Degradation of simazine by heat-activated peroxydisulfate process: A coherent study on kinetics, radicals and models

Recently, studies on the degradation of emerging pollutants by activated persulfate (PS) have been widely reported. As a classic process, heat-activated peroxydisulfate (PDS) has been extensively used in practical engineering. However, the establishment of the quantitative relationship between the reduction of pollutants and PDS and the kinetic model of the heat-activated PDS process are rarely reported. In this study, triazine herbicide simazine (SMZ), which is frequently found in the environment, was selected as the target pollutant, and a series of coherent studies including kinetics calculation, radicals identification, and product analysis provided the basis for the establishment of the model. The steady-state model and unsteady-state model initially described the process of heat-activated PDS and degradation effect on SMZ. It was found that in the process of heat/PDS, the degradation of SMZ was significantly related to the decomposition of PDS. The decomposition of each unit of PDS at the beginning of the reaction could lead to the degradation of 1.616 units of SMZ. In addition, during the reaction, sulfate radical (SO4 center dot- ) was the dominant radical and could be partly transformed to hydroxyl radical (center dot OH) to participate in the reaction (with the ratio of 25:1). Finally, it was noted that the reaction intermediates could not be ignored in the establishment of the unsteady-state model. This study provides a set of coherent research methods, which is conducive to further simulation of the heat-activated PDS process.