Activation of Bisulfite with Pyrophosphate-Complexed Mn(III) for Fast Oxidation of Organic Pollutants.

Aqueous complexes of Mn(III) ion with ligands exist in various aquatic systems and many stages of water treatment works, while HSO is a common reductant in water treatment. This study discloses that their encounter results in a process that oxidizes organic contaminants rapidly. Pyrophosphate (PP, a nonredox active ligand) was used to prepare the Mn(III) solution. An approximate 71% removal of carbamazepine (CBZ) was achieved by the Mn(III)/HSO process at pH 7.0 within 20 s, while negligible CBZ was degraded by Mn(III) or HSO alone. The reactive species responsible for pollutant abatement in the Mn(III)/HSO process were SO and HO. The treatment efficiency of the Mn(III)/HSO process is highly related to the dosage of HSO because HSO acted as both the radical scavenger and precursor. The reaction of Mn(III) with HSO follows second-order reaction kinetics and the second-order rate constants ranged from 7.5 × 10 to 17 M s under the reaction conditions of this study, suggesting that the Mn(III)/HSO process is an effective process for producing SO. The pH and PP:Mn(III) ratio affect the reactivity of Mn(III) towards HSO. The water background constituents, such as Cl and dissolved organic matter, induce considerable loss of the treatment efficiency in different ways.