A simulation study of the decomposition, biotoxicity, and transfer of LCMs in LCD panels after being in contact with sulfuric acid and extraction/stripping agents

Abstract

For indium recycling from LCD panels, the decomposition of 9 commonly used liquid crystal monomers (LCMs) that were in contact with sulfuric acid (i.e., leaching agent) and extraction/stripping agents, has been investigated in the present study. Also their biological toxicity changes and transfer have been studied. The results showed that 7 of the 9 LCMs were decomposed in the sulfuric acid agent, while the reaction time and temperature had no effect on the types of the decomposition products. The maximum decomposition rate was 96% when the concentration of the sulfuric acid was increased to 12 M. The time required for a 100% decomposition of the various LCMs in a 5 M sulfuric acid ranged from 41 h to 150 h. Also, Estimation Programs Interface (EPI) and ECOSAR calculations were used to compare the biotoxicity of the LCMs and the decomposition products. The results from the EPI calculations showed that the biological half-lives of the decomposition products were significantly reduced as compared with the LCMs, from the original highest value of 329.2 days–92.71 days. Furthermore, the ECOSAR calculations showed that the biological toxicity of the decomposition products for aquatic organisms was lower than for the LCMs, but they were still toxic and harmful substances. In addition, the transfer rates of the undecomposed LCMs and decomposition products in different extractants remained above 90%, and reached 100% at most. After stripping with hydrochloric acid, more than 70% of the undecomposed LCMs became enriched in the aqueous solution, while the products were enriched in the extractant.