Hydroxyl-functionalized hypercrosslinked polymers with ultrafast adsorption rate as an efficient adsorbent for phenol removal

In the present study, the adsorptive potential of hypercrosslinked polymers (HCPs) was investigated for the removal of phenol from aqueous solutions. Herein, two HCPs were one-step synthesized by the Friedel-Crafts reaction using 4,4′-biphenyldiol (BPD) or hydroquinone (HQ) as the building unit and 1,4-bis(chloromethyl)benzene (DCX) as the external crosslinker. The results showed that the HCPs, derived from BPD and DCX (called as BPD-D), exhibited more excellent pore structures with the higher surface area of 697 m2 g−1 and the micropore volume of 0.23 cm3 g−1 and allowed for the extremely fast equilibrium adsorption of phenol, attributed to the hierarchical pore structure and the great hydrophilicity; meanwhile, the maximum adsorption capacity of BPD-D towards phenol was calculated to be 156.74 mg g−1. Moreover, the adsorption equilibrium and kinetic processes of BPD-D towards phenol were well described by the Freundlich model (R2 > 0.99) and the pseudo-second-order kinetic model (R2 > 0.9999) at 303 K. Moreover, negative changes in Gibbs free energy and enthalpy reflect that the adsorption of BPD-D for phenol is a spontaneous and exothermic process. In addition, adsorption performances were investigated under different conditions, e.g., the initial concentrations of phenol, the dosage of the BPD-D, the initial pH of phenol aqueous solution and recyclability. Our finding demonstrates that HCPs show potential application prospects in the removal of organic pollutants from wastewater.