The purpose of this study is to develop froth flotation to separate polyvinyl chloride (PVC) from automobile shredder residue (ASR) plastic mixtures of variable composition. Some polymers in ASR polymer mixtures have similar density and hydrophobicity with PVC and thus selective flotation of PVC from ASR polymer mixtures cannot be achieved. The present study focused on the surface modification of PVC with ozonation, and then the modified PVC can be separated from other polymers by the following froth flotation. The results of this study indicate that the selective recovery of PVC from real ASR polyethylene tetra pethelate (PET), polymethyl methacrylate (PMMA), polybutyl methacralate (PBMA), ethyl acrylate (EA), polycarbonate (PC) and rubber mixtures can be accomplished in a three-step process involving a gravity separation, ozonation and froth flotation. The rubber was removed from other heavy ASR (PVC, PET, PMMA, PBMA, EA and PC) polymers by froth flotation without mixing. It was found that ozonation process produced the desired difference in contact angle required (from 89.5 to 73.0 degrees ) for separation of PVC from other heavy ASR polymers, whereas the contact angles of other polymers was slightly decreased. The most of the load ASR, i.e. about 72.4% is floated away and 27.6% was settled down. The highest component 96.7% of PVC was recovered in the settled fraction. As a result of this research effort, the surface modification of PVC with ozonation can be efficiently useful to separate the PVC from other similar density ASR mixed polymers.

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Selective surface modifi cation of polyvinyl chloride (PVC) by ozonation was evaluated to facilitate the separation of PVC from other heavy plastics with almost the same density as PVC, especially polyethylene terephthalate (PET), by the froth fl otation process. The optimum froth fl otation conditions were investigated, and it was found that at 40°C, 90% of PVC and PET plastics fl oated. The bubble size became larger and the area covered with bubbles on the plastic surface was reduced with increasing temperature. Optimum PVC separation was achieved with the fl otation solution at 40°C and mixing at 180-200 rpm, even for sheet samples 10 mm in size. Combined treatment by ozonation and froth fl otation is a simple, effective, and inexpensive method for PVC separation from waste plastics.

The surface modification mechanism of polyvinyl chloride (PVC) by ozonation was investigated to study the selective hydrophilization of PVC surface among other plastics. Infrared analysis confirmed the increase of hydrophilic groups. XPS analysis revealed that the increase was due to the structural change in chlorine group in PVC to hydroxylic acid, ketone, and carboxylic groups by ozonation. This chemical reaction by ozone could occur only for polymers with chlorides in its structure and resulted in the selective hydrophilization of PVC among various polymers.