Effective especially sustainable degradation of antibiotics in water via a stable slow-release persulfate hydrogel encapsulated by gelatin

Persulfate (PS) has been proven to be a promising oxidant in the in-situ chemical oxidation (ISCO) process, but its practical application is severely limited due to low utilization rates. This study proposed to prepare a slow-release PS material (Gel-PS) via a green encapsulating method by regulating the mass fractions of gelatin aimed to the continuous and sustainable degradation of tetracycline (TC) in water. The results showed that the 20 % Gel-PS exhibited the best slow-release performance, and the release period reached 11 days and even above 15 days under static and dynamic conditions, respectively. Besides, Gel-PS had a long-term oxidation ability without the aid of catalyst and TC degradation efficiency consistently exceeded 40 % within 6 days. The cumulative TC degradation amount by Gel-PS was 2.18 times higher than single PS system. When Gel-PS was in-situ injected, the degradation efficiency of TC increased to over 70 % and the cumulative amount improved by 1.4 times and 2.96 times compared to Gel-PS hydrogel and single PS. The TC degradation mechanism was further explored based on a series of quenching experiments and EPR analysis. In addition to PS direct oxidation, the contribution of SO 4 •− to TC degradation generated from PS activation by alkaline groups in gelatin even reached to 42.11 %. This work provides an efficient and expandable functionalized PS-based oxidant for in-situ continuous and sustainable water remediation.