Enhanced photogenic self-cleaning of superhydrophilic Al2O3@GO-TiO2 ceramic membranes for efficient separation of oil-in-water emulsions

Abstract

In the emulsion separation process, the adhesion of oil-contamination severely hampers the long-term operation of ceramic membranes, and photocatalytic membranes present a promising approach to mitigate membrane fouling and enhance membrane performance. The present study describes the fabrication of a novel Al2O3@GO-TiO2 composite photocatalytic membrane through a two-step dip-coating method. TiO2 particles were uniformly deposited onto the surface of the pristine membrane via a thermal coating method, while the pleated graphene oxide (GO) formed a laminar-flow-like coating through stirring-ultrasonication, ultimately being stably anchored to the composite membrane's surface by co-built connections with TiO2. Due to the successful coating of hydrophilic groups, the composite membrane exhibited super hydrophilic-underwater superoleophobic properties to separate stable water-in-diesel emulsions with excellent permeation flux (4347.17 L∙m−2∙h−1) and oil removal rate (94.98 %). The composite membrane showed excellent oil resistance stability and durability in severe environment hydrodynamic washout and cycling tests. In addition, the combined modification of GO-TiO2 endowed the composite membranes with strong photocatalytic ability, which made the membranes exhibit a good recovery of membrane performance in the separation of oilfield-produced water (OPW). The thick oil layer was completely removed by •OH, •O2– and 1O2 generated by UV irradiation excitation. After 6 h of operation, the flux and oil removal rate of the Al2O3@GO-TiO2 membrane were 31.91 % and 2.1 % higher than those of the Al2O3@TiO2 membrane, demonstrating enhanced light self-cleaning performance. The exceptional oil–water separation capability coupled with its efficient photocatalytic degradation potential positions the ceramic membrane as a promising solution for treating actual OPW.