Superhydrophobic Cu Mesh Combined with a Superoleophilic

Apr 9, 2014 - Polyurethane Sponge for Oil Spill Adsorption and Collection. Fajun Wang,* Sheng Lei, Changquan Li,* Junfei Ou, Mingshan Xue, and Wen Li...
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Superhydrophobic Cu Mesh Combined with a Superoleophilic Polyurethane Sponge for Oil Spill Adsorption and Collection Fajun Wang,* Sheng Lei, Changquan Li,* Junfei Ou, Mingshan Xue, and Wen Li School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang, 330063 Jiangxi, P. R. China S Supporting Information *

ABSTRACT: We present a miniature collector for the adsorption and collection of oil spill. The collector composed of a superhydrophobic copper mesh miniature box embedded with a superoelophilic polyurethane sponge. The superhydrophobic Cu mesh was fabricated by a simple immersing method, and the PU sponge is a commercial available material with superoleophilicity in itself. The miniature collector can adsorb different oils on water surface in the pores of the superhydrophilic PU sponge while repelled water due to the superhydrophobicity of the mesh. In addition, the adsorbed oils could be easily separated from the sponge by squeezing and then be collected for reuse. After the separation of adsorbed oil, the sponge could be used repeatedly with high separation efficiency. Furthermore, the as-prepared Cu mesh possesses stability in various solvents and corrosion resistance in NaCl aqueous solution. The findings might provide a simple method for oils spill cleanup.

1. INTRODUCTION Removal of oil spills is a challenging task for the protection of marine environment due to the frequent accidents of oil spills.1−4 The common methods and techniques for oil spill cleanup include in situ burning, oil skimmer, oil containment boom, despersants, and sorbent materials.1 The limitations of these methods are obvious, ranging from inefficiency to poor recyclability, low adsorption capacity, environmental harmfulness, and high cost.1 Recently, filter materials (usually mesh films or filter papers) with both superhydrophobicity and superhydrophilicity have been used in the filed of oil−water separation. These materials could selectively filter oil due to their superhydrophilicity, while completely repelled water due to their superhydrophobicity.3,5−11 For example, Feng et al. fabricated a coating mesh film by spray a emulsion containing polytetrafluoroethylene (PTFE). The low surface energy PTFE combined with the rough surface of the mesh contribute the superhydrophobic and superhydrophilic properties of the mesh. Oil permeates through the mesh pores completely within 240 ms, while water droplet rolls off the surface rapidly, thus achieving oil−water separation.6 Apart from that, various materials based on surface superhydrophobic and superhydrophilic properties, including meshes,6,11−13 filter paper,14 porous polymer and ceramic materials,8−10,15 etc., were fabricated and used for oil−water separation. Though these materials could filter oil from the mixture of oil and water, they cannot be used for in situ oil spill cheanup, because the surface oil should be first collected and then be filtered from top to bottom.10 For example, by pouring oil−water mixture onto the superhydrophobic and superoleophilic surface of a mesh or a filter paper, oil passed through the surface easily while water remained on the surface.11−14 Another strategy for oil−water separation is to make use of the adsorbent materials (usually particles or powders) with superhydrophobic and oleophilic properties. For example, Arbatan et al. treated the calcium carbonate powder with stearic acid to endow the powder with superhydrophobic and © 2014 American Chemical Society

oleophilic properties. Ihe treated powder could separate oil from oil−water mixture with high separation efficiency.7 Zhang and co-workers reported a similar separation method using superhydrophobic polydivinylbenzene materials with nanoporous sthurctures which are synthesized by a solvothermal route.8 Nevertheless, these techniques are mainly focused on the cleanup of the spilled oil and ignored the collection and reuse of the oil, which caused a significant waste of oil resources.7,10 More recently, bulk porous sponge materials with hydrophobicity have been proposed for the separating of oils from the water surface.10,16−19 For example, Choi et al. reported a hydrophobic polydimethylsiloxane (PDMS) sponge for the selective removal of oil from water.3 The absorbed oils can be readily collected by squeezing. The PDMS sponge is hydrophobic but not superhydrophobic. As a result, water adhesion to the surface of the sponge was observed due to the high sliding angles. Zhu et al. developed superhydrophobic and superoleophilic sponges for the oil adsorption and recovery from water surface.17 Oils on water surface were adsorbed in the pores of the sponges while water was absolutely excluded. The adsorbed oils were collected by squeezing. Other sponge materials, such as carbon nanotube sponges,16 graphene-based sponges,19 and other PU sponges18 with superhydrophobicities and superoleophilicities were also fabricated for the separation of oils from water surface. Although they possess advantages such as high selectivity, high adsorption capacity, and reusability, they are prepared from expensive raw materials and involved in complicated processes, which limits their large scale application. In this work, we report a low cost, highly selective, recyclable, stable, and environmentally friendly miniature collector (see Received: Revised: Accepted: Published: 7141

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cycles. Importantly, the copper mesh showed desirable stability of its superhydrophobicity when stored in air, suffered from the temperature variation, and subjected to different solvents (aqueous solution of acid, base, and salt as well as organic solvent). Therefore, our miniature collector may provide a novel and useful method in the application in oil spill cleanup and organic pollutants removal from the surface of water.

Figure 1) for the collection of oil spill. The miniature device composed of a superhydrophobic and superoleophic Cu mesh

2. EXPERIMENTAL SECTION The copper mesh were provided by Jiangxi Dali Mesh Co., Ltd., China. DT was provided by Beijing Chemical Reagent Co. Ltd., China. PU sponge was purchased from Yantai Wanhua Polyurethanes Co. Ltd., China. The rapeseed oil was purchased from Nanchang Guihua Food Co. Ltd., China. The gasoline, diesel oil, and kerosene were purchased from Sinopec Group Company (China). The crude oil was obtained from Daqing Petro Chemical Company (China). A sheet of copper mesh (6.5 cm × 5.5 cm) was folded to a miniature box with 4.5 cm × 3.5 cm × 1.0 cm in size (see Figure 1). Then, the miniature box was successively washed with 1.0 M HCl solution for 10 s and acetone for 10 s to remove surface impurities. Afterward, the mesh was immersed into an ethanol solution of DT (1 mM) for about 5 min. After blow drying, the obtained miniature box was subjected to further characterizations. The surface microstructures of the copper and the PU sponges were studied using a Field Emission Scanning Electron Microscopy (FESEM, FEI Nova NanoSEM450). The surface chemical compositions of the DT modified copper mesh were analyzed by a Thermo ESCALAB 250 X-ray photoelectron spectroscopy (XPS). Contact angles for water (WCAs) were measured using a Krüss DSA 100 apparatus using a water droplet (4 μL). Sliding angles for water (WSAs) were measured by gradually inclining the tilting stage. The WSA is the slope of the tilting stage, on which a water droplet begins to roll away. WCAs and WSAs were obtained by averaging six measurement results on different areas of the sample surface. Electrochemical corrosion resistance was measured using an electrochemical workstation (CHI660C, China). Before test, the mesh samples were immersed in a 3.5% NaCl solution for 1 h. A piece of PU sponge with size of about 3.5 cm × 3.0 cm × 2.0 cm was cut from a bulk commercial PU sponge. The miniature collector was simply obtained by placing the PU sponge into the as-prepared miniature box. The adsorption and

Figure 1. Optical image of a miniature collector composed of a miniature Cu mesh box embedded with a piece of superoleophilic PU sponge.

miniature box embedded with a superoelophilic polyurethane (PU) sponge. The superhydrophobic and superoleophilic Cu mesh was prepared by immersing the copper mesh in an ethanol solution of 1-decanethiol (DT) for only 2 min. As can be seen from Figure S1 (see the Supporting Information), though the superhydrophobic Cu mesh could successfully separate oil from water surface [Figure S1(e)], the separated oils could not be collected by the box [Figure S1(f)]. In addition, the polyurethane sponge is a cheap and commercial available porous meterial with superoleophilicity in itself. However, it usually absorbs both oils and water, which may reduce the oil separation efficiency and selectivity [see the Supporting Information, Figure S2(a)-(f)]. The combination of superhydrophobic Cu mesh and superoleophilic PU sponge provides a good solution [see Figure 2(a)-(f)]. When our miniature collector floats on the surface of oil−water mixtures, oils penetrate through the walls of Cu mesh and then diffuse into the pores of the sponge rapidly due to the superoleophilicity of the two materials, whereas water is completely repelled because of the superhydrophobicity of the mesh. All of the starting material is commercially available and fluorine-free, and the fabrication process is convenient and efficient. The miniature collector can selectively absorb various oils while repelling water completely. Additionally, the adsorbed oil in the sponge can be quickly released by squeezing, thus achieving an efficient way to collect the absorbed oil. Furthermore, the collector exhibits good repeatability in oil−water separation

Figure 2. (a)-(e) A schematic illustration of the oil separating and collection process from water surface by using the miniature collector. 7142

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collection of oils from water surface was carried out by floating the miniature collector onto the surface of an artificial oil− water mixture. The oils used for the purpose of simulating spilled oil were toluene, rapeseed oil, gasoline, diesel oil, and kerosene. The oil separation capacity (kc) of the sponge was determined by the equation kc = (m1−m2)/m0, where m0 is the weights of the blank sponge, m1 is the weights of the sponge absorbed with oil, m2 is the weights of the sponge after releasing of oil. The oil separation efficiency (ke) was calculated by the equation ke = V/V0, where V0 is the volume of the oil in oil−water mixture, and V is the volume of the oil which can be collected by this device.

absorption would also take place when PU sponge contacts with oil−water mixtures.17 The PU sponge is flexible and elastic. The sponge can be easily compressed by hand with a large volume reduction over 75% [see Figure 3(b)] and recovers its initial shape perfectly after releasing the external force [see Figure 3(c)]. The morphology of the PU sponge was measured by SEM [Figure 3(d)]. It is observed that the sponge possesses an interconnected porous structure. The pore sizes ranges from 200 to 600 μm, which belongs to macropores according to the classification of IUPAC.28,29 We expect that the porosity, flexibility, and elasticity of the PU sponge can provide a desirable oil adsorption, releasing, and collection properties. The copper mesh shows superhydrophobicity after DT modification. Figure 4(a) and (b) show the optical images of water droplets on the inside and outside surfaces of a miniature box which was enfolded from a sheet of DT modified copper mesh. The WCA is 165.1°, and the WSA of water is 4.2° [see the inset of Figure 4 (a)], demonstrating the superhydrophobicity of the miniature box. As presented in Figure 4(b), the toluene droplet diffuses into the mesh pores immediately as soon as it makes contact with the mesh. The obtained value of SA is 0°, which proved the superoleophilicity of the surface. Figure 5(a) shows the SEM images of the

3. RESULTS AND DISCUSSION Figure 3(a) was shown to demonstrate the hydrophobicity and superoleophilicity of the PU sponge. The CAs is about 130.5°

Figure 3. Optical images of (a) water droplets (dyed with methylene blue for the purpose of clear observation) sit on the surface and adhere to the flank of a piece of sponge and toluene droplet (dyed with Solvent Black) diffuses in the sponge; (b) the sponge was compressed by hand and (c) the sponge recovered its initial shape; (d) SEM image of the sponge. The inset of (a) showed the WCA on the surface of the sponge.

on the sponge surface, far from superhydrophobicity. Water droplets can stick to the flank (titling angle is 90°) of the sponge, which indicated the strong adhesion between the water droplets and the sponge. In addition, a toluene droplet diffused into the sponge very quickly, demonstrating the superoleophilicity of the sponge. However, only the PU sponge cannot separate oil from water completely because water

Figure 5. FE-SEM images of copper mesh surfaces at different magnifications: (a) and (b) before DT modification; (c) and (d) after DT modification.

received copper mesh with a square pore side length of about 74 μm and a wire diameter of about 45 μm. The wire surface of the initial mesh is smooth even at high magnification [Figure

Figure 4. Optical images of (a) ball-like shape water droplets on the surface of the box; (b) toluene droplets diffused on the outside surface of the box. The insets in (a) correspond to contact angle and sliding angle for water on the inside surface of the box. The inset in (b) corresponds to contact angle for toluene on the outside surface of the box. 7143

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931.8 eV are attributed to Cu 2p1/2 and Cu 2p3/2 (the bottom inset of Figure 6),21 respectively. The results demonstrate that a stable monolayer of DT has already come into being on the surface of the Cu mesh. It is generally believed that alkanethiol molecules chemisorb on Cu by the dissociative adsorption of a S−H bond to yield a copper thiolate.23,24 The hydrogens in the S−H bond are first chemically adsorbed to Cu and then form H2, which desorbs from Cu. The reaction between the Cu mesh with DT can be described as follows:25−27

5(b)]. After DT modification, no obvious variation of the pore size could be observed at low magnification in Figure 5(c). However, one can see some pores existed on the wire surface at high magnification [Figure 5(d)], which might be caused by the removal of surface impurities in the process of cleaning. In addition, the coating of DT cannot be observed by SEM measurement [Figure 5 (c) and (d)]. XPS analysis is carried out to determine the surface composition of the as-prepared Cu mesh modified with DT. Figure 6 shows the full spectrum of the modified Cu mesh. The

Cu + C12H 25SH → C12H 25SCu + 1/2H 2

(1)

The as-prepared miniature box floated freely on the water surface when in contact with water [Figure 7(a)]. Figure 7(b) shows the water repellent property of the miniature box. The miniature box is immersed in water until its upper edges closed to the horizontal; no water penetration from the pores of the box can be observed. In fact, the tolerance of water pressure for a superhydrophobic miniture box is a key factor for oil separation on water surface, because only oil could penetrate into the box while water was absolutely excluded outside of the box even when the bottom of the box was subjected to water pressure. The maximum water pressure that the superhydrophobic mesh could bear was measured by a homemade device [see Figure 7(c)]. As can be seen in Figure 7(c), a sheet of superhydrophobic Cu mesh was fix carefully at the bottom of a transparent glass tube (diameter is 2 cm). For the maximum water pressure measurement, water was poured into the tube slowly until water leakage from the mesh pores was observed, and the corresponding height of the water column was recorded as the resulting water pressure value. The effects of the mesh number on the wettabilities and the water pressure resistance of the DT-modified Cu mesh surfaces were also systematically studied. Figure 7(d) shows the effects of mesh number on the WCAs and WSAs of the Cu mesh (The mesh

Figure 6. XPS survey spectra of the as-prepared mesh modified with DT, the insets are S 2p, C 1s, and Cu 2p scan, respectively.

insets in Figure 4 give the higher resolution spectra of the asprepared Cu mesh. The peak at 162.2 eV corresponded to the binding energy of S 2p (the top left inset of Figure 4).20 The peak at 284.8 eV corresponded to the binding energy of C 1s (the top right inset of Figure 4).21,22 The peaks at 951.6 and

Figure 7. Optical images of (a) the miniature box floats on water surface freely with water droplets loaded on the box; (b) the miniature boat was immersed in water by loading of weight; (c) water pressure resistant measurement of the DT-modified Cu mesh; (d) WCAs and WSAs for water of the DT-modified Cu mesh as a function of mesh number; (e) the maximum water pressure (the height of water column) that the DT-modified Cu mesh can bear as a function of mesh number. 7144

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Figure 8. (a)-(f) Photographs of the oil separation and collection process. The inset of (d) showed the toluene absorbed in the bottom of the sponge.

Figure 9. The absorbed oil in sponge was separated by squeezing. (a) Oil absorbed in sponge before squeezing; (b) squeezing. The inset show photographs of PU sponge: (a) oil absorbed in the sponge and the sponge swelled; (b) the sponge recovers to its original shape after oil released by squeezing.

weak pressure resistance to oil may ensure the DT-modified Cu mesh to apply in oil−water separation. In an attempt to investigate the oil-sorption ability of the miniature collector composed of a superhydrophobic Cu mesh box embedded with a superoleophilic PU sponge, an oil−water separation experiment was carried out. Toluene (dyed with Solvent Black for the purpose of clear observation) was added onto the surface of water [Figure 8(a)], and then the miniature collector was held to approach the toluene [Figure 8(b)]. The toluene penetrated into the boat bottom and was absorbed by the sponge as soon as it made contact with the bottom of the collector [see inset of Figure 8(d)] due to the superoleophilicity of the copper mesh and the PU sponge. After repeating the absorption process, the miniature collector approaches its maximum loading capacity (21 times weight of the blank PU sponge) [Figure 8(e)]. The PU sponge swelled because the adsorption of toluene in its interconnected pores [Figure 8(e)]. After the collector was taken up from the water surface, no apparent residual of toluene was observed in Figure 8(f). This experiment suggested that the miniature collector possesses excellent oil adsorption performance from the surface of water. The absorbed oils in the PU sponge can be released and collected by squeezing [Figure 9(a) and (b)]. 10 mL of oil was poured onto the surface of 1000 mL of water in a beaker for the purpose of simulating spilled oil. Then, the miniature collector was used to separate and collect the oil to evaluate its separation capacities and separation efficiencies. The oil separation capacities (kc) of the miniature collector for the

number used in this work is 40, 80, 120, 160, 200, 300, 400, and 635, respectively.). One can see that the DT-modified Cu mesh surface with a mesh number of 40 has an WCA of 132.5° and an WSA of 63.5°, which is only hydrophobic but not superhydrophobic. When the mesh number is larger than 40, all of the DT-modified Cu meshes are superhydrophobic, with WCAs larger than 150° and WSAs lower than 10°. In addition, the WCAs increase and the WSAs decrease with increasing the mesh number. However, when the mesh number is larger than 400, the increasing tendency of WCAs and the decreasing tendency of WSAs become indistinct. The maximum WCA is about 168.2° and the minimum WSA is about 2.5° when the mesh number is 600. The water pressure resistance of the modified mesh surfaces increases nearly linearly with the increase of the mesh number [Figure 7(e)]. The mesh surface with a mesh number of 40, 200, and 635 can bear a maximum water pressure of about 39, 195, and 525 cm, respectively. The high water pressure resistance of our superhydrophobic mesh surfaces ensures their practical applications in oil−water separation from water surface. For toluene measurement, all of the contact angles of the DT-modified meshes with different mesh numbers are 0° and the sliding angles are none (do not slide at any tilting angle). As a result, a toluene droplet of 4 μL [the obtained height is about 1.97 mm (diameter of the toluene droplet)] spread quickly on the mesh surface, demonstrating the toluene pressure resistance of the mesh surface is rather weak. Therefore, the superhydrophobic and superoleophilic properties as well as the high pressure resistance to water and 7145

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Figure 10. (a) Oil separation capacities (kc) and (b) oil separation efficiencies (ke) of the sponge for different kinds of oils after different separation cycles.

of the initial copper mesh and DT coated copper mesh samples were shown in Figure 11. The polarization current of the initial

different oils are listed in Figure 10(a). The sponge could adsorb 13 times its weight of oil in the first separation cycle. It was noted that kc gradually decreased with the increasing of separation cycles. However, the kc was always larger than 11 after 20 separation cycles, which demonstrated its repeatability. The decreases of oil absorption capacity were caused by the small amount of oils remained in the pores of the sponge and the copper mesh. In addition, the separation efficiencies (ke) of the sponge were all larger than 90% for each kind of oils after repeated cycles except the first cycle [Figure 10(b)]. This could be interpreted by the fact that the initial sponge is blank without any oil adsorbed before the first cycle, while a small amount of residual oils were always remained in the sponge after the squeezing and collection process in the following cycles. The amount of the residual oils in the sponge for each kind of oil remained nearly unchanged according to the weight measurement. Moreover, when this experiment was carried out in 3.5 wt % NaCl aqueous solution for the purpose of mimicking the composition of seawater, a similar degree of absorption was observed. After we separated five kinds of oils with low viscosity, we attempted to separate crude oil, which is the most common type of spilled oil and is of high viscosity (about 65 cP). Figure 1S shows the separation process of crude oil from water surface by using our miniature device. Fortunately, the device works equals well, as can be seen in Figure S3(a)-(f). However, the separating rate decreased obviously when compared with the separation process of low-viscosity-oil/water mixture. For example, the separating of 10 mL toluene from water surface needs only 1 min. While for the crude oil (10 mL), it needs nearly 5 min. The decrease of separating rate could be attributed to the high viscosity of the crude oil. In addition, the oil separation capacities (kc) and separation efficiencies (ke) of the sponge in the miniature device are also decreased, which is about 8.9 and 74.6%, respectively. The decrease of kc and ke might attribute to the multicomponent of the crude oil. The polar component in crude oil cannot be adsorbed completely by the miniature device, which results in the decrease of kc and ke. When the superhydrophobic copper mesh is used in marine environment or other water system, the seawater might severely corrode the copper mesh, and the superhydrophobic properties could be immediately changed. The corrosion resistances of the initial copper mesh and the superhydrophobic mesh were investigated by electrochemical measurements. The Tafel plots

Figure 11. Polarization curves of bare Cu mesh and 1-decanethiol modified Cu mesh.

copper mesh is about 7.334 × 10−6 A, shown in Figure 11. After modified with 1-DT, the polarization current is reduced apparently to 1.496 × 10−7 A, which is only 1/50 of the former. The lower polarization current corresponds to the better corrosion resistance.30,31 Hence, the coating of DT could increase the corrosion resistance of the copper mesh significantly. In addition, the superhydrophobic copper mesh would make contact with seawater and oils frequently when the device was applied in the practical engineering applications. Therefore, the superhydrophobic stability of the sample in the solvents needs to be studied. After immersed in various solvents for about 12 h, the WCA and WSA of the DT modified copper mesh were measured and summarized in Table 1. It was noticed that both the WCA and the WSA altered little, and the superTable 1. WCA and WSA on 1-Decanethiol Modified Cu Mesh Surface after Immersing with Different Solvents for 12 h

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liquids

WCA

WSA

0.1 M HCl 0.1 M NaOH 3.5 wt % NaCl aqueous solution toluene

164.3° 165.2° 163.3° 162.5°

2.7° 3.3° 3.4° 2.8°

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Field (Grant Nos. 20133BBE50007 and 20123BBE50080) and Social Development Field (Grant No. 20122BBG70165).

hydrophobicity of the sample remained after immersing treatment. It could be interpreted by the fact that the densely packed, chemisorbed monolyers of alkanethiols on the surface of copper mesh could provide effective corrosion resistance in aqueous environments.32−35 The temperature stability of superhydrophobicity of the sample was also investigated by heating the sample at 100 °C for 12 h. The WCA and WSA of the sample were measured in room temperature. Fortunately, the WCA and WSA remained nearly unchanged after thermal treatment. Moreover, the superhydrophobic samples could be stored in air for at least half a year without losing its superhydrophobicity by WCA and WSA measurement. The WCA is always larger than 160° and WSA is always lower than 10°, which demonstrates its long-term stability.

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(1) Al-Majed, A. A.; Adebayo, A. R.; Hossain, M. E. A sustainable approach to controlling oil spills. J. Environ. Manage. 2012, 113, 213− 227. (2) Ventikos, N. P.; Vergetis, E.; Psaraftis, H. N.; Triantafyllou, G. A high-level synthesis of oil spill response equipment and countermeasures. J. Hazard Mater. 2004, 107, 51−58. (3) Choi, S. J.; Kwon, T. H.; Im, H.; Moon, D. I.; Baek, D. J.; Seol, M. L.; Duarte, J. P.; Choi, Y. K. A polydimethylsiloxane (PDMS) sponge for the Sselective absorption of oil from water. ACS Appl. Mater. Interfaces 2011, 3, 4552−4556. (4) Li, A.; Sun, H. X.; Tan, D. Z.; Fan, W. J.; Wen, S. H.; Qing, X. J.; Li, G. X.; Li, S. Y.; Deng, W. Q. Superhydrophobic conjugated microporous polymers for separation and adsorption. Energy Environ. Sci. 2011, 4, 2062−2065. (5) Korhonen, J. T.; Kettunen, M.; Ras, R. H. A.; Ikkala, O. Hydrophobic nanocellulose aerogels as floating, sustainable, reusable, and recyclable oil absorbents. ACS Appl. Mater. Interfaces 2011, 3, 1813−1816. (6) Feng, L.; Zhang, Z. Y.; Mai, Z. H.; Ma, Y. M.; Liu, B. Q.; Jiang, L.; Zhu, D. B. A Super-hydrophobic and Ssuper-oleophilic coating mesh film for the separation of oil and water. Angew. Chem., Int. Ed. 2004, 43, 2012−2014. (7) Arbatana, T.; Fang, X. Y.; Shen, W. Superhydrophobic and oleophilic calcium carbonate powder as a selective oilsorbent with potential use in oil spill clean-ups. Chem. Eng. J. 2011, 166, 787−791. (8) Zhang, Y. L.; Wei, S.; Liua, F. J.; Dua, Y. C.; Liu, S.; Ji, Y. Y.; Yokoib, T.; Tatsumib, T.; Xiao, F. S. Superhydrophobic nanoporous polymers as efficient adsorbents for organic compounds. Nano Today 2009, 4, 135−142. (9) Su, C. H.; Xu, Y. Q.; Zhang, W.; Liu, Y.; Li, J. Porous ceramic membrane with superhydrophobic and superoleophilic surface for reclaiming oil from oily water. Appl. Surf. Sci. 2012, 258, 2319−2323. (10) Calcagnile, P.; Fragouli, D.; Bayer, I. S.; Anyfantis, G. C.; Martiradonna, L.; Cozzoli, P. D.; Cingolani, R.; Athanassiou, A. Magnetically driven floating foams for the removal of oil contaminants from Water. ACS Nano 2012, 6, 5413−5419. (11) Yang, H.; Zhang, X. J.; Cai, Z. Q.; Pi, P. H.; Zheng, D. F.; Wen, X. F.; Cheng, J.; Yang, Z. R. Functional silica film on stainless steel mesh with tunable wettability. Surf. Coat. Technol. 2011, 205, 5387− 5393. (12) Wang, C. F.; Tzeng, F. S.; Chen, H. G.; Chang, C. J. UltravioletDurable Superhydrophobic zinc oxide-coated mesh films for surface and underwater-oil capture and transportation. Langmuir 2012, 28, 10015−10019. (13) Wang, C. X.; Yao, T. J.; Wu, J.; Ma, C.; Fan, Z. X.; Wang, Z. Y.; Cheng, Y. R.; Lin, Q.; Yang, B. Facile Approach in fabricating superhydrophobic and superoleophilic surface for eater and oil mixture separation. ACS Appl. Mater. Interfaces 2009, 1, 2613−2617. (14) Wang, S. H.; Li, M.; Lu, Q. H. Filter paper with selective absorption and separation of liquids that differ in surface tension. ACS Appl. Mater. Interfaces 2012, 2, 667−683. (15) Yu, Q. B.; Tao, Y. L.; Huang, Y. P.; Lin, Z. Q.; Zhuang, Y. L.; Ge, L. L.; Shen, Y. H.; Hong, M.; Xie, A. J. Preparation of porous polysulfone microspheres and their application in removal of oil from water. Ind. Eng. Chem. Res. 2012, 51, 8117−8122. (16) Gui, X. C.; Wei, J. Q.; Wang, K. L.; Cao, A. Y.; Zhu, H. W.; Jia, Y.; Shu, Q. K.; Wu, D. H. Carbon nanotube sponges. Adv. Mater. 2010, 22, 617−621. (17) Zhu, Q.; Pan, Q. M.; Liu, F. T. Facile removal and collection of oils from water surfaces through superhydrophobic and superoleophilic sponges. J. Phys. Chem. C 2011, 115, 17464−17470. (18) Zhu, Q.; Chu, Y.; Wang, Z. K.; Chen, N.; Lin, L.; Liu, F. T.; Pan, Q. M. Robust superhydrophobic polyurethane sponge as a highly reusable oil-absorption material. J. Mater. Chem. A 2013, 1, 5386− 5393.

4. CONCLUSION In summary, we demonstrated an efficient approach for the cleanup of oil spill by using a novel miniature device which was fabricated by a superhydrophobic copper mesh combined with a superoleophilic polyurethane sponge. The superhydrophobic copper mesh was fabricated by a simple immersing method for only 1 min. The PU sponge is a cheap and commercial available material with superoleophilicity in itself. The simple fabrication process and the cheap starting materials enable the mass manufacturing and large-scale application of our oil separating device. The miniature device could adsorb different types of oils from water surface with high separation selectivity and efficiency while not adsorbing any water. Importantly, the adsorbed oil by the device could be collected by squeezing. In addition, the device could be directly used repeatedly without any cleaning and recovery process, while still maintaining its high separation ability and efficiency. Moreover, the superhydrophobic properties of the copper mesh were stable when it was stored in air, contacted with corrosive solvent and organic solvent, or suffered from the temperature variation. Therefore, our oil−water adsorption and collection device might find practical applications in future oil spills.

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ASSOCIATED CONTENT

S Supporting Information *

Figure S1. A schematic illustration of an attempt for the separating of oils from water surface by using the superhydrophobic copper mesh box. Figure S2. A schematic illustration of the oil−water separation process from the water surface by using the as-received PU sponge. Figure S3. Process of the separating of crude oil from water surface by using the miniature device. This material is available free of charge via the Internet at http://pubs.acs.org.

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REFERENCES

AUTHOR INFORMATION

Corresponding Authors

*Phone: +86-791-6453210. Fax: +86-791-6453210. E-mail: [email protected] (F.W.). *E-mail: [email protected] (C.L.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Grant No. 51263018) and Science and Technology Supporting Plan of Jiangxi Province, Industrial 7147

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dx.doi.org/10.1021/ie402584a | Ind. Eng. Chem. Res. 2014, 53, 7141−7148