| As a kind of scattered metal,indium is only 1/6 of that of gold in the earth’s crust.It is widely used in electronics,semiconductors,space flight and pharmaceutical fields.More than70% indium is used to produce liquid crystal display(LCD).With the rapid upgrading of electronic display products,the amount of waste LCD is huge,and the content of indium is often several times that of natural ore,which makes waste LCD extremely valuable resource.The indium regeneration process in waste LCD panel based on hydrometallurgy technology is often adopted with the advantages of short process and low emission.Therefore,the research on indium leaching conditions and extraction stripping separation technology of waste LCD has important reference value for optimizing indium regeneration process.In this study,the leaching law of indium and iron,aluminum,silicon and tin during the leaching process of waste LCD panel was investigated by regulating the concentration of sulfuric acid,leaching time and liquid-solid ratio.The kinetic equation was established by studying the change of leaching rate with time in different sulfuric acid concentration and leaching temperature.By comparing different extraction systems,extraction time,concentration of extraction agent and A/O ratio of extraction solution,indium extraction/stripping solution enrichment and impurity ion separation enrichment were completed.The recovery efficiency and purity of indium plate under different current conditions were studied by electrodeposition experiments of high concentration indium liquid under different current conditions.Through the above exploration,the following conclusions are drawn:(1)Under the condition of sulfuric acid concentration of 15% indium leaching effect is the best,reaching 93.77%.After that,increasing the acid concentration can inhibit the leaching of iron and silicon,but the leaching rate of aluminum will increase accordingly.Time has a great influence on the leaching rate of indium,and the best leaching rate can be reached within5 h.However,other impurity ions leaching rate changes little with time.Under the experimental conditions,the overall effect of liquid-solid ratio on the leaching efficiency of each element is small.(2)By screening the model,establishing the kinetics equation of indium leaching process,and the synchronous leaching regulation rule of impurity elements under the condition of forming high indium leaching rate was studied.The results show that the leaching process of indium from the waste LCD panel is in accordance with the shrinkage model,and the reaction is controlled by chemical reaction in the early stage and diffusion control in the later stage.The apparent activation energy of the reaction in the chemical reaction control stage and diffusion control stage is 42.28 k J/mol and 6.08 k J/mol respectively.Increasing the concentration of sulfuric acid and temperature can obviously speed up the reaction rate and shorten the time of chemical reaction control stage,which is conducive to the efficient leaching reaction.(3)In the extraction and reverse extraction experiments,the extraction agent 25% P204+5%TBP has a high selectivity for indium extraction,and the extraction rate can reach 98.36%.Extraction acidity and extraction time are important factors affecting the extraction effect,and too small extraction pH will greatly affect the extraction effect.The backstripping agent was2mol/L hydrochloric acid.Compared with A/O=1:2,the backstripping rate of indium could reach 99.27%.The overall recovery of indium is 97.64%,and the removal rates of impurities are about 99.9% of iron,98.1% of aluminum,99.9% of silicon and 99.4% of tin.Three-stage counter-current extraction can be used to improve the reaction efficiency.After three-stage counter-current extraction,indium recovery is above 96% in the experiment.(4)Using the principle of electrodeposition to carry out regeneration technology research,under the condition of 0.20 A current,smooth and dense indium plate can be stripped from the cathode.The recovered indium plate has low oxygen content and its purity can reach more than 99%.Increasing the deposition time can increase the deposition amount of indium. |
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