Ultrafast degradation of SMX and TC by CoSiOx activated peroxymonosulfate: efficiency and mechanism

Abstract

To address the concern about residual antibiotics in effluent of sewage treatment plants, cobalt silicate (CoSiO_x) was prepared by hydrothermal method and employed as an activator of peroxymonosulfate (PMS) for the rapid degradation of antibiotics. Taking sulfamethoxazole (SMX) and tetracycline (TC) as representatives of antibiotics, the effects of operation parameters (CoSiO_x and PMS dosage) and water quality parameters (temperature, solution pH, bicarbonate, chloride, and natural organic matter) on degradation of target pollutants by a CoSiO_x activated PMS process (CoSiO_x/PMS) were investigated. The mechanism involved in the interaction of CoSiO_x and PMS was also elucidated. The results indicated that CoSiO_x/PMS can degrade SMX and TC at fast pseudo-first-order rate constants (0.47 and 0.56 min⁻¹ respectively) under optimal conditions. Increasing the dosage of PMS and CoSiO_x appropriately was beneficial to the degradation of antibiotics. Chloride, bicarbonate, and HA showed negative effects on the degradation process due to their free radical-scavenging ability and were ranked as chloride < bicarbonate < HA. Abundant Co–OH_s and oxygen vacancies on the surface of CoSiO_x contributed to its excellent activation capability towards PMS. The radical scavenging experiments indicated that target pollutant degradation mainly resulted from the attack of sulfate radicals (43.0% contribution) and hydroxyl radicals (52.9% contribution). The practicality of CoSiO_x/PMS was verified by continuous flow test. This study provides a cheap, highly efficient, and feasible advanced depollution method based on CoSiO_x.