Highly efficient Cu-BiOCl catalysts for continuous microwave-assisted water treatment

Abstract

The accelerated impacts of climate change have led to increased variability in raw water quality, compromising the efficiency of conventional water treatment facilities and challenging regulatory compliance. Microwave (MW) assisted advanced oxidation processes (AOPs) present a promising approach by accelerating reaction rates and improving treatment efficiency, enabling adaptation to variable water quality conditions. Realizing this potential requires catalysts with strong MW absorption and high catalytic activity. In parallel, practical strategies for catalyst separation or immobilization are essential for continuous system integration. In this study, we synthesized a highly active Cu-BiOCl catalyst exhibiting a needle and sheet morphology for application in MWassisted Fenton-like reactions. The Cu-BiOCl exhibited excellent performance across a broad pH range (3-8), with particularly high degradation efficiency at neutral to mildly alkaline conditions (pH 7 and 8). Remarkably, the catalyst maintained structural and chemical integrity over 10 consecutive cycles without intermediate washing, confirming its high stability and reusability. To bridge the gap between laboratory performance and real-world application, a MW-assisted continuous flow system was implemented, in which the Cu-BiOCl catalyst was immobilized onto inert carrier beads. This immobilization strategy enabled stable catalyst placement and eliminated the need for post-reaction separation. The system exhibited a linear increase in degradation efficiency with the number of catalyst-coated beads, confirming its scalability and operational practicality for large-scale treatment. These findings highlight the importance of catalyst immobilization and flow system design in translating MW-assisted AOPs into viable solutions for next-generation water treatment infrastructure.