Benzimidazole-based hyper-cross-linked polymers for effective adsorption of chlortetracycline from aqueous solution

Abstract In this study, benzimidazole-based hyper-cross-linked polymers (HCPs) with hierarchical pores were synthesized through facile one-step Friedel-Crafts reaction and applied to the adsorption of chlortetracycline from aqueous solution. The mole ratio of benzene to benzimidazole exerted a significant impact on the morphology and adsorption performance. The nano-layer structures of HCPs brought in considerable surface area while the hierarchical canals allowed free mass transfer, which facilitated effective contact between Lewis basic active sites and guest molecules. The chlortetracycline adsorption capacity of HCPs reached 456 mg g-1, higher than that of many other reported adsorbents. The adsorption equilibrium was achieved within 6 h and the kinetics complied with the pseudo-second-order rate equation. The equilibrium data were in good line with the Freundlich isotherm model, by which the adsorption thermodynamic parameters were obtained. Electron donor-acceptor (EDA) interaction, π−π interaction and hydrogen bonding were considered to be the main adsorption mechanism. HCPs could be easily regenerated by ethyl acetate elution. Moreover, HCPs could also adsorb other organic pollutants containing phenolic hydroxyl groups. The low-cost preparation, high adsorption capacity and easy regeneration proved the as-synthesized HCPs were ideal adsorbents for the removal of organic pollutants from wastewater.