Treatment of liquid crystals and recycling indium for stripping product gained by mechanical stripping process from waste liquid crystal display panels

In the past, most of technologies adopted whole crush for waste LCD panels to treat liquid crystals and indium but had low recovery due to its low concentration. In this work, a mechanical stripping process was proposed firstly to gain stripping product enriched liquid crystals and indium. Liquid crystals are enriched from 0.3 wt% in waste LCD panels to 53 wt% in the stripping product. Likewise, indium is enriched from 0.02 wt% to 7.95 wt%. Liquid crystals in stripping product should be removed in advance since it is disadvantage for indium recovery. This study can successfully remove liquid crystals by pyrolysis process. The results were summarized as follows: (i) Liquid crystals in waste LCD panels were mainly TFT type liquid crystals by thermal gravimetric analysis and chromatograph-mass spectroscopy. (ii) Liquid crystals can be well separated under optimized condition of 873 K, 40 min and 2 L/min N2 flow rate. Oil and gas produced in pyrolysis process can be reused as energy and fuel. (iii) Pilot scale experiments were utilized to assess the actual effect of pyrolysis separation; decomposition rate of liquid crystals can reach 80%. It gives some valuable information for industrial separation of liquid crystals and provides a necessary preparation for further recovery of indium.