Research on Flotation Technique of Separating PET from Plastic Packaging Wastes

Abstract

Flotation, as one efficient waste plastic separation technology, is an effective method to improve the recycling rate of packaging waste. Polyethylene terephthalate (PET) widely used in packaging industry, has a large number of consumption and high recovery value. Aiming at separating PET from plastic packaging wastes, a designed flotation column was used in laboratory to investigate the effects of parameters, such as wetting agent species and wetting agent concentration, on the flotation behaviors. The results showed that the primary flotation of PET/polyvinyl chloride(PVC)/polycarbonate(PC)/ polystyrene(PS)achieved the optimal effect with PS as floating materials and PET/PC/PVC sinking materials under 70mg/L of sodium dodecyl sulfate as wetting agent. When 3mol/L sodium hydroxide used to modify the mixed plastics and 8mmol/L of dibutyl sebacate (DBS) used as wetting agent, PET/PC/PVC separation in the secondary flotation achieved the optimal effect with PET floating rate being 3.56% and PC/PVC floating rate being 97.45% and 92.91% respectively. After two stages of flotation screening, the purity of recycled PET finally reached 90.91%, which indicated that the flotation process developed could effectively separate PET from four kinds of mixed plastics.