Degradation of contaminants of PPCPs by photocatalysis for water purification: Kinetics, mechanisms, and cytotoxicity analysis

Abstract

Pharmaceuticals and personal care products (PPCPs) have drawn increasing regulatory attention and research interest in recent years. Since it does not require any additional dissolved oxidants, heterogeneous photocatalytic technology has attracted much interest in the efficient degradation of PPCPs in recent years. The present study examined the degradation kinetics of PPCPs using Fe-ZnS@TiO2/nickel foam photocatalytic system (ZTN PS) in Milli-Q water and a solid surface water background, including estrone, diclofenac, cyclophosphamide, triclosan, and sulfamethoxazole. To evaluate ZTN PS, MF-treated water samples from the Songhua River (SR) were obtained and used as reaction matrices with spiked additions of PPCPs. The influence of single ion addition on degradation kinetics was investigated to determine the degradation rule under various water parameter conditions. Using high-resolution mass spectrometry to identify transformation products (TPs), potential degradation pathways of a few PPCPs were hypothesised. During photocatalysis, the oxidation properties of different oxidants (photogenic holes, OH, O2−) on different structural sites of PPCPs were analysed. To examine possible environmental impacts of PPCP degradation by ZTN PS, cytotoxicity and estrogen (ER) receptor-binding activity were evaluated. It was found that ZTN PS substantially reduced cytotoxicity and estrogenic activity while degrading PPCPs in Milli-Q water. Also, the presence of complex substances in water did not significantly affect the toxicity of mixed PPCP degradation TPs. However, comparing natural water to Milli-Q water, the toxicity and ER-binding activity of TPs under natural water background increased marginally (9%–13％). Thus, this study aimed to understand the effects of post-ZTN PS PPCPs and TPs on human and environmental health at the cellular level.