Photocatalytic and Antimicrobial Activities of Bi ₂ WO ₆ ‐ZnO/GO Nanocomposites for Water Treatment With Visible Light Utilization

ABSTRACT Zinc oxide (ZnO) and bismuth tungstate (Bi 2 WO 6 ) are promising semiconductor materials for photocatalytic applications due to their unique optical and electronic properties. However, rapid electron‐hole recombination limits their efficiency. This research used solvothermal and hydrothermal methods to prepare Bi 2 WO 6 ‐ZnO/graphene oxide (GO) nanocomposites. Characterization confirmed successful heterostructures, with GO improving surface area, charge separation, and visible‐light absorption. Under visible light, the Bi 2 WO 6 ‐ZnO/GO (3 wt%) photocatalyst removed 87.9% of methylene blue (20 mg L −1 , pH 6.07) in 180 min. The composite displayed good reusability, maintaining a degradation efficiency above 69.7% after five cycles. This enhanced performance is attributed to GO's role in reducing electron‐hole recombination and providing a large surface area. Scavenger experiments identified hydroxyl radicals (•OH) as the primary reactive species driving MB degradation. The nanocomposites also exhibited strong antimicrobial activity against Escherichia coli under visible light. Notably, GO incorporation resulted in a sixfold enhancement in photocatalytic activity. The reaction rate constant (k) increased significantly from 0.0015 min −1 for the Bi 2 WO 6 ‐ZnO (0.3:1) composite to 0.0089 min −1 for the Bi 2 WO 6 ‐ZnO (0.3:1)/3GO system. These findings underscore the potential of Bi 2 WO 6 ‐ZnO/GO composites for environmental applications, including pollutant degradation and water disinfection, offering a scalable solution for addressing water contamination challenges.