The Study On Technology And Kinetics Of Indium Leaching From Zinc Oxidation Slag Dust Enhanced By Microwave Roasting

Indium, a rare metal, is widely used in optoelectronics, national defense and nuclear industry fields. It is very important to recover indium from low grade indium-contained materials because the high grade indium resources are gradually exhausted. In order to efficiently recover indium from low grade indium-contained materials, the scientific researchers have found that extraction of indium could be enhanced by pressurized oxidation, mechanical activation, concentrated sulfuric acid curing, sulphation roasting in a lot of research. On the basis of previous studies, it puts forward to enhance leaching process of low grade indium-contained materials by microwave technology in this paper.Zinc oxidation slag dust from a factory in Liuzhou, Guangxi is used as the research object and the means of microwave roasting is adopted to enhance extraction of indium. The main research contents are technology and kinetics of extraction of indium enhanced by microwave roasting. The technological conditions of microwave roasting and leaching process are optimized by single factor method in experiments. The leaching process of indium is described by Avrami equation.The research results are as follows: (1) The dissolution of zinc oxidation slag dust not only spends less time but also becomes less sensitive to reaction temperature and H2SO4concentration after microwave roasting.(2) The optimum process conditions in the experimental range are that the microwave power is750W, the roasting time is3min, the dosage of additive is300g/kg, the leaching time is30min, the leaching temperature is60℃, the acid concentration is5mol/L, the ratio of liquid-solid is5:1, and the stirring speed is200r/min. Under this condition, the leaching rate of indium can reach87.6%. Compared with the maximum leaching rate of indium in the conventional leaching process, it increases by24.9%.(3) The conventional leaching process and leaching process enhanced by microwave roasting can all be described by Avrami equation. Two leaching processes respectively belong to hybrid control and internal diffusion control. In leaching process enhanced by microwave roasting, the apparent activation energy of indium extraction is decreased from18.3kJ/mol to7.8kJ/mol and the reaction order of indium extraction is decreased from0.59to0.43. The macroscopic reaction kinetics equations of two leaching processes are as follow.