Unraveling new reactivity pathways of cobalt(II) ammonium phosphate toward activation of peroxymonosulfates and subsequent degradation of antibiotic pollutants in water

Abstract

This study is aimed at unraveling the catalytic activity of cobalt(II) ammonium phosphate (NH4CoPO4) in activation of peroxymonosulfate (PMS) and degradation of various antibiotics. It was found that NH4CoPO4 enabled swift and efficient removal of ciprofloxacin (CIP) at a high initial concentration (30 mg/L) using very low catalyst loading (10 mg/L) in just several minutes of the reaction. The CIP degradation rate in the presence of NH4CoPO4 was approximately 3.5 times higher than that observed for the well-known and highly active Co3O4 catalyst (k = 0.121 vs. 0.031 min−1, respectively). Catalytic tests with the use of reactive oxygen species scavengers revealed that the primary oxidizing agent responsible for degradation of CIP were cobalt(IV)-oxo species. It was also established that NH4CoPO4 could efficiently degrade CIP even in environmental water samples (e.g., river water). This study contributes to a better understanding of the reactivity of NH4CoPO4 in the degradation of antibiotic pollutants.