Synthesis of N-Methylimidazolium Functionalized Strongly Basic Anion Exchange Resins for Adsorption of Cr(VI)

N-Methylimidazolium functionalized strongly basic anion exchange resins in the Cl- form (RCI) and SO46- form (R2SO4) were synthesized and employed for adsorption of Cr(VI) from aqueous solution. FT-IR and elementary analysis proved the structures of anion exchange resins and the content of functional groups. The gel-type strongly basic anion exchange resins had high thermal stability according to TGA and good chemical stability under the experimental conditions. The adsorption behaviors of Cr(VI) on RCI and R2SO4 were studied using the batch technique. It was shown that adsorption equilibrium was reached rapidly within 60 min. The adsorption data for RCI and R2SO4 were consistent with the Langmuir isotherm equation. The maximum adsorption capacities of RCI and R2SO4 were 132 and 125 mg/g, respectively, with almost all active sites fully occupied. RCI and R2SO4 Could be used in the wide pH range 1-12 and were very suitable to remove Cr(VI) at a low concentration level. They also showed great preference to Cr(VI) compared to the other counterions. RCI was easily regenerated using the mixed solution of 0.3 mol/L NaOH and 0.3 mol/L NaCl, and retained nearly 100% of its orginal capacity during four cycles.