Modification And Biofouling Control Of Highly Efficient Photocatalytic PVDF Membranes

In the background of deteriorating environment,bacterial and fungal pollution are threatening human health.Photocatalytic sterilization technology is a promising environment-friendly technology that can achieve efficient removal of microorganisms in water.However,nanometer-sized powder photocatalysts had problems such as limited activity and difficulty in recycling.Membrane separation technology is an effective water treatment technology,but its wider application in water treatment is restricted due to the issue of membrane fouling.So,coupling photocatalytic technology with membrane separation technology can construct a multifunctional separation membrane with photocatalytic ability(photocatalytic-membrane system).Coupling gives us the opportunity to integrate self-cleaning performance into membrane runs during which biofouling could be resisted,enabling long-term operation.As a new generation of composite membrane,photocatalytic membrane has great research and development value and has broad prospects in the field of water treatment in the future.The research content of this paper mainly includes three aspects:the development of a high-efficiency photocatalytic bactericide:coating chitosan(CS)on spherical carbon nitride(CNS);the synthetic high-efficiency photocatalytic bactericide(4CS/CNS)mixed with polyvinylidene fluoride(PVDF)membrane to construct a photocatalytic-membrane system to resist bacterial pollution;turning the research perspective to fungi,looking for a high-efficiency photocatalytic fungicide Zn-Ti layered double hydroxide(Zn-Ti LDH).The specific research contents are as follows:(1)CNS was prepared by hydrothermal and calcination methods,and CS was coated with cross-linking method to obtain sample 4CS/CNS.S.aureus and E.coli were used as model bacteria to test the photocatalytic efficiency of the samples.The success of the synthesis was proved by XRD,FTIR,SEM and TEM;the optimal experimental conditions were found through the initial bacterial concentration,p H value,catalyst concentration and cycle stability tests,and it was proved that4CS/CNS could be sterilized in complex water environments and exhibited excellent aging resistance;the efficient sterilization results were verified by SEM,CLSM and sterilization tests;the sterilization mechanism was proposed through the above tests and K~+leakage tests.(2)4CS/CNS was incorporated into PVDF membrane by spin coating method to obtain4CS/CNS/PVDF-0.6.S.aureus and E.coli were used as model bacteria to test the anti-biological(bacterial)contamination ability of samples.The successful preparation of the membrane was proved by XRD and SEM;the properties of the membrane were tested by Uv-vis DRS,porosity,water absorption value,water contact angle and Zeta potential;the death of bacteria was verified by SEM and CLSM;the membrane flux(cycle),interception rate(cycle),and bactericidal tests tested the anti-bio-fouling ability;through the above tests,the anti-biofouling mechanism was proposed.(3)Zn-Ti layered double hydroxide(Zn-Ti LDH)was prepared by hydrothermal method,and Aspergillus fumigatus was used as a model mold to test the photocatalytic efficiency of the sample.The success of the synthesis was proved by XRD,FTIR,SEM and XPS;the optimal experimental conditions were found through the initial bacterial concentration,p H value,catalyst concentration and cycle stability tests,and it was proved that Zn-Ti LDH could be extinguished in a complex water environment.The efficient sterilization results were verified by SEM,CLSM,sterilization tests;through capture agent experiments and K~+leakage tests,a possible mechanism of fungi sterilization was proposed.