Polymers recycling from automobile shredder residue (ASR): Separation of poly vinyl chloride (PVC) from ASR by froth flotation with ozonation

摘要

The research work was designed to find total ASR polymer recycling system. Main problem of ASR recycling is associated with PVC, which is contained about 5-10%, since the thermal degradation of PVC leads to generation of environmental hazardous chlorinated compounds such as hydrogen chloride and dioxins. Four-step process was successfully applied for real ASRs; a gravity separation, alkaline washing, ozonation and froth flotation. Ozonation with pre-washing of ASR by alkaline solution selectively modified PVC surface to hydrophilic without little change in other heavy polymers. The contact angles of PVC changed from 80.7 to 55.7, 82.4 to 59.1 and 82 to 59.6 for three ASR samples, whereas little decreases of the contact angles were observed on other heavy ASR polymers. During ozonation rubber was recovered as a settled fraction. Although polymers including PVC were floated during ozonation, adequate mixing made PVC settled down and other polymers floated. As a result, more than 80-85% of heavy polymers could be recovered with less than 1% of PVC.