Separation of plastic mixtures by sink-float combined with froth flotation

Abstract

The aim of this research was to separate a mixture of six post-consumer plastics (PS, PMMA, PVC-D, PVC-M, PET-D and PET-S) by combination of sink-float separation and froth flotation.. In sink-float method two mediums of separation were used: sodium chloride water solution and ammonium nitrate water solution. Sink-float method allowed complete separation of the less dense plastic (PS) from intermediate density plastics (PMMA and PVC-D) and from high density plastics (PET-S, PET-D and PVC-M); also allowed good separation of intermediate density plastics (PMMA and PVC-D) from high density plastics (PVC-M, PET-D and PET-S) with an efficiency close to 100%. Separation of PVC-M from PET-D and PET-S by sink-float method led to fair results allowing a separation efficiency of about 60%. Since PMMA and PVC-D have similar density, their separation was achieved by froth flotation, using sodium lignosulfonate as selective wetting agent of PVC-D, with a separation efficiency of 85%.

Keywords:
density separation; plastic; mixture; particle size