Faculty of Applied Sciences
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Item Influence of temperature on molecular interactions of imidazolium-based ionic liquids with acetophenone: thermodynamic properties and quantum chemical studies(Royal Society of Chemistry, 2016) Bahadur, Indra; Masilo, Kgomotso; Ebenso, Eno, E.; Redhi, Gan G.The physicochemical properties namely: densities (ρ), sound velocities (u), viscosities (η), and refractive indices (nD) of a series of alkyl imidazolium-based ionic liquids (ILs) with same cation and different anion and vice versa of ILs: 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM]+[BF4]−, 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM]+[PF6]−, 1-ethyl-3-methylimidazoium ethyl sulphate [EMIM]+[EtSO4]− and 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM]+[BF4]−, with acetophenone over the wide range of composition and at (293.15, 303.15, 313.15, 323.5 and 333.15) K under atmospheric pressure is reported in this study. The excess molar volumes, (VEm), deviation in isentropic compressibilities (Δκs), deviation in viscosities (Δη) and deviation in refractive indices (ΔnD) were derived from experimental results. The VEm, Δκs and ΔnD values for the mentioned systems are both negative and positive over the entire composition range while the Δη values are negative under the same experimental conditions. The derived properties were fitted to the Redlich–Kister polynomial equation to check the accuracy of experimental results. Furthermore, the inter-ionic interactions between the cations and anions of the ILs both in vacuo and in acetophenone (using continuum solvation) were confirmed using quantum chemical technique such as [Density Functional Theory (DFT)]. The quantum chemical results are in good agreement with the experimental results suggesting that there exist appreciable interactions between the ILs and acetophenone. The theoretical and measured data were interpreted in terms of intermolecular interfaces and structural effects between similar and dissimilar molecules upon mixing in order to obtain more information on the thermophysical and thermodynamic properties of ILs and their binary mixtures. This study will contribute to the data bank of thermodynamic properties of IL mixtures, so as to establish principles for the molecular design for chemical separation processes and to enhance the applications of ILs in certain aspects of research or industrial application.Item Synthesis and characterization of 2′,3′-epoxy propyl-N-methyl-2-oxopyrrolidinium salicylate ionic liquid and study of its interaction with water or methanol(Royal Society of Chemistry, 2016) Vasanthakumar, Arumugam; Bahadur, Indra; Redhi, Gan G.; Gengan, Robert MoonsamyImportant physico-chemical properties of ionic liquids (ILs) can be manipulated by adjusting the nature of the cation or anion. These properties are exploited in applications such as organic synthesis, catalysis and electrochemical processes to mention a few. In this work, the novel pyrrolidone ionic liquid N-(2′,3′-epoxypropyl)-N-methyl-2-oxopyrrolidinium salicylate [EPMpyr]+[SAL]− was synthesized using two steps and characterized. The temperature dependent density and speed of sound for ionic liquid, methanol, water, and their corresponding binary mixtures of {IL (1) + methanol or water (2)} were measured over the entire range of mole fractions at temperatures from T = (293.15 to 313.15) K in steps of 5 K, under atmospheric pressure. The calculated thermodynamic properties such as excess molar volume VEm, isentropic compressibility ks, intermolecular free length Lf, and deviation in isentropic compressibility Δks, were derived from the investigated density and speed of sound data. The resulting experimental data for excess molar volumes VEm, intermolecular free length Lf, and deviation in isentropic compressibility Δks, were well fitted to the Redlich–Kister polynomial equation. The effect of temperature and concentration on thermophysical properties was also provided.Item Efficient catalytic activity of ionic liquid-supported NiFe2O4 magnetic nanoparticle doped Titanium Dioxide nano-composite(IJCEA, 2016-12) Vasanthakumar, Arumugam; Redhi, Gan G.; Gengan, Robert MoonsamyIn this work the author disclose an effective and environment-friendly approach to the preparation of an ionic liquid supported, magnetic nanoparticle doped titanium oxide nanocomposite. The novel ionic liquid N-(2′, 3′-epoxypropyl)-N-methyl-2- pyrrolidonium salicylate was first synthesized and characterized by 1H-NMR, 13C-NMR, elemental Analysis and FTIR. It was subsequently used for the preparation of a composite material by traditional protocols. This ionic liquid is able to connect the NiFe2O4 magnetic nanoparticles with titanium dioxide via strong ionic liquid interactions. The composite was characterized by FT-IR, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDS) analysis, Transmission Electron Microscopy (TEM), High-Resolution Transmission Electron Microscopy (TEM) and Diffraction studies (DF). The catalytic activities of these composites were assessed by the reduction of nitro aniline with the aid of UV spectroscopy. Furthermore, the composite material was easily recovered and re-used with negligible loss of its catalytical activity.Item Analysis of lubricating grease by ICP-OES : a case study on preparation methodology(Asian Publication Corporation, 2016-01-30) Marume, Cathrine; Kumar, Bhajanthri Natesh; Redhi, Gan G.The aim of this study was to develop simple, cost effective and reliable sample preparation methods for the analysis of lubricating grease samples. Direct dilution, microwave digestion and emulsification methods were designed and compared for the analysis of Ca, B, Al, Na, Mo, Zn and Ba with inductively coupled plasma optical emission spectroscopy (ICP-OES). The direct dilution method gave most inconsistent results in terms of percentage recovery. The optimized microwave digestion and emulsification methods compared well and showed good reliability in terms of sensitivity and selectivity. The calibration curves resulting from oil emulsion has no significant difference with that of aqueous emulsions, but the stability of the emulsified samples was very low. The limit of detection and limit of quantification values obtained from the microwave digestion method were very low and therefore it is superior amongst the three methods for the analysis of various lubricating grease samples.Item Spectrophotometric determination of Cadmium(II) in water and soil samples using Schiff's bases(Asian Publication Corporation, 2016) Kumar, Bhajanthri Natesh; Kumar, S. Himagirish; Redhi, Gan G.A simple and rapid method was developed with the two novel Schiff ’s base ligands, (E)-N'-(2-hydroxy-5-nitrobenzylidene)isonicotinoylhydrazone and 2-(4-fluoro benzlideneamino)benzenothiol for monitoring the cadmium(II) in different water and soil samples. The two ligands react with cadmium(II) at pH 4.9/5.7 to form pale yellow/pale brown complexes with stoichiometric ratios of 1:1 (M:L). The complexes obeyed Beer’s law in the range of 2.0 and 2.5 mg L-1 with an excellent linearity in terms of the correlation coefficient of 0.99. The molar absorptivity and Sandell’s sensitivity of the complex systems were found to be 3.68 × 104, 4.32 × 104 L mol-1 cm-1 and 0.00298, 0.0034 μg cm-2, respectively. The limit of detection for cadmium(II) was noted as 0.042 and 0.063 μg L-1, respectively for these ligands. Furthermore, in vitro antimicrobial activities of both ligands and their complexes were successfully examined and reported.Item Excess molar volumes of binary mixtures (an ionic liquid + water) : A review(Elsevier, 2015-03) Bahadur, Indra; Singh, Sangeeta; Redhi, Gan G.; Venkatesu, Pannuru; Letcher, Trevor M.This review covers recent developments in the area of excess molar volumes for mixtures of {ILs (1) + H2O (2)} where ILs refers to ionic liquids involving cations: imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium and ammonium groups; and anions: tetraborate, triflate, hydrogensulphate, methylsulphate, ethylsulphate, thiocyanate, dicyanamide, octanate, acetate, nitrate, chloride, bromide, and iodine. The excess molar volumes of aqueous ILs were found to cover a wide range of values for the different ILs (ranging from −1.7 cm3 · mol−1 to 1.2 cm3 · mol−1). The excess molar volumes increased with increasing temperature for all systems studied in this review. The magnitude and in some cases the sign of the excess molar volumes for all the aqueous ILs mixtures, apart from the ammonium ILs, were very dependent on temperature. This was particularly important in the dilute IL concentration region. It was found that the sign and magnitude of the excess molar volumes of aqueous ILs (for ILs with hydrophobic cations), was more dependent on the nature of the anion than on the cation.