Plastic waste as a valuable resource: strategy to remove heavy metals from wastewater in bench scale application.

Single-use plastic waste is gradually considered a potential material for circular economy. Ion exchange resin obtained from polystyrene waste by sulfonating with HSO was used for heavy metal removal from electroplating wastewater. Batch mode experiments of Cu, Zn, and Cd were carried out to determine effect of pH, initial concentration, equilibrium time, and the isotherm and kinetic parameters; the stability of the resin in continuous operation was then evaluated. Finally, the longevity of the resin after being exhausted was explored. The results indicated that at pH 6, a pseudo-second-order kinetic model was applicable to describe adsorption of studied heavy metals by sulfonated polystyrene with adsorption capacities of 7.48 mg Cu/g, 7.23 mg Zn/g, and 6.50 mg Cd/g, respectively. Moreover, the ion exchange process between sulfonated polystyrene resin and Cu, Zn, Cd ions followed the Langmuir isotherm adsorption model with R higher than 96%. The continuous fixed-bed column in conditions of a sulfonated polystyrene mass of 500 g, and a flow rate of 2.2 L/h was investigated for an influent solution with known initial concentration of 20 mg/L. Thomas and Yoon-Nelson models were tested with regression analysis. When being exhausted, the sulfonated polystyrene was regenerated by NaCl in 10 min with ratio 5 mL of NaCl 2 M per 1 g saturated resins. After 4 times regeneration, the heavy metal removal efficiency of sulfonated polystyrene was reduced to 50%. These aforementioned results can figure out that by sulfonating polystyrene waste to synthesize ion exchanging materials, this method is technically efficient and environmentally friendly to achieve sustainability.