Degradation of a mixture of pharmaceuticals through photoelectrochemical oxidation

Abstract

Organic micropollutants such as pharmaceuticals pose significant environmental and public health risks. These contaminants not only contribute to the spread of antibiotic resistance but also disrupt aquatic ecosystems. Advanced oxidation processes are known to effectively degrade pharmaceuticals, and among these, photoelectrocatalysis (PEC) offers a promising method for removing contaminants present at trace levels (μg/L to ng/L). The focus of the presented study was to assess the influence of five quaternary ammonium compounds (QACs) on BiVO₄ photoanodes, modifying the structural properties and enhancing photoelectrocatalytic performance. The QAC-modified BiVO₄ photoanode variants were characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, UV-Vis spectroscopy, and linear sweep voltammetry. PEC degradation experiments were conducted using effluent, collected after secondary treatment, at a wastewater treatment plant, spiked with 10 selected pharmaceuticals at an initial concentration of 10 μg/L. The removal efficacy of the modified BiVO₄ photoanodes was evaluated under simulated solar irradiation. Among the tested variants, the photoanode modified with the alkyl trimethyl ammonium compound ATMAC C18 modified exhibited the most rapid degradation, with several pharmaceuticals removed within the first 15 minutes. However, dialkyl dimethyl ammonium compound DADMAC C18 modified photoanode was identified as the best-performing variant, with sulfamethoxazole emerging as the critical compound due to its longest half-life.