Hierarchical Ultrafiltration-Catalysis Ceramic Membrane for Enhanced Oily Wastewater Treatment: The Synergy Effect between High-Efficiency Catalysis and Separation

Abstract

Catalytic membranes that enable simultaneous micropollutant degradation during oil/water separation have emerged as a promising candidate for treating complex emulsified oily wastewater. However, this hybrid system suffers from membrane fouling and subsequent radical quenching. Herein, we overcome these challenges by developing a novel hierarchical filtration-catalysis ceramic membrane to achieve efficient gradient decontamination. This membrane comprises a top hydrophilic MWCNT layer deposited on a CuFe2O4-immobilized ceramic membrane to construct CCuFeCM. A pristine ceramic membrane (CM) and a CuFe2O4-immobilized membrane (CuFeCM) served as controls. Our results demonstrated that CCuFeCM presents the most alleviated fouling potential (∼18% of flux decline) and TOC removal (91%) when treating synthetic textile wastewater containing a mineral oil-in-water emulsion with RhB. Besides that, CCuFeCM achieves the highest PMS-based RhB degradation capability (100%) and initial reaction rate (0.684 min–1). Quenching experiments and EPR analyses show that SO4 –•, •OH, and 1O2 are responsible for the CCuFeCM/PMS oxidation system, and 1O2 is the dominant reactive species. The synergistic effect of oil separation and catalytic decomposition is mainly ascribed to the ordered arrangement of selective separation in advance to avoid interference with subsequent AOPs, which allows for micropollutants that are transmitted into internal membrane channels for confined catalytic oxidation. Furthermore, replication filtration tests indicate that CCuFeCM shows durable stable degradation and antifouling performance after simple cleaning. The specific functionality of oil isolation, catalyst anchor, and mass transfer effect reaction compartmentation provides a novel strategy for efficient gradient removal of multiple pollutants in water, which highlights promising application potential under realistic conditions.