Discussion on Pressure Acid Leaching of Sphalerite Concentrate

To investigate the reaction mechanism in high pressure acid leaching of sphalerite concentrate,artificial zinc sulfide crystal is prepared.Such relatively pure sphalerite concentrate is leached in a pressure autoclave,with or without iron ion added.Experimental results show that in the iron-absence leaching experiments,dissolution kinetics of sphalerite concentrate is very low,and even in the 180 min and 160 ℃ pressure acid leaching experiments,dissolution of zinc is only 11.06%.While in the iron-added experiments,dissolution kinetics is relatively high,and in the 180min and 160℃ high pressure acid leaching experiments,it is 62.55%.But such high kinetics caused by iron occurs only when the leaching temperature is 150℃ or above.Dissolution rate of zinc in sphalerite concentrate and oxidation rate of ferrous ion have the same trend in term of kinetics,though they do not increase proportionally.Leaching kinetics of spalerite concentrate is greatly depended on the concentration iron ion,but there is an optimal one to achieve the highest kinetics.To some extent oxidation of ferrous ion is an indispensable step in HPAL.Within a range of certain concentration,leaching kinetics is determined by the concentration of ferric ion.The mechanism related to oxidation of ferrous ion is described.