C, H, Cl, and In Element Cycle in Wastes: Vacuum Pyrolysis of PVC Plastic To Recover Indium in LCD Panels and Prepare Carbon Coating

Resource recycling of millions of solid waste is a worldwide problem. Because the element is the basic unit of all wastes, the essence of wastes recycling is to realize cycle of elements in waste. In this paper, a new concept of element cycle in waste is proposed. Under the guidance of the element cycle, various wastes have a common connection point. The concept is clarified by a case of C, H, Cl, and In element cycle from waste poly(vinyl chloride) (PVC) plastic and liquid crystal display (LCD) panels. In this paper, a vacuum pyrolysis of waste PVC was proposed to recycle indium in LCD and simultaneously prepare a carbon coating. Cl in PVC, combined with In in LCD, was mainly regenerated in the form of InCl3. Meantime, C and H in PVC were reused to prepare a carbon coating and energy products such as pyrolysis oil and gas. The recycling system means to change two types of waste into resources by their own element characteristics. Under optimized conditions, the recovery rate of indium exceeded 98%. Meantime, with increasing temperature, the microstructure of carbon coating is gradually clear. The formation mechanism of the carbon coating was presented in detail. This study is meaningful for the sustainable development of resources recycling in waste.