Electrostatic Separation of Mixed Plastic Resins


A new report provides insight into a series of experiments that were conducted to determine the feasibility of expanding sorting technologies to a range of rigid plastics (after removal of PET and HDPE bottles) in order to reduce sorting costs and increase revenue. The work was supported by Stewardship Ontario with technical assistance from the Environment and Plastics Industry Council (EPIC) and included electrostatic separation of mixed plastic resin (three to seven rigids) after an initial wash/float/sink separation.

The experiment involved approximately two tons of shredded rigid mixed plastics residues. The sink fraction consisted of 40% PET, 31% polystyrene, 24% vinyl and 4% polypropylene. An electrostatic separator was used to try to separate this material, but the charging of the particles was found to be inconsistent. Additional drying did provide some improvement and a relatively concentrated fraction of polystyrene in order to provide a stream suitable for processing. The other resins in the mixture could not be separated in an adequate fashion.

Results of the experiment show that electrostatic separation of mixed rigid plastic resins after an initial float/sink separation is unlikely to prove efficient when compared to optical sorting of rigid plastic containers through the use of optical and infrared sensors

See plastics.ca/epic.

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