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Gate-Embedding Strategy for Pore Size Manipulation on Stainless Steel Mesh: Toward Highly Efficient Water-in-Oil Nanoemulsions Separation Jingcheng Du, Cailong Zhou, Li Chen, Jiang Cheng, Pihui Pi, Jihao Zuo, Weifeng Shen, Saimeng Jin, Luxi Tan, and Lichun Dong Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.9b03263 • Publication Date (Web): 30 Jul 2019 Downloaded from pubs.acs.org on August 6, 2019

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Industrial & Engineering Chemistry Research

Gate-Embedding Strategy for Pore Size Manipulation on Stainless Steel Mesh: Toward Highly Efficient Water-in-Oil Nanoemulsions Separation Jingcheng Du,† Cailong Zhou,*,†,‡ Li Chen,† Jiang Cheng,§ Pihui Pi,§ Jihao Zuo,§ Weifeng Shen,†,‡ Saimeng Jin,†,‡ Luxi Tan,†,‡ and Lichun Dong†,‡

† School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, PR China ‡ National-Municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing University, Chongqing 400044, PR China § School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, PR China

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Industrial & Engineering Chemistry Research 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

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KEYWORDS. Stainless steel mesh; Superhydrophobicity; High durability; Nanoemulsions separation; Controllable pore size ABSTRACT. Separation of water-in-oil nanoemulsions is with great significance but difficult. In this work, using a facile brush-painting method, a paste containing PDMS, graphite, TiO2 and ethyl cellulose was coated on low-mesh-number stainless steel mesh, forming hierarchical micro/nano- structures and endowing the mesh with excellent superhydrophobicity. Meanwhile, the coating regulated the original pores of the stainless steel mesh, toward a gate-embedding effect, giving rise to form suitable micro pores for separating water-in-oil nanoemulsions. The separation efficiencies for various nanoemulsions were larger than 99.9% with the residual droplets smaller than 8 nm, showing outstanding separation ability. Furthermore, the wettability of the as-prepared mesh possessed good resistance to acidic, alkaline, salty, organic solvents and UV light exposed environments. Even if the mesh was abraded by sandpaper, its separation capability was almost totally maintained. The findings in the present work provide a novel strategy for addressing industrial water-in-oil emulsions problem especially in the transportation fields. INTRODUCTION The moisture content of fuel oil, containing primarily gasoline and diesel oil, is one of the most significant parameters for the engine that holds the title of “heart” of vehicles, and must be controlled severely.1 If the content of moisture exceeds the specified high limitation, it will cause a series of serious consequences.2,3 Firstly, the oxidation and corrosion on metal parts would occur when water droplets condense on them.4 Secondly, water freezes in the fuel in cold weather, blocking the oil flow to pass through the tubing and causing the engine to run out of fuel.5


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Furthermore, the problem that the ice mixes together with the wax is more difficult to deal with. Thirdly, it will provide an environment for the growth of bacteria in the fuel tank and lead to degradation of fuel property.2,6,7 In addition, more moisture in the fuel will also cause a suddenly extinguished fire of the starter, resulting in accidents.8 Therefore, separation of moisture from fuel oil is highly desired in industry and academia. Generally, free water in oil is relatively simple to remove because it would generate a clear layer owing to the almost insolubility between oil and water. Whereas separating emulsified water in oil, especially for surfactant-stabilized nanoemulsions (< 1 µm) that are highly stable still remains a significant challenge.9 Traditional oil/water separation technologies such as air ﬂotation,10 gravity separation,11 and biological treatment12 have many shortcomings and especially unable to separate oil/water emulsions efficiently, let alone for nanoemulsions. Membranes with special wettability are thought to be promising for separating oil/water emulsions because of the advantages of relatively simple treating process, low-energy consumption and high separation efficiency.13 For instance, Chen et al. fabricated a free-standing thin PVDF membrane with thickness of 5 µm, which can separate surfactant-stabilized water-inoil nanoemulsions with high efficiency of 99.64%.14 Zhang et al. modified PDVB polymer onto PVDF microfiltration membrane during polymerization procedure, obtaining hydrophobic membrane with water contact angle of 135.7o. Separation results showed that the membrane could filtrate various water-in-oil emulsions with the separated water droplets around 100 nm.15 Nevertheless, general polymeric membranes usually suffer from poor resistance (such as dissolution or swelling) to organic solvents, causing destruction of membranes, while the composition of oils is usually chemically complicated.16,17 In comparison, metal mesh-based membranes such as stainless steel mesh (SSM),18 titanium mesh,19 copper mesh,20 and nickel


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mesh21 are always competent in harsh operating conditions by virtue of their good compatibility with oils, as well as the excellent mechanical properties, wide availability and relatively low cost, making them become ideal substrate materials for industrial separation applications. Among them, SSM is the most widely used metal mesh, nevertheless, it seems hard to separate oil/water emulsions for its large inherent pores (several micrometers to several hundred micrometers). Usually, an effective emulsion separation membrane has to provide suitable pore size that less than the diameter of emulsion droplets to acquire a pore size-sieving effect.22 Given this principle, adopting SSM to separate nanoemulsions is much more difficult since that the droplets of dispersed phase are only several hundred nanometers in size and even smaller. In order to realize emulsions separation by SSM, large mesh-number substrates such as cross-knitted ones are usually needed because smaller pores could help to block the dispersed droplets better, so most of the work chose SSMs with mesh number larger than 800.23-26 However, greater mesh number of the SSMs means they would spend much more, increasing the production cost. Hong et. al prepared a carbon nanofibers (CNFs) and PDMS coated SSM (the mesh was square-knitted and mesh number was only 635), while the water droplets in the separated oil were still 0.57 ± 0.09 µm, which means that the as-prepared mesh could only prevent emulsified droplets more than around 500 nm, thus unable to separate nanoemulsions.27 Therefore, it is urgent to develop new strategy to prepare low-mesh number SSM-based membranes through facile method for nanoemulsions separation. In this work, we tried to separate moisture from water-in-oil nanoemulsions using a superhydrophobic SSM prepared by a simple route. In order to achieve this goal, the pristine pores of SSM should be well tailored by a superhydrophobic coating. Herein, we designed a superhydrophobic paste which could be brush-painted onto the SSM surface. The paste contained


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ingredients of micro-sized graphite, TiO2 nanoparticles, polydimethylsiloxane (PDMS), terpineol and ethyl cellulose. Graphite is a naturally-occurring form of crystalline carbon with good heatresistant, lightweight and highly thermal-conductive properties.28 Most important, the graphite is much cheaper than other similar carbon materials such as carbon nanotube and graphene. Owing to high viscosity of the as-formed paste, it can form a uniform and compact film when painting on the substrate and vaporizing the solvent terpineol. The surface of the coated SSM (described as GTSSM afterwards) possessed unique micro-/nano- structures, which endowed the mesh with extreme hydrophobicity and suitable liquid channels. We demonstrated that various surfactantstabilized water-in-oil nanoemulsions (e.g. water-in-gasoline nanoemulsions) can be separated with high separation efficiency by the GTSSM. The chemical and mechanical durability of the GTSSM were also assessed systematically. Not only is the superhydrophobic SSM impressive for its superior oil/water nanoemulsions separation performance but also it comprises green and commercially available materials using a scalable operating approach. EXPERIMENTAL SECTION Materials. Hydrochloric acid, ethanol, n-hexane, dichloromethane, xylene, isooctane, terpineol, methanol, chloroform, N,N-dimethylformamide (DMF), methylene blue, Sudan III and Span 80 were purchased from Cologne Chemical Co., Ltd. (Chengdu, China). Oxide nanoparticles (including SiO2, Al2O3, Fe3O4 and ZnO), Karl-Fischer reagent and ethyl cellulose (EC, 18~22 mPa∙s) were obtained from Aladdin Industrial Co. (Shanghai, China). PDMS prepolymer (Sylgard 184A) and the curing agent (Sylgard 184B) were purchased from Dow Corning Co. (Shanghai, China). Graphite powder (5000 mesh) was bought form Jinglongtetan Technical Co., Ltd. (Beijing, China). Titanium dioxide (P25) was purchased from Evonik Industries AG (Essen, Germany). Gasoline was purchased from SINOPEC (Beijing, China).


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Colza oil was bought from a local market. All the above reagents were used as purchased without further puriﬁcation. Stainless steel mesh (80, 200, 300 and 400 mesh) was produced by Fuhang Metallic Materials Co., Ltd. (Anping, China). Fabrication of the GTSSM. The SSM was sheared into small square with the size of 4 × 4 cm2 and washed ultrasonically in 1 M of HCl solution, ethanol and deionized water for each 15 min. It was then dried in an oven at 60 oC for 0.5 h. To prepare to the painting paste, a typical method was performed as follows: 0.5 g of Sylgard 184A , 0.05 g of Sylgard 184B and 0.25 g of EC were simultaneously added into 5 g of terpilenol and stirred vigorously for 30 min to obtain a well milky and dispersed mixture. Afterwards, 0.5 g of graphite powder and 0.5 g of P25 were added into the mixture and stirred strongly for 1 h to obtain a well dispersed paste. Ultimately, GTSSM was prepared by brush-painting the paste onto the as-cleaned SSM uniformly and dried at 200 °C for 1 h. Scheme 1 briefly displays the preparation process of GTSSM and its application in water-in-oil nanoemulsion separation.

Scheme 1 Schematic of the preparation and oil/water separation application of GTSSM.


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Water-in-Oil Nanoemulsions Separation. I. Preparation of water-in-oil nanoemulsions: 0.5 mL of deionized water, 45 mL of oil and 0.2 g of Span 80 were mixed together and magnetically stirred for 1 h, obtaining the water-in-oil nanoemulsions. II. Separation of the water-in-oil nanoemulsions: the separation device comprises a glass joint and a glass tube, which can fix the GTSSM membrane between them (Figure S1). The nanoemulsions were poured into the upper glass tube with adding an additional negative pressure of 0.004 MPa under the membrane during the separation. Six kinds of nanoemulsions formed by oils (n-hexane, dichloromethane, xylene, isooctane, colza oil and gasoline) and water were used to explore the separation ability of the GTSSM membrane. Mechanical Durability Test. The mechanical abrasion tests were performed to investigate the mechanical durability of GTSSM, using SiC sandpaper (1000 grid) as the abrasion material. As one time of abrasion, the GTSSM with a load of 100 g was forced to move in two perpendicular dimensions each for 10 cm. The water contact angles (WCAs), oil permeating flux and separation efficiency were explored after each 5 times of abrasion. Instrumentation and Characterization. The surface morphology of GTSSM was investigated by a scanning electron microscopy (SEM, ZEISS Merlin). X-ray diffraction data of GTSSM was obtained using an X-ray diffractometer (XRD, Bruker D8 Advance). The surface elements and composition of GTSSM were investigated using energy dispersive X-ray spectrometer (EDS, Oxford Instruments Inca400) and X-ray photoelectron spectroscopy (XPS, Perkin Elmer PHI5000C ESCA). Particle size distribution of water droplets in different oils was detected by a dynamic light scattering particle analyzer (DLS, Malvern Zetasizer Nano ZS90) and an optical microscopy (Olympus BX51TRF). The wetting properties of GTSSM were measured using a contact angle analyzer (Shanghai Zhongchen Powereach JC2000D1A), and the volume of testing


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water droplet was 5 μL. The moisture content in oil was obtained by a micro-moisture meter (Shanghai Anting Electronic Instrument ZSD-2) through Karl-Fischer method. The separation efficiency (η) could be further calculated by Eq. (1):  A F   = 1    100% W  

(1)

where A is the volume (mL) of Karl-Fischer reagent consumed by filtrate; F=m/n, m and n are the weight (mg) of deionized water and the volume (mL) of Karl-Fischer reagent consumed by the deionized water, respectively. So F is that each volume of Karl-Fischer reagent is equal to the weight of water; W is the weight of the collected oil after separation. RESULTS AND DISCUSSION For preparation of the painting paste, PDMS was used as the low surface energy material for superhydrophobicity, terpineol was the solvent, solid graphite/TiO2 were used to create micro/nano- structures in the coating, and EC acted as a binder to combine the ingredients, respectively. All these components facilitated formation of the final paste with high viscosity, as seen in Scheme 1. Owing to the good adhesive and film-forming properties of the paste, SSM can easily be covered compactly when printing it on. As well known that, the pore size of a membrane is significant to the separation of oil-water emulsions: too small or too large is neither suitable. The original SSMs can not be used for oil-water emulsions separation because of their big pores that unable to hinder permeation of the dispersed liquid droplets, even though the ones with ultrahigh mesh number. So pore size regulation of SSMs is of great significance for their application on emulsions separation.29 Figure 1a-d exhibit the SEM images of GTSSMs with different mesh numbers (80, 200, 300 and 400), to demonstrate the pore size managing effect of the paste. The


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original 80-mesh SSM possesses square pores with average size of around 180 µm (Figure S2). While the pores were partly sealed by the paste coating and exhibited "cross star" appearance (Figure 1a), which could be explained as the shrink effect of the solvent volatilization under high temperature. Similar as the 80-mesh SSM, pores of other SSMs with higher mesh numbers (e.g. 200, 300 and 400) were also embedded firmly by the coating (Figure 1b-d), indicating outstanding blocking ability of the paste. Overall consideration of pore size and separation capability, we chose 300-mesh SSM to carry out the subsequent experiments. The morphologies of the coating on SSM with high magnifications were further investigated by SEM (Figure 1e-g). There were a good deal of small pores among the coatings with the average size of about 8~9 microns (Figure 1e), which could play a significant role in the oilwater emulsions separation. We could clear observe that many rough and irregular protuberances conglomerated in the coating under larger magnification (Figure 1f), which was composed of the agglomerates of micro-scaled flake-like graphite powder (Figure S3). As shown in Figure 1g, many TiO2 nanoparticles with the size of 20~80 nm appear on the graphite, when further magnifying the SEM image. The graphite in micro- scale and TiO2 in nano-scale formed the final hierarchical micro-/nano- structures with dual-scale roughness, which can enhance the superhydrophobic property of the coating, similar as the lotus surface,30,31 The chemical elements of the coating surface were investigated by EDS. The GTSSM contains element of Fe, Ni, Mn, Cr, C, O, Si and Ti, where Fe, Ni, Mn and Cr derived from SSM, Si from PDMS and Ti from P25, respectively (Figure S4). EDS-element mapping images in Figure 1h demonstrate that C, O, Si, Ti elements uniformly distributed on the prepared coating surface. The components of the GTSSM were investigated by XRD, from which we can see that all the diffraction peaks are well-accorded with standard peaks of P25, graphite and stainless steel mesh, respectively (Figure


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1i). Figure 1j shows XPS spectrum of the GTSSM, and strong peaks assign to O 1s, Ti 2p, C 1s, Si 2s and Si 2p can be seen in the full spectrum. The detailed information of C 1s, Si 2p and Ti 2p can be seen in Figure S5.

Figure 1 (a-d) SEM images of the GTSSMs with different mesh numbers: (a) 80, (b) 200, (c) 300, and (d) 400 mesh, respectively. (e-g) SEM images of the GTSSM (300-mesh) in different magnifications, and inset of (e) is the pore size distribution of the GTSSM. (h) EDS-element mapping images, (i) XRD pattern and (j) XPS full spectrum of the GTSSM.

The effect of TiO2 and graphite on the film formation was deeply evaluated. Generally speaking, when maintain the amount of TiO2 to 0.5 g, increasing the component of graphite


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would result in decrease in the pore size of SSM. If no or small amount of graphite (0.1 g) was applied in the paste, it showed weak pore size embedding ability on the SSM (Figure 2a and b). Too much graphite powder (1.0 g) in the paste, however, would cause exaggerated compactness on the SSM instead (Figure 2c), which might decrease the separation flux. The schematic illustration of the effect of graphite on the pore size regulation can be seen in Figure 2d. On the other hand, the amount of TiO2 was also quite important to the final film on SSM. When the paste composed of 0.5 g graphite and only 0.1 g TiO2, the pores of SSM could not be totally sealed because low viscosity of the paste (Figure S6). By contrast, appropriate pore size and compactness on SSM regulated by the moderate paste as showed in Figure 1c, e-g played a critical role in the later separation experiment of water-in-oil nanoemulsions. As an extended research, some other oxide nanoparticles (e.g. SiO2, ZnO, Al2O3, and Fe3O4) have also been employed to fabricate coatings on SSM, which might broaden applications of the membrane (e.g. magnetic property), and results indicate that painting pastes contained of all these particles as participants possessed similar gate-embedding effect for SSM (Figure S7).


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Figure 2 (a-c) SEM images of the GTSSMs prepared by varying the amount of graphite in paste: (a) 0 g, (b) 0.1 g and (c) 1.0 g, respectively. (d) Schematic illustration showing the effect of graphite on the pore size regulation of SSM.

Figure 3 demonstrates that the as-prepared GTSSM has excellent superhydrophobic and superoleophilic properties. WCA of pristine SSM is about 97.3o (Figure S8), while water droplets showed spherical shape on the GTSSM with a WCA about 151.5o, which mainly profits from the hierarchical micro-/nano- structures of the coating (Figure 3a). A water droplet could easily roll on the superhydrophobic GTSSM surface without any vestige due to the lack of adhesive force, similar as it on a lotus leaf (Video S1 and Figure 3b). Furthermore, when compelling the GTSSM to immerse into water, it showed the typical phenomenon of silver mirror (Video S2 and Figure 3c), which owes to the presence of an air layer trapped on the surface.32 After taking out of the GTSSM from water, there was no water adhering on its surface, indicating good water-proof


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performance (Figure 3d left). All the phenomena prove that the GTSSM possesses outstanding superhydrophobicity. Meanwhile, its oleophilicity was also assessed, when we put the GTSSM into oil (isooctane) and then took it out, the mesh was totally infiltrated with a contact angle of near 0o (Figure 3d right and Figure S9), manifesting superior oil affinity. By the way, as an excellent conductor, graphite, can significantly improve the electrical conductivity of the coating. Materials with both electrical conductivity and superhydrophobicity show promising applications in highly effective catalytic electrodes,33 electrowetting,34,35 thin-film heater,36 electromagnetic shielding,37 electronics38,39 and so forth, thus achieving great interests. Here, a glass slide coated with the superhydrophobic film was used to light up a light-emitting diode (LED) lamp in an electric circuit. The LED lamb could easily be irradiated because effective electronic transmission channels formed by the graphite in the coating, as shown in Figure 3e. The chemical stability and UV resistance of wettability for the GTSSM were measured by contact angle. Figure 3f displays that the CAs of water droplets with pH values from 1 to 14 on the GTSSM were all around 150o, indicating good acid and alkali resistance. Moreover, the WCA of different salt solutions with concentrations from 2 wt% to 25 wt% on the GTSSM was researched, the result revealed that the WCAs maintained high degrees (> 149o), indicating that the GTSSM possessed good resistance to high concentration of salt solution (Figure 3g). Another chemical stability measurement was performed by immersing the GTSSM into various organic solvents (e.g. xylene, n-hexane, isooctane, dichloromethane, ethanol and DMF) for certain durations and then testing the WCAs. As shown in Figure 3h, even immersed the GTSSM into these solvents for 15 days, its extreme wettability was almost not affected. Furthermore, UV resistance of the GTSSM was also investigated as depicted in Figure 3i. After 8 h of irradiation, the WCA slightly decreased to 147o, which might be caused by the structural change at TiO2


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surface in the coating upon UV light illumination.40 Fortunately, the influence of UV light on the coating is weak because TiO2 particles were well wrapped by other hydrophobic components.

Figure 3 (a) Photograph of water droplets on the GTSSM and the model of lotus leaf state. (b) Photograph showing rolling status of a water droplet on the GTSSM. (c) Silver mirror phenomenon of the GTSSM when being immersed in water. (d) Digital images of the wetting status of GTSSM after been immersed in water (left, colored by methylene blue) and oil (right, colored by Sudan III), respectively. (e) Lighting up an LED lamp by connecting it with the superhydrophobic coating on glass and the schematic illustration of its work mechanism. CAs of water droplets with (f) different pH values and (g) different concentrations of salt on the GTSSM. WCAs of the GTSSMs after (h) immersion in different solvents and (i) irradiation under UV light, for certain duration.


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To evaluate the capability of the GTSSM in emulsions separation, various water-in-oil nanoemulsions (oils include gasoline, isooctane, xylene, dichloromethane, and n-hexane) were produced and filtered. As shown in Figure 4a1-e1, there were a mass of water droplets in the milky nanoemulsions before filtration, while all the samples turned transparent and no water droplets were discovered in the filtered liquid, indicating that they have been successfully separated from the nanoemulsions by the GTSSMs (Figure 4a2-e2). DLS recorded the particle size distribution of the water droplets in the emulsions before and after separation. The size of emulsified water droplets was between 50 to 900 nanometers in the above five oils, which formed typical nano-scale emulsions. Taking water-in-gasoline nanoemulsions as an example, the emulsified droplets were about 300~700 nm, but they sharply decreased to 4~8 nm after separation (Figure 4a3), demonstrating preeminent filtration effect. For the other four nanoemulsions, effective separation were realized without exception), achieving filtrates with less than 8 nm of residual droplets (Figure 4b3-e3). The separation efficiencies of the GTSSM for separating these nanoemulsions were all larger than 99.85% measured by the Karl-Fischer method, and among which it reached high up to 99.94% for gasoline (Figure 4f). For water-incolza oil emulsions, which has relatively high viscosity, the GTSSM also showed good separation ability with a separation efficiency of 99.87% (Figure S10). The oil permeation flux J was calculated using the Eq. (2):

J=

V S  t

(2)

Where V (L) is the volume of permeated oil, S (m2) is the active area of the mesh, and Δt (h) is the oil permeation time. The permeation fluxes of different oils were about 134.9, 186.4, 38.8, 58.5 and 85.6 L·m-2·h-1, for surfactant-stabilized water-in-gasoline, water-in-isooctane, water-in-


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xylene, water-in-dichloromethane and water-in-n-hexane nanoemulsions, respectively (Figure 4g). In general, despite sacrificing the permeation flux on account of gate-embedding filtration membrane was employed, the separation of water-in-oil nanoemulsions was highly successful. It is worth noting that, although the pore size of coating on the SSM was several microns investigated by SEM, much larger than that of the emulsified water droplets, the separation successfully occurred. It can be mainly explained by the following three factors: Firstly, the good superoleophilicity of the GTSSM endowed it with good oil affinity. An oil film could bridge among the coating skeletons immediately, resulting in oil filling in the micro pores and blockage of the emulsified water droplets passing though the pores. Secondly, the coalescence and seceding processes of the water droplets in the structure. As illustrated in Figure 4h, when the oil film is formed, the micro pore structure turns to a bowl-like architecture, making the water droplets fall down to the bottom due to the gravity and coalesce to larger ones.41 Then the large water droplet would secede the pore and form "self-ascending" behavior owing to the surface energy release.42 Thirdly, EC in the coating might act as not only a binder, but also a demulsifier during the separation, which facilitates the proceeding of demulsification, similar as it worked in the water/asphaltene/toluene emulsion system.43 Consequently, for the GTSSM, even when its pore size is larger than the emulsified water droplet size, effective separation of water-in-oil nanoemulsions can be also realized because of its particular wettability, unique multiscaled structure and the functional ingredients.


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Figure 4 Optical images of different water-in-oil nanoemulsions before (a1-e1) and after (a2-e2) filtration; size distribution of the water droplets in feed and filtrate (a3-e3): (a) gasoline, (b) isooctane, (c) xylene, (d) dichloromethane, and (e) n-hexane, respectively. Separation efficiency (f) and oil flux (g) of the GTSSMs for separating various water-in-oil nanoemulsions. (h) Schematic illustration of the water coalescence, demulsification and seceding processes.

Mechanical stability is quite significant for separation membranes when they come to practical applications.44 Here, a mechanical stability test on the GTSSM was performed as illustrated in Figure 5a. The mesh loaded with a 100 g weight was put on a SiC sandpaper and forced to move for 10 cm in two vertical directions respectively, recording as one time of abrasion. The water contact angle, separation efficiency and fluid flux were measured after every five times of


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abrasion. For continuous fifty times of abrasion, the GTSSM showed robust perseverance for water-in-oil nanoemulsions separation. As shown in Figure 5b, taking water-in-isooctane as an example, the liquid flux of the mesh decreased slightly, implying that the passing channels were not affected by the abrasion. Meanwhile, the separation efficiency maintained high level to larger than 99.9% all the time, indicating good abrasion resistance of the GTSSM (Figure 5c). The WCA, however, decreased markedly to about 130° after dozens of abrasion thus losing the superhydrophobicity, which is mainly attributed to the destroyed GTSSM with smooth surface. In our previous work, we have expounded the relationship between lose of extreme wettability and separation efficiency durability.45,46 Although the hydrophobicity was affected by the mechanical abrasion, the framework of the mesh play an important role on the steadiness of high separation ability as normal. Nevertheless, the battered mesh could be repaired quickly and simply by immersing it into a chloroform solution containing PDMS (2.0 wt% Sylgard 184A and 0.2 wt% of Sylgard 184B) for 5 min. After being taken out and dried in 80 oC, the WCA of GTSSM improved distinctly to near 150o after each five times of abrasion, showing good repairable capability (Figure 5d).


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Figure 5 (a) Schematic illustration of the friction test of GTSSM. (b) The liquid flux measurement after different abrasion numbers. (c) The separation efficiency and WCA after different abrasion numbers. (d) The variation of WCA using repair agent to deal with after abrasion.

Among a large number of research with respect to water-in-oil emulsions separation, SSM substrate based filtration membranes were quite scarce, and the majority of some state-of-the-art materials are summarized in Table 1 according to our knowledge. Comparing to the reported work, we realized surfactant-stabilized water-in-oil nanoemulsions separation by using the SSM with only 300 of mesh number in this work. Furthermore, the preparation method, brush painting is simple, effortless and easy to scale up, making the GTSSM quite shining among the existing membranes.


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Table 1. Summary of some SSM-based filtration membranes for water-in-oil emulsions separation. Mesh

Chemical composition

Method

CNFs/SWCNTs/PDMS,

pump suction and

CNFs/PDMS

modification

1250

fluoropolymer/SiO2

~350

Rejection

Operability

Ref.

not given

moderate

23,27

spin-coating

>99.0

complex

1

copper stearate/Fe3O4

dip-coating

not given

simple

47

1400

PDMS/PS

phase inversion method

>99.99

simple

24

2300

PPy, PANI

electrochemical method

>99.9

moderate

25,26

> 800

SiO2

>99.6

moderate

48

radical polymerization

>99.0

complex

49

brush painting

>99.9

simple

number 1000, 635

400

300

mussel-inspired chemistry and stöber method

PDMAEMA and PDVB (double-layer structure) graphite/TiO2/PDMS/EC

(%)

this work

CONCLUSIONS In conclusion, the non-toxic graphite and environmentally friendly titanium dioxide were successfully coated on the stainless steel mesh through a simple brush-painting method. Polydimethylsiloxane and ethyl cellulose also acted as good adhesives in the hydrophobic system. The coating achieved effective regulation on the pores of the stainless steel mesh to form a unique inlay-gated structure, making them able to separate various water-in-oil nanoemulsions. The separation efficiencies were high up to 99.9% with the residual emulsified droplets smaller


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than 8 nm, showing excellent separation ability. Moreover, the wettability of the as-prepared mesh displayed good resistance to acidic, alkaline, salty, organic solvents and UV light exposed environments. Even if the mesh was abraded by sandpaper for 50 times, its separation capability for water-in-oil nanoemulsions was almost totally maintained. In addition, the abrasion induced decreasing of water contact angle could mostly restore after PDMS repairing. We envision that the findings in the present work would provide a novel strategy for realizing industrial water-inoil nanoemulsions separation.

ASSOCIATED CONTENT Supporting Information. Other information of the pristine SSM and GTSSM. (PDF) A water droplet easily rolls on the GTSSM surface. (AVI) The phenomenon of silver mirror. (AVI)

AUTHOR INFORMATION Corresponding Author Cailong Zhou

E-mail: [email protected]

ORCID Cailong Zhou: 0000-0003-1980-7659 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.


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Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work is supported by the National Natural Science Foundation of China (21676102, 21776094, 21776025), the Fundamental Research Funds for the Central Universities (2019CDXYHG0013), and the Graduate Scientific Research and Innovation Foundation of Chongqing (CYS19010). ABBREVIATIONS PVDF = polyvinylidene fluoride PDVB = polydivinylbenzene SSM = stainless steel mesh PDMS = polydimethylsiloxane GTSSM = graphite and TiO2 coated stainless steel mesh DMF = N,N-dimethylformamide EC = ethyl cellulose CA(s) = contact angle(s) WCA(s) = water contact angle(s) SEM = scanning electron microscopy XRD = X-ray diffractometer EDS = energy dispersive X-ray spectrometry XPS = X-ray photoelectron spectroscopy DLS = dynamic light scattering CNFs = carbon nanofibers ACS Paragon Plus Environment

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SWCNTs = single-walled carbon nanotubes PS = polystyrene PPy = polypyrrole PANI = polyaniline PDMAEMA = poly-(N,N-dimethylaminoethyl methacrylate)

REFERENCES (1) Zeng, X. J.; Qian, L.; Yuan, X. X.; Zhou, C. L.; Li, Z. W.; Cheng, J.; Xu, S. P.; Wang, S. F.; Pi, P. H.; Wen, X. F. Inspired by Stenocara Beetles: From Water Collection to High-Efficiency Water-in-Oil Emulsion Separation. ACS Nano 2017, 11, 760-769. (2) Hansted, A. L. S.; Nakashima, G. T.; Martins, M. P.; Yamamoto, H.; Yamaji, F. M. Comparative Analyses of Fast Growing Species in Different Moisture Content for High Quality Solid Fuel Production. Fuel 2016, 184, 180-184. (3) Kamiński, J.; Kurzydłowski, K. J. Use of Impedance Spectroscopy to Testing Corrosion Resistance of Carbon Steel and Stainless Steel in Water-Biodiesel Configuration. J. Corros. Measur. 2008, 5, 35. (4) Fazal, M. A.; Haseeb, A. S. M. A.; Masjuki, H. H. Comparative Corrosive Characteristics of Petroleum Diesel and Palm Biodiesel for Automotive Materials. Fuel Process. Technol. 2010, 91, 1308-1315. (5) Yeong, Y. H.; Milionis, A.; Loth, E.; Sokhey, J. Self-Lubricating Icephobic Elastomer Coating (SLIC) for Ultralow Ice Adhesion with Enhanced Durability. Cold Reg. Sci. Technol. 2018, 148, 29-37.


23


Page 24 of 38

(6) Wang, Z. W.; Wu, S.; Huang, Y. H.; Huang, S.; Shi, S. G.; Cheng, X. B.; Huang, R. H. Experimental Investigation on Spray, Evaporation and Combustion Characteristics of EthanolDiesel, Water-Emulsified Diesel and Neat Diesel Fuels. Fuel 2018, 231, 438-442. (7) Wang, C. H.; Pan, K. L.; Ueng, G. J.; Kung, L. J.; Yang, J. Y. Burning Behaviors of Collision-Merged Water/Diesel, Methanol/Diesel, and Water + Methanol/Diesel Droplets. Fuel 2013, 106, 204-211. (8) Zhou, J. Y.; Bandekar, A.; Chase, G. G. Evaluation of Electrowet Coalescer in Series with PVDF-HFP Electrospun Fiber Membranes for Separation of Water from ULSD. Fuel 2018, 225, 111-117. (9) Brian, R.; Solomon, M.; Hyder, N.; Varanasi, K. K. Separating Oil-Water Nanoemulsions Using Flux-Enhanced Hierarchical Membranes. Sci. Rep. 2014, 4, 5504. (10) Al-Shamrani, A. A.; James, A.; Xiao, H. Separation of Oil from Water by Dissolved Air Flotation. Colloids Surf. A 2002, 209, 15-26. (11) Mazumdar, M.; Roy, S. Gravity Induced Coalescence in Emulsions with High Volume Fractions of Dispersed Phase in the Presence of Surfactants. AIChE J. 2017, 63, 4379-4388. (12) Li, J. H.; Sun, S. S.; Yan, P.; Fang, L.; Yu, Y.; Xiang, Y. D.; Yang, D.; Gong, Y. J.; Gong, Y. J.; Zhang, Z. G. Microbial Communities in the Functional Areas of a Biofilm Reactor with Anaerobic-Aerobic Process for Oily Wastewater Treatment. Bioresour. Technol. 2017, 238, 7-15. (13) Peng, Y. B.; Guo, Z. G. Recent Advances in Biomimetic Thin Membranes Applied in Emulsified Oil/Water Separation, J. Mater. Chem. A 2016, 4, 15749-15770.


24

Page 25 of 38 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


(14) Chen, L. W.; Si, Y. F.; Zhu, H.; Jiang, T.; Guo, Z. G. A Study on the Fabrication of Porous PVDF Membranes by In-Situ Elimination and Their Applications in Separating Oil/Water Mixtures and Nano-Emulsions. J. Membr. Sci. 2016, 520, 760-768. (15) Zhang, W. F.; Liu, N.; Cao, Y. Z.; Chen, Y. N.; Xu, L. X.; Lin, X.; Feng, L. A Solvothermal Route Decorated on Different Substrates: Controllable Separation of an Oil/Water Mixture to a Stabilized Nanoscale Emulsion. Adv. Mater. 2015, 27, 7349-7355. (16) Yang, C.; Han, N.; Wang, W. J.; Zhang, W. X.; Han, C. Y.; Cui, Z. Y.; Zhang, X. X. Fabrication of a PPS Microporous Membrane for Efficient Water-in-Oil Emulsion Separation. Langmuir 2018, 34, 10580-10590. (17) Pan, J.; Xiao, C. F.; Huang, Q. L.; Liu, H. L.; Zhang, T. ECTFE Hybrid Porous Membrane with Hierarchical Micro/Nano-Structural Surface for Efficient Oil/Water Separation. J. Membr. Sci. 2017, 524, 623-630. (18) Song, J. L.; Huang, S.; Lu, Y.; Bu, X. W.; Mates, J. E.; Ghosh, A.; Ganguly, R.; Carmalt, C. J.; Parkin, I. P.; Xu, W. J.; Megaridis, C. M. Self-Driven One-Step Oil Removal from Oil Spill on Water via Selective-Wettability Steel Mesh. ACS Appl. Mater. Interfaces 2014, 6, 19858-19865. (19) Zhou, C. L.; Cheng, J.; Hou, K.; Zhao, A.; Pi, P. H.; Wen, X. F.; Xu, S. P. Superhydrophilic and Underwater Superoleophobic Titania Nanowires Surface for Oil Repellency and Oil/Water Separation. Chem. Eng. J. 2016, 301, 249-256. (20) Du, J. C.; Zhou, C. L.; Yang, Z. J.; Cheng, J.; Shen, Y. Y.; Zeng, X. J.; Tan, L. X.; Dong, L. C. Conversion of Solid Cu2(OH)2CO3 into HKUST-1 Metal-Organic Frameworks: Toward an Under-Liquid Superamphiphobic Surface. Surf. Coat. Technol. 2019, 363, 282-290.


25


Page 26 of 38

(21) Zhou, C. L.; Feng, J. X.; Cheng, J.; Zhang, H.; Lin, J.; Zeng, X. J.; Pi, P. H. Opposite Superwetting Nickel Meshes for On-Demand and Continuous Oil/Water Separation. Ind. Eng. Chem. Res. 2018, 57, 1059-1070. (22) Chen, Y.; Wang, N.; Guo, F. Y.; Hou, L. L.; Liu, J. C.; Liu, J.; Xu, Y.; Zhao, Y.; Jiang, L. A Co3O4 Nano-Needle Mesh for Highly Efficient, High-Flux Emulsion Separation. J. Mater. Chem. A 2016, 4, 12014-12019. (23) Lin, X. D.; Choi, M.; Heo, J.; Jeong, H.; Park, S.; Hong, J. Cobweb-Inspired Superhydrophobic Multiscaled Gating Membrane with Embedded Network Structure for Robust Water-in-Oil Emulsion Separation. ACS Sustainable Chem. Eng. 2017, 5, 3448-3455. (24) Wang, C. F.; Tsai, Y. J.; Kuo, S. W.; Lee, K. J.; Hu, C. C.; Lai, J. Y. Toward Superhydrophobic/Superoleophilic Materials for Separation of Oil/Water Mixtures and Water-inOil Emulsions Using Phase Inversion Methods. Coatings 2018, 8, 396. (25) Liu, M. M.; Hou, Y. Y.; Li, J.; Guo, Z. G. Stable Superwetting Meshes for On-Demand Separation of Immiscible Oil/Water Mixtures and Emulsions. Langmuir 2017, 33, 3702-3710. (26) Liu, M. M.; Li, J.; Guo, Z. G. Electrochemical Route to Prepare Polyaniline-Coated Meshes with Controllable Pore Size for Switchable Emulsion Separation. Chem. Eng. J. 2016, 304, 115120. (27) Lin, X. D.; Heo, J.; Jeong, H.; Choi, M.; Chang, M.; Hong, J. Robust Superhydrophobic Carbon Nanofiber Network Inlay-Gated Mesh for Water-in-Oil Emulsion Separation with High Flux. J. Mater. Chem. A 2016, 4, 17970-17980


26

Page 27 of 38 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


(28) Suasmoro, S.; Wati, F. A. R.; Muhaimin, N. Ti-Zr Coating on Graphite through Powder Immersion Reaction-Assisted Coating (PIRAC) and Its Oxidation Kinetics at T=1000 oC. Bull. Mater. Sci. 2019, 42, 126. (29) Lin, X. D.; Heo, J.; Hong, J. Cobweb-Inspired DNA-Based Membranes for Multicomponent Pollutant-Oil-Water Emulsions Separation. Chem. Eng. J. 2018, 348, 870-876. (30) Tian, Y.; Su, B.; Jiang, L. Interfacial Material System Exhibiting Superwettability. Adv. Mater. 2014, 26, 6872-6897. (31) Darmanin, T.; Guittard, F. Superhydrophobic and Superoleophobic Properties in Nature. Mater.Today 2015, 18, 273-285. (32) Zhou, C. L.; Chen, Z. D.; Yang, H.; Hou, K.; Zeng, X. J.; Zheng, Y. F.; Cheng, J. NatureInspired Strategy toward Superhydrophobic Fabrics for Versatile Oil/Water Separation. ACS Appl. Mater. Interfaces 2017, 9, 9184-9194. (33) Lei, Y. J.; Sun, R.; Zhang, X. C.; Feng, X. J.; Jiang, L. Oxygen-Rich Enzyme Biosensor Based on Superhydrophobic Electrode. Adv. Mater. 2016, 28, 1477-1481. (34) Han, J. T.; Kim, S. Y.; Woo, J. S.; Lee, G. W. Transparent, Conductive, and Superhydrophobic Films from Stabilized Carbon Nanotube/Silane Sol Mixture Solution. Adv. Mater. 2008, 20, 3724-3727. (35) Chen, Y. C.; Suzuki, Y. J.; Morimoto, K. Electrowetting-Dominated Instability of Cassie Droplets on Superlyophobic Pillared Surfaces. Langmuir 2019, 35, 2013-2022.


27


Page 28 of 38

(36) Han, J. T.; Kim, B. K.; Woo, J. S.; Jang, J. I.; Cho, J. Y.; Jeong, H. J.; Jeong, S. Y.; Seo, S. H.; Lee, G. W. Bioinspired Multifunctional Superhydrophobic Surfaces with Carbon-NanotubeBased Conducting Pastes by Facile and Scalable Printing. ACS Appl. Mater. Interfaces 2017, 9, 7780-7786. (37) Jia, L. C.; Zhang, G. Q.; Xu, L.; Sun, W. J.; Zhong, G. J.; Lei, J.; Yan, D. X.; Li, Z. M. Robustly Superhydrophobic Conductive Textile for Efficient Electromagnetic Interference Shielding. ACS Appl. Mater. Interfaces 2019, 11, 1680-1688. (38) Su, X. J.; Li, H. Q.; Lai, X. J.; Chen, Z. H.; Zeng, X. R. Highly Stretchable and Conductive Superhydrophobic Coating for Flexible Electronics. ACS Appl. Mater. Interfaces 2018, 10, 10587-10597. (39) Choi, B.; Lee, J.; Han, H.; Woo, J.; Park, K.; Seo, J.; Lee, T. Highly Conductive Fiber with Waterproof and Self-Cleaning Properties for Textile Electronics. ACS Appl. Mater. Interfaces 2018, 10, 36094-36101. (40) Banerjee, S.; Dionysiou, D. D.; Pillai, S. C. Self-Cleaning Applications of TiO2 by PhotoInduced Hydrophilicity and Photocatalysis. Appl. Catal. B: Environ. 2015, 176, 396-428. (41) Wang, Z. D.; Xiao, C. M.; Wu, Z. J.; Wang, Y. T.; Du, X.; Kong, W.; Pan, D. H.; Guan, G. Q.; Hao, X. G. A Novel 3D Porous Modified Material with Cage-Like Structure: Fabrication and Its Demulsification Effect for Efficient Oil/Water Separation. J. Mater. Chem. A 2017, 5, 58955904.


28

Page 29 of 38 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


(42) Cao, M. Y.; Li, K.; Dong, Z. C.; Yu, C. M.; Yang, S.; Song, C.; Liu, K. S.; Jiang, L. Superhydrophobic “Pump”: Continuous and Spontaneous Antigravity Water Delivery. Adv. Funct. Mater. 2015, 25, 4114-4119. (43) Liu, J.; Zhao, Y. P.; Ren, S. L. Molecular Dynamics Simulation of Self-Aggregation of Asphaltenes at an Oil/Water Interface: Formation and Destruction of the Asphaltene Protective Film. Energy Fuels 2015, 29, 1233-1242. (44) Hou, K.; Zeng, Y. C.; Zhou, C. L.; Chen, J. H.; Wen, X. F.; Xu, S. P.; Cheng, J.; Lin, Y. G.; Pi, P. H. Durable Underwater Superoleophobic PDDA/Halloysite Nanotubes Decorated Stainless Steel Mesh for Efficient Oil-Water Separation. Appl. Surf. Sci. 2017, 416, 344-352. (45) Chen, Z. D.; Zhou, C. L.; Lin, J.; Zhu, Z. T.; Feng, J. X.; Fang, L. D.; Cheng, J. ZrO2Coated Stainless Steel Mesh with Underwater Superoleophobicity by Electrophoretic Deposition for Durable Oil/water Separation. J. Sol-Gel Sci. Technol. 2018, 85, 23-30. (46) Du, J. C.; Zhang, C. Y.; Pu, H.; Li, Y. F.; Jin, S. M.; Tan, L. X.; Zhou, C. L.; Dong, L. C. HKUST-1 MOFs Decorated 3D Copper Foam with Superhydrophobicity/Superoleophilicity for Durable Oil/Water Separation. Colloids Surf. A 2019, 573, 222-229. (47) Cao, C. Y.; Cheng, J. Fabrication of Superhydrophobic Copper Stearate@Fe3O4 Coating on Stainless Steel Meshes by Dip-Coating for Oil/Water Separation. Surf. Coat. Technol. 2018, 349, 296-302. (48) Cao, Y. Z.; Chen, Y. N.; Liu, N.; Lin, X.; Feng, L.; Wei, Y. Mussel-Inspired Chemistry and Stöber Method for Highly Stabilized Water-in-Oil Emulsions Separation. J. Mater. Chem. A 2014, 2, 20439-20443.


29


Page 30 of 38

(49) Cai, Y. H.; Chen, D. Y.; Li, N. Y.; Xu, Q. F.; Li, H.; He, J. H.; Lu, J. M. A Facile Method to Fabricate a Double-Layer Stainless Steel Mesh for Effective Separation of Water-in-Oil Emulsions with High Flux. J. Mater. Chem. A 2016, 4, 18815-18821.


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TOC Graphic


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205x49mm (200 x 200 DPI)


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Schematic of the preparation and oil/water separation application of GTSSM. 274x123mm (200 x 200 DPI)



(a-d) SEM images of the GTSSMs with different mesh numbers: (a) 80, (b) 200, (c) 300, and (d) 400 mesh, respectively. (e-g) SEM images of the GTSSM (300-mesh) in different magnifications, and inset of (e) is the pore size distribution of the GTSSM. (h) EDS-element mapping images, (i) XRD pattern and (j) XPS full spectrum of the GTSSM. 775x489mm (96 x 96 DPI)


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(a-c) SEM images of the GTSSMs prepared by varying the amount of graphite in paste: (a) 0 g, (b) 0.1 g and (c) 1.0 g, respectively. (d) Schematic illustration showing the effect of graphite on the pore size regulation of SSM. 278x175mm (200 x 200 DPI)



(a) Photograph of water droplets on the GTSSM and the model of lotus leaf state. (b) Photograph showing rolling status of a water droplet on the GTSSM. (c) Silver mirror phenomenon of the GTSSM when being immersed in water. (d) Digital images of the wetting status of GTSSM after been immersed in water (left, colored by methylene blue) and oil (right, colored by Sudan III), respectively. (e) Lighting up an LED lamp by connecting it with the superhydrophobic coating on glass and the schematic illustration of its work mechanism. CAs of water droplets with (f) different pH values and (g) different concentrations of salt on the GTSSM. WCAs of the GTSSMs after (h) immersion in different solvents and (i) irradiation under UV light, for certain durations. 308x180mm (200 x 200 DPI)


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Optical images of different water-in-oil nanoemulsions before (a1-e1) and after (a2-e2) filtration; size distribution of the water droplets in feed and filtrate (a3-e3): (a) gasoline, (b) isooctane, (c) xylene, (d) dichloromethane, and (e) n-hexane, respectively. Separation efficiency (f) and oil flux (g) of the GTSSMs for separating various water-in-oil nanoemulsions. (h) Schematic illustration of the water coalescence, demulsification and seceding processes. 509x388mm (150 x 150 DPI)



(a) Schematic illustration of the friction test of GTSSM. (b) The liquid flux measurement after different abrasion numbers. (c) The separation efficiency and WCA after different abrasion numbers. (d) The variation of WCA using repair agent to deal with after abrasion. 255x171mm (200 x 200 DPI)


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Gate-Embedding Strategy for Pore Size ... - ACS Publications

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