Kinetic and mechanistic investigations of the degradation of sulfachloropyridazine in heat-activated persulfate oxidation process

Sulfachloropyridazine (SCP) has significant threat to natural environment and human health worldwide. Efforts have been made to remove SCP using traditional water treatment technologies but the outputs achieved are limited. In this study, we focused on heat-activated persulfate oxidation of SCP. Various factors have been investigated, such as PS concentration, initial pH, temperature and natural water constituent effects. The results showed that the SCP removal rate constants (k(obs)) followed a quadratic relationship with initial persulfate concentrations (k(obs) = -1.526 * 10(-6) [PS](0)(2) + 5.621 * 10(-4) [PS](0) + 0.01158, R-2 = 0.923, [PS](0) = 17.5-280 mu M) and excellent fitting with the Arrhenius equation (ln (k(obs)) = - 19487.9/T + 59.63, R-2 = 0.967, T = 303.15-323.15 K). The pH tests were applied at a wide range of 3.0-10.0, the quickest degradation rate observed at pH 3.0. The consumption rate of PS was strengthened at elevated temperatures, and 40 degrees C was determined to be an optimal condition. The presence of chloride (Cl-), bicarbonate (HCO3-) and humic acid all showed inhibitory effects. The radical scavenging experiments revealed that HO. and SO4.- were predominant oxidizing species responsible for SCP removal. These oxidizing species were further verified by EPR tests. LC-MS/MS analysis confirmed seven kinds of byproducts during the removal process which are mainly deriving from SO2 extrusion/Smile-type rearrangement and S-N bond cleavage. Efficiencies of the antibiotics removal were over 85% when 50 g L-1 PS was added to piggery anaerobic fermentation slurry. This remediation technology may appear as a promising way for the removal of highly antibiotics-contaminated water in a small scale.