Synthesis and characterization of novel solid-supported salicylate-based ionic liquid for adsorptive removal of Pb(ii) and Ni(ii) ions from aqueous solution.

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 1H 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.

Synthesis and Characterization of Novel Thiosalicylate-based Solid-Supported Ionic Liquid for Removal of Pb(II) Ions from Aqueous Solution.

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 (R2), i.e., 0.99, as compared to the Langmuir isotherm model.

Experimental and Mathematical Modelling of Factors Influencing Carbon Dioxide Absorption into the Aqueous Solution of Monoethanolamine and 1-Butyl-3-methylimidazolium Dibutylphosphate Using Response Surface Methodology (RSM).

This paper investigated the solubility of carbon dioxide (CO2) 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 CO2 absorption. Response surface methodology (RSM) based on central composite design (CCD) was used to design the CO2 solubility experiments and to investigate the effects of three independent factors on the solubility of CO2 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 CO2 (2-30 bar). The experimental data were fitted to a quadratic model with a coefficient of determination (R2) 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 CO2 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.