A novel xanthan-chitosan based peroxydisulfate controlled-release material for in-situ sustained degradation of tetracycline: Performance, mechanism and application

Abstract

In situ chemical oxidation (ISCO) is a promising technology to remove the organic pollutants from groundwater on site. In order to ensure the sustainable and long-term treatment performance, the oxidant controlled-release materials (CRMs) are required. In this study, a novel environmentally friendly and low-cost peroxydisulfate CRM (XG/CS-PDS) was synthesized via the mixing and mold method with xanthan, polyvinyl alcohol and chitosan as the binders for the first time. The XG/CS-PDS possessed significantly stable controlled-release properties under different pH and co-anions. 80% PDS in the CRMs could continuously and slowly release within 50 days. The simulation of PDS controlled-release process indicated that the process was controlled by the non-Fickian diffusion. Then the as-prepared CRM was applied to remove tetracycline (TC) from synthesized groundwater with nanoscale zero-valent iron (nZVI) as the PDS activator. The XG/CS-PDS/nZVI system could achieve 100% removal efficiency at different initial TC concentrations (5‐40 mg/L) and had a good anti-interference ability to pH, inorganic co-anions and humic acid. The quenching experiments and electron spin resonance (ESR) revealed that SO4•-, •OH and 1O2 were the main reactive oxygen species (ROS) for the degradation of TC, while SO4•- played the more dominant role. The intermediates and possible degradation pathway of TC were proposed and the toxicity of TC and its intermediates were evaluated. This study provided a new conception for the design of controlled-release material and theoretical strategies for in-situ remediation of groundwater.