As(V) retention and As(III) simultaneous oxidation and removal on a MnO2-loaded polystyrene resin
Résumé
Based on KMnO4 oxidative capacity, a polystyrene matrix loaded with manganese dioxide was synthesized from an anionic commercial resin in chloride form.This medium, called R-MnO2, was tested for As(V) retention and for As(III) simultaneous oxidation and removal.Equilibrium was reached in 2 h and isotherms showed that R-MnO2 maximal capacities towards As(III) and As(V) are, respectively, 0.7 and 0.3 mmolyg.Various mechanisms were involved in As(III) retention: oxidation of H3AsO30 by MnO2(s) leading to the formation of HAsO42- and Mn2+, fixation of As(V) formed on the resin beads and precipitation of Mn3 (AsO4 )2 with Mn2+ released.Successive arsenic desorption and retention steps were performed and showed that the quantity desorbed was low compared to the quantity removed during the first stage of the process. A second removal step, carried out under the same conditions as the first one, proved that the matrix second-removal capacity was weak.This solid sorbent, although not reusable, can be considered in field application as arsenic retention is really strong.