| With the fast popularization liquid crystal display (LCD), the market share of LCD grows rapidly. Large number of end-of-life LCD is becoming as an important part of the electronic waste (WEEE) and constitutes enormous potential threat to environment. Therefore, the harmless treatment, utilization and pollution control of the used liquid crystal display (LCD) have became a pressing matter of the moment. In this paper, basing on the main elemental composition analyzed, the study of the indium recycling technology in shredded particles of waste TFT-LCD panels was conducted. And the main influencing factors and mastered the key technical parameters of indium recycling process were defined. The above researches provided a basis for the recycling technology of indium and other valuable metal in waste TFT-LCD panels.The main elemental composition was analyzed by XRF (X-ray fluorescence analyzer) technique. The results showed that the main elements in the waste TFT-LCD panels including Si, Al, Ca, Sr, Fe, Ba, K, As, Zn, Ti, In, Cu, Sn, Cr and so on. Waste TFT-LCD panels was digested at160degrees using concentrated hydrochloric acid, nitric acid, sulfuric acid et al (six kinds of acid system). The elemental concentration of Al, Sr, Fe, As, Zn, Ti, In, Cu, Sn, Cr in shredded particles of waste TFT-LCD panels were tested by ICP-AES technique under different acid system, and the leaching properties of Al, etc were studied under different acid system. Using the recovery mode of standard addition detected the suitability of ICP-AES method for testing the main elements in TFT-LCD glass panels. The results showed that The dissolution property of In changed little under different acid systems (2.83-3.06mg/L). Fe showed similar properties to In, and Fe was the main accompanying ions. Al and Sr were easily dissolved out under concentrated hydrochloric acid. The dissolution rate of As (100%) in concentrated nitric acid was higher than in the other leaching system. However, the leaching rate of As was extremely low only about2.93%in the absence of nitric acid. It was difficult to dissolve out Zn, Ti, Cu, Sn and Cr, which concentrations were lower than1mg/L under all acid systems, and were not suitable for recovery. The RSD of the most elements’determination results were less than3%and the recovery rate of standard was86-110%. ICP-AES method can meet the error requirement of the elements’determination, and can be well applied to determine the main elements in TFT-LCD glass panels.Basing on testing the contents and analyzing dissolution properties of the main elements in the waste TFT-LCD panels, fractional leaching method was used to make the target elements into different leaching agents step by step. Firstly, concentrated nitric acid or concentrated sulfuric acid was selected to leach Indium. Secondly, the residue was dissolved by concentrated hydrochloric acid and a large number of Sr was dissolved out in the solution. This paper mainly focused on the first step (the extraction of indium). The results showed that large number of Indium in the waste TFT-LCD panels can be dissolved out by concentrated nitric acid or concentrated sulfuric acid. The liquid solid ratio(Acid volume than sample quality) was1:1.The Indium in sulfuric acid leaching solution of waste TFT-LCD panels was extracted by P204and striped with HCl. The factors of influence, such as volume fraction of extractant, phase ratio, interference of with ions, pH values of liquids, concentration of stripping agent on extraction and stripping were investigated. The results indicated that the optimum effect of extraction was under the conditions of30%P204of aviation kerosene, phase ratio (O/A) of1:(3-9), acidity of0.5-1.5mol/L (H2SO4concentration), and time of3～5min. Stripping with4mol/L HCl, phase ratio (O/A) of5/1, time of15min, stripping rate of indium was more than97.06%. The stripping rate of Indium increased with the concentration of stripping agent increasing, and the most suitable concentration of stripping agent was4～6mol/L.Basing on comparing the various refining method of indium the method of precipitation with NaOH solution and heating by Ma Feilu for refining indium in the stripping liquid was used in order to get the indium oxide in this paper. The recovery rate of refining indium was94.75%. The recovery rate was90.71%for the whole process of recovery indium from the waste TFT-LCD panels. |
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