Adsorptive performance of single walled carbon nanotubes for divalent manganese sorption characterized by X ray absorption spectroscopy

The adsorptive performance of divalent manganese onto single walled carbon nanotubes SWCNTs is investigated by X ray absorption spectroscopy XAS . The study is focused on the one hand, on the use of SWCNT as adsorbent to remove divalent manganese II pollutant controlling batch parameters such as pH, adsorbent dose and contact time; and on the other hand, on the characterization of manganese adsorbed by SWCNT Mn SWCNT adsorbent to probe the chemical composition, oxidation state, and local structural environment of Mn absorber. Freundlich adsorption isotherm well fitted the experimental data and suggested the maximum adsorption capacity at pH 2. Ion exchange was proposed as the main adsorption mechanism for removing manganese using SWCNT. XAS results revealed the change in the oxidation state of manganese. The effect of pH, adsorbent dose, and contact time is shown. XAS also showed that Mn SWCNT material is principally composed of MnCl2, Mn2O3, MnO2, Mn3O4, and MnO in decreasing order with MnCl2 and Mn2O3 as major compounds