Remediation of ciprofloxacin in soil using peroxymonosulfate activated by ball-milled seaweed kelp biochar: Performance, mechanism, and phytotoxicity

This study explores the catalytic performance of simple physically modified ball-milled kelp-seaweed (Laminaria japonica) biochar (KBCBM) for organic degradation in the soil. The present study is the first attempt at CIPcontaminated soil (CIPsoil) remediation using KBCBM with peroxymonosulfate (PMS) and exploring the phytotoxicity of the intermediates in the treated soil. The surface characterization of the KBCBM catalyst was investigated using different instrumental analyses. The CIPsoil/KBCBM/PMS system showed excellent performance in CIP degradation (96.06%, C0 = 126.15 +/- 0.7 mg kg- 1) under the conditions of 1.0 mM PMS, 1.5 mg g- 1 of KBCBM and unadjusted pH (6.3) condition. The co-existing anions: such as Cl-, HCO3-, and HPO42- enhanced the CIP degradation in the CIPsoil/KBCBM-800/PMS system. However, SO42-, NO3- , and organic matter (HA) showed negligible impacts on pollutant degradation in the KBCBM/PMS system. Reactive oxygen species (ROS) formation was confirmed by chemical scavengers and electron spin resonance spectroscopy (ESR) analysis. The non-radical reaction pathway was verified by electrochemical analysis of linear sweep voltammetry (LSV) and potentiodynamic testing (i-t curve) methods in the KBCBM/PMS. In addition, the phytotoxicity analysis was evaluated by the germination percentage of cucumber seeds with and without remediated soil. The possible CIP degradation mechanisms were proposed using UPLC-MS/MS analysis. The KBCBM/PMS system demonstrated encouraging capabilities in the treatment of CIP-contaminated soil.