Studies On Extracting Indium And Tin From Indium Tin Oxide Residues Enhanced By Microwave Pretreatment

Indium, a kind of rare metal, is an important strategic resource, it has intensive use in radio and electronics technology and semiconductor industry fields due to its unique physical and chemical properties. With the development of the society and application of electronic products, the demands for indium are growing in the world. But the high grade indium resources (such as:smelting slag and soot) are gradually exhausted. How to efficiently recover indium from solid wastes is a problem to be dealt with urgently in production. This study has focused on the use of microwave pretreatment on the enhanced extraction of indium and tin from ITO waste acid leach residue, which is the production of industry. A novel technology of recovering indium and tin from hydrochloric acid leach solution of ITO waste acid leach residue which is the use of untreated and microwave pretreatment,based on these theory study,the kinetic of extracting indium from ITO waste acid leach residue was also investigated. The main contents and conclusions are as follows:(1) We investigated the influence of single factor on indium and tin leaching with two different leaching processes, namely untreated leaching and microwave pretreated leaching. Under the conditions of microwave power800W, microwave pretreatment time2.5min, the quantities of added NaOH6.0g, reaction time120min, HCl concentration10mol/L, reaction temperature90℃, stirring speed400r·min-1, liquid/solid ratio15experiment, It was found that the impact of each factor on leaching behavior of indium and tin in ITO waste acid leach residue was different in different leaching processes. Results in the experiments confirm that microwave pretreatment ITO waste acid leach residue can greatly enhance indium and tin leaching rate, which can reach from54.56%,3.35%in normal leaching to above92.32%,72.29%, Increased by60%, respectively.(2) Based on single factor experiments, response surface methodogy, with a Box-Behnken design, was used to optimize the leaching conditions of extracting indium and tin from ITO waste acid leach residue by microwave pretreated leaching. Four independent variables such as reaction time, microwave pretreatment time, HCl concentration and liquid/solid ratio were investigated. By multiple regression analysis, the experimental data obtained were fitted to the second-order polynomial equations, which showed the empirical relationship indium extractions from ITO waste acid leach residue and four test variables. Model capable of predicting the maximum indium leaching efficiencies were established and the optimum leaching conditions were determined as follows:reaction time139min, microwave pretreated time2.9min, HCl concentration10mol/L and liquid/solid ratio18.19, and the value of indium leaching efficiencies predicted using this model equations were94,2%. Under these optimum conditions, the mean experimental values of indium leaching efficiencies were93.8%, which were well matched with the value predicted by the model.(4) According to the experimental data, the kinetics equation of untreated and microwave pretreatment ITO waste acid leach residue was deduced as follows:(untreated)(microwave pretreatment)(5)Through credibility F tests, the confidence coefficient of the two kinetics equation were over than99%, it’s indicated that the two kinetics equation have a significantly reliability.