Study Of Waste Liquid Crystal Display Indium Recovery Methods And Safety

With the growing amount of liquid crystal display(LCD) waste, it has posed great threats to the environment. Traditionally widely-used incineration or landfill for LCD treatment have been proved to be harmful to atmosphere, soil, water. In addition, given the scarce indium due to the absence of independent indium ore, direct disposal of LCD waste will lead to enormous loss of indium. Therefore, it is particularly important to recycle LCD wast.Since the high viscosity and density of tributyl phosphate(TBP) and bis(2-ethylhexyl) phosphate(P204), it seemed that direct extraction by these two extractants was not beneficial to target ions complexation and complexes migration, leading to the decrease of extraction rate. However, it was suggested that the performance of these extractants could be greatly improved by adding some diluent. Besides, adding n-hexane to the extractant can achieve a higher extraction rate than adding sulfonated kerosene.After dismantling LCD waste and leaching glass sheet powder, the extraction of indium by TBP and P204 as the extractants, and n-hexane as the diluent as well as experimental parameters have been investigated. The results showed that n-hexane as the diluent was more effective than sulfonated kerosene when TBP was the extractant, and the optimal extraction parameter was obtained as follow: the TBP concentration(n-hexane as solvent) was 2.5 mol/L; acidity of feed liquid was 6mol/L HCl; ratio of oil to water was 2:1; oscillation time and frequency were 5 min and 200 rpm; 96.9% of indium was extracted. In contrast, the optimal extraction parameter for P204 was also obtained as follow: the P204 concentration(n-hexane as solvent) was 1 mol/L; acidity of feed liquid was 6mol/L H2SO4; ratio of oil to water was 1:9; oscillation time and frequency were 5 min and 200 rpm; 99.4% of indium was extracted in the final.Refer to reversed phase extraction of P204 with indium containing in oil phase by using 4mol/L HCl, the parameter was optimized as follow: ratio of oil to water was 4:1; oscillation time and frequency were 20 min and 200 rpm. And 90.9% of indium was extracted. By adding 1.5 times of theoretical amount of iron powder into 0.5mol/L H2SO4, Fe3+ was reduced to Fe2+ which was not extracted by P204 after heating for 4 hours at 60℃. In the p H of 1.4, 90.8% of indium was displaced by zinc sheet after heating for 36 hours. In general, the total recovery efficiency of indium reached 82.4%.The harm of indium recovery methods mainly include: burns, poisoning, fire and explosion, the human body damage. The risk grade of burns, poisoning and human damage is grade II, fire and explosion danger is grade III, trigger conditions are controllable.In this study, by using n-hexane as the diluent, the TBP extraction of indium was more effective than by common sulphonated kerosene. What’s more, the price of n-hexane is only 1/4 of that of sulphonated kerosene, indicating that this method for indium recovery from LCD waste not only is technologically feasible, but also increase economic benefits.