Synthesis of magnetic hyper-crosslinked polymer from waste-expanded polystyrene as efficient sorbent for removal of Congo red and crystal violet

Given that water contaminants pose a huge threat to the environment and human health, the significance of water pollution treatments becomes increasingly evident. In the meantime, white pollution is still a huge headache to the surroundings. Herein, based upon the concept of turning trash into treasure, a series of hyper-crosslinked polymers (named as EPS-HCPs: EPS-FDA, EPS-DCX, EPS-BCMBP) were fabricated through one-step Friedel-Crafts alkylation by adopting wasted expanded polystyrene (EPS) as the raw material and taking formaldehyde dimethyl acetal (FDA), dichloroxylene (DCX) and 4,4′-bis(chloromethyl)-1,1′-biphenyl (BCMBP) as cross-linker, respectively. EPS-HCPs were applied to remove Congo red and crystal violet from aqueous solution, and the EPS-BCMBP exhibited distinctly excellent removal performance. For the convenient separation and recycling of the sorbent, the EPS-BCMBP was modified with magnetism to produce magnetic EPS-BCMBP (M-EPS-BCMBP). The maximum adsorption capacity of M-EPS-BCMBP reached 2160 mg g−1 for Congo red and 303 mg g−1 for crystal violet, with extremely fast adsorption equilibrium time (5 min). The M-EPS-BCMBP could be served as one of ideal candidates for removal of dye pollutants. This work sheds light on establishing a facile strategy for converting wasted EPS into robust sorbents for dyes removal, which plays a key part in sustainable treatment of wastewater.