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 O2 ) 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 H2O2 and 1 O2 . 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.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.