Thermal treatment of liquid crystal display panel scraps: The metals migration and potential environmental risk in solid residue

Abstract

Thermal treatment has been proved to be an efficient and promising method for organics removal from LCD panels and for resource recycling. Considering with the toxic metals contained in LCD panels and their potential risk, it is necessary to study and evaluate the metals behavior and potential risk associated with the thermal treatment of LCD panels. In this study, the migration and transformation behavior of ten metals (Cr, As, Al, In, Ni, Cu, Zn, Cd, Fe, Sn) in LCD panels were investigated during thermal treatment, as well as their potential environmental risk and leaching toxicity in solid residue were evaluated. Results showed that Cr, Ni, In, Cu and Fe exhibit obvious migration behavior from solid into gas phase/fly ash during thermal treatment, with the maximum migration rate of 52.8%, 54.7%, 37.7%, 30.8%, and 34.9% respectively under the experimental condition. Speciation transformation for the metals of Cr, Ni, In, Cu, Fe and Zn was also observed in solid residue after thermal treatment, which leads to the ecological risk increase of Cu, In and contamination risk increase of Fe. Meanwhile, the leachable concentration and leaching toxicity of Cu and Ni in solid residue showed increasing trend after thermal treatment. The results indicate that attentions should be paid on the emission control of Cr, Ni, In, Cu, Fe during thermal treatment of LCD panel scraps. Environmental risk of Cu, In, Fe and the leaching toxicity of Ni in solid residue after thermal treatment should also be concerned.