Cobalt atom sites anchored on sulfhydryl decorated UiO-66 to activate peroxymonosulfate for norfloxacin degradation

Abstract

Developing heterogeneous catalysts with dispersed single-atom sites is highly desirable to enhance peroxymonosulfate (PMS) activation for pollutant degradation. Herein, a novel PMS activation catalyst, single-atom Co anchored on sulfhydryl decorated UiO-66 (Zr-MSA-Co), was synthesized via the strong coordination between Co and sulfhydryl. The batch and fixed-bed column degradation of norfloxacin (NOR) in Zr-MSA-Co/PMS system showed that the Zr-MSA-Co/PMS system could degrade NOR effectively. Moreover, the degradation performance of the Zr-MSA-Co/PMS system for NOR could be enhanced in the presence of anions (except NO3-) and in complex waters. Particularly, the NOR removal efficiency in secondary wastewater by the fixed-bed reactor could reach 99% within 26 h. The radical quenching experiment and electron paramagnetic resonance confirmed that SO4•-, •O2- and 1O2 were the major reactive oxygen groups. Three plausible NOR degradation pathways (defluorination, piperazine ring opening and decarboxylation) were occurred. Density functional theory (DFT) calculations indicated that S-Co-S was the active site for PMS adsorption and activation. Toxicity evaluation results suggested that the antibacterial effect of the intermediates after degradation was reduced significantly. This work provides a new and green approach to anchor single-atom sites on the exposed termination of metal-organic frameworks for catalytic activation of PMS to degrade pollutants.