SELECTIVE SEPARATION OF PVC FROM PET/PVC MIXTURE USING FLOATATION BY TANNIC ACID DEPRESSANT

Abstract

ABSTRACT Key Words: Selective Separation of PVC from PET/PVC MixtureUsing Floatation by Tannic Acid Depressant Mohammad Abbasi 1* , Mohammad Mehdi Salarirad 1 , and Ismail Ghasemi 2 (1) Department of Mining & Metallurgy Engineering, Amirkabir University of Technology, P.O. Box: 15875-4413, Tehran, Iran(2) Iran Polymer and Petrochemical Institute, P.O. Box: 14965/115, Tehran, IranReceived 17 May 2009; accepted 25 May 2010 P roduction 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 of plastics 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 and limitations. 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 is particularly 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 the depressant 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% separation efficiency was achieved at optimum conditions. Also, in virgin and postconsumer materials, 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.