Selective recovery of PVC-free polymers from ASR polymers by ozonation and froth flotation

Abstract

The present study focused on the selective recovery of poly(vinyl chloride) (PVC)-free polymers from automobile shredder residue (ASR) polymers by ozonation and froth flotation. Three different heavy ASR polymer samples were used. Appropriate alkaline washing was done as a pretreatment for the removal of the pollutants from the ASR polymer surface. The samples grinded by two different methods (two-shaft shear shredder and single-shaft rotary grinder) were compared for the behavior of PVC in the froth flotation. Ozonation with pre-washed by alkaline solution of PVC polymer in ASR has been found to significantly modify the hydrophilicity when compared to PVC polymer without pre-washing with alkaline solution. Whereas, alkaline washing did not change the surface hydrophobicity of other heavy polymers. It is found from the results that ozonation (with alkaline washing) has changed the contact angle of PVC from 80.7° to 55.7°, 82.4° to 59.1° and 82° to 59.6°, whereas little decrease of the contact angle was observed on other heavy ASR polymers. This result indicates that 93.5–96.4% PVC-free ASR polymer was successfully recovered with less than 0.1–0.2% of PVC by the froth flotation after ozonation in different ASR compositions. Ozonation with pre-washed by alkaline solution of ASR has significantly improved the PVC purity.