Preparation of an ionic liquid-based hydrogel with hyperbranched topology for efficient removal of Cr(VI)

摘要

An imidazolium salt-based hydrogel with hyperbranched topology (hbGel-PEG-TTIm(+)Br(6)(-)) was proposed for efficient adsorption towards anionic hexavalent chromium ions (Cr(VI)). For the purpose, a bromo-terminated A(3) type monomer and a imidazole-terminated B-3 type monomer were firstly synthesized via O-esterification and Michael addition, respectively. Then, hbGel-PEG-TTIm(+)Br(6)(-) was obtained by the one-pot step polymerization of "A(3) + B-3" approach via N-alkylation reaction. The chemical structure and morphology of the as-prepared hydrogel were confirmed by Fourier transform infrared and scanning electron microscope. The cross-linking network structure was calculated according to the Flory-Rehner equilibrium swelling equation. The effects of solution pH, adsorbent dosage, contact time and initial Cr(VI) concentration on the adsorption performance were also investigated, and the maximum adsorption capacity could reach similar to 238 mg g(-1). In addition, the adsorption process of Cr(VI) on hbGel-PEG-TTIm(+)Br(6)(-) was well described by the pseudo-second-order kinetic model, and the adsorption equilibrium data fitted with Langmuir isotherm model better than Freundlich isotherm model. This novel hydrogel with hyperbranched topology can potentially be applied in the treatment of wastewater containing Cr(VI).