Synergistic effect of lignin incorporation into polystyrene for producing sustainable superadsorbent

Lignin has gained intensive interest as an excellent raw material for the generation of advanced green products. Polystyrene (PS) is known for its worldwide application in water purification processes. To induce a sustainable PS, kraft lignin (KL) and polystyrene were polymerized via free radical polymerization in a facile aqueous emulsion process. KL enhanced surface area and porosity of PS. The physicochemical properties of induced KL-PS were analyzed, and the fate of lignin in KL-PS was discussed fundamentally. Wettability and surface energy analyses were implemented to monitor the surface properties of KL, PS and KL-PS. Incorporation of KL in PS (40 wt%) boosted its surface energy and oxygen content, which led to KL-PS with better compatibility than PS with copper ions in aqueous systems. A quartz crystal microbalance with dissipation (QCM-D) confirmed the noticeably higher adsorption performance of copper ion on KL-PS than on PS and KL. The sorption mechanism, which was revealed by FTIR studies, was primarily attributed to the coordination of Cu(ii) and hydroxyl group of KL-PS as well as the quadrupolar system of KL-PS.