Construction of a multiple reactive species-mediated Co9S8/NBC-PMS Fenton-like system for tetracycline degradation with broadened adaptability to water background

Abstract

A Fenton-like system based on peroxymonosulfate (PMS) oxidant has high potential for antibiotic degradation, However, various complex water background factors, including pH, coexisting ions, and dissolved organic matter, can adversely affect degradation efficiency. This work constructed a PMS oxidative Fenton-like system activated by cobalt polysulfide/N-doped biochar composite (Co9S8/NBC) for the degradation of tetracycline (TC) and achieving approximately 99 % removal of TC. Furthermore, the removal efficiency was maintained above 90 % across a broad pH range (3−11), in the presence of various coexisting anions (Cl−, NO3− and CO32−), even at high concentrations of humic acid. The characterization of Co9S8/NBC through various techniques confirmed that Co9S8 nanoparticles were uniformly loaded within the porous NBC structure. Electron paramagnetic resonance and reactive oxygen species (ROSs) quenching experiment revealed that the effectiveness of TC degradation in the Co9S8/NBC/NBC-PMS system arises from the cooperation of radical and non-radical species rather than the single mechanism. Moreover, the analysis of the contribution ratios of ROSs to TC degradation indicates that the contribution of non-free radicals exceeds that of free radicals, and it is capable of adapting to changes in pH. The characterization of the post-reaction catalyst suggested that Co9S8 and NBC synergistically participated in the activation of PMS. Moreover, the practical examination proved that the disabled Co9S8/NBC catalyst can recover the catalytic activity via a reheat treatment, the leaching concentration of Co ions was lower than the emission limit of China. The river water and lake water as the matrix water have little negative impact on the degradation of TC. The Co9S8/NBC-PMS system is expected to provide a practical pathway for the treatment of antibiotic wastewater.