Separation of virgin plastic polymers and post-consumer mixed plastic waste by sinking-flotation technique

The main objective of this research is to separate virgin polymers (PA, PC, PP, HDPE; PS and ABS) and post-consumer plastic waste from municipal solid waste (MSW) using the sinking-flotation technique. The separation was carried out on a pilot scale in a container of 800 l of useful volume with agitation of 160 rpm for one hour. Tap water, ethanol solutions and sodium chloride at different concentrations were used as the densification medium. The virgin polymers were separated into two groups, that is, a group of low-density polymers (HDPE and PP) and a group of high-density polymers (PS, ABS, PA, and PC). Polymers whose density was less than that of the medium solution floated to the surface, while those whose density was greater than that of the medium solution sank to the bottom. The experimental results showed that the complete separation of HDPE from PP was achieved at 23% v/v of ethanol. For the separation of the high-density polymers, up to 40% w / v sodium chloride was used. The recoveries of the polymers ranged from 70 to 99.70%. In post-consumer recycled plastic waste, fractions of 29.6% polyolefins, 37.54% PS, 11% ABS, 8% PA and 12% PC, PET and PVC were obtained. Finally, cast plates were made of the post-consumer waste to improve the identification of the type of polymer present in the separated fractions.