Hierarchical tetrazolium-based hyper-crosslinked polymer for rapid nitrophenol removal from wastewater

In this work, a novel nitrogen-rich hierarchical porous hyper-crosslinked polymer (HCP) is fabricated from tetrazolium (TTC) to effectively remove p-nitrophenol (4-NP) from aqueous solution. HCP is prepared through the facile Friedel-Crafts alkylation, using dimethoxymethane as the crosslinker and benzene as the co-monomer, which is aimed at adjusting the degree of crosslinking, as well as the pore structures of the material. HCP presents hierarchical flocculent structures formed by the random accumulation of tremendous nanoparticles, with a BET surface area up to 1185 m2 g−1. Its adsorption capacity for 4-NP is ca. 434.8 mg g−1 at room temperature in a solution with an initial concentration of 1 mg g−1. Its adsorption complies with pseudo-second-order dynamic model and its isotherms accord with Freundlich equation. The adsorption is an enthalpy-driven spontaneous process and the equilibrium can be established in 10 min. Thermodynamic properties and IR spectra analyses reveal that electrostatic attraction, H-bonds and π-π interactions collaboratively contribute to the adsorption. The HCP is stable enough that its adsorption capacity retains more than 90% after 6 cycles, which offers guarantee for its practical application in phenol removal.