Arsenic control in process tailings: continuous coprecipitation of As(V) with iron sulphate media

Arsenic constitutes a serious environmental problem for the mineral processing industries. The removal of high concentrations of arsenic in the case of uranium milling process effluents is done by adjusting the iron to arsenic molar ratio to four (MFe_tot/MAs=4) and subsequently neutralizing with slaked lime in a continuous coprecipitation (CCPTN) circuit. This paper investigates the production of arsenic-bearing phases though CCPTN from simulated waste process effluents and their long term stability at accelerated conditions. In particular, special attention is given to a two stage continuous reactor set-up. Moreover, the effect of a fraction of total iron as ferrous iron and the presence of co-ions such as nickel and aluminum on the stability of the products was investigated. (author)