Inspired by Stenocara Beetles: From Water Collection to. High-Efficiency Water-in-Oil Emulsion Separation

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1 Inspired by Stenocara Beetles: From Water Collection to High-Efficiency Water-in-Oil Emulsion Separation -Supporting Information- Xinjuan Zeng 1, Long Qian 2, Xianxia Yuan 3, Cailong Zhou 1, Zhaowen Li 1, Jiang Cheng 1, Shouping Xu 1, Shuangfeng Wang 1, Pihui Pi 1*, Xiufang Wen 1* 1. School of Chemical and Chemical Engineering, South China University of Technology, Guangzhou, , P.R.China 2. Department of Biology and Center for Genomics and Systems Biology, New York University, NY 10003, USA 3. Department of Chemical Engineering, Shanghai Jiao Tong University, Shanghai,, P.R.China Supporting Information contains: Supplementary Methods Supplementary Discussions Supplementary Figures S1 S7 Supplementary Tables S1 S2

2 Supplementary Methods Synthesis of the fluorinated block copolymer P(MMA-BA-HEMA-SMA)-b- PFMA The synthesis process of the fluorinated block copolymer have been reported previously by our group. 1 In this approach, P(MMA-BA-HEMA-SMA)-b-PFMA was obtained using macro-initiator (P(MMA-BA-HEMA-SMA)-Br) (4.0 g) and FMA (2.1g) via a classic ATRP method. The macro-initiator (P(MMA-BA-HEMA-SMA) -Br) was first synthesized and monomers were added with weights MMA (4.6g), BA(7.0g), HEMA(2.4g), and SMA(3.45g). Supplementary Discussions Structural analysis of the fluorinated block copolymer Fluoropolymer P(MMA-BA-HEMA-SMA)-b-PFMA were obtained by block copolymerization of MMA, BA, HEMA, SMA and PFMA via the typical ATRP method. The chemical structure of P(MMA-BA-HEMA-SMA)-b-PFMA was verified by FTIR (Figure S1a) and 1 H NMR (Figure S1b). Fig 1a shows the characteristic absorption peaks located at 1452 and 1338 cm -1, representing the CH 3 groups in MMA. Three peaks at 2957, 2927 and 2854 cm -1 were due to the stretching vibration of -CH 3 and -CH 2 - in HEMA, BA, SMA and FMA. The wide absorption band at 3658 cm -1 indicated the stretching vibration of -OH from HEMA. The strong peak at 1731 cm -1 was ascribed to the stretching vibration of carbonyl group, indicative of the presence of methacrylate. Two peaks at 1241 and 1149 cm -1 were attributed to -CF 2 and -CF 3 groups from FMA, and the two medium bands at 703 and 655cm -1 were resulted from a combination of rocking and wagging vibrations of -CF 2 -CF 3. The

3 peaks at 963 and 846cm -1 were characteristic of BA. The peak at 748cm -1 was ascribed to -(CH 2 )n-(n 4) group from SMA. Meanwhile, the absence of double bond at 1640cm -1 implied successful copolymerization when MMA, HEMA, BA, SMA and FMA monomers had been covalently bonded together. The fluorinated block copolymer structure was further confirmed by 1 H NMR spectrum (Figure S1b). The peak at 3.62 ppm (a) was attributed to OCH 3 from MMA, and the peaks at 3.86 ppm (b), and 4.1ppm (c, d,e) were attributed to -OCH 2 - in BA, HEMA and SMA. The protons at 4.4 ppm (f) and 2.35 ppm (g) were ascribed to -OCH 2 - and -CH 2 - in FMA. The peak at 1.29 ppm was much stronger and attributed to -CH 2 - from BA and -(CH 2 )n-(n 4) from SMA, indicative of the presence of SMA. These results indicate that the synthetic product was the block polymer of P(MMA-BA-HEMA-SMA)-b-PFMA. Zeta potential of hydrophilic silica microparticles The surface charge of microparticles is often approximated as the zeta potential which is considered a key parameter to control the colloidal stability in polar solvents. 2 The charged state of the hydrophilic silica microparticle aqueous suspension has been characterized by Zetasizer Nano ZS. The observed value is mv and smaller than -30 mv in Figure S2, and therefore the silica particles can disperse homogeneously in water and adhere tightly on the stainless steel mesh surface by electrostatic interactions. For the silica microparticles, this charge is mainly due to the dissociation of the surface silanol groups Si OH, and the surface of silica microparticles is hydrophobic. Wetting property of S-SSM and SBS-SSM

4 As shown in Figure S3, the shape of water droplets, which were dyed blue, on the S-SSM and SBS-SSM was like a ball. After the oil droplets were dipped onto S-SSM and SBS-SSM, they spread and penetrated them rapidly. It suggests that S-SSM and SBS-SSM was superhydrophobic and superoelophilic, and hydrophilic silica micropartilces did not decrease the lipophilicity of the SBS-SSM. The separation performance of clean stainless steel mesh Prior to confirming the separation efficiency of SBS-SSM, clean stainless steel mesh was used for separating water-in-oil emulsion. As shown in Figure S3, there were no noticeable differences between the surfactant-stabilized water-in-toluene emulsion before and after separation by clean stainless steel mesh. It is dramatically demonstrated that clean stainless steel mesh had no ability to separate water-in-oil emulsions. Droplet size distributions of surfactant-free emulsions in feed and filtrate Optical microscopy images of surfactant-free water-in- toluene emulsions before and after filtration by S-SSM and SBS-SSM are shown in Figure S4. Emulsion droplets in micrometer size are clearly observed in the feed solution. However, no droplets were observed in both Filtrate I and Filtrate II, indicating the separation efficiency of the surfactant-free water-in-oil emulsion samples are not much different for the two types of mesh filters. Droplet size distributions of surfactant-stabilized emulsions in feed and filtrate Optical microscopy images of surfactant-stabilized water-in-isooctane emulsions before and after filtration by S-SSM and SBS-SSM are shown in Figure S5. Small

5 water droplets were still present in the filtrate by S-SSM, while none were observed in the filtrate by SBS-SSM. Recycle separation capability of SBS-SSM filter Surfactant-stabilized water-in-isooctane emulsion was poured into SBS-SSM filter and the separation was achieved driven only by gravity where oil passed through the filter and water was rejected. The SBS-SSM filter was simply dried by an air blower after every cycle. The change of oil purity with cycle times is shown in Figure S7. It can be seen that the oil purity exceeded 99.91% after five cycle. It indicated a good cyclic performance of SBS-SSM filter. Comparison between some state-of-the-art materials There are a few literatures about SSM filter to separate oil emulsions, and the pore size of SSM filter comparable with or small than the emulsified water droplets are commonly explored in oil emulsions separation. Most of the SSM filters were used to separate the mixture of oil and water, which were layered and did not need to demulsify ( Table S1 ). We used SSM with pore size of 10μm to separate emulsified water droplets with size from 3 nm to 6 μm. Comparing with other kinds of state-of-the-art materials, SBS-SSM had outstanding demulsification property and high separation efficiency (Table S2).

6 Supplementary Figures Figure S1. FTIR spectra (a) and 1 H NMR spectra (b) of P(MMA-BA-HEMA-SMA) -b-pfma

7 Figure S2. Zeta potential characterization of silica microparticles aqueous suspension

8 Figure S3. Photographs of water (dyed blue) and oil drops onto (a) S-SSM and (b) SBS-SSM.

9 Figure S4. Photographs of the surfactant-stabilized water-in-toluene emulsion (a) before and (b) after separation by clean stainless steel mesh.

10 Figure S5. Optical microscopy images of the surfactant-free water-in-toluene emulsion before and after separation. FiltrateⅠ and filtrate Ⅱ are the samples separated by S-SSM and SBS-SSM, respectively.

11 Figure S6. Optical microscopy images of the surfactant-stabilized water-in-isooctane emulsion before and after separation. Filtrate I and filtrate II are the samples separated by S-SSM and SBS-SSM, respectively.

12 Figure S7. The change of oil purity in filtrate with cycle times when separating surfactant-stabilized water-in-isooctane emulsion by SBS-SSM filter. After separation in every cycle, the oil-polluted SBS-SSM filter was dried by an air blower.

13 Supplementary Tables Table S1. Comparison between some modified SSM filters Filter type Water/oil mixture type Separation efficiency Method for separation efficency Reference SBS-SSM with pore size of 10μm polyaniline coated SSM with pore size of 5 μm Polyaniline coated SSM with pore size of 5 μm SiO 2 NPs deposited stainless steel fiber with pore size of 5 μm Surfactant-stabilized water-in-oil emulsion Surfactant-stabilized water-in-oil emulsion Surfactant-free oil-in-water emulsion Surfactant-free oil-in-water emulsion Oil purity (wt%) This work 99.9 Oil purity (wt%) 3 40mg/L (about 99.5) Oil contents in the collected filtrate > 95.0 Water purity (wt%) 5 4 Polydivinylbenzene modified SSM with pore size of 12.5 μm Polyaniline coated SSM and polypyrrole coated SSM with pore size of 12.5μm Superhydrophobic CS and silica coated SSM with pore size of 47 μm Fluoropolymer@silica hybrid coated SSM with pore size of 47μm Oil/ water mixture Oil purity (wt%) 6 Oil/ water mixture >98.0 Oil purity (wt%) 7 Oil/ water mixture 99.0 Oil volume ratio 8 Oil/ water mixture 99.0 Oil mass ratio 9 ZnO nanorod array-coated SSM with pore size of 74 μm Oil/ water mixture 97.0 Oil mass fraction ratio 10 Epoxy/attapulgite nanocomposite coat SSM with pore size of 149 μm Oil/ water mixture 98.0 Not metion 11

14 Table S2. Comparison between some state-of-art material filters Material Emulsion Emulsifier Demulsifiction efficiency Reference SBS-SSM with pore size of 10μm W/ O (1% V/ V) 1-2 mg/ ml Span This work PVDF membrane with pore size of 0.22 μm W/ O (1% V/ V) 2.5mg/mL of Span Hydrocarbon modified HESM-18 with pore size of μm W/ O (10% V/ V) 0.5mg/mL of Span Ethyl cellulose polymer W/ O(5% V/ V) Without Superhydrophobic filter paper W/ O (0.86% V/ V) 0.4g/ 58 ml Span Calcium sulphate hemihydrate particles W/ O (1% v/ V) 1mg/ ml Span

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