Electrostatic separation is able to process mixtures of plastics from waste electrical and electronic equipment. The efficiency of the electrostatic separation depends on the electric charge acquired by the particles in the appropriate tribocharging devices. The aim of the present work is to validate the possibility of using a roll-type electrostatic separator to sort mixtures of particles which are difficult to process by other means. In this type of separator, the plastic particles are charged by triboelectric effect. Two types of charging devices have been used: fluidized bed and rotating-multicylinder. Two series of experiments were performed with samples composed in equal proportions of: (1) acrylonitrile butadiene styrene (ABS) and polystyrene (PS); (2) polypropylene (PP) and polyethylene (PE). A third series of experiments were carried out with a mixture of three plastics: polypropylene (PP), polyethylene (PE) and acrylonitrile butadiene styrene (ABS), and the last series of experiment were carried out with a mixture four plastics of (PE / PP / ABS / PS), with an average particle diameter ranginig between 3 mm and 6 mm. The efficiency of the electrostatic separation was evaluated by measuring the charge, the purity and the recovery of the granules collected at the outlet of the electrostatic separation. The results confirm that the separation of ABS / PS and PP / PE mixtures is feasible and the best separation results were obtained using the fluidized bed tribocharger.

The aim of this paper is to quantify the effects of dielectric barrier discharge (DBD) exposure on the physico-chemical and tribo-electric properties of polymers. The study was conducted in atmospheric air on polypropylene, polyethylene and polyvinyl-chloride. These three types of polymers are widely used in industry. The polymers were characterized by means of an optical profilometer, a fourier-transform infrared (FTIR) spectrometer and an electric charge measurement system. The latter is composed of a Faraday pail connected to an electrometer. The profilometer analyses showed that the DBD plasma treatment has increased the surface roughness of the three polymers. FTIR revealed that oxygen atoms and polar groups were grafted on their surfaces, thereby conferring them a hydrophilic character. The short (2 sec) DBD plasma treatment has considerably improved the electrostatic charge acquired by the polymers during electrostatic tribo-charging, while longer exposures conferred the polymer anti-static properties and decreased its tribo-charging capability. The correlation between the results of the physico-chemical analyses and the tribo-electric behavior has been discussed.