| Waste liquid crystal displayers (LCDs) have a great value of marketing, while the process of indium discovery discharges coexistent metal elements. Therefore, resource the pollutant has been the urgent affairs. The object of this thesis is waste TFT-LCDs, studying the transfer regularity of coexisting metal ions during acid leaching, extraction, stripping and electrolytic refining of indium. The research of selective recovery of indium in waste LCDs in accompany with a variety of elements is conducted to provide a scientific prerequisite for clean recycling technology of waste LCDs disposal.Waste TFT-LCDs were leached by two acids (H2SO4and HC1), and leaching metal iron were analyzed by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Flame Atomic Absorption Spectrometry (FAAS). The results showed that in two acid solutions, leaching amounts of In3+were almost the same, while coexisting elements in H2SO4was lower. In other to relieve the impact of coexisting elements for recovery of indium, H2SO4was chosen as the decomposition solution for waste TFT-LCDs. In the leachant, the amount of Fe3+was big, as well as In3+、B3+、 Al3+, while the amount of other elements was little.Extracted by P204and then stripped by HC1, transfer regularity of coexisting elements during the recovery of indium was analyzed. The results showed that30%P204was chosen as the extractant. Fe(Ⅲ)-Al(Ⅲ) were extracted by P204in the extraction process of indium. Therefore by controlling extraction time, the amount of iron and aluminum declined in the extractant. During extraction in P204, the content of iron and aluminum was affected by acidity and coexisting anions. Although the amount of Al3+and B3+was big in the leachant, the extraction rate and stripping rate were low. The extraction rate of Sn2+was high, while stripping rate was low, but in the leachant the amount of Sn2+was low. Therefore, indium can effectively selected from other coexisting elements.Waste TFT-LCDs lichant was concentrated to3,4,8times, and extracted to analysis the influencing factors of indium extraction. The results showed that Fe3+、B3+、Al3+and Ti4+in the lichant left impact on indium extraction, while the effect of each ion on indium extraction rate was below5%.There are impacts of Sn2+to indium extraction. Increasing concentration multiple of lichant, the extraction capability of P204declined. By adjusting the acidity of concentrated lichant, indium extraction rate could reach99%.The extraction and stripping process by the Centrifugal Extractor was explored. The results showed that the Centrifugal Extractor has a high efficiency to extract In3+in a very short time to achieve optimum extraction efficiency. The first stage extraction rate is over99%in the In3+standard solution of unconcentrated and concentrated. Because of the effect by coexisting ions, it needed a two stage extraction to make the In3+extraction rate over98%using the Centrifugal Extractor to extract concentrated and non-concentrated sulfuric acid leachant of waste TFT-LCDs. Sn2+stripping extraction rate is low. Because of the extraction enrichment with multiple usage of extraction solvent made the extraction agent aging. Therefore, this should be considered in the actual engineering applications. Three stage stripping rate of waste TFT-LCDs sulfuric acid leaching solution was92.02%, whereas the three times concentrated stripping rate was64.38%.By electrolytic refining, solide indium was obtained in Cathode. For the perpose of indium recovery, the technics and index of indium recovery of waste TFT-LCDs would be developed. |
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