Selectively leaching Cu( Ⅱ ) and Ni( Ⅱ ) from acid mine drainage sludge by using ethylenediamine-ammonium sulfate

摘要

A method based on controlling the complexation-precipitation equilibrium of metal ions was proposed to selectively recover nickel and copper from hydroxide sludge formed by lime neutralization of acid mine drainage (AMD). Ethylenediamine(EDA) and ammonium sulfate were chosen as complex reagent and precipitating reagent, respectively, to dissolve target metal hydroxides from sludge and limit useless metal ions in the pregnant solution. Results from both synthetic and natural samples show the excellent selectivity for the target metals (copper and nickel) against Fe( Ⅲ ), Ca( Ⅱ ) and Mg( Ⅱ ), 99% recovery of Cu( Ⅱ ) and Ni( Ⅱ ) and shorter leaching time can be reached by this process, and the resultant solution can be used for direct electrowinning. The optimum operating conditions are: pH = 9 ～ 11, ρ(EDA) = 40 g/L, ammonium sulfate 50 g/L, leaching time 5h(for natural sample) and 2. 5 h(for synthetic sludge), liquid to solid ratio being 4 with mechanical stirring at room temperature.