Exploring simulated sunlight sulfite process for enhanced removal of mixed pharmaceutical and personal care products from aqueous solution

Pharmaceuticals and personal care products (PPCPs) in natural aquatic environments pose potential risks to the environment. Effective removal of mixed PPCPs is thus imperative. This study represents a novel application of a simulated sunlight-sulfite process for removing mixed PPCPs. The influence of sunlight irradiation, sulfite ion dosage and initial concentration of PPCPs were systematically studied. The degradation mechanism was explored using sulfamethoxazole as a model compound through scavenger experiments, byproduct analysis, and also toxicity assessment. Hydroxyl and sulfate radicals were identified as the primary agents responsible for PPCPs removal, along with hydrated electrons, hydrogen radicals, superoxide radicals, and singlet oxygen. Singlet oxygen was identified as a reactive species for the first time. The degradation pathways of sulfamethoxazole were examined, identifying five byproducts, and assessing the toxicity of these byproducts, finding minimal Microtox® toxicity. The influence of water matrix constituents and the effect of a real water matrix on mixed PPCPs removal were also explored. The results indicate that water matrix constituents compete for light absorption and quench hydroxyl radicals, leading to decreased degradation efficiency. The study demonstrated the simulated sunlight sulfite process as a promising approach for real application based on the overall removal effectiveness.