Electro-Fenton degradation of ciprofloxacin with highly ordered mesoporous MnCo2O4-CF cathode: Enhanced redox capacity and accelerated electron transfer

Abstract

The emergence of antibiotics in the environment, especially in drinking water, poses potential harm to human health. It’s urgent to develop effective methods to remove antibiotics in drinking water. In this work, a series of mesoporous MnxCo3−xO4 nanoparticles with high surface area were successfully synthesized and firstly used as effective stable electro-Fenton catalysts to degrade ciprofloxacin (CIP). The removal of CIP achieved to 100% within 5 h. Experimental and density functional theory (DFT) studies verified the existence of redox pairs of Mn2+/Mn3+ and Co2+/Co3+. Scanning electrochemical microscopy (SECM) results suggested that the redox reaction capacity of MnCo2O4 was enhanced and the electron transfer rate on the surface of this bimetallic oxide was 2.67 and 1.6 times the number of MnO2 and Co3O4, respectively. The effective degradation of CIP was mainly associated with the increased electron transfer rate and advanced redox reactivity owing to the synergistic effect of manganese and cobalt entrapped in the matrix of mesoporous structure which provided more accessible active sites. The degradation intermediates and possible process mechanism were investigated in detail. The reusability of MnCo2O4-CF cathode was evaluated five cycles with minimal ion leaching which the concentration of Mn and Co in the system was lower than 2.5 and 3.4 ppm, respectively. This work provides further understanding for removal process of organic pollutants by investigation of redox couple and electron transfer rate of the promising MnCo2O4-CF cathode.