Degradation of Bisphenol A by manganese minerals: The impact of inorganic and organic ligands

Abstract

Manganese minerals are ubiquitous in aquatic environments, where both inorganic and organic components can form complexes with them, thereby impacting the release of reactive Mn(III) and the fate of pollutants. The available information about these processes remains insufficient, however, impeding the study of the migration and transformation of pollutants in the environment. In this study, pyrophosphate and humic acid were selected as inorganic and organic ligands typical of aquatic environments, and their impacts on the degradation of Bisphenol A by the β- and δ- variants of MnO2 were investigated. The results indicate that 1.0–5.0 mM pyrophosphate promotes the generation of reactive Mn(III) from β-MnO2, resulting in enhanced degradation of Bisphenol A. Pyrophosphate inhibits δ-MnO2-mediated degradation of Bisphenol A due to competition for reactive sites. Humic acids increase the degradation of Bisphenol A mediated by δ-MnO2 by forming complexes with reactive Mn(III) released from the δ-MnO2. The degradation of Bisphenol A mediated by minerals in the presence of ligands occurs primarily through hydroxylation, one-electron transfer, and free radical coupling. These findings provide new insights into the role of ligands in the reductive dissolution of manganese minerals and their synergistic effect on the fate of Bisphenol A in aqueous environments.