Co-adsorption of arsenate and copper on amorphous Al(OH)_3 and kaolinite

摘要

We investigated the distribution and speciation of arsenate (As(V)) and copper (Cu(II)) in mineral suspensions of either kaolinite or amorphous (am-) Al(OH)_3. Copper and arsenate are pervasive contaminants in auriferous mining areas with highly antagonistic surface and hydrolysis chemistry, which makes their simultaneous stabilization/ remediation highly challenging. Our results show that even at acidic pH (5.2) the two ions will co-react on the mineral surfaces forming ternary A-type complexes on am-Al(OH)_3 as well as hydrated complexes or highly hydrated precipitates that take on the forms of euchroite (am-Al(OH)_3) or clinoclase (kaolinite). The implications from the speciation results are that the solubility of either Cu(II) or AsO_4 is strongly codependent on the speciation of the co-reacting counterion.