Revealing the membrane fouling behavior and interfacial interaction mechanism in a combined visible light photocatalysis-ultrafiltration system for advanced purification of NOM

Abstract

A novel visible photocatalysis nanomaterials Bi2O3/rGO/TiO2 (BRGT) was combined with polyethersulfone membrane (PES) and ceramic membrane (CM), respectively, to investigate the natural organic matter (NOM) removal performance, membrane fouling behavior and interfacial interactions. The results showed that NOM removal mainly by superoxide radical-dominated photocatalysis followed by membrane rejection enhancing the removal of fluorescent humic and proteins. Compared with PES, CM could more effectively retain the low molecular weight acidic intermediates and transitional or/and hydrophilic organic fractionations generated by photocatalysis. The mixture of NOM with BRGT (without photocatalysis) reduced the reversible fouling of the PES, causing an increase in the interfacial energy barrier of the fouling layer, while the opposite phenomenon was observed for CM. The photocatalysis time affected the membrane fouling, with short photocatalysis times (5 min) causing an increase in irreversible fouling. Extending the photocatalysis time, the interfacial interaction of the PES dominated by Lewis acid-base repulsive interaction gradually increased. And the gradual decreased of interfacial interaction of CM dominated by Lewis acid-base and Lifshitz-van der Waals attractive interactions reduced the possibility of reversible and irreversible fouling, respectively. This study provided a deeper mechanistic understanding for the application of a novel photocatalyst in combination with ultrafiltration.