Selective Separation of PVC from PET/PVC Mixture Using Floatation by Tannic Acid Depressant

Production and consumption of plastic materials have increased in recentdecades. The increase in plastic production and consumption has been largelyresponsible for the increase in plastics waste production. The problem ofplastics waste is quite important in terms of environmental sustainability and solidwaste management. Plastics recycling requires the separation of materials insofar asbeing almost pure. To achieve this goal in an economical way, technologies developedin mineral processing are of great help. Each method has certain capabilities andlimitations. Instance separation of PET and PVC by gravity techniques is practically notapplicable, due to slight differences in density. In this research, separation of PET andPVC by selective floatation was studied. The use of floatation for plastic separation isparticularly challenging because of inherent hydrophobic nature of plastics surfaces. Toseparate PET and PVC, from the mixture of the two, by floatation should make one ofthem hydrophilic and wettable by water. This can be achieved by several methodsamong which the addition of a wetting agent that interacts with the surface layer is oneof many techniques designed. In this study, tannic acid was employed as thedepressant of PET. The results showed that, virgin materials can be separated with99.62% efficiency. In the case of post-consumer PET and PVC, 88.40% separationefficiency was achieved at optimum conditions. Also, in virgin and postconsumermaterials, difference in the contact angles of PET and PVC increased as tannic aciddosage increased. Besides, the results indicated that the pH of the conditioning step isvital with respect to separation efficiency.