From fate-aware risk assessment to practical application: γ-Ag2WO4@ultrathin SrWO4 microreactor for visible-light erlotinib elimination

Erlotinib (ERL) is a hazardous anticancer pharmaceutical whose environmental priority is shaped by persistence, ionization, interfacial enrichment, and transformation-product risk, rather than by concentration alone. This study integrates a fate-aware environmental risk assessment with the development of a visible-light tungstate microreactor for the destructive elimination of ERL. The European Medicines Agency (EMA) Phase I predicted environmental concentration (PEC) and a refined public environmental risk assessment (ERA)-based PEC were compared with a chronic no-observed-effect concentration (NOEC)-derived predicted no-effect concentration (PNEC). Although the resulting risk quotients were below unity, ERL persistence, near-neutral hydrophobic/neutral speciation, and unresolved hotspot and mixture risks supported oxidative treatment instead of adsorption-driven phase transfer. Accordingly, γ-Ag 2 WO 4 @SrWO 4 (5 wt.%) was synthesized by seeded low-supersaturation dual-feed deposition, combining a visible-active γ-Ag 2 WO 4 core with an ultrathin SrWO 4 stabilizing shell. Structural, vibrational, microscopic, surface, textural, optical, and photoelectrochemical analyses confirmed phase coexistence, hydroxylated tungstate surfaces, Ag/Sr/W/O distribution, enhanced mesoporous accessibility, preserved visible absorption, reduced charge-transfer resistance, stronger photocurrent response, n-type behavior, and interfacial electronic modulation. Under visible light (λ > 420 nm) at pH 7, the optimized composite removed 99% of ERL within 35 min at ERL concentrations of 2.5 mg L -1 and catalyst concentrations of 50 mg L -1 , with an apparent rate constant of 1.03 × 10 -1 min -1 . Hydroxyl radicals and photogenerated holes dominated oxidation, with secondary contributions from superoxide radicals and minor singlet oxygen. Fourteen-cycle reuse retained approximately 86% removal, supporting γ-Ag 2 WO 4 @SrWO 4 as a risk-informed candidate for visible-light polishing of pharmaceutical effluents.