Fabrication And Oil/Water Separation Performance Of Durable Superhydrophobic Sponge

Frequent oil spill accidents and discharge of industrial oily wastewater caused serious harm to the ecological environment,and brought immeasurable economy loss.By virtue of low cost,high porosity,low density and good compressibility,the sponge has become an ideal adsorption material for oil/water separation.Aiming at the problems that the modifiers used in most reported sponges are easy to fall off,resulting the low separation efficiency,and some modifiers are prone to secondary pollution.This work fabricated a novel superhydrophobic sponge,respectively for heterogeneous oil/water mixture and oil/water emulsion separation.The dynamic/static wetting behavior of the sponge in the air was studied,optimal preparation conditions and key preparation factors were investigated.In addition,oil/water separation performance,recycling performance,superhydrophobic stability in complex environments and mechanical properties of the sponge were investigated.Firstly,through one-step dipping method,polydimethylsiloxane(PDMS)was employed to bind the hydrophobic SiO2 nanoparticles and WS2 microparticles onto sponge,obtaining the superhydrophobic PDMS@SiO2@WS2 sponge.SEM,EDS,XRD,FTIR and other characterization results observed the micro/nano rough structure of the sponge and three modified components existing,dynamic/static wetting behavior exhibited a large amount of air was captured on the surface of sponge in order to prevent water droplets and promote the infiltration of oil droplets.The average water contact angle(WCA)of PDMS@SiO2@WS2 sponge was 158.8°.The optimal preparation conditions were determined by WCA:the mass ratio of SiO2 to WS2 was 3:1,the impregnation time was 50 min,and impregnation solvent selected n-hexane.PDMS@SiO2@WS2 sponge could separate 13 types of common oil and organic solvents,ranging from 21 to 112 times its own weight,and the separation efficiency was more than 99.5%,oil purity after separation was more than 99%,displaying excellent oil/water separation performance.DFT calculation showed that the three modified components had no adsorption towards H2O molecules,while SiO2 and WS2 had exothermic adsorption with different degrees towards benzene molecules,and Si02 had the strongest adsorption with-5.346 eV adsorption energy.PDMS@SiO2@WS2 sponge had the potential to deal with marine oil spill accident:the flux of continuous oil/water separation was up to 104.9 L·h-1·g-1.The adsorption capacity remained stability during 10 compression and adsorption cycles,and the stress only decreased by 3.9%during 10 loading and unloading compression cycles.PDMS@SiO2@WS2 sponge could maintain superhydrophobic stability in high temperature,corrosion,exposure and turbulent marine environment.In regard to emulsion separation system,hydrophobic modified UiO66-SiOR particles were introduced to construct a superhydrophobic PDMS@SiO2@UiO66SiOR sponge.XRD,FTIR,EDS and other characterization results proved the existing of SiO2 and UiO66-OSiR particles.The WCA of the sponge analyzed was 160.7°,and oil contact angle analyzed by OCA was 0°.PDMS@SiO2@UiO66-OSiR sponge could separate common water-in-oil emulsions of toluene,paraffin,petroleum ether,and nhexane with droplet sizes above 5 μm.The separation efficiency was more than 98%,and the separation flux was higher than 970 L·m-2·h-1.The emulsion separation performance was closely related to pore size and wettability of the sponge:small pore size contributed to capture the emulsion droplets,and strong superhydrophobicity was beneficial to the demulsification.PDMS@SiO2@UiO66-OSiR sponge had superior mechanical properties and super-hydrophobic stability.The stress only decreased by 5%during 10 loading/unloading compression cycles with a constant strain of 60%;WCA of the sponge in organic solvent immersion and ultrasonic environment was above 152°.In this work,the wettability of the sponge material was tuned by one-step dipping method,promoting the sponge to achieve superhydrophobic stability in complex environment while separating oil/water mixture efficiently,providing a new idea for the remediation of marine oil spill accidents and the treatment of industrial oily wastewater.