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

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.