Recycling of plastic waste by density separation: prospects for optimization.

A review of existing industrial processing and results of alternative processing investigations for separating solid mixtures and specifically recycling plastic waste by density separation is presented. Media density separation is shown to be fundamental for separation and/or pre-concentration in the recycling of plastics. The current use of static media processes limits the capacity and size of material that can be treated commercially. Investigations have shown that the hydroscopic properties of plastics can be reduced to improve such separations. This indicates that an alternative processing method is required to increase the commercial recovery of recyclable plastics. Cylindroconical and cylindrical cyclone-type media separators, such as those used for processing coal, are reviewed and suggested as a potential substitute. Both have superior production capacities and are able to process a larger range in particle sizes treated. A summary of results of investigations with cyclone media devices for recycling plastics is presented.