Study On Extraction Of Indium From Secondary Zinc Oxide Waste

People have paid more and more attention to the environmental problem because of the dangers brought by the massive flood of industrial solide castoff. One of the main ways to solve this problem is to make that junk can be utilized again. The waste of sencondary zinc oxide is raw material in this paper, containing so much indium that can be used for extraction and separation. Recently, indium has wide range of applications in the electronic industry. But mineral resources are one-off and characetrized by limited and non-renewable. So it is necessary to recycle this kind of industrial waste.There are two process routes have been studied in this paper. One is sulfuric acid leaching method and the other is coke potassium sulfate melting method. Effects of reaction conditions on leaching have been investigated. The determination method was also studied in the process. EDTA complexometric method and ERB spectrophotometry have been established finally. Main achievements were listed as follows:In this paper, two ways of leaching in the prcess have been investigated. Discussed the influence coming from reaction time, temperature and liquid-solid ratio. The optimum reaction conditions were determined in sulfuric acid process. When liquid-solid ratio was8:1and the reaction was started with1.6mol/L H2SO4, reacted6hours in80degrees in the bath, the leaching rate could reached75%. In the melting process, the influence coming from K2S2O7dosage, melting time and temperature have been considered. And the optimum conditions are:in600degrees reaction3hours with6g K2S2O7. The leaching rate can reached91%in this way,16%higher than sulfuric acid leaching way.Subsequently, we found that zinc ion can be removed completely with the twice ammonia water precipitation operation. In the alkaline leaching, the influence which come from alkalinity and reaction time have been considered. And the leaching rate could reach91%when the reaction was happened under boiling state for30min with22%NaOH.At last, the EDTA titrimetric method in the application of detection was studied. And the stability conditions of color system have also been studied. The maximum absorbance is at the wavelength of607nm, the molar absorptivity is ε’607nm=1-207×104L/mol-cm. Bear’s law is obeyed in the range of47～79μg/10mL. The method has been applied to the determination of indium in Second Zinc Oxide waste with satisfactory results.