Micro-Octahedron Cu₂O-Based Photocatalysis-Fenton for Organic Pollutant Degradation: Proposed Coupling Mechanism in a Membrane Reactor

The degradation efficiency of organic pollutants was enhanced with the combination of visible-light photocatalysis and Fenton catalysis upon the dual-functional catalyst Cu2O. As-prepared micro-octahedrons of Cu2O enclosed with eight (111) facets were proved to have photoactivity and Fenton activity. It was found that the decolorization rate of methyl blue (50 mg/L) in water increased from 68% in the photocatalysis process to 92% in the combined photocat-Fenton process for 120 min. The reaction duration was remarkably shortened from 120 to 20 min by membrane feeding of H2O2. The degradation reaction rate constant showed a 10-fold increase at k = 0.200 min-1 in the membrane-assisting visible/Cu2O/H2O2 system. The reduction of chemical oxygen demands (CODs) in industrial paper-mill wastewater (CODs = 813 mg/L) was 79% using the membrane-intensified oxidation approach. A synergistic merge of photoredox and copper catalysis could be realized upon fast collision, micromass transfer, and efficient electron transfer. The facet-dependent oxidation coupling mechanism is proposed to explain the mutual stimulating effect. Hence, the photocatalysis-Fenton membrane process is powerful to degrade persistent organic pollutants in water and wastewater.