Cupric Phosphate Nanosheets-Wrapped Inorganic Membranes with

Subscriber access provided by ECU Libraries

Article

Cupric Phosphate Nanosheets-Wrapped Inorganic Membranes with Superhydrophilic and Outstanding AntiCrude-Oil Fouling Property for Oil/Water Separation Shenxiang Zhang, Gaoshuo Jiang, Shoujian Gao, Huile Jin, Yuzhang Zhu, Feng Zhang, and Jian Jin ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.7b08121 • Publication Date (Web): 03 Jan 2018 Downloaded from http://pubs.acs.org on January 6, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Nano is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 33 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

ACS Nano

Cupric

Phosphate

Nanosheets-Wrapped

Inorganic Membranes with Superhydrophilic and

Outstanding

Anti-Crude-Oil

Fouling

Property for Oil/Water Separation Shenxiang Zhang†§, Gaoshuo Jiang§, Shoujian Gao†§, Huile Jin‡, Yuzhang Zhu§, Feng Zhang§*, and Jian Jin†§*

†

School of Nano-Tech and Nano-Bionics, University of Science and Technology of

China, Hefei, 230026, China. ‡

College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou,

Zhejiang, 325035, China. §

i-Lab, CAS Center for Excellence in Nanoscience, and CAS Key Laboratory of

Nano-Bio Interface, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, 215123, China.

ABSTRACT: Developing an effective and sustainable solution for cleaning up or separating oily water is highly desired. In this work, we report a completely inorganic mesh membrane made up of cupric phosphate (Cu3(PO4)2) in a special intersected nanosheets-constructed structure. Combing the hierarchical structure with strong hydration ability of Cu3(PO4)2, the nanosheets-wrapped membrane exhibits a superior superhydrophilic and underwater anti-oil fouling and anti-bio fouling property for

ACS Paragon Plus Environment

ACS Nano 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 2 of 33

efficient oil/water separation to various viscous oils such as heavy diesel oil, light crude oil, and even heavy crude oil with underwater oil contact angles (CAs) all above 158° and nearly zero underwater oil adhesive force even when a large preload force up to 400 µN applied on the oil droplet. Simultaneously, the membrane exhibits a high chemical and thermal stability, outstanding salt tolerance. Continuous separation operated on a cross-flow filtration apparatus demonstrates a large separation capacity and long-term stability of the membrane during treating a 2000 L crude oil/water mixture with constantly stable permeating flux of ~4000 L/m2 h and oil content in the filtrate below 2 ppm. The excellent anti-oil-fouling property, high separation capacity, and easily scaled-up preparation process of the membrane show great potential for practical application in treating oily wastewater.

KEYWORDS:

crude

oil/water

separation

·

inorganic

membrane · superhydrophilic/underwater superoleophobic property · cupric phosphate nanosheets · anti-crude-oil fouling

In the past few years, the demand for fossil fuels has dramatically increased, especially for crude oil. The large-scale crude oil extraction leads to a high frequency of oil spills.1-2 Simultaneously, processes of oil extraction generate large volumes of complicated oily wastewater which brings about serious damage to marine ecosystem and human health if it cannot be cleaned properly.3-5 Separating oil from oily water is thus important and becoming more and more urgent.6-15 However, collecting or separating viscous oil from oily wastewater is still a challenge. This is because of the high viscosity and adhesive property of crude oil, which always causes a serious pollution to base materials and gives rise to the invalidation of related instruments.


Page 3 of 33 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

ACS Nano

Designing superhydrophilic/underwater superoleophobic membranes based on the combination of high-surface-energy material and surface roughness provides us an effective way by separating oil/water mixture in a bio-inspired way.16-25 However, most of reported superhydrophilic membranes are more effective to light oils with low viscosity more than viscous oils such as crude oil and heavy oil.26-27 Recent studies revealed that materials with high water affinity such as polymer hydrogel13,28-31 and zwitterionic molecules32-36 work well for treating viscous oil due to their excellent water-absorbing and water-retaining capacities. However, these organic materials still face the problems of either poor mechanical strength, weak environmental adaptability and stability, or requirement of complex preparation process, which restrict their use for practical application.37 From this point of view, inorganic membranes attract considerable attentions in consideration of their good mechanical and thermal stability under severe conditions.27,38-40 As same as the design of organic membranes with superhydrophilic and underwater superoleophobic property, surface microstructure and hydration ability of membranes themselves are the two important factors for designing inorganic membrane with desired wetting property.41-42 Despite some progress have been made, a facile and scale-up methodology to fabricate all inorganic membranes with anti-oil-adhesion property for efficient crude oil/water separation is still limited. Besides the requirement for the inorganic material itself to be water-favoring, the fine surface configuration of the material has a great impact on its oil repellent capability.43-44 Previous results showed that the vertical-arrayed nanosheets structure can firmly hold water to form a more stable oil/water/solid three-phase interface and thus exhibit better oil-repellent performance than nanowires-constructed structure.27 Moreover, anti-bio-fouling property is also highly required besides oil-repellence in practical oil/water separation.45-47


ACS Nano 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

We report in this work a completely inorganic mesh membrane made up of intersected Cu3(PO4)2 nanosheets vertically grown on a copper mesh. Cu3(PO4)2 is well-known to be chemically and thermally stable. More importantly, Cu3(PO4)2 possess a much higher water affinity than most of other metal oxides and metal hydroxides. Thus the Cu3(PO4)2 nanosheets-constructed structure makes the mesh membrane more beneficial to hold water and facilitate an extremely stable oil/water/solid three-phase interface. As a result, the Cu3(PO4)2 nanosheets-wrapped mesh membrane exhibits a superior anti-crude-oil fouling and anti-bio fouling property for efficient oil/water separation to various viscous oils such as heavy diesel oil, light crude oil, and even heavy crude oil with underwater oil contact angles (CAs) all above 158° and nearly zero underwater oil adhesive force. The membrane demonstrates a large separation capacity of continuous separation of thousands of liters of oil/water mixture without loss of flux and separation rejection.

RESULTS AND DISCUSSION The Cu3(PO4)2 nanosheets-wrapped mesh membrane was prepared by a facile electrochemical deposition method in a phosphate buffer (pH=7) at the potential of 1 V vs. Ag/AgCl by using a commercial copper mesh as a base membrane and a working electrode as well. Figure 1a is a 50 × 60 cm mesh membrane after reaction, which shows a grey-blue color. SEM image shows that the skeletons of copper mesh are completely wrapped by closely arrayed nanostructure that makes every skeleton rather rough (Figure 1b). Figure 1c shows the enlarged SEM images of the membrane surface where numerous vertically arranged intersected ultrathin nanosheets can be clearly observed. Cross-section SEM image along a skeleton of the mesh shows that the nanosheets grow compactly around the whole skeleton by forming a wrapping


Page 4 of 33

Page 5 of 33 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

ACS Nano

layer in ~10 µm thick (Figure 1d and 1e). To confirm the composition of the nanosheets and examine the nanosheets in detail, the nanosheets grown on the mesh membrane were peeled off from the mesh via sonication and dispersed in water for characterization. X-ray diffraction (XRD) spectrum indicates that the nanosheets are composed of Cu3(PO4)2·3H2O crystals which is in good agreement with the values in the standard card JCPDS No. 22-0548 (Figure 1f).48 The further characterization of Cu3(PO4)2 nanosheets was performed by transmission electron microscopy (TEM) and atomic force microscope (AFM) observation. Figure 1g shows the typical TEM image of a single Cu3(PO4)2 nanosheet spanning over a micrometer hole with a clear and sharp edge. The corresponding selected-area electron diffraction (SAED) pattern displays face-center cubic diffraction spots, indicating the single crystalline property of the nanosheet (inset in Figure 1g). The thickness of the nanosheet as measured by AFM is about 20 nm (Figure 1h). The surface charge property of the Cu3(PO4)2 nanosheets was also examined by measuring the zeta potential of Cu3(PO4)2 nanosheets. It gives a zeta potential peak at -5.99 mV (Figure 1i), indicating that the Cu3(PO4)2 nanosheets are slightly negatively charged. Our experimental results demonstrate that the reaction time has great influence on the size and density of the grown Cu3(PO4)2 nanosheets. As shown in Figure 2a-2e, the growth of Cu3(PO4)2 nanosheets occurs immediately on the copper mesh when the electrochemical deposition reaction begins. At 1 min, a few of nanosheets randomly distribute on the mesh (Figure 2a). The density of the nanosheets increases quickly and a dense nanosheet layer that completely cover the whole skeleton of copper mesh is produced at 10 min (Figure 2b-2d). Correspondingly, the size of Cu3(PO4)2 nanosheets increases gradually with increasing the reaction time. Further increasing the reaction time to 30 min, no obvious change on nanosheet size and density is


ACS Nano 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 6 of 33

observed (Figure 2e). This is because that once Cu3(PO4)2 nanosheets completely cover the copper mesh, the release of Cu2+ from base membrane is prevented and the further electrochemical reaction is prohibited. The surface wettability of the Cu3(PO4)2 nanosheets-wrapped mesh membranes with different reaction time are also characterized by measuring the water CAs and underwater crude oil adhesive force (Figure 2f). The water CAs decease with increasing the reaction time from 37.5° at 1 min to ~0° at 10 min. Meanwhile, the underwater crude oil adhesive forces decease from 33.2 µN at 1 min to less than 1.2 µN at 10 min. It reveals that the coverage of Cu3(PO4)2 nanosheets directly affect the membrane wetting property and fully covered

Cu3(PO4)2

nanosheets

endows

the

membrane

with

superhydrophilic/underwater anti-crude-oil-fouling property. Herein, we chose to fix the Cu3(PO4)2 nanosheets-wrapped mesh membrane grown for 10 min for further comprehensive investigation, as such a reaction time yields the best hydrophilic and underwater oleophobic performance. To further examine the wetting behavior of water on the Cu3(PO4)2 nanosheets-wrapped mesh membrane, dynamic spreading process of a water droplet on the membrane is recorded. As shown in Figure 3a, when a 3 µL water droplet contacts the membrane in air, it spreads out quickly within 0.30 s, indicating a superior water-wetting property. When using 1,2-dichloroethane as a representative oil to examine the oil-repellent property of the membrane, an underwater oil CA of 150° is observed, meanwhile a sliding angle as small as about 1° is obtained, showing an excellent underwater superoleophobicity (Figure 3b). Moreover, the membrane exhibits superior repellency to crude oil with underwater crude oil CA of 158° (Figure 3c). As for other oils with different surface tensions, including isooctane, hexadecane, soybean oil, diesel oil, and silicone oil, our membrane exhibits excellent underwater


Page 7 of 33 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

ACS Nano

superoleophobic property with all oil CAs more than 159° and oil adhesive forces less than 1 µN (Figure 3d). In principle, the underwater superoleophobic property of a membrane is mainly determined by its water hydration ability. The stronger the hydration ability is, the better underwater oleophobicity and lower oil adhesive force achieve. As for general hydrophilic materials with weak hydration ability, oil droplets are easy to break through and penetrate the adsorbed water layer to the surface of membrane directly under a certain pressure from either water flow or hydrostatic water pressure, which result in the adhesion of oils on the membrane. To examine the hydration ability of our membrane, the underwater anti-crude-oil adhesion of the membrane was measured under different preloading forces. As shown in Figure 4a-4d, underwater a droplet of crude oil suspended by a mental cap was forced to contact the membrane surface under four different preload force 100 µN, 200 µN, 300 µN, and 400 µN respectively, and then detached from the membrane surface. It could be seen that with the increase of preload force, the oil droplet was squeezed out of shape seriously. Still, no any adhesion was observed during lifting process even when the preload force is as large as 400 µN. It is worth to note that 100 µN was usually used as preload force to examine the underwater anti-oil-adhesion force for most of the previously reported materials.17,27,41 Our Cu3(PO4)2 nanosheets-wrapped mesh membrane displays an ultralow underwater crude oil adhesive force (1-2 µN) even when the preload force is as high as 300 µN (Figure 4e and 4f). At 400 µN preload force, the detected oil adhesive force is around 6 µN. This result suggests that our membrane possesses extremely strong hydration ability to prevent oil penetrating. Due to its excellent underwater anti-oil-adhesion property, the Cu3(PO4)2 nanosheets-wrapped mesh membrane exhibits outstanding underwater self-cleaning


ACS Nano 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

property to both light and viscous oils. Figure 5a shows that underwater a trickle of isooctane (dyed blue) can bounce off the membrane surface without leaving any oil droplet. Furthermore, when a per-wetted mesh membrane is adhered by crude oil in the air, the crude oil spontaneously levitates off the membrane surface once the membrane is immersed in water (Figure 5b). Besides copper mesh, the Cu3(PO4)2 nanosheets-wrapped structure can be grown on diverse copper base materials via the same electrochemical deposition method and could serve as anti-oil-fouling coating. As an example, Figure S1 and S2 show the morphology and wetting property characterizations of Cu3(PO4)2 nanosheets grown on a copper foil. As shown in Figure 5c, when the Cu3(PO4)2 nanosheets-covered copper foil is immersed in a heavy crude oil/water mixture and then lifted up repeatedly, the copper foil is free of oil fouling and keep clean underwater. In control experiments, the same materials without Cu3(PO4)2 nanosheets are seriously adhered and fouled by crude oil without self-cleaning capability underwater (figures were circled by red frames in Figure 5a-5c). To elucidate the reason why the Cu3(PO4)2 nanosheets-covered surface has such strong hydration ability and superior underwater anti-oil-adhesion property, water adsorption energy (∆Eads) of Cu3(PO4)2 crystal was calculated based on spin-polarized density functional theory (DFT) calculation as follows: ∆Eads = E(H2O/crystal) - E(crystal) - E(H2O) Where E(H2O/crystal), E(crystal), E(H2O) are the optimized potential energy of a crystal unit adsorbed by a water molecule, the pure crystal unit, and a free water molecule, respectively. Besides Cu3(PO4)2, water adsorption energies of other commonly developed inorganic materials such as Cu(OH)2, CuO, Co3O4 were also calculated as comparison (see Methods section for detail description of the calculation). The


Page 8 of 33

Page 9 of 33 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

ACS Nano

calculated data are shown in Figure 6a. Corresponding, the DFT optimized geometries of Cu3(PO4)2, Cu(OH)2, CuO, Co3O4 crystal units adsorbed by a water molecule are also presented in Figure 6b-6e. The results reveal that different inorganic materials exhibit different ∆Eads, -0.794 eV for Cu3(PO4)2, -0.396 eV for Cu(OH)2, -0.415 eV for CuO, and -0.483 eV for Co3O4. Among them, the ∆Eads of Cu3(PO4)2 is the lowest one, indicating an extremely strong hydration ability. Continuous crude oil/water separation was carried out on a homemade cross-flow filter equipped with a membrane horizontally placed as schematically shown in Figure 7a. The crude oil/water mixture (v:v = 1:4) is pumped into the upper membrane cell by peristaltic pump. The crude oil is rejected above the membrane and collected by side exit and the water passes through the mesh membrane as filtrate to flow away from downward. During the whole process, water flux and oil content in the filtrate water are monitored continuously. It shows that the mesh membrane maintains a stable permeating flux up to 4000 ± 100 L/m2 h and a constant oil content in the filtrate water below 2 ppm in the test of 2000 L crude oil/water mixture (Figure 7b). The

mechanical,

chemical

and

thermal

stability

of

the

Cu3(PO4)2

nanosheets-wrapped mesh membranes were evaluated in detail. For abrasion tests, the mesh membrane is scratched repeatedly by fingers under the pressure in the range of 10-15 N. The water CAs and underwater crude oil CAs of the mesh membrane after abrasion are then measured. As shown in Figure S3, the mesh membrane maintains the underwater superoleophobicity with underwater crude oil CAs above 153° and ultralow adhesive force less than 3 µN after 150 abrasion cycles. As for pH stability, the membranes were immersed in water solutions with different pH values for 12 hours firstly and their water CAs and underwater oil adhesive force were then


ACS Nano 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

detected. As shown in Figure 8a, the membranes keep their superhydrophilicity (water CAs ~0°) and ultralow underwater crude oil adhesive forces all less than 2 µN at the pH of 4-12. At pH value lower than 4, their water CAs sharply increase to 15° and underwater crude oil adhesive fore increase simultaneously to 9 µN. It indicates that the mesh membrane is chemically unstable at low pH condition. The salt resistance of the membrane was evaluated by monitoring its underwater crude oil CA and adhesive force after immersing in 30 mg/mL NaCl, KCl, CaCl2, Na2SO4, and MgSO4 solutions for 7 days, respectively. No obvious changes are detected before and after salt immersion. The membranes maintain a high underwater crude oil CAs above 158° and ultralow adhesive force less than 3 µN after immersed in all the salts (Figure 8b). Even immersed in sea water for as long as 20 weeks, the membrane still exhibits a stable underwater superoleophobicity and ultralow oil adhesive property (Figure 8c). The amount of Cu2+ ions released from the Cu3(PO4)2 nanosheets-wrapped mesh membrane into water with time was also monitored via inductive coupled plasma emission spectrometry (ICP) measurement where 0.5 g mesh membrane was immersed in 50 ml water for 30 days. The result shows that the concentration of Cu2+ ions increases quickly with time from 11.3 ppb at 1 day to 36.1 ppb at 3 days and then slowly increases to 42.0 ppb after 30 days (Figure 8d). According to the US EPA Federal standard of 1.3 ppm for copper in drinking water, the Cu2+ ions released by our membrane is far below this official standard, indicating the membrane is safe when used for treating wastewater. The thermal stability of the membrane was evaluated by heating the membranes up to 100 °C, 200 °C, 300 °C, and 400 °C for 12 hours, respectively. Their surface morphologies, water CAs and crude oil adhesive forces were examined. It shows that the Cu3(PO4)2 nanosheets structure maintains well within 300 °C (Figure 9a-9c). Up


Page 10 of 33

Page 11 of 33 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

ACS Nano

to 400 °C, the nanosheets structure starts to collapse (Figure 9d). Correspondingly, the membrane keeps a good superhydrophilic property with water CAs of ~0° and underwater superoleophobic property with underwater crude oil CAs above 156° and oil adhesive force less than 4 µN within 300 °C (Figure 9e). After heated at 400 °C, the water CA of the membrane increases to 17.3° and underwater crude oil adhesive force increases to 26.0 µN (Figure 9e). This result indicates that the membrane is thermally stable up to at least 300 °C. To test the anti-bio fouling property of the membrane, 200 L water containing either ~107 cell/L E. coli, 100 mg/L humic acid, or 100 mg/L bovine serum albumin (BSA), respectively, was continuously filtered through a membrane with a diameter of 38 mm and the real-time water flux was monitored during filtration. As shown in Figure 10, no obvious flux decrease is observed during the whole filtration process. These results indicating almost no foulants adsorbed on the membrane. The membrane thus displays a good anti-bio fouling property. We suppose that the negatively charged surface of the membrane is beneficial to the improvement of anti-bio fouling. It is widely acknowledged that negatively charged surface could provide much electrostatic repulsion against biomolecules to thus create better anti-bio fouling property.49-50

CONCLUSION In summary, we have developed a completely inorganic mesh membrane made up of Cu3(PO4)2 with a special intersected nanosheets-constructed structure. DFT calculation revealed that the Cu3(PO4)2 crystals possess much higher water adsorption energy than most of common inorganic materials used as oil/water separation membranes, indicating the strong hydration ability of Cu3(PO4)2. Due to the


ACS Nano 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

combination of hierarchical structure of nanosheets with strong hydration ability of Cu3(PO4)2 material, the Cu3(PO4)2 mesh membrane exhibited superhydrophilic and underwater superoleophobic property, especially a superior underwater anti-crude-oil fouling and anti-bio fouling property. It showed excellent separation performance for treating oily water with large handling capacity and long-term stability. The all inorganic mesh membrane simultaneously behaved high thermal stability up to 300°C, good chemical stability and a wide range of salt tolerance. This is by far one of the best superwetting inorganic membranes for oil/water separation with separation performance outperforming almost all existing inorganic mesh membranes. It shows potential for purifying real oily wastewater produced in industry and daily life and for treating high viscosity oil polluted water.

METHODS Materials. Copper meshes (400 mesh) used in this work were obtained from Anping Fengbang Co., Ltd, China. Copper foils were obtained from Hefei Kejing Materials Technology Co., Ltd, China. The diesel oil, silicone oil, crude oil was supplied by SINOPEC SABIC Tianjin Petrochemical Co., Ltd, China. Na2HPO4·12H2O and NaH2PO4·2H2O and other chemicals were analytical grade, commercially available from Shanghai Chemical Reagent Co., Ltd, and used as received without further purification. Millipore deionized water was used in this work. Preparation of Cu3(PO4)2 nanosheets-wrapped mesh membranes. Electrochemical deposition method was used for in-situ growth of Cu3(PO4)2 nanosheet on copper substrates. Commercial available copper meshes were used as working electrode. They were cleaned by immersing in a 0.1 mol L-1 HCl aqueous solution for 10 min, rinsed three times by using deionized water, and then dried with N2. Pt wire was used


Page 12 of 33

Page 13 of 33 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

ACS Nano

as counter electrode. The gray-blue nanosheets-wrapped membranes were obtained at a overpotential of 1 V vs. Ag/AgCl in a 0.8 mol/L phosphate buffer pH = 7 (500 ml water containing 88.8 g Na2HPO4·12H2O and 23.8 g NaH2PO4·2H2O) for a certain time according to demand. The membranes were taken out and washed with deionized water. The Cu3(PO4)2 nanosheets grown on other kinds of copper base materials such as copper foil was obtained via the same electrochemical deposition method. Oil/Water Separation Experiment. The as-prepared membrane was sandwiched in a homemade cross-flow filtration apparatus with a diameter of 12 cm. 2000 L oil/water mixtures were pumped into the upper membrane cell driven by a peristaltic pump with flow rate of 2 L/min. The separation was achieved driven by gravity with liquid height of 3 cm. The filtrate water was collected and the oil content in the water was determined by a total organic carbon analyzer. Characterization. SEM images were obtained using a Quanta 250 SEM (FEI, America). TEM was conducted on a Tecnai G2 F20 S-Twin field-emission transmission electron microscope. XRD was recorded on a Bruker D8 using Cu/K α radiation. Water CA and underwater oil CA were measured on an OCA20 machine (Data-physics, Germany). The underwater oil-adhesive force was measured using a high-sensitivity micro-electro-mechanical balance system (Data-Physics DCAT11, Germany). Oil content in filtrate water was detected on a total organic carbon analyzer (Aurora 1030W, America). The membrane was immersed in water first. A droplet of oil was suspended with a metal cap and controlled to contact with the surface of the membrane with a constant speed of 0.005 mm s−1, and then controlled to leave. The force during the entire process was recorded. The amount of Cu2+ ions released from membrane was measured via inductive coupled plasma emission spectrometry (ICP), Agilent 720.


ACS Nano 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 14 of 33

Calculation of water adsorption energy. We performed periodic DFT calculations to calculate the water adsorption energy of some organic materials by using the Vienna Ab-initio Simulation Package (VASP).51 The generalized gradient approximation (GGA)

functional

was

adopted

with

the

Perdew–Burke–Ernzerhof

(PBE)

exchange-correlation description.52 The projector augmented wave (PAW) method was used to describe the electron-ion interaction.53 Dipole moment corrections were adopted to cancel the interactions between the slab and its periodic images for all calculations. The structure was optimized until the force on each atom was smaller than 0.02 eV/Å. To avoid the interlayer interaction, we added a vacuum of 15 Å between the slabs. (001) crystal surface of Cu3(PO4)2, (010) crystal surface of Cu(OH)2, (001) crystal surface of CuO, and (100) crystal surface of Co3O4 were chosen for the calculation of water absorption energy because they are relatively more stable and most frequently occurring facets. To compare the water absorption capacity of different inorganic materials, the water adsorption energy as: ∆Eads = E(H2O/crystal) – E(crystal) – E(H2O) Where E(H2O/crystal) , E(crystal) , E(H2O) are the optimized potential energy of a crystal unit adsorbed by a water molecule, the pure crystal unit, and a free water molecule, respectively. ASSOCIATED CONTENT

Supporting Information Available: Morphology characterization and wetting ability tests of Cu3(PO4)2 nanosheet grown on copper foil. The anti-crude-oil-fouling and anti-biofouling test of Cu3(PO4)2 nanosheets-wrapped mesh membranes. These materials are available free of charge via the internet at http://pubs.acs.org.


Page 15 of 33 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

ACS Nano

AUTHOR INFORMATION Corresponding Authors *E-mail (F. Zhang): [email protected]; *E-mail (J. Jin): [email protected] ORCID Jian Jin: 0000-0003-0429-300X Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS We thank Prof. Jin Zhao for help with DFT calculation. This work was supported by the National Natural Science Funds for Distinguished Young Scholar (Grant No. 51625306), the Key Project of National Natural Science Foundation of China (Grant No. 21433012), the National Natural Science Foundation of China (Grant No. 51603229, 21406258, and 51403231) and the Natural Science Foundation of Jiangsu Province (Grant No. BE2015072).

REFERENCES 1.

Kintisch, E. An Audacious Decision in Crisis Gets Cautious Praise. Science 2010,

329, 735-736. 2.

Aurell, J.; Gullett, B. K. Aerostat Sampling of PCDD/PCDF Emissions from the

Gulf Oil Spill in situ Burns. Environ. Sci. Technol. 2010, 44, 9431-9437. 3.

Peterson, C. H.; Rice, S. D.; Short, J. W.; Esler, D.; Bodkin, J. L.; Ballachey, B.

E.; Irons, D. B. Long-Term Ecosystem Response to the Exxon Valdez Oil Spill.


ACS Nano 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 16 of 33

Science 2003, 302, 2082-2086. 4.

Chu,

Z.;

Feng,

Y.;

Seeger,

S.

Oil/Water

Separation

with

Selective

Superantiwetting/Superwetting Surface Materials. Angew. Chem. Int. Ed. 2015, 54, 2328-2338. 5.

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. 6.

Kwon, G.; Kota, A. K.; Li, Y.; Sohani, A.; Mabry, J. M.; Tuteja, A. On-Demand

Separation of Oil-Water Mixtures. Adv. Mater. 2012, 24, 3666-3671. 7.

Zhang, X.; Li, Z.; Liu, K.; Jiang, L. Bioinspired Multifunctional Foam with

Self-Cleaning and Oil/Water Separation. Adv. Funct. Mater. 2013, 23, 2881-2886. 8.

Tuteja, A.; Choi, W.; Ma, M.; Mabry, J. M.; Mazzella, S. A.; Rutledge, G. C.;

McKinley, G. H.; Cohen, R. E. Designing Superoleophobic Surfaces. Science 2007, 318, 1618-1622. 9.

Gao, X.; Xu, L.-P.; Xue, Z.; Feng, L.; Peng, J.; Wen, Y.; Wang, S.; Zhang, X.

Dual-Scaled Porous Nitrocellulose Membranes with Underwater Superoleophobicity for Highly Efficient Oil/Water Separation. Adv. Mater. 2014, 26, 1771-1775. 10. Dudchenko, A. V.; Rolf, J.; Shi, L.; Olivas, L.; Duan, W.; Jassby, D. Coupling Underwater Superoleophobic Membranes with Magnetic Pickering Emulsions for Fouling-Free Separation of Crude Oil/Water Mixtures: An Experimental and Theoretical Study. ACS Nano 2015, 9, 9930-9941.


Page 17 of 33 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

ACS Nano

11. La, Y. H.; McCloskey, B. D.; Sooriyakumaran, R.; Vora, A.; Freeman, B.; Nassar, M.; Hedrick, J.; Nelson, A.; Allen, R. Bifunctional Hydrogel Coatings for Water Purification Membranes: Improved Fouling Resistance and Antimicrobial Activity. J. Membr. Sci. 2011, 372, 285-291. 12. Joo, M.; Shin, J.; Kim, J.; You, J. B.; Yoo, Y.; Kwak, M. J.; Oh, M. S.; Im, S. G. One-Step Synthesis of Cross-Linked Ionic Polymer Thin Films in Vapor Phase and Its Application to an Oil/Water Separation Membrane. J. Am. Chem. Soc. 2017, 139, 2329-2337. 13. Zhang, J.; Seeger, S. Polyester Materials with Superwetting Silicone Nanofilaments for Oil/Water Separation and Selective Oil Absorption. Adv. Funct. Mater. 2011, 21, 4699-4704. 14. Gupta, R. K.; Dunderdale, G. J.; England, M. W.; Hozumi, A. Oil/Water Separation Techniques: a Review of Recent Progresses and Future Directions. J. Mater. Chem. A 2017, 5, 16025-16058. 15. Kota, A. K.; Kwon, G.; Choi, W.; Mabry, J. M.; Tuteja, A. Hygro-Responsive Membranes for Effective Oil-Water Separation. Nat. Commun. 2012, 3, 1025-1033. 16. Cai, Y.; Lu, Q.; Guo, X.; Wang, S.; Qiao, J.; Jiang, L. Salt-Tolerant Superoleophobicity on Alginate Gel Surfaces Inspired by Seaweed (Saccharina japonica). Adv. Mater. 2015, 27, 4162-4168. 17. Liu, X.; Zhou, J.; Xue, Z.; Gao, J.; Meng, J.; Wang, S.; Jiang, L. Clam's Shell Inspired High-Energy Inorganic Coatings with Underwater Low Adhesive Superoleophobicity. Adv. Mater. 2012, 24, 3401-3405.


ACS Nano 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

18. Dou, Y.; Tian, D.; Sun, Z.; Liu, Q.; Zhang, N.; Kim, J. H.; Jiang, L.; Dou, S. X. Fish Gill Inspired Crossflow for Efficient and Continuous Collection of Spilled Oil. ACS Nano 2017, 11, 2477-2485. 19. Liu, Y.; Wang, X.; Fei, B.; Hu, H.; Lai, C.; Xin, J. H. Bioinspired, Stimuli-Responsive, Multifunctional Superhydrophobic Surface with Directional Wetting, Adhesion, and Transport of Water. Adv. Funct. Mater. 2015, 25, 5047-5056. 20. Cai, Y.; Lin, L.; Xue, Z.; Liu, M.; Wang, S.; Jiang, L. Filefish-Inspired Surface Design for Anisotropic Underwater Oleophobicity. Adv. Funct. Mater. 2014, 24, 809-816. 21. Zhu, Q.; Pan, Q. Mussel-Inspired Direct Immobilization of Nanoparticles and Application for Oil-Water Separation. ACS Nano 2014, 8, 1402-1409. 22. Zeng, X.; Qian, L.; Yuan, X.; Zhou, C.; Li, Z.; Cheng, J.; Xu, S.; Wang, S.; Pi, P.; Wen, X. Inspired by Stenocara Beetles: From Water Collection to High-Efficiency Water-in-Oil Emulsion Separation. ACS Nano 2017, 11, 760-769. 23. Yang, H. C.; Hou, J.; Chen, V.; Xu, Z. K. Janus Membranes: Exploring Duality for Advanced Separation. Angew. Chem. Int. Ed. 2016, 55, 13398-13407. 24. Xu, Z.; Zhao, Y.; Wang, H.; Wang, X.; Lin, T. A Superamphiphobic Coating with an Ammonia-Triggered Transition to Superhydrophilic and Superoleophobic for Oil-Water Separation. Angew. Chem. Int. Ed. 2015, 54, 4527-4530. 25. Hayase, G.; Kanamori, K.; Fukuchi, M.; Kaji, H.; Nakanishi, K. Facile Synthesis of Marshmallow-like Macroporous Gels Usable under Harsh Conditions for the Separation of Oil and Water. Angew. Chem. Int. Ed. 2013, 52, 1986-1989.


Page 18 of 33

Page 19 of 33 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

ACS Nano

26. Gao, S.; Sun, J.; Liu, P.; Zhang, F.; Zhang, W.; Yuan, S.; Li, J.; Jin, J. A Robust Polyionized Hydrogel with an Unprecedented Underwater Anti-Crude-Oil-Adhesion Property. Adv. Mater. 2016, 28, 5307-5314. 27. Li, Y.; Zheng, X.; Yan, Z.; Tian, D.; Ma, J.; Zhang, X.; Jiang, L. Closed Pore Structured NiCo2O4-Coated Nickel Foams for Stable and Effective Oil/Water Separation. ACS Appl. Mater. Interfaces 2017, 9, 29177-29184. 28. Fan, J.-B.; Song, Y.; Wang, S.; Meng, J.; Yang, G.; Guo, X.; Feng, L.; Jiang, L. Directly Coating Hydrogel on Filter Paper for Effective Oil-Water Separation in Highly Acidic, Alkaline, and Salty Environment. Adv. Funct. Mater. 2015, 25, 5368-5375. 29. Manna, U.; Lynn, D. M. Synthetic Surfaces with Robust and Tunable Underwater Superoleophobicity. Adv. Funct. Mater. 2015, 25, 1672-1681. 30. Liu, M.; Wang, S.; Wei, Z.; Song, Y.; Jiang, L. Bioinspired Design of a Superoleophobic and Low Adhesive Water/Solid Interface. Adv. Mater. 2009, 21, 665-669. 31. Lin, L.; Liu, M.; Chen, L.; Chen, P.; Ma, J.; Han, D.; Jiang, L. Bio-Inspired Hierarchical

Macromolecule-Nanoclay

Hydrogels

for

Robust

Underwater

Superoleophobicity. Adv. Mater. 2010, 22, 4826-4830. 32. He, K.; Duan, H.; Chen, G. Y.; Liu, X.; Yang, W.; Wang, D. Cleaning of Oil Fouling with Water Enabled by Zwitterionic Polyelectrolyte Coatings: Overcoming the Imperative Challenge of Oil-Water Separation Membranes. ACS Nano 2015, 9, 9188-9198.


ACS Nano 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 20 of 33

33. Jiang, S.; Cao, Z. Ultralow-Fouling, Functionalizable, and Hydrolyzable Zwitterionic Materials and Their Derivatives for Biological Applications. Adv. Mater. 2010, 22, 920-932. 34. Zhu, Y.; Zhang, F.; Wang, D.; Pei, X. F.; Zhang, W.; Jin, J. A Novel Zwitterionic Polyelectrolyte Grafted PVDF Membrane for Thoroughly Separating Oil from Water with Ultrahigh Efficiency. J. Mater. Chem. A 2013, 1, 5758-5768. 35. Chen, S.; Zheng, J.; Li, L.; Jiang, S. Strong Resistance of Phosphorylcholine Self-Assembled Monolayers to Protein Adsorption: Insights into Nonfouling Properties of Zwitterionic Materials. J. Am. Chem. Soc. 2005, 127, 14473-14478. 36. Wang, Z.; Wang, Y.; Liu, G. Rapid and Efficient Separation of Oil from Oil-in-Water Emulsions Using a Janus Cotton Fabric. Angew. Chem. Int. Ed. 2016, 55, 1291-1294. 37. Xu, L.-P.; Peng, J.; Liu, Y.; Wen, Y.; Zhang, X.; Jiang, L.; Wang, S. Nacre-Inspired

Design

of

Mechanical

Stable

Coating

with

Underwater

Superoleophobicity. ACS Nano 2013, 7, 5077-5083. 38. Liu, M.; Li, J.; Hou, Y.; Guo, Z. Inorganic Adhesives for Robust Superwetting Surfaces. ACS Nano 2017, 11, 1113-1119. 39. Zhang, F.; Zhang, W. B.; Shi, Z.; Wang, D.; Jin, J.; Jiang, L., Nanowire-Haired Inorganic Membranes with Superhydrophilicity and Underwater Ultralow Adhesive Superoleophobicity for High-Efficiency Oil/Water Separation. Adv. Mater. 2013, 25, 4192-4198. 40. Zhang, E.; Cheng, Z.; Lv, T.; Qian, Y.; Liu, Y. Anti-Corrosive Hierarchical


Page 21 of 33 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

ACS Nano

Structured Copper Mesh Film with Superhydrophilicity and Underwater Low Adhesive Superoleophobicity for Highly Efficient Oil-Water Separation. J. Mater. Chem. A 2015, 3, 13411-13417. 41. Guo, T.; Heng, L.; Wang, M.; Wang, J.; Jiang, L. Robust Underwater Oil-Repellent Material Inspired by Columnar Nacre. Adv. Mater. 2016, 28, 8505-8510. 42. Huang, S.; Wang, D. A Simple Nanocellulose Coating for Self-Cleaning upon Water Action: Molecular Design of Stable Surface Hydrophilicity. Angew. Chem. Int. Ed. 2017, 56, 9053-9057. 43. Han, K.; Heng, L.; Jiang, L. Multiphase Media Antiadhesive Coatings: Hierarchical Self-Assembled Porous Materials Generated Using Breath Figure Patterns. ACS Nano 2016, 10, 11087-11095. 44. Yu, Z.; Yun, F. F.; Gong, Z.; Yao, Q.; Dou, S.; Liu, K.; Jiang, L.; Wang, X. A Novel Reusable Superhydrophilic NiO/Ni Mesh Produced by a Facile Fabrication Method for Superior Oil/Water Separation. J. Mater. Chem. A 2017, 5, 10821-10826. 45. Li, L.; Yan, B.; Yang, J.; Chen, L.; Zeng, H. Novel Mussel‐Inspired Injectable Self‐Healing Hydrogel with Anti‐Biofouling Property. Adv. Mater. 2015, 27, 1294-1299. 46. Krishnan, S.; Weinman, C. J.; Ober, C. K. Advances in Polymers for Anti-Biofouling Surfaces. J. Mater. Chem. 2008, 18, 3405-3413. 47. Xu, J.; Wang, Z.; Yu, L.; Wang, J.; Wang, S. A Novel Reverse Osmosis Membrane with Regenerable Anti-Biofouling and Chlorine Resistant Properties. J.


ACS Nano 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

Membr. Sci. 2013, 435, 80-91. 48. Ge, J.; Lei, J.; Zare, R. N. Protein-Inorganic Hybrid Nanoflowers. Nat. Nanotechnol. 2012, 7, 428-432. 49. Reddy, A.; Mohan, D. J.; Bhattacharya, A.; Shah, V.; Ghosh, P. Surface Modification of Ultrafiltration Membranes by Preadsorption of a Negatively Charged Polymer: I. Permeation of Water Soluble Polymers and Inorganic Salt Solutions and Fouling Resistance Properties. J. Membr. Sci. 2003, 214, 211-221. 50. Wang, Z.; Jin, J.; Hou, D.; Lin, S. Tailoring Surface Charge and Wetting Property for Robust Oil-Fouling Mitigation in Membrane Distillation. J. Membr. Sci. 2016, 516, 113-122. 51. Kresse, G.; Furthmüller, J. Efficiency of ab-initio Total Energy Calculations for Metals and Semiconductors Using a Plane-Wave Basis Set. Comp. Mater. Sci. 1996, 6, 15-50. 52. Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, 1758-1775. 53. Liu, L.; Zhao, J. Formaldehyde Adsorption and Decomposition on Rutile (110): A First-Principles Study. Surf. Sci. 2016, 652, 156-162.

TOC graphic


Page 22 of 33

Page 23 of 33 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

ACS Nano


ACS Nano 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

Figure 1. Structure characterization of Cu3(PO4)2 nanosheets-wrapped mesh membrane (reaction time of 10 min). (a) Photograph of a 50 × 60 cm membrane. Top-view (b and c) and cross-section (d and e) SEM images of the membrane in different magnification. (f) XRD pattern of Cu3(PO4)2 nanosheets and corresponding diffraction peaks of Cu3(PO4)2·3H2O in standard card. (g) TEM and SAED (inset) images of a Cu3(PO4)2 nanosheet. (h) AFM image and corresponding height profile of a Cu3(PO4)2 nanosheet. (i) Zeta potential of Cu3(PO4)2 nanosheets in water. For XRD, TEM, AFM and zeta potential characterizations, Cu3(PO4)2 nanosheets were peeled off from mesh membrane by ultrasonication.


Page 24 of 33

Page 25 of 33 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

ACS Nano

Figure 2. Study of the growth of Cu3(PO4)2 nanosheets on mesh membrane. (a-e) SEM images of the membranes reacted for 1, 3, 5, 10, 30 mins, respectively. (f) Water CAs and underwater crude oil adhesive force of the corresponding membranes.


ACS Nano 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

Figure 3. Water and oil wetting behavior of Cu3(PO4)2 nanosheets-wrapped mesh membrane. (a) A water droplet spreading on the membrane within 0.3 s. (b) Photograph of an underwater 1,2-dichloroethane droplet sliding on the membrane. (c) Underwater oil CA of a crude oil droplet on the membrane. (d) Underwater oil CAs and adhesive forces of various oils.


Page 26 of 33

Page 27 of 33 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

ACS Nano

Figure 4. Crude oil repellent performance of Cu3(PO4)2 nanosheets-wrapped mesh membrane. (a-d) Photographs of a crude oil droplet forced to and lifted from the membrane under different preload force of 100 µN, 200 µN, 300 µN, and 400 µN, respectively. (e) Real-time recorded force-distance curves during the dynamic oil-adhesion measurements on the membrane. (f) Underwater crude oil adhesive force as a function of preload force.


ACS Nano 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

Figure 5. Underwater anti-oil-adhesion and self-cleaning property of Cu3(PO4)2 nanosheets-wrapped mesh membrane and copper foil. (a) Isooctane and (b-c) crude oil used to demonstrate the anti-oil-adhesion and self-cleaning performance. Optical images in the red frames display the oil fouling of the materials without Cu3(PO4)2 nanosheets wrapping.


Page 28 of 33

Page 29 of 33 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

ACS Nano

Figure 6. Water adsorption energy calculation. (a) Comparison of optimized energy of crystal unit adsorbed by a water, pure crystal unit, a free water among several materials as calculated based on DFT theory. (b-e) DFT optimized geometries of a water adsorbed on the crystal units of Cu3(PO4)2·3H2O, Cu(OH)2, CuO, and Co3O4, respectively, and corresponding calculated water adsorption energy. Water molecule is marked by dashed frame. Cu: reddish-orange, O: red, H: white, P: violet, Co: blue.


ACS Nano 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

Figure 7. Continuous separation of crude oil/water mixture. (a) Schematic illustration of our cross-flow oil/water separation filter. (b) Permeating flux and oil content in the filtrate during the separation of 2000 L crude oil/water mixture.


Page 30 of 33

20

0

10 -5 0 3

c

4

5

6

200

7 8 9 10 11 12 pH value Underwater oil CA Oil adhesive force

180

-10

25

160 140

20

120

15

100

10

80

5

60

0

0

2

4

6

8 10 12 14 16 18 20 Time (week)

Oil adhesive force

20 16

160 12

120

8

80

4

40 0

d

30

Underwater oil CA

200

NaCl

KCl

CaCl2 Na2SO4 MgSO4

Oil adhesive force (µN)

5

Underwater crude oil CA (°)

Water CA (°)

30

b

10

0

60

2+

Water CA Oil adhesive force

Cu concentration (ppb)

40


a

Underwater crude oil CA (°)

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

ACS Nano


Page 31 of 33

50 40 30 20 10 0

0

1

2

3

4 5 6 Time (day)

30 2 79.8 30.0 7

Figure 8. Stability test of Cu3(PO4)2 nanosheets-wrapped mesh membrane. (a) Water CAs and underwater crude oil adhesive forces of the membranes after being kept in water with pH values for 7 days. (b) Underwater crude oil CAs and adhesive forces of the membranes after being kept in water containing 30 mg/mL NaCl, KCl, CaCl2, Na2SO4, and MgSO4 for 7 days. c) Long-term stability of the membrane in seawater for 20 weeks. d) Amount of Cu2+ ions released from membrane as a function of time.


ACS Nano 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

Figure 9. Thermal stability of Cu3(PO4)2 nanosheets-wrapped mesh membrane. SEM images of the membranes after heated at (a) 100 °C, (b) 200 °C, (c) 300 °C and (d) 400 °C for 12 hours, respectively. (e) Water CAs and underwater oil adhesive forces of the membranes after heated at different temperatures.


Page 32 of 33

Page 33 of 33

12000 10000

2

Water flux (L/m h)

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

ACS Nano

8000 Containing E. coli 12000 10000 8000

Containing humic acid

12000 10000 8000 6000

Containing BSA 0

20 40 60 80 100 120 140 160 180 200 Volume of water (L)

Figure 10. Anti-bio fouling performance of Cu3(PO4)2 nanosheets-wrapped mesh membrane. Real time monitoring of water flux as a function of water volume. The water contains ~107 cell/L E. coli, 100 mg/L humic acid, and 100 mg/L BSA, respectively.


Cupric Phosphate Nanosheets-Wrapped Inorganic Membranes with

Recommend Documents