Cationic Modified Benzimidazole-Linked Polymer: One-Pot Functional Synthesis and High Efficiency Adsorb Cr(VI) from Water

In this study, a cationic modified benzimidazole-linked polymer (BILP-NMP) was synthesized by a one-pot solvothermal method using 1,2,4,5-benzenetetraamine tetrahydrochloride and 1,3,5-triformylbenzene as reaction monomers that the imidazole groups were accidentally modified by the N-methyl-2-pyrrolidone (NMP) molecules for efficient adsorption of Cr(VI) in water. The structure of BILP-NMP was determined by a series of characterization methods. These results showed that the benzimidazole and cation-modified groups were synthesized successfully. The effects of pH, adsorbent dosage, temperature, coexisting ions, and initial concentration of Cr(VI) on adsorption were studied. BILP-NMP has a rapid adsorption process, which is superior to that of most previously reported adsorbents. The adsorption equilibrium can be quickly reached within 4 min, and the removal rate of Cr(VI) can reach more than 95%. The adsorption kinetics of Cr(VI) followed the pseudo-second-order model, the adsorption isotherm exhibited a significant correlation with the Langmuir isotherm model, and the adsorption capacity could reach 154.5 mg g^–1. Importantly, BILP-NMP maintained its efficiency and selectivity in adsorbing Cr(VI) even in the presence of metal cations and anions. These studies showed that BILP-NMP is a promising adsorbent for the efficient removal of Cr(VI) from wastewater.