Fixed-Bed and Stirred-Tank Studies of Manganese Sorption by Calcite Limestone

Abstract

This study addressed manganese removal from mine waters in a stirred tank as well as fixed-bed experiments. Manganese sorption on limestone is described by pseudo first-order kinetics. Equilibrium sorption was modeled by the Langmuir isotherm, and limestone showed maximum manganese uptakes ranging from 0.92 mg/g in the absence of sulfate to 1.08 mg/g in the presence of 600 mg/L of the species. Fixed-bed testing showed limestone uptakes that increased with the flow rate at low manganese concentration (1.5 mg/L) but decreased for mine water containing 15 mgMn/L. The Thomas model was fitted to breakthrough curves to determine the characteristic design parameters of the column. The maximum uptake was 46.85 mg/L-bed for a 15 mg/L manganese solution at 1 mL/min, and sulfate did not affect the manganese sorption. The solid residues obtained during the removal process were characterized, and the presence of manganese carbonate (MnCO3) on the limestone surface was confirmed by IR during the experiments with mine w...