Optimization of froth flotation procedure for poly(ethylene terephthalate) recycling industry

This article addresses the separation of polyethylene terephthalate (PET) from ternary blends with polyvinyl chloride (PVC) and polystyrene (PS) by froth flotation. The experimental work was carried out with representative samples from post-consumer waste packages collected at drop-off-points. Previous to froth flotation, PET selective wetting was achieved by alkaline treatment followed by surfactant adsorption. For this purpose, an aqueous solution of NaOH and an industrial detergent commonly used for waste plastic washing were tested as alkaline treatment, and calcium lignosulphonate and Hostaphat were tested as surfactants. An enriched product with 98.9% grade in PET and only 0.6% in PVC was recovered in the nonfloated product. The PET recovery in this product was 97% while 96% of PVC and 91% of PS were recovered in the floated product. An analytical method was developed for the quantification of the waste plastic composition. The method was based on the selective dissolution of the plastics in the mixture.Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ECM/60335/200