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Novel solid-supported ionic liquid (Si-Sal-SSIL) was synthesized by immobilization of 1-methyl-3-(3-trimethoxysilylpropylimidazolium) salicylate [MTMSPI][Sal] ionic liquid onto the activated silica gel. First, the [MTMSPI][Sal] ionic liquid was derived from the reaction of a metathesis product of 1-methyl-3-(3-trimethoxysilylpropylimidazolium) chloride [MTMSPI][Cl] with sodium salicylate through an ion-exchanged reaction. [MTMSPI][Sal] was purified and characterized through ion-chromatography, CHN and Karl-Fischer titration analyses. Further characterizations on [MTMSPI][Sal] were carried out by 1 H NMR and FTIR analyses. Si-Sal-SSIL was successfully prepared and confirmed through BET and solid-state NMR analyses. Si-Sal-SSIL showed better removal capacities towards Pb(ii) and Ni(ii) ions in comparison to native activated silica gel. Si-Sal-SSIL was then applied as solid adsorbent for an efficient removal of Pb(ii) and Ni(ii) from the aqueous solution. A series of batch sorption study were performed to explore the influence of parameters i.e. , loading ratio of activated silica gel to [MTMSPI][Sal], pH, mixing time, initial concentration of analyte towards the adsorption of Pb(ii) and Ni(ii) ions onto Si-Sal-SSIL as a function of removal efficiency. Under optimized conditions, the sorption kinetics for removal of both metals agreed with pseudo-second order linear plots. The mechanism of Pb(ii) and Ni(ii) sorption by Si-Sal-SSIL gave good fits for Langmuir model., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The main objectives of this study are to synthesize a new solid-supported ionic liquid (SSIL) that has a covalent bond between the solid support, i.e., activated silica gel, with thiosalicylate-based ionic liquid and to evaluate the performance of this new SSIL as an extractant, labelled as Si-TS-SSIL, and to remove Pb(II) ions from an aqueous solution. In this study, 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium thiosalicylate ([MTMSPI][TS]) ionic liquid was synthesized and the formation of [MTMSPI][TS] was confirmed through structural analysis using NMR, FTIR, IC, TGA, and Karl Fischer Titration. The [MTMSPI][TS] ionic liquid was then chemically immobilized on activated silica gel to produce a new thiosalicylate-based solid-supported ionic liquid (Si-TS-SSIL). The formation of these covalent bonds on Si-TS-SSIL was confirmed by solid-state NMR analysis. Meanwhile, BET analysis was performed to study the surface area of the activated silica gel and the prepared Si-TS-SSIL (before and after washing with solvent) with the purpose to show that all physically immobilized [MTMSPI][TS] has been washed off from Si-TS-SSIL, leaving only chemically immobilized [MTMSPI][TS] on Si-TS-SSIL before proceeding with removal study. The removal study of Pb(II) ions from an aqueous solution was carried out using Si-TS-SSIL as an extractant, whereby the amount of Pb(II) ions removed was determined by AAS. In this removal study, the experiments were carried out at a fixed agitation speed (400 rpm) and fixed amount of Si-TS-SSIL (0.25 g), with different contact times ranging from 2 to 250 min at room temperature. The maximum removal capacity was found to be 8.37 mg/g. The kinetics study was well fitted with the pseudo-second order model. Meanwhile, for the isotherm study, the removal process of Pb(II) ions was well described by the Freundlich isotherm model, as this model exhibited a higher correlation coefficient (R 2 ), i.e., 0.99, as compared to the Langmuir isotherm model.

This paper investigated the solubility of carbon dioxide (CO 2 ) in an aqueous solution of monoethanolamine (MEA) and 1-butyl-3-methylimidazolium dibutylphosphate ((BMIM)(DBP)) ionic liquid (IL) hybrid solvents. Aqueous solutions of MEA-(BMIM)(DBP) hybrid solvents containing different concentrations of (BMIM)(DBP) were prepared to exploit the amine's reactive nature, combined with the IL's non-volatile nature for CO 2 absorption. Response surface methodology (RSM) based on central composite design (CCD) was used to design the CO 2 solubility experiments and to investigate the effects of three independent factors on the solubility of CO 2 in the aqueous MEA-(BMIM)(DBP) hybrid solvent. The three independent factors were the concentration of (BMIM)(DBP) (0-20 wt.%), temperature (30 °C-60 °C) and pressure of CO 2 (2-30 bar). The experimental data were fitted to a quadratic model with a coefficient of determination ( R 2 ) value of 0.9791. The accuracy of the developed model was confirmed through additional experiments where the experimental values were found to be within the 95% confidence interval. From the RSM-generated model, the optimum conditions for CO 2 absorption in aqueous 30 wt% MEA-(BMIM)(DBP) were 20 wt% of (BMIM)(DBP), a temperature of 41.1 °C and a pressure of 30 bar.