Modeling Mn(II) autocatalytic sorption on MnOx-coated filtration media

Abstract

This study reports a newly developed kinetic model for predicting manganese (Mn) removal in Mn-coated filtration media. Manganese oxides (MnOx) adsorb and catalyze the oxidation of Mn in the liquid phase to regenerate sorption sites. The most common kinetic models (pseudo-first- and second-order models) do not consider the regeneration of reactive sites, thereby inadequately describing the long-term uptake of Mn(II) by MnOx. We propose a new kinetic model that considers both the rapid initial sorption of Mn(II) onto MnOx and its subsequent slow oxidation to Mn(Ox). This model was generalized to account for different pH, temperatures, and initial Mn concentrations. The enhanced model demonstrated a prediction error of +/−1 % on the Mn(II) concentration measured in the column effluent of two different MnOx media recovered from industrial filters. Although the contribution of oxidation was found to be 10 times smaller than that of adsorption, it is important to consider if for the prediction of Mn(II) uptake over a 4-h column experiment.