| Copper is an important raw material in the development of our country economy. With the exploitation and consumption of ore, domestic copper resources perform several adverse features:the total reserve of copper mineral resources has been decreasing; lean ore is more than rich ore; the separation property of ore is poor because numerous copper in ore symbiosis with other impurity elements such as iron, lead, zinc, sulfur and nickel, associating with harmful elements such as arsenic and etc. In China, the grade of about 56% of copper which has been found is less than 0.7%. In addition, the flotation properties of copper and lead is similar, the conventional beneficiation methods are difficult to extract copper, lead, iron and other qualified concentrate, on the contrary,it often produced large quantities of low grade and complex multi-metal sulfide ore.The lead content is relatively high copper content, in the pyrometallurgical process, no matter what kind of smelting as raw materials, it is difficult to get higher recovery of copper and lead. There are two types of treatment method on the hydrometallurgy of complex multi-metal sulfide copper ore have been reported:One is roasting pretreatment—acid leaching process; the other is direct acid leaching process.In this study, two kinds of methods for leaching copper was compared which included calcification roasting—acid leaching process and oxidation roasting-acid leaching process, the effects of particle size, roasting temperature, roasting time, additives, leaching agent concentration, stirring speed, liquid-solid ratio, leaching time and leaching temperature on the rate of copper and iron leaching were studied. and the optimal roasting process route and process parameters were determined as pellet size 1.0±0.1cm, roasting temperature 820℃, roasting time 1h, CaO 50%, under the condition, sulfur fixation rate is 97.77%, sulfur fixation effect is remarkable. The optimal parameters of acid leaching process is liquid-solid ratio=6: 1, leaching agent concentration 120g/L, stirring speed500r/min, particle size - 75μm, leaching temperature85℃, leaching time 3.Oh, under this condition, the leaching rate of copper and iron respectively were 98.6%,18.96%.The leaching kinetics of copper from calcification roasting ore was simulated using the shrinking core model of liquid-solid heterogeneous reaction. The effects of leaching temperature, leaching agent concentration, liquid-solid ratio, stirring speed on the rate of copper leaching were studied. Kinetics studies indicate that leaching kinetic model follows the shrinking core model and the apparent activation energy is calculated as 19.21 kJ/mol, and the reaction orders with respect to sulfuric acid concentration, liquid-solid ratio and stirring speed were determined to be 1.72,1.25 and 0.94, respectively. The rate of the reaction could be expressed as: 1+2(1-x)-3(1-x)2/3=3.6x[H2SO4]1.72×(L/S)125×w0.94exp(-19210/RT)t.The effects of three factors such as leaching temperature, liquid-solid ratio and acidity and their interactions to leaching rate of copper and iron were studied by the response surface methodology (RSM) and based on central composite design (CCD).The results showed that leaching temperature, liquid-solid ratio and acidity are significant. The leaching rate of copper and iron reached 96.05% and 15.14%.Under setting condition of copper leaching rate is maximum, the leaching rate of iron is minimum, the optimum leaching conditions were as follow:leaching temperature was 70℃, liquid-solid ratio was 7.99:1, acidity was 102.44 g/L. Under the above conditions, the copper and iron average leaching rate reached 96.17%, 15.14% respectively, between optimal value and validation value is smaller error. This suggests that the model is accurate and the optimization results can be trusted. |
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