Reducing substances-enhanced degradation of pollutants by permanganate: The role of in situ formed colloidal MnO.

Permanganate is one of common oxidants used for organic pollutant abatement in water treatment. This study showed that the degradation rate of bisphenol A (BPA) by permanganate at pH 5.0 in the presence of aniline is much higher than that in the absence of aniline. 2, 5, and 10 μM of aniline enhanced BPA degradation rate by 104%, 326% and 601%, respectively. Colloidal MnO was formed through the reduction of permanganate by aniline and contributed to BPA oxidation considerably. The reactivity of MnO is sensitive to pH and is high under acidic conditions, resulting in the observed enhancement of aniline on BPA removal by permanganate at pH < 7.0. The role of MnO was further confirmed by the relationship of MnO formation and BPA/aniline removal, the inhibitory effect of Ca on the oxidation of BPA in the presence of aniline. Besides the aniline/BPA system, the pollutants which react with permanganate rapidly are likely to enhance the degradation of coexisting pollutants which show high reactivity towards MnO. Due to the reduction of permanganate and stabilization of the in situ formed colloidal MnO by water matrix, the oxidation rate of pollutant in real water is higher than that in pure water.