Elimination of arsenic traces contained in liquid effluents by chromatographic treatment

Our present work is included in a development plan of a two-step detoxication process of arsenical by-products originated from chemical warfare destruction effluents [1]. The first method studied was classical anion exchange chromatography. Less than 1% of the anion exchanger capacity is used to fix arsenate ions for a Cl$^-$/AsO$_4^{3-}$ concentration ratio equal to 100. Because of the lack of anion exchanger selectivity, the use of more selective adsorbents has been investigated, namely a macroporous cation exchange resin (BioRad AGMP-50 resin). We confirm that the As$^{\rm III}$ and As$^{\rm V}$ retention does not depend on the nature of the resin functional groups and that only the ferric hydroxide precipitate is involved in the retention. We also show that the arsenic available exchanger capacity is not significantly affected by high concentrations in chloride ions (1 mol L$^{-1}$), and it seems that the kinetics of arsenite and arsenate ions fixation is better in presence of chlorides. The use of the exchanger for the complete detoxication of arsenic trace (10 ppm) solutions in presence of high contents in chlorides (1 to 3 mol L$^{-1}$) leads to an effluent volume equal to 280 and 540 times the resin bed volume, for AsIII and AsV respectively. The effluent thereby obtained has an arsenic concentration lower than the M.C.L. (100 ppb)