Adsorptive characteristics of iron(III) onto hydrous manganese dioxide in model lake water under acidic conditions

The adsorption of iron(III) onto hydrous manganese dioxide was studied in the model water of Lake Tjeukemeer, The Netherlands, as a function of pH under the condition where no precipitation of iron(III) hydroxide occurs.Adsorption isotherms obtained in the pH range 3.5–5.0, fitted the Langmuir equation. Langmuir constants were strongly pH-dependent and increased with an increase in pH.Especially, the value for the conditional adsorption binding constant for iron(III), log B, was relatively high compared to that for copper in natural water. The extent of iron(III) adsorbed was more affected by the surface loading at lower pH. According to the Kurbatov plot, the average number of protons released to solution per mole of iron(III) adsorbed was estimated to be 2.2.