Removal Performance Of Modified G-C₃N₄ Photocatalytic Membrane For Organic Pollutants And Its Self-cleaning Ability

With the development of social economy and technology,a large number of toxic and harmful chemicals,such as soluble organic dyes,antibiotics and plastic wastes,have been produced,leading to the aggravation of the global water pollution crisis.Membrane separation technology as an effective and safe means of water treatment,has been widely used,but in the process of filtering for a long time,the accumulation of pollutants in the membrane surface,cause the clogging in the hole of film,and the formation of membrane fouling,shorten the life span of the membrane,increased operating costs,and reduce the processing efficiency of pollutants,which limits large-scale application of membranes in wastewater treatment.Recently,the combination of photocatalytic technology and membrane separation technology has attracted people’s attention.The photocatalytic membrane not only enables the traditional membrane to have the separation and selection properties,and degrades pollutants under light irradiation,but also enables the membrane to achieve the performance of self-cleaning and alleviating membrane fouling.This study conducted the research of removal performance for organic pollutants and self-cleaning ability of modified g-C₃N₄photocatalytic membrane.Firstly,this study dissolved melamine and cyanuric acid and urea in dimethyl sulfoxide（DMSO）as precursors to fabricate MCU（DMSO）-C₃N₄with excellent photocatalytic performance.Filtering it via vacuum as photocatalytic layer on the PVDF membrane,then orderly filtering polyethylene glycol and glutaraldehyde as crosslinkers.Thus,MCU-C₃N₄/PVDF membrane with different content of MCU-C₃N₄was prepared.Secondly,AFM and FE-SEM were used to characterize the surface of MCU-C₃N₄/PVDF membrane,and examined the photocatalytic efficiency and self-cleaning performance.The results show that the membrane flux decreases with the increase of the content of MCU-C₃N₄.The photocatalytic efficiency of MCU-C₃N₄/PVDF for degrading rhodamine B and tetracycline hydrochloride was 84.24%and 71.26%,respectively,which was 8 times higher than that of the original PVDF membrane.A four-stage filtration system was used to evaluate the self-cleaning performance of photocatalytic films and the flux recovery rate（FRR）was calculated.After filtrating 1wt%alginate solution,fully fouled MCU-C₃N₄/PVDF membrane was irradiated via visible light（λ>420 nm）for 30 min,the maximum of FRR reached 91%.Meanwhile,the proportion of reversible pollution resistance（Rr）was higher than that of irreversible pollution resistance（Rir）,which took the dominant position,indicating that the degree of membrane fouling could be alleviated by MCU-C₃N₄/PVDF membrane after light irradiation.This new method of membrane modification with MCU-C₃N₄gives us a new understanding of the photocatalysis and self-cleaning properties of photocatalytic membrane and provides a theoretical basis for its wide application.