Simultaneous dissolution of nickel, copper and cobalt from low grade nickel matte by (NH4)2S2O8-H2SO4 oxidative leaching

This study proposes a novel process for simultaneous extraction of valuable metals by oxidative leaching of low grade nickel matte in a mixed solution of (NH4)2S2O8 and H2SO4. The effects of some factors, such as particle size of matte, stirring speed, leaching time, leaching temperature, mass ratio of ammonium persulfate to matte (A/M) and sulfuric acid concentration, on metal extraction in the leaching process were systematically investigated. The way of adding saturated ammonium persulfate solution was investigated to improve the extraction of metal. The most suitable leaching conditions were determined as follows: matte particle size 96-106 & mu;m, stirring speed 450 rpm, liquid-to-solid ratio 20 mL:1 g, leaching temperature 80 degrees C, leaching time 4 h, A/M 4.5:1, sulfuric acid concentration 0.25 mol/L, and dropwise speed of adding saturated ammonium persulfate solution 0.48 mL/min. The highest extraction of nickel, copper, cobalt and iron reached 91.8%, 96.1%, 96.6% and 66.9%, respectively.