Cobalt-loaded carbon nanotubes boosted aerobic ciprofloxacin transformation driven by sulfide:A comprehensive mechanism investigation

Sulfide oxidation under aerobic conditions can produce active oxygen for the transformation of organic pollutants in aquatic environments.However,the catalytic performance of transition metal-supported carbon material on this process is poor understood.This study found that Co-loaded carbon nanotubes(CNTs)was able to realize the efficient aerobic transformation of antibiotic ciprofloxacin(CIP)by sulfide,with the pseudo-first order reaction rate constant improved from 0.013 h^(-1)without catalyst to 0.44–0.71 h^(-1)with 100 mg/L Co-loaded CNTs.Singlet oxygen(^(1)O_(2))was the main active specie playing key roles in the process of CIP aerobic transformation with presence of Co-loaded CNTs.Mechanism studies indicated that the excellent electron transfer ability of Co-loaded CNTs might play an important role to promote the electron transfer and facilitate the formation of intermediate H_(2)O_(2)and^(1)O_(2).Additionally,the Co-loaded CNTs/sulfide system effectively reduced the acute toxicity of organic pollutant,and Co-loaded CNTs showed remarkable cycling stability and negligible leaching.This study gives a better understanding for the Co-loaded CNTs mediated aerobic antibiotics transformation by sulfide,and provide a reference for the application of Co-loaded carbon materials on organics aerobic transformation by sulfide.