Removal of chlortetracycline from water using spent tea leaves-based biochar as adsorption-enhanced persulfate...

Antibiotic compounds have caused serious environmental concerns. In this study, we developed an effective technology for treatment of chlortetracycline (CTC), a widely used antibiotic compound. A natural heteroatom-doped spent tea leaves-based biochar (STLB) with excellent adsorption and catalytic property was prepared by simple thermal treatment. An adsorption-promoted persulfate-based advanced oxidation process (PS-AOP) using STLB was studied for CTC removal. The results showed that the as-prepared STLB presented favorable adsorption affinity towards CTC with the maximum adsorption capacity of 627 mg g^-1. Meanwhile, CTC enriched on the surface of STLB was good for in-situ decomposition of CTC and nearly 97.4 % of CTC was removed within 30 min of pre-adsorption and 60 min of subsequent degradation. The STLB had excellent recyclability and wide pH tolerance range of 3.0-9.0 in combined pre-adsorption and PS-AOP. Reactive oxygen species analysis confirmed that CTC degradation was mainly due to non-radical (singlet oxygen, ¹O₂) and radicals (SO₄^- and OH). This study suggests that STLB is a promising adsorption-enhanced PS activator for the treatment of refractory wastewater and also provides a strategy of waste control by spent tea leaves.