Triboelectric Charging and Electrostatic Separation of Granular Polymers Containing Brominated Flame Retardants

Abstract

The general purpose of the present article is to study the feasibility of removing brominated flame retardant (BFR) polymers from mixed granular wastes using triboelectric charging and electrostatic separation techniques. The study was carried out on mixtures consisting of equal quantities of plastic particles either BFR-free or containing 4.8% of hexabromobenzene (i.e., 40 000 ppm of bromine). Three triboelectric charging devices were used-a vibrating tribocharger [a container made of stainless steel, polystyrene (PS), or polypropylene (PP), and fixed on a vibrating table], a rotating cylinder tribocharger made of polyvinyl chloride, or a fluidized bed tribocharger, the walls of which were made of either poly methyl methacrylate, PS, PP, or polyethylene (PE). The experiments were carried out on three granular mixtures [BFR high impact PS (HIPS)/BFR-free HIPS, BFR PP/BFR-free PP, BFR PE/BFR-free PE]. The selective sorting of the granular mixtures was performed using a roll-type electrostatic separator. The results confirm that separating BFR plastics from BFR-free plastics is feasible. Best separation results were obtained for the mixtures tribocharged in the fluidized bed tribocharger.