Research On The Preparation Of Bionic Super-wetting Surface And Its Oil-water Separation Performance

The increasingly serious pollution of oily wastewater has attracted widespread attention.Although traditional separation methods can treat oily wastewater,there are still many limitations.In recent years,with the development of bionics,researchers have prepared materials with special wettability to treat oily wastewater.These kind of special wettability materials show opposite wettability to water and oil,and show high efficiency in oil/water separation,which is of great significance to environmental protection and energy utilization.In this article,materials with special wettability are fabricated by chemical etching and low surface energy modification,electrodeposition,hydrothermal synthesis and freeze drying,electrostatic spinning method to separate oily wastewater.The effect of microstructure and chemical composition on surface wettability was studied,the mechanical stability and corrosion resistance of the surface were tested,and the oil-water separation mechanism was explored.The main conclusions are summarized as follows:(1)Fe foam with superhydrophobic/superlipophilic property was prepared through chemical etching and stearic acid modification.After annealing at 250?,the surface changed from superhydrophobic/superoleophilic to superhydrophilic/underwater superoleophobic.Re-modification by stearic acid can restore superhydrophobicity/superlipophilicity and realized the controllable conversion of wettability.Based on the unique wettability,the as-prepared foam could be used to separate various oil/water mixtures,and the separation efficiency was higher than 95%.The Fe foam with special wettability could on demand separate different kinds of oil/water mixtures,providing a new idea for the efficient separation of oily wastewater.(2)The Cu@Cu₂O membrane with special wettability was fabricated on the stainless steel surface via electrochemical deposition method.After the membrane was pre-wetted by water,the Cu@Cu₂O membrane surface showed superhydrophilic/underwater superoleophobic property,which could effectively prevent oil pollution.After pre-wetted with oil,the membrane exhibited superlipophilic/underoil superhydrophobic characteristics.Based on the special wettability and suitable pore size,the as-prepared Cu@Cu₂O membrane could be used to separate surfactant-stabilized oil-in-water and water-in-oil emulsions,and showed high separation efficiency.In addition,as visible light catalysis materials,Cu₂O could be applied to degrade organic pollutants under light irradiation.This kind of Cu@Cu₂O membrane could effectively separate oil/water emulsions and degrade organic pollutants,which have broad prospects in the oily wastewater treatment.(3)The GO/g-C₃N₄/TiO₂(GCT)foam with special wettability was prepared through hydrothermal synthesis and freeze-drying methods.The foam showed superhydrophilic/underwater superoleophobic and superlipophilic/underoil Superhydrophobic property,which can separate various oil/water mixtures with separation efficiency of 98%.Besides,it also showed super-high separation efficiency for various surfactant-stabilized emulsions(>99%).Thanks to the large specific surface area and negatively charged oxygen-containing groups of GO,the as-prepared GCT foam could selective adsorb organic pollutants.In addition,the g-C₃N₄and TiO₂in the GCT foam were used as light-responsive materials,which could degrade oil pollutants under visible light irradiation,endowing its excellent anti-oil fouling and self-cleaning ability.(4)Inspired by spider silk collecting water in air,the membrane with spindle-knot structure was prepared by electrostatic spinning method.Based on the spindle-knot structure of the membrane surface,small oil droplets in the oil-in-water emulsion can quickly accumulated on the membrane surface.In the emulsion separation process,oil droplets quickly gathered and floated to the water surface to form interfacial oil film,while water directly penetrated the membrane,the separation efficiency for various emulsion was higher than 99.9%.The artificial fiber with micron-sized spindle structure was prepared by dip coating method.The accumulation and movement process of oil droplets in the liquid medium were observed,the movement and aggregation process of oil droplets in the emulsion were analyzed,and the mechanism of emulsified oil droplet aggregation was explored.