Separation of PET from other plastics by flotation combined with alkaline pretreatment

Abstract

Plastics are naturally hydrophobic, so the selective flotation of plastic mixtures is impossible without changing their surface properties. The objective of this research is flotation separation of PET from PS, PMMA and PVC combined with sodium hydroxide pretreatment. NaOH pretreatment had a strong effect on PET's floatability, medium effect on PMMA and PVC and limited effect on PS. The reduction of PET floatability is ascribed to a sharp decline of contact angle. The optimal pretreatment conditions were: 10% NaOH concentration, 70 °C (PET/PMMA and PET/PVC) to 80 °C (PET/PS) and plastic treatment times in the alkaline solution of 20 min (PET/PMMA and PET/PVC) to 30 min (PET/PS). Flotation separations were achieved efficiently and the best results were obtained for the PET/PS mixture, with a floated PS grade of 98% and a sunk PET grade of 100%. PET and PS was separated effectively, implying that sodium hydroxide treatment possesses superior applicability.

Separation of PET and PS from PET/PS/PP plastic mixture and their use in synthesis of composite floating sorbent materials for dyes removal

“…The floatability of PET is almost complete over the pH range 2-7, reduced to 80% at pH 8, and to 60% at pH = 10. Flotation reduction of PET particles with the increase of pH may be attributed to PET's hydrolysis in alkaline pH 41 or to the formation of carboxyl acid and the appearance of hydroxyl ester end groups, 42 the last of which eventually renders the particles hydrophilic. In the pH range 2-10, the floatability of both PP and PS remained unaffected, both polymers being naturally hydrophobic.…”

The Use of Froth Flotation for Selective Separation of Plastic Wastes from Soil

“…The theoretical density (not measured; obtain from literature) of the plastics ranged from 0.86 g/cm 3 (PP), 0.96 g/cm 3 (PS), and 1.372 g/cm 3 (PET), [1], with particle size range of -2.36 to +2mm obtained by dry sieving. The flotation experiments were carried out by using, 0.1 g/L concentration of tannic acid (wetting agent) and Methyl isobutyl carbinol (MIBC); frothing reagent [6].…”

The Use of Froth Flotation for Selective Separation of Plastic Wastes from Soil

“…The theoretical density (not measured; obtain from literature) of the plastics ranged from 0.86 g/cm 3 (PP), 0.96 g/cm 3 (PS), and 1.372 g/cm 3 (PET), [1], with particle size range of -2.36 to +2mm obtained by dry sieving. The flotation experiments were carried out by using, 0.1 g/L concentration of tannic acid (wetting agent) and Methyl isobutyl carbinol (MIBC); frothing reagent [6].…”