Dopamine‐Assisted Polyethyleneimine Deposition Modification of Hypercrosslinked Polystyrene for Enhanced Adsorption of the Dye Congo Red

ABSTRACT Congo red dye wastewater is highly toxic and nondegradable, posing a significant threat to the environment. Hypercrosslinked porous materials (HCP) are effective candidates for the removal of dyes from wastewater. In this study, hypercrosslinked polystyrene (HCPS) with high specific area (1073.08 m 2 /g) was synthesized by using waste expanded polystyrene (EPS) as starting material. HCPS was then modified through a simple dopamine‐assisted deposition of polyethyleneimine, resulting in the modified material HCPS@PDA/PEI, which retained a significant specific surface area of 738.36 m 2 /g and a porous structure with abundant functional groups. HCPS@PDA/PEI exhibits remarkable efficacy as a high‐performance adsorbent for the removal of Congo red (CR) from aqueous solutions. The adsorption process of CR conforms to the pseudo‐second‐order kinetic model. Further fitting with the Langmuir isotherm model elucidates that the adsorption of CR occurs as a monolayer chemical adsorption, with a maximum adsorption capacity of 1030.31 mg/g, which is triple that of the unmodified HCPS (291.54 mg/g). The adsorption activation energy and thermodynamic parameters substantiate that the adsorption process is chemical in nature, spontaneous, and endothermic. Consequently, HCPS@PDA/PEI holds considerable promise for applications in the treatment of dye‐contaminated wastewater.