Supporting Information

Transcription

1 Supporting Information Amphiphobic Polytetrafluoroethylene Membranes for Efficient Organic Aerosol Removal Shasha Feng, Zhaoxiang Zhong*, Feng Zhang, Yong Wang, Weihong Xing* State Key Laboratory of Materials-Oriented Chemical Engineering, National Engineering Research Center for Special Separation Membrane, NanjingTech University, Nanjing , China Corresponding Authors: * (Z. Z.); (W. X.) S-1

2 Pore Size Distribution of Membranes The pore size of the membranes were test by a pore-size distribution analyzer (PSDA-20, China) based on a bubble point method. A membrane is wet-out with an appropriate test fluid such as isopropyl alcohol. The inverse pressure pore size relationship for a cylindrical pore is expressed by the equation: (D=4γcosθ/ P) where D is pore diameter, γ is the surface tension of wetting fluid, θ is the contact angle of wetting fluid on membrane surface, and P is the pressure difference between gas and liquid. The results of the samples is shown in Fig. S1, the most probable distribution of pristine membrane is 5.8 µm. Without ZnO-ALD treatment process (Fig. S1(b)), a bimodal distribution of pore size demonstrated the generation of big pores, which happened in the dipping and plasma process. For the ZnO-ALD treatment membrane, the fibrils became thicker than the pristine ones under the effects of ALD process and monomer grafting process. Therefore, the most probable distribution of PFDAE-grafted ZnO@PTFE is 4.5 µm (Fig. S1 (c)). Figure. S1. Pore size distribution of different samples (a)pristine membrane; (b)pfdae-grafted membrane;(c)pfdae-grafted ZnO@PTFE membrane. S-2

3 The Structure of PFDAE and the Grafted mechanism According to XRD, XPS and FT-IR spectrograms and theoretical investigations, 1H,1H,2H,2H-perfluorodecyl acrylate (PFDAE) were grafted on the membrane with the C=C broken and combined with the free radical. Without the ALD process, the active site was produced by plasma process during the graft process. The ZnO-ALD process result in a new structure (Zn-O-Zn and Zn-F) Fig. S2. The monomer may grafted on the fluorocarbon chain at the position marked by red triangles. Figure S2. The mechanism of ZnO-ALD and grafting monomer process. The Relationship between ALD Cycles and Liquid Contact Angle The surface wettability was characterized by contact angle measurements (DropMeterA-100P, China). 5 µl hexadecane or water was dropped on different regions of the membranes. The experiment was triplicated for averaging and standard deviation values and each droplet stayed on the samples for 30 s before the test. The ZnO-ALD process may lead to the CA drop to a low level, since ZnO is a hydrophilic material. 1 Two different deposition cycles were used 70 (Fig. S3 (b)-1) and 150 (Fig. S3 (b)-2). As shown in Fig. S3 (b)-1, the fibrils were smooth due to sparse deposition of the ZnO particles on the fibers. The hydrophilic property of the ZnO leads to lower water contact angle. However, when the deposition cycles of the ALD process was increased to 150, the size of ZnO particles became bigger and the fiber surfaces became rougher than that of the lower deposition cycles. The rough surfaces affect the anti-wetting property, 2 causing the water contact angle to increase a little as compared to of lower deposition cycles. Table S1 shows the contact angle values of different samples. S-3

4 (a) Contact angle/deg OCA of ZnO@PTFE OCA of PFDAE-grafted ZnO@PTFE WCA of ZnO@PTFE WCA of PFDAE-grafted ZnO@PTFE ALD cycles (b) (c) Figure.S3 (a) Water/oil contact angle of ZnO@PTFE membrane and PFDAE-grafted ZnO@PTFE membrane; (b) SEM image and schematic of membrane with deposition cycle of 70; (c) SEM image and schematic of membrane with deposition cycle of 150. Table S1. The contact angle of different samples. Samples Water contact angle/degree Oil contact angle/degree Pristine membrane 122± PFDAE-grafted membrane 145.2± ±2.1 ALD70 cycles membrane 136.0± ±0.5 ALD100 cycles membrane 127.2± ±0.5 ALD120 cycles membrane 132.2± ±0.5 ALD150 cycles membrane 141.3± ±0.5 The Optimized PFDAE Concentration S-4

5 We have measured the water and oil contact angle of the samples to evaluate the effects of PFDAE concentration. PFDAE was first dissolved in ethyl alcohol with its concentration 40%, 60%, 80%, and 100%. Then the solution with different concentration was grafted on the membrane by the plasma process. The water and oil contact angle were used to evaluate the optimized PFDAE concentration. Fig. S4 shows that he oil or water contact angle was increased along with the concentration of PFDAE. So the best concentration of PFDAE is 100%. 160 Water contact angle Oil contact angle 140 Contact angle/degree (1) (2) (3) Samples (4) (5) Figure S4. The water and oil contact angle of different samples; (1) pristine membrane; (2) 40% PFDAE-alcohol solution-grafted ZnO@PTFE membrane; (3) 60%; (4) 80%; (5) 100%. Video S1 & Video S2 The schematic representation of the oil aerosol filtration process The videos were carried out to demonstrate the schematic of oil filtration process. Membranes were put on a flat and rotate it about 80 degree. Hexadecane was dyed by oil soluble yellow (Yongfa chemical Co. Ltd). The oil droplets was ejected on the surface of the membrane by the injector. The oil easily infiltrated the pristine membrane, while for amphiphobic membrane, the oil droplets rolled down from the surface quickly. Fig. S5 shows the surface morphologies after oil aerosol filtration. The images were captured by Tabletop Microscope (Hitachi-TM3000, Japan). The oil composition adhered on the membrane surface and turned into a layer of oil-film (Fig. S5(a)), resulting in the sharp increase of the filtration pressure drop from 0.5 kpa to 3.3 kpa. For the modified membrane, the pore structure was retained after the S-5

6 (b) (a) Figure S5. Surface morphologies after oil aerosol filtration: (a) pristine membrane; (b) PFDAE-grafred membrane. filtration. Filtration Performance of PFDAE-grafted Membrane The filtration performance of PFDAE-grafted membrane without ZnO is shown below (Fig. S6), the operation condition is the same with PFDAE-grafted membrane in the manuscript. The outlet oil aerosol concentration was about 800 mg m-3, which is much higher than the membrane with ZnO-ALD. Figure S6. Oil aerosol filtration result of PFDAE-grafted membrane. References 1. Li, G.; Yi, Z.; Wang, H.; Jia, C.; Zhang, W., Factors Impacted on Anisotropic Photocatalytic Oxidization Activity of ZnO: Surface Band Bending, Surface Free Energy and Surface Conductance. Applied Catalysis B: Environmental 2014, , Tian, Y.; Su, B.; Jiang, L., Interfacial Material System Exhibiting Superwettability. Adv Mater 2014, 26 (40), S-6