Removal of organic compounds by adsorption on pyrolusite (β-MnO2)

This paper deals with the determination of the adsorption capacities of various organic compounds in water suspension on MnO2 pyrolusite which can be present in the natural environment and in potabilisation treatment. The adsorption was linearised according to Langmuir and Freundlich models. Humic acids were adsorbed on MnO2 under the working conditions used in this study. Tannic acid was also removed by MnO2 but at a lesser level and the model appeared to be more complex, thus suggesting tannic acid precipitation at the surface of MnO2. More generally, it was observed after studying the adsorption capacity of various molecules, that negatively charged molecules were poorly adsorbed on MnO2 probably because of electrostatic interactions whereas cationic molecules were easily adsorbed. Hydrophobic interactions seemed to be a second factor making adsorption on MnO2 much easier. Electrokinetic potential measurement of suspended particles of MnO2 was in good correlation with these hypotheses.