Underwater Oleophobic Silk Fibroin-based Membranes For Oily Wastewater Treatment

Oil spill pollution accidents occur frequently in oil field exploitation and petroleum transportation projects.In addition,a large amount of oily wastewater would be discharged in industrial production,which poses a serious threat to the earth’s ecosystem and the health of animals and plants.Therefore,there is an urgent need to develop an energy-saving and environmentally friendly oily wastewater treatment method.In recent years,there are mainly two kinds of oil-water separation technologies based on wettability difference:selective filter and superhydrophobic/superlipophilic adsorption.In this paper,three kinds of silk fibroin protein based membrane materials were prepared by spraying for oily wastewater,using silk fibroin as binder,loading functionalized nanomaterials and metal oxides,to construct micro/nano-scale structures,regulate the surface energy and realize the separation and treatment of oily wastewater.The main contents are as follows:（1）Palygorskite-silk fibroin hydrophilic-underwater superoleophobic composite membrane was prepared and oil-water separation performance was tested.The hydrophilic palygorskite-silk fibroin coating material was sprayed on the surface of mesh to achieve the purpose of surface modification,and a hydrophilic/underwater superoleophobic coated mesh was prepared.The results showed that the water and oil contact angles of the coated mesh resched 30°and 156°,respectively.By simulating the oil-water separation experiment,the oil/water separation efficiency was 99.7%,and the separation efficiency remained above 98%after 50 cycles.（2）Si O₂-silk fibroin hydrophilic-oleophobic composite membrane was prepared and oil-water separation performance was tested.To improve the hydrophilicity of the mesh,the hydrophilic/underwater superhydrophobic mesh was prepared by the composite of hydrophilic nano-silica and silk fibroin protein.The water and oil contact angles reached 10°and 151°,respectively.After 50 cycles,the oil/water separation efficiency is still 98.6%.Through the simulation experiment of different oil,it is proved that the coated mesh can adapt to different kinds of oil.And it has a certain mechanical stability,can adapt to different environments.（3）Zinc oxide-silicon dioxide-silk fibroin superhydrophilic-superoleophobic composite membrane was prepared and oil-water separation performance was tested.The water contact Angle of the composite membrane material was 3°,and the oil-water separation efficiency is up to 99.8%.After 50 cycles,it can still be close to99%,which proves the excellent stability of oil and water separation.At the same time,the separation efficiency is still very stable in oil-water separation experiments with different p H values of oily wastewater and different types of oils.In addition,the mesh also exhibits a photocatalytic effect on MB dyes and a certain antibacterial property.