FLOTATION SEPARATION OF PLASTICS USING SELECTIVE DEPRESSANTS

Four important plastics, namely polyvinyl chloride (PVC), polycarbonat es (PC), poly acetal (POM) and polyphenylene ether (PPE) were successf ully separated from their synthetic mixtures using common wetting agen ts like sodium ligninsulfonate, tannic acid, Aerosol OT and saponin. T he efficient flotation separation amongst these naturally hydrophobic polymers could be attributed to the selective reduction in hydrophobic ity (measured as the drop in contact angle) as a consequence of surfac tant adsorption. The relative order of floatability measured with the help of column flotation experiments in the presence of various depres sants selected for this study was found to be PPE > POM > PC > PVC, a trend consistent with the critical surface tension values determined f or these solids except PPE. A flowsheet was developed on the basis of flotation results. It was possible to accomplish almost a perfect sepa ration using the proposed flowsheet involving heavy media separation f ollowed by flotation in two stages.