Temporal Dynamics of Oxidation Capacity in Biogenic Manganese Oxides: Role of Superoxide Anion Intermediation

Abstract

Biogenic manganese (Mn) oxides, formed via microorganism activity, contribute markedly to biogeochemical cycles. The active contribution to the decomposition and conversion of organic carbon is mainly attributed to its oxidation activity. This attribute also underscores their effectiveness as environmentally friendly bioremediation materials. The reactive variation of Mn oxides, however, has been inadequately described in the literature. In this study, the removal of tetracycline (Tc) was utilized as a model to elucidate their oxidation reaction kinetics. The research results revealed that the oxidation capacity of Mn oxides was most pronounced at the peak generation rate, subsequently declining gradually by over 30% within an 8-h period. It was discovered that such variation was significantly correlated with the superoxide anion (·O2 –) intermediation. The proportion of Mn(III) was relatively higher during the period of Mn oxide formation and subsequently decreased following the cessation of Mn(II) oxidation activity, which was mediated by ·O2 – as the primary source. This study has expanded the understanding of the biotic Mn(II) oxidation, contributing to its potential applications in environmental and biological contexts.