Defect-mediated electron/hole trapping in Bi2WO6 for concurrent Cr(VI) decontamination and ciprofloxacin mineralization.

Abstract

The remediation of multicomponent wastewater containing high-valent heavy metals and organic pollutants remains a significant environmental challenge. Visible-light-driven photocatalysis holds promise for concurrent pollutants decontamination, but is often hindered by sluggish interfacial charge transfer, rapid electron-hole recombination, and inadequate redox-active carriers. In this work, we present a dual-vacancy-incorporated Bi₂WO₆ (V-BWO) photocatalyst, featuring strategically introduced oxygen vacancies (OVs) and bismuth vacancies (BiVs), to overcome these constraints. Integrated theoretical and experimental investigations uncover a defect-mediated charge dynamics mechanism: OVs function as shallow electron traps enabling ultrafast charge capture, while BiVs function as deep relaxation sites that-under Cr(VI)-induced electron quenching-synergistically stabilize holes and extend their lifetime. This synergistic vacancy modulation achieves exceptional performance: a ciprofloxacin (CIP) degradation rate constant of 3.3 × 10^-2 min^-1 with concurrent Cr(VI)-to-Cr(III) conversion (0.036 mmol/L reduced after 60 min). Notably, the catalyst sustains robust > 80.6 % contaminant removal efficiency in continuous-flow operation across diverse pollutants including CIP, bisphenol A (BPA), and rhodamine B (RhB). These findings elucidate the pivotal role of dual-defect states in tuning carrier dynamics and establishes a robust platform for integrated photocatalytic detoxification of multicomponent wastewater streams.