Preparation Of Bacterial Cellulose/Titanium Dioxide/Zinc Oxide Multifunctional Superhydrophilic Membrane And Its Application To Wastewater Treatment

Global water contamination has become a major concern.Super-wetting membrane-based technology has received a lot of attention because of its easy operation,low energy consumption,and high efficiency to remove various pollutants from water.As a result,it is critical to create an updated multifunctional separation membrane that can be used for the efficient treatment of oil-bearing wastewater.Bacterial cellulose（Bacterial cellulose,BC）is a natural polysaccharide gel membrane made from the appropriate condition of cellulosic microorganisms.It has many advantages,such as good hydrophilicity,easy modification of nano-fiber network structure,excellent mechanical properties and so on which has a potential material for wastewater treatment.However,the tightened arrayed nanofibers and small pores limit its applications as a filtering membrane for oil/water separation with high efficiency.The presence of abundant hydroxyl groups on the BC microfibers facilitates the adsorption of metal oxide nanoparticles,these NPs improve the specific surface area of the BC and create adjustable pores in the membrane,which can help in selective permeation with a high flux rate.In a single semiconductor（TiO₂-NPs or ZnO-NPs）,quick recombination of electron-hole pairs occurs,which reduces their photocatalytic activity and makes their use difficult.The combination of the two is conducive to the migration of electron-hole pairs,which can improve the lifetime of charge carriers,and thus present an ideal combination pattern.In this study,the adsorption capacity of BC was used to combine TiO₂-NPs and ZnO-NPs into nanofibers and fabricate BC/TiO₂@ZnO composite membrane.Its structural properties were characterized and applications such as oil/water separation,bacteriostatic,photocatalytic activity,dye adsorption properties were investigated.BC/TiO₂@ZnO composite membrane was fabricated by sol-gel method,TiO₂-NPs were added into 1%（w/v）BC nano-slurry by sol-blending method,and Zn²⁺was added into the mixture to prepare ZnO-NPs.BC was served as the substrate,and BC/TiO₂@ZnO superhydrophilic multifunctional membrane was fabricated by vacuum-assisted filtration method.The two nanoparticles successfully combined on BC nanofibers were verified by ATR-FTIR,XRD,TGA,SEM results,etc.The composite membrane can successfully separate kerosene/water mixture with high efficiency and surfactant stabilized oil-in-water emulsion,and the maximum separation water flux is 8315.43±702.34 L?m^-2?h^-1,1498.65±74.65 L?m^-2?h^-1,respectively.The separation efficiency is above 99%.Excellent antifouling properties were investigated by edible soybean oil and dichloromethane model oil.The surface wetting results show that the underwater contact angle of dichloromethane is 151.4°,which confirms the underwater superhydrophobic characteristics of the composite membrane.The results of the inhibition zone and colony-forming unit method showed that the BC membrane had no bacteriostatic activity,while the BC/TiO₂@ZnO membrane could effectively inhibit the growth of S.aureus and E.coli,the bacteriostatic rate increased with the increase of ZnO-NPs content.We also investigated visible light photocatalytic degradation of pigments,Congo red adsorption properties,and mechanism exploration.The catalytic degradation of methylene blue rhodamine B pigments was achieved by BC/TiO₂@ZnO composite membrane under visible light.Owing to the unique affinity of Congo red molecules for cellulose,the composite membrane can effectively adsorb Congo red pigment in solution.