Although permanganate activation by sulfite (Mn(VII)/S(IV)) has shown great potential for rapid abatement of organic contaminants, its limited reactivity under alkaline conditions and undesirable Mn residual may prevent its widespread application. To solve these challenges, calcium sulfite (CaSO3) was employed as a slow-release source of S(IV) to activate Mn(VII). The application of CaSO3 solid extend the effective working pH range of Mn(VII)/S(IV) from ≤7.0 to ≤9.0 with very low Mn residual (&lt;0.05 mg/L). Mn(VII)/CaSO3 system is a unique two-stage oxidation process in terms of reaction kinetics and reactive oxidants. Specifically, Mn(VII) was rapidly consumed and reactive Mn intermediates (e.g., Mn(VI), Mn(V)), SO4●−, and HO● were produced in Stage I, while SO4●− and HO● were produced in Stage II during the interaction between MnO2 and S(IV). Taking advantage of an automatic titrator, high-concentration of S(IV) was found to greatly quench the generated radicals but not reactive Mn species.

Enhanced oxidation of organic contaminants by Mn(VII)/CaSO3 under environmentally relevant conditions: Performance and mechanisms

ACS Fall 2021

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