Photocatalytic Self-Cleaning ZnO-Decorated Ceramic Membranes for Rhodamine B Degradation

The increasing occurrence of persistent and bio-recalcitrant organic pollutants in aquatic environments necessitates the development of more resilient and efficient water treatment technologies. Conventional treatment processes often fail to remove such stable contaminants, prompting growing interest in integrated advanced systems. Photocatalytic membranes represent a promising solution due to the synergistic combination of separation and catalytic degradation. In this study, ZnO thin films were deposited by spin coating onto smectite–zeolite ceramic membranes (MS10/Z90), with one to three layers applied to control catalyst thickness (M1–M3). SEM analysis showed that increasing the number of layers led to a thicker, more homogeneous ZnO coating, while XRD confirmed enhanced crystallinity and larger crystallite size. Water permeability decreased from 623 L.h-1.m-2.bar-1 for the uncoated MS10/Z90 membrane to 506, 439, and 350 L.h-1.m-2.bar-1 respectively for M1, M2, and M3 after coating. Photocatalytic performance was assessed using Rhodamine B (RhB) as a model dye, achieving degradation efficiencies of 83.0%, 94.6%, and 99.1% for M1, M2, and M3, respectively, following pseudo-first-order kinetics. The free radical scavenging assays confirmed that hydroxyl radicals (•OH) were responsible for the RhB conversion.These results highlight the key influence of ZnO layer thickness and mass transfer on photocatalytic performance, de-monstrating the multifunctionality of ZnO-coated membranes, including efficient pollu-tant degradation and self-cleaning capability.