara Rao, A.; Latthe, S. S.; Nadargi, D. Y.; Hirashima, H.; Ganesan, V. Preparation of MTMS based Transparent Superhydrophobic Silica Films by Sol-gel Method. J. Colloid Interface Sci. 2009, 332, 484−490. (16) Jiang, H.; Zheng, Z.; Xiong, J.; Wang, X. Studies on Dialkoxysilane Hydrolysis Kinetics under Alkaline Conditions. J. Non-Cryst. Solids 2007, 353, 4178−4185. (17) Zhao, L. Z.; Liu, F. L.; Peng, Y.; An, W.; Sha, C. W.; Wang, Z. L.; Liu, J. J.; Ye, H. L. Research Development and Key Scientific and Technical Problems on EMHD Marine Oil Film Recovery Technology. Aquatic Procedia 2015, 3, 21−28. (18) Ge, J.; Ye, Y. D.; Yao, H. B.; Zhu, X.; Wang, X.; Wu, L.; Wang, J. L.; Ding, H.; Yong, N.; He, L. H.; Yu, S. H. Pumping through Porous Hydrophobic/Oleophilic Materials: An Alternative Technology for Oil Spill Remediation. Angew. Chem., Int. Ed. 2014, 53, 3612−3616. (19) Chen, W.; Zhang, J.; Fang, Q.; Li, S.; Wu, J.; Li, F.; Jiang, K. Solgel Preparation of Thick Titania Coatings Aided by Organic Binder Materials. Sens. Actuators, B 2004, 100, 195−199. (20) Habibi, M. H.; Nasr-Esfahani, M.; Egerton, T. A. Preparation, Characterization and Photocatalytic Activity of TiO/Methylcellulose Nanocomposite Films Derived from Nanopowder TiO and Modified Sol-gel titania. J. Mater. Sci. 2007, 42, 6027−6035. (21) Baharia, A.; Taghavia, K.; Ghorbanzadehb, N.; Asadolahzadehb, S. Investigation of NiO/SiO2 Nanostructural Properties via XRD, Xpowder and FTIR Techniques. Proceedings of the 4th International Conference on Nanostructures, Kish Island, Iran, 12−14 March, 2012. (22) Reis, M. O.; Zanela, J.; Olivato, J.; Garcia, P. S.; Yamashita, F.; Victoria, M.; Grossmann, E. Microcrystalline Cellulose as Reinforcement in Thermoplastic Starch/Poly(butylene adipate-co-terephthalate) Films. J. Polym. Environ. 2014, 22, 545−552. (23) Müller, C. M. O.; Laurindo, J. B.; Yamashita, F. Effect of Cellulose Fibers on the Crystallinity and Mechanical Properties of Starch-based Films at Different Relative Humidity Values. Carbohydr. Polym. 2009, 77, 293−299.

Figure 13. Plot of the flux under a circulatory apparatus system.

sample could return to the original shape after 20 loading−unloading cycles of 70% compression strain. Besides, MCC-CH3 is proved to be superhydrophobic with a contact angle as high as 166.4°, thus being efficient in absorbing a wide range of oily target compounds with an absorption capacity up to 13 times their own weight. The designed oil−water separation apparatus with MCC-CH3 exhibits excellent performance in the oil spill remediation. The discharge flow of n-hexane is about 11700 g·h−1·g−1, and the oil ratio of the discharge mixture reaches 99% under a continuous operation. Interestingly, it can be imagined that the oil−water separation apparatus can be devised to achieve free navigation and make a route planning for itself in the oil and chemical spills/leaks area with the help of GPS and a wireless control system.



AUTHOR INFORMATION

Corresponding Authors

*Phone: +86 10 62336615. Fax: +86 10 62336900. E-mail: [email protected] (H.W.). *Phone: +86 10 58802736. Fax: +86 10 58802739. E-mail: [email protected] (Z.B.). ORCID

Bitao Liu: 0000-0002-8829-6357 Hui Wang: 0000-0002-6299-4034 Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENTS This work was supported by the Beijing Natural Science Foundation (No. 8172035) and the National Natural Science Foundation of China (Nos. 51278053 and 21373032).



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DOI: 10.1021/acs.iecr.6b04854 Ind. Eng. Chem. Res. 2017, 56, 5795−5801