Enhanced removal of tetracycline by sandwich layer composite membrane based on the synergistic effect of photocatalysis and adsorption

Environmental pollution has become increasingly serious, especially the abuse of tetracycline (TC) antibiotics, which has brought serious problems to human life. Therefore, the residual TC in the environment has become an urgent problem to be solved. To improve the efficiency of TC wastewater purification and solve the problem of powder material recovery during photocatalysis, a sandwich layer photocatalytic composite membrane with catalytic/adsorption synergistic effect was prepared in this study. The first layer of the composite membrane is composed of a polyether sulfone (PES) membrane loaded with UiO-66-NH2/Bi2.15WO6 (UN/BWO) photocatalyst (named as UN/BWO@PES), the middle layer is a support layer composed of polyester/cotton fabric, and the lower layer is composed of a calcium alginate/diatomite (CA@DE) membrane with adsorption for tetracycline (TC). Under dark conditions, the rejection percentage of TC by sandwich composite membrane (M4.5 D0.02-3) can reach 50.81%, while under light conditions, the removal efficiency of TC by M4.5 D0.02-3 can reach 93.94%. Even after four cycles of use, the removal percentage of TC by M4.5 D0.02-3 can still reach 87.10%. Therefore, the visible light responsive photocatalytic composite membrane developed in this study has dual advantages of photocatalysis and membrane adsorption filtration, and has enormous application potential in wastewater treatment, which can minimize membrane pollution and improve the reusability of photocatalysts.