Supporting Information Nanosecond laser induced underwater superoleophobic and underoil superhydrophobic mesh for selective oil/water separation Zhongxu Lian, Jinkai Xu, Zuobin Wang, Zhanjiang Yu, Zhankun Weng, Huadong Yu*, National and Local Joint Engineering Laboratory for Precision Manufacturing and Detection Technology, Changchun University of Science and Technology, Changchun, 130022, China International Research Centre for Nano Handling and Manufacturing of China, Changchun University of Science and Technology, Changchun, 130022, China * Corresponding Author: yuhuadong@cust.edu.cn 1
Figure S1 Diagram of the fabrication process for the brass mesh with the underwater superoleophobicity and underoil superhydrophobicity. Figure S2 EDXS analysis of the brass meshes before and after the laser treatment process. 2
Figure S3 Diagram of wettability behavior on air/liquid/solid and oil/water/solid systems. (a) Water droplet on the treated mesh wire in air. (b) Oil droplet on the treated mesh wire under water. (c) Oil droplet on the treated mesh wire in air. (d) Water droplet on the treated mesh wire under oil. Figure S4 Wetting behavior of the untreated mesh toward (a) water and (b) light oil, respectively. The light oil of kerosene was selected as the detecting probe. 3
Figure S5 Wetting behavior of the treated mesh for the 1,2-dichloroethane (DCE) contact angle under water and water contact angle under kerosene with the conversion times (the conversion condition: cleaning the mesh with ethanol). Figure S6 Oil water separation efficiency of kerosene water mixture after 20 repeated separation tests. 4
Figure S7 Plot showing the percentage of the separation efficiency for the treated mesh. Oil water mixtures were prepared using kerosene and either NaCl (3.5 wt%), HCl (ph = 1), NaOH (ph = 13), or hot water (80 C). Figure S8 Contact angles of kerosene under different solutions: NaCl (3.5 wt%), HCl (ph = 1), NaOH (ph = 13), or hot water (80 C). 5
Figure S9 (a,b) Schematic illustration showing the formation of the water/oil layer on the treated mesh. (c,d) Schematic illustration explaining the oil/water-repellent property of the water/oil layer by the Laplace equation. (e,f) When the pressure reaches the limit (α = 0 ), the liquid of the wetting phase will penetrate through the mesh. Table S1 Surface tension values of different test liquids. Liquid Surface tension (mn/m) Density (g/cm3) Water 72.8 1.00 1,2-dichloroethane 33.3 1.26 Soybean oil 30.3 0.92 Chloroform 27.5 1.50 Dodecane 25.4 0.75 Kerosene 24.1 0.80 6
Oils tend to form a film (or a pancake-like bubble) on the water surface, so an approximate equality can be added: 1 γ L1L 2 γ L1A γ L2A where γ L1L2 is the surface tension of liquid (L1) liquid (L2) interface, γ L1A is the surface tension of the liquid (L1) air interface, and γ L2A is the surface tension of the liquid (L2) air interface. The surface tensions of different liquid air interface are shown in Table S1. 2,3 Therefore, according to the eqn, the surface tension of liquid (L1) liquid (L2) interface (γ L1L2 ) can be calculated, shown in Table S2. Table S2 Surface tension values of liquid (L1) liquid (L2) interface (γ L1L2 ). Liquid(L1) liquid(l2) Surface tension (mn/m) Water 1,2-dichloroethane 39.5 Water soybean oil 42.5 Water chloroform 45.3 Water dodecane 47.4 Water kerosene 48.7 7
Figure S10 Schematic illustration of the separation of light (left) or heavy (right) oil water mixtures. The non-wetting phase droplets cannot penetrate through the mesh once they are prewetted with the liquid of the wetting phase. The wetting behavior (middle) suggests that the water/oil layer on the prewetted mesh acted as a selective gating liquid, which prevents the permeation of oil(up)/water(down). 8
Figure S11 Liquid (oil and water) fluxes of the treated mesh. REFERENCES [1] Hejazi, V.; Nosonovsky, M. Wetting Transitions in Two-, Three-, and Four-Phase Systems. Langmuir 2012, 28, 2173 2180. [2] Yong, J. L.; Chen, F.; Yang, Q.; Huo, J.; Hou, X. Superoleophobic Surface. Chem. Soc. Rev. 2017, DOI: 10.1039/c6cs00751a [3] http://www.surface-tension.de/. 9