Purity prediction of the two-stage high voltage electrostatic separation of a mixture of three polymers

Clean and efficient separation is an important requirement for the high-value-added recycling of end-of-life automobile polymers. In this study, polymer particles for vehicles were considered as research objects, and a two-stage electrostatic separation device was designed to separate a mixture of three polymer particles. A kinematic model of friction-charged particles in a two-stage free-fall separator was established. Then, a suitable time period for triboelectrostatic charging with regard to electrostatic separation was determined, and a charge-mass ratio distribution of mixed-polymer particles, that is, polyamide (PA), polypropylene (PP), and polyethylene (PE), was measured using a Faraday cage based on the triboelectrostatic charging experiment of three types of particles in a friction barrel-type tribocharger. The theoretical purities of PA, PP, and PE were calculated using the motion and particle charge-mass ratio distribution models were 100.00%, 89.51%, and 92.95% respectively. The experimental purities of PA, PP, and PE were 94.68%, 80.76%, and 84.27%, respectively, which is consistent with the theoretical purity. Results of the study can provide a theoretical and experimental reference for one-pass electrostatic separation of three kinds of plastic particles.