Enhanced degradation of carbamazepine in water by a chitosan-supported tea polyphenols/nano-zero-valent iron system: Mechanistic insights and toxicological risk assessment

The sulfate-based advanced oxidation processes (AOPs) are an emerging and efficient remediation technology in the water treatment field, but developing efficient and eco-friendly heterogeneous catalysts remains challenging. In this study, we synthesized chitosan/tea polyphenol-functionalized nanoscale zero-valent iron (CS/GT-nZVI) to activate low-toxicity sulfite species. Compared with traditional iron-based catalytic materials, CS/GT-nZVI effectively overcomes agglomeration and oxidation issues and exposes more active sites. The system achieved high degradation efficiency for the representative PPCPs, carbamazepine (CBZ). Furthermore, it demonstrated strong performance in pilot-scale tests, effectively treating CBZ in both wastewater purification tail water and pharmaceutical tailwater samples. Degradation pathways and corresponding ecotoxicological assessments revealed the toxicity of intermediate products generated during incomplete CBZ degradation, emphasizing the need for complete mineralization to mitigate ecological risks. This study provides a safe and cost-effective approach for mitigating PPCPs pollution sourced from urban water treatment system, with significant implications for enhancing water quality and ecological safety.