Abatement of 2-Methylisoborneol and Geosmin by Mn(VII)/S(IV) Process: The Key Role of Reactive Manganese Species

This study explores the degradation efficiency and mechanisms of 2-methylisoborneol (2-MIB) and geosmin (GSM) in permanganate/bisulfite [Mn(VII)/S(IV)] process. In ultrapure water, with a 20 μM Mn(VII) dosage and a [Mn(VII)]:[S(IV)] ratio of 1:7 at neutral pH, the degradation of 2-MIB and GSM reached ∼85% and 89%, respectively. Multiple pieces of evidence indicate that reactive manganese species (RMnS) are chiefly responsible for the abatement of 2-MIB and GSM. This high reactivity toward the pollutants is attributed to their electron-rich sites in the stereochemical structure rather than hydroxyl functional groups. The study also comprehensively investigated the effect of solution conditions like Mn(VII) dosage, pH, and common coexisting substances (dissolved organic matter, HCO₃⁻, and Cl⁻) in real water on pollutant degradation and the reactive species distribution. Additionally, calcium metabisulfite (CaS₂O₅), a slightly soluble agent, was proposed as a sustained-release source of HSO₃⁻ to optimize the Mn(VII)/S(IV) process. Compared to the scenario of using HSO₃⁻ as an activator, the Mn(VII)/CaS₂O₅ system achieved complete pollutant degradation. Furthermore, the performance and cost-effectiveness of Mn(VII)/S(IV) and Mn(VII)/CaS₂O₅ process was compared with four other Advanced oxidation processes in natural water. This work strongly suggests the feasibility of the Mn(VII)/CaS₂O₅ process for removing odor compounds in water treatment applications.