Preparing Microgranules from Waste Polystyrene through a Novel Temperature- and Nonsolvent-Induced Phase Separation Method for Potential Adsorbent

Recycling post-consumer waste polystyrene (WPS) into useful high-value products is of great environmental and engineering interest. In this study, microgranules were prepared from WPS and were used as a potential adsorbent for heavy metal removal from aqueous solution. In comparison with the conventional approach preparing polymer particles from dilute polymer solutions, a new process that can use semidilute or concentrated polymer solutions to prepare microgranules was developed. The process employed a method of combined temperature- and nonsolvent-induced phase separation to prevent the possible aggregation of the polymer particles and, thus, made it possible to obtain microgranules from semidilute or concentrated polymer solutions. Depending on the concentration of the polymer solution, irregular and more porous or spherical and less porous microgranules were prepared. As a potential application, microgranules were coated with poly (acrylic acid) (PAA) and examined as an adsorbent for lead ion removal. It was found that the coated microgranules had good adsorption performance and fast adsorption kinetics in removing lead ions from aqueous solution. The work illustrates the great potential in reducing WPS from the solid waste stream and converting WPS into high-value microgranules that might have many applications as adsorbents in water and wastewater treatment or other industrial processes.