Recovering plastics for recycling by mineral processing techniques

Abstract

Patents and other literature on recycling post-consumer plastics from various sources (e.g., municipal solid waste) indicate that unit operations common to minerals processing have been seriously considered at various times. A review of the available literature and statistics on recoverable plastics reveals that only 2.4 percent is recycled. This article presents a flowsheet that we developed and tested in a bench-scale pilot plant. It shows that a combination of mineral processing techniques, including comminution, heavy media separation, and flotation, can be successfully adapted to the recycling of post-consumer plastics. The gamma flotation process, which operates on the basis of solution surface tension control to facilitate the separation of inherently hydrophobic solids, combined with the alkali-treatment of a mixed polyvinal chloride-polyethylene terephthalate feedstock generates clean polymer concentrates at high recoveries.