In 2003, 2.16 million tons of polyvinyl chloride (PVC) have been produced in Japan, i.e. the third large proportion of plastic production. However, only 20% of PVC wastes have been recycled, while the rest was disposed or incinerated. In order to improve the PVC recycling rate, a two-stage separation process that combines the triboelectric separation and the air tabling has been designed. The developed process is able to sort PVC from other types of plastics.
The efficiency of the process was investigated for two three-component plastic mixtures, i.e. (1) ABS (acrylonitrile-butadiene-styrene), PP (polypropylene) and PVC, which are used in production of home electric appliances or automobiles; and (2) PET (polyethylene terephthalate), PP and PVC, which are utilized in production of plastic containers or everyday products.
In order to sort the ABS-PP-PVC mixture, the triboelectric separator was employed in the first stage of process to collect the ABS flakes as positively charged fraction. The negatively charged fraction of PP and PVC was then separated by means of the air table by taking advantages of differences in density. Hence, at the end of the process, the collected PVC fraction had a grade and a recovery of 90.2% and 78.0%, respectively. Regarding the separation of the PET-PP-PVC mixture, the air table was used in the first stage to collect the PP flakes as a low-density fraction. Then, the triboelectric separator was employed in the second stage to recover 89.0% of PVC with a grade of 93.7%.
