Hydroxyl and sulfate radical mediated degradation of ciprofloxacin using nano zerovalent manganese catalyzed S2O82−

Abstract

Nano zerovalent manganese (nZVMn, Mn0) materials have been synthesized in this study and used for degradation of ciprofloxacin (CIP), an emerging water pollutant. The investigation of physiological characteristics of Mn0 by different characterization techniques proved successful formation of Mn0 by the chemical reduction method and found it to be highly crystalline. The Mn0 was highly efficient and resulted in 63% degradation of CIP using [CIP]0 = 10 mg/L and [Mn0]0 = 1.0 g/L at a reaction time of 80 min. Addition of S2O82− to Mn0 promoted removal efficiency of CIP from 63 to 95% at a reaction time of 80 min using the conditions of [CIP]0 = 10 mg/L, [Mn0]0 = 1.0 g/L, and [S2O82−]0 = 50 mg/L. The presence of OH and SO4− scavengers inhibited the degradation of CIP by Mn0/S2O82−. The comparable second-order rate constants of CIP with OH and SO4− were calculated to be 2.35 × 109 and 2.10 × 109 M−1 s−1, respectively. High S2O82− and Mn0 concentrations and low pH accelerated the degradation of CIP. However, removal efficiency of CIP by Mn0 with the added S2O82− was inhibited using high CIP concentration, high pH, inorganic anions, and NOM. Degradation pathways from OH and SO4− based degradation of CIP were developed. Acute and chronic toxicities of CIP and its products were estimated, showing the final product to be non-toxic. The as-synthesized Mn0 was found to be stable as well as environmentally friendly for treating CIP. This study suggests that Mn0 with the added S2O82− is a promising alternative for potential remediation and detoxification of CIP and other emerging water pollutants.