Green recycling approach to obtain nano- and microparticles from expanded polystyrene waste

In this study, we develop a completely green process that could generate a recycled and value added product of polystyrene (PS), such as micro- and nanosized particles, from waste expanded PS (EPS). The process uses the eco-friendly solvent, d-limonene for dissolving waste EPS. We show the first time use of water as a nonsolvent for the recovery of micro- and nanosized PS particles based on an emulsification-diffusion method. Water forms a low boiling azeotrope with d-limonene and reduces the operating temperatures significantly. Poly(vinyl alcohol) (PVA), a water-soluble polymer, is used for stabilizing the oil-water emulsion and to control the particle size. The obtained particles were characterized using scanning electron microscopy, FTIR and dynamic light scattering techniques. Effect of PS and PVA concentrations, stirring speed and oil to water (o/w) ratio on the yield and particle size were investigated. The spent solvent was recovered using a distillation process that was carried out along with the emulsification-diffusion, making the process more efficient and sustainable.