Preparation of sol-gel materials doped with ionic liquid and extractant for cerium(III) extraction

Silica materials (ILDEHPASGs) consisting of ionic liquids and di-(2-ethylhexyl)phosphoric acid (DEHPA) for Ce(III) extraction was prepared by a sol-gel method using the hydrophobic ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim]PF6) as porogen and solvent medium. The ILDEHPASGs were characterized by scanning electron microscopy, Brunauer-Emmett-Teller surface area, Fourier transform infrared, and thermogravimetric analyses. The results indicated the doping of DEHPA and [C8mim]PF6 in ILDEHPASG-3 would evidently affect the formation of porous structure of sol-gel materials. ILDEHPASG-3 also possessed more channels and macropores than the blank sorbent; the surface area and pore volume of ILDEHPASG-3 were 409 m2 g-1 and 0.444 cm3 g-1, respectively. [C8mim]PF6 and DEHPA were only physically confined or entrapped in the growing covalent silica network rather than chemically bound to the inorganic matrix. The majority of [C8mim]PF6 and DEHPA were stably immobilized in the gel. Then, the effects of contact time and pH were determined. The results showed the sorption of Ce(III) strongly depended on the contact time and pH, and ILDEHPASGs had high sorption ability for Ce(III). The results were analyzed by both Langmuir and Freundlich adsorption isotherm models, and the latter was found to give a better fit. (author)