Simultaneous determination of peroxydisulfate and bisulfite concentrations with quenching-agent-assisted iodometry

Abstract

Fenton/Fenton-like reactions have gained popularity for their remarkable proficiency in decomposing organic pollutants, especially when enhanced by reductants addition for accelerating the Fe²⁺ regeneration. Nevertheless, these works predominantly centered on the formation and utilization of hydroxyl radicals (•OH) in the process, neglecting the evolution of oxidant and reductant due to the difficulty in the simultaneous determination of these two components. By employing the quenching-iodometric method, we could simultaneously determine the concentrations of HSO₃^- and peroxydisulfate (PDS). This method first employed an excess of peroxymonosulfate (PMS) to effectively quench HSO₃^-, and then used the iodometric spectrophotometry to simultaneously determine the concentrations of PMS and PDS in the reaction system. Finally, through precise stoichiometric relationships, we could accurately calculate the concentration of HSO₃^-. Based on this method, we achieved concentration measurements that, upon linear fitting, yielded a correlation coefficient (R²) surpassing 0.99, unequivocally affirming the method's accuracy and trustworthiness. In this work, an innovation approach for determining the concentrations of HSO₃^- (reductant) and PDS(oxidant) was explored.

Additionally, the resilience of the method was verified across different pH levels and in the presence of diverse impurity ions. The results ensured precise concentration measurements in the real wastewater. This method was characterized by its simplicity, rapid analysis, and environmental friendliness, offering a new analytical strategy for the determination of PDS and HSO₃^- in environmental samples. The method enables more meticulous monitoring of chemical usage in water treatment, facilitating optimized dosing strategies and assessments of reductant-enhanced Fenton or Fenton-like system in water purification.