Manganese (Mn) oxides possess extraordinary metal sorption and oxidation properties and thus affect environmental fate and transport of toxic metals and organic pollutants. There are more than 30 different types of Mn oxides that can be grouped into layered (LMOs), tunneled (TMOs), and low-valence (LVMOs) Mn oxides. The Mn in LMOs and TMOs is mainly Mn(IV) with some species containing Mn(III), while Mn exists as Mn(II), Mn(III) or both in LVMOs. It has been challenging to understand the formation of such a high diversity of phases in the environment. Recent studies showed that Mn(II) can promote transformation of LMOs to TMOs and LVMOs at room temperature, and the transformation products are controlled by the Mn(II)/LMO ratio and solution chemistry. The Mn(II)-Mn(IV) redox reaction drives the transformation, in which Mn(II) acts as either a catalyst or a reactant. In this presentation, I will give an overview of the controlling factors and mechanisms of the transformation.

Mn(II)-promoted phase transformation of manganese oxides

ACS Spring Meeting 2021

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