Flotation characterization of PET and PVC in the presence of different plasticizers

Abstract

Plastic is one of the most widely used materials in our daily life and industry. Recycling is an important activity in the minimization of waste that results from human activities. Depending on plastics surface characteristics, they can be separated from each other by flotation method which is useful mineral processing technique with its low cost and simplicity. To succeed in a separation of mixed polymers based on polymer type using selective flotation, it is necessary to render one surface more hydrophilic while the others are still in a hydrophobic state. The separation could be achieved with the help of appropriate plasticizer.In this paper, the characteristics of plastics particles and flotation behaviors of polyethylene terephthalate (PET) and polyvinyl chloride (PVC) were studied. The contact angle, liquid surface tension, zeta potential measurements and FITR analysis were performed in order to investigate the effect of plasticizer reagents and the success of froth flotation at plastic recycling. It was observed that contact angle values of PVC were smaller than PET in the presence of lignin alkali (LA) and diethylene glycol dibenzoate (DIB). Both plasticizer render PVC more hydrophilic and cause higher wettability. Therefore, PVC remains in the floatation cell while air bubbles are attaching to PET. At the end of the selective flotation experiments, PET was separated from the mixture of PET and PVC with 97% content and more than 99% recovery when using 25g/t LA as a plasticizer at pH 8. To succeed in a separation of PET from PVC by selective flotation, 250g/t DIB was added into the solution at pH 5 and PET particles were separated from the mixture at 90% content and 95% recovery.