Direct synthesis of ordered N-methylimidazolium functionalized mesoporous silica as highly efficient anion exchanger of Cr(vi)

Abstract

Ordered N-methylimidazolium functionalized mesoporous silica (SBA-15) anion exchangers were directly synthesized by co-condensation of tetraethoxysilane with 1-methyl-3-(triethoxysilylpropyl)imidazolium chloride. The prepared samples with rod-like morphology showed high surface areas (>400 m² g⁻¹), well-ordered pores (>58 Å), and excellent thermal stability up to 387 °C. The adsorption behaviors of Cr(VI) from aqueous solution on the anion exchangers were studied using the batch method. The anion exchangers had high adsorption capacity ranging from 50.8 to 90.5 mg g⁻¹, over a wider pH range (1–8) than amino functionalized mesoporous silica. The adsorption rate was fast, and the maximum adsorption was obtained at pH 4.6. The adsorption data for the anion exchangers were consistent with the Langmuir isotherm equation. Most active sites of the anion exchangers were easily accessible. The mixed solution of 0.1 mol L⁻¹ NH₃·H₂O and 0.5 mol L⁻¹ NH₄Cl was effective desorption solution, and 95% of Cr(VI) could be desorbed.