Faculty of Applied Sciences
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Item Industrial application of ionic liquids for the recoveries of spent paint solvent(Elsevier, 2016) Moodley, Kandasamy; Mabaso, Mbongeni Hezekia; Bahadur, Indra; Redhi, Gan G.The recovery of industrially valuable organic solvents from liquid waste, generated in chemical processes, is economically crucial to countries which need to import organic solvents. In view of this, the main objective of this study was to determine the ability of selected ionic liquids, namely, 1-ethyl-3-methylimidazolium ethylsulphate, [EMIM][ESO4] and 1-ethyl-3-methylpyridinium ethylsulphate, [EMpy][ESO4] to recover aromatic components from spent paint solvents. Preliminary studies done on the liquid waste, received from a paint manufacturing company, showed that the aromatic components were present in the range of (6–21)% by volume. The separation of the aromatic components was performed with the ionic liquids listed above. The phases, resulting from the separation of the mixtures, were analysed with a gas chromatograph (GC) coupled to a FID detector. Chromatograms illustrate that the chosen ZB-Wax-Plus column gave excellent separation of all components of interest from the mixtures, including the isomers of xylene. The concentrations of aromatics recovered from the spent solvents were found to be in the % ranges of (13 − 33) and (23–49), respectively for imidazolium and pyridinium based ionic liquids. These results also show that there is a significant correlation between π-character of ionic liquids and the level of extraction. It is therefore concluded that ionic liquids have the potential for macro-scale recovery of re-useable solvents present in liquid waste emanating from paint manufacture.Item Extraction of aromatic solvents from reformates and paint solvent wastes during ionic liquids(2016) Mabaso, Mbongeni Hezekia; Redhi, Gyanasivan Govindsamy; Moodley, K. G.The work conducted in this study comprised three aspects: syntheses, characterizations, and multi-component liquid-liquid extractions. The main objectives of the project were: (1) to evaluate the efficacy and efficiency of ionic liquids to extract aromatic components from catalytic reformates and paint solvent wastes, and (2) to validate the method(s) used in this project to qualitatively and quantitatively analyze the aromatic molecules (BTEX) in multi-component mixtures. Therefore, this research critically investigated the major effects of the chosen ionic liquids as extractive solvents for the recovery of BTEX components from model and industrial organic mixtures. The project was concerned with the nature of solvents currently used in most industries for the separation by extraction of aromatic hydrocarbons from non-aqueous or organic mixtures. Most solvents currently employed for this purpose are highly volatile; hence they contribute significantly towards environment pollution. In addition, the extraction efficiency of these conventional solvents is limited only to mixtures containing aromatic hydrocarbons of 20% or more. Furthermore, conventional solvents are organic compounds which are generally toxic, flammable, and expensive to recover or regenerate from extract phases due to methods which involve several steps. In addition, they demand high energy input for the distillation steps. used in the analysis of aromatic components were evaluated for validity. According to the literature no such work was carried out by previous researchers. The study targeted four ionic liquids, namely, 1-ethyl-3-methylimidazolium ethyl sulphate [EMIM][ESO4], 1-ethyl-3-methylpyridinium ethyl sulphate [EMpy][ESO4], 1- Butyl-1-methyl-2-pyrrolidonium bromide [BNMP][Br], and 1,1-Dimethyl-2- pyrrolidonium iodide [MNMP][I] in an attempt to address this concern. These ionic liquids were synthesized and characterized in our laboratories using previously accepted methods. After synthesis and purification, they were characterized by techniques including FTIR, 1H-NMR, and 13C-NMR. The densities and moisture content of both the synthesized and standard ionic liquids were also determined using density meters and Karl-Fischer apparatus, respectively. The extractions were carried out on both the model and industrial mixtures using ionic liquids. Each ionic liquid was mixed with a target mixture in a water-jacketed vessel and then stirred vigorously at constant temperature achieved by a thermostatically controlled water-bath. After a selected period of time the operation was stopped and the resulting mixture was left to stand overnight to allow phase equilibration to be reached. The two phases were then separated and analyzed for the content of individual aromatic components in each phase using GC-FID calibrated with external standards of the components present in the mixtures being investigated. According to the results obtained from the synthesis and characterization methods the percentages yield of ionic liquids were reasonably high (> 95%). In addition, spectral studies showed high purity with fewer traces of impurities based on the observed relative intensities. Results from GC-FID indicated a relatively lower concentration of aliphatic hydrocarbons in the extract phase. On the other hand, the concentrations of aromatic II components in the extract phase were relatively higher than those of aliphatic hydrocarbons. The results obtained from the three extraction stages showed the total recovery of greater than 50% for the aromatic components. This suggests that at least six extraction stages would be required in order to achieve a total recovery of 100% aromatic components which is an indication of good efficiency. Also noticeable was that the first extraction stages for all ionic liquids recovery values were much higher than those values obtained from successive stages which showed approximately the same extraction results. In most experiments, 1-ethyl-3-methylpyridinium ethyl sulphate gave higher recovery values than the other three ionic liquids. It was also noted that the recovery values obtained from the extractions performed on model mixtures of the entire concentration range (0.5 – 25%) of individual aromatic components did not show any significant difference. Proportional difference in recoveries occurred across the entire concentration range of model mixtures. The results also indicated that the solubility of aromatic hydrocarbons in the ionic liquids decreases in the order: benzene > toluene > ethyl benzene >xylenes. This phenomenon is attributed to a decrease in π-π, cation- π, cation- anion interactions occurring between the ionic liquid and each of the aromatic molecules in this order. The recovery values for BTEX ranged from 80 to 120 % by volume for the three extraction stages. This is in line with results previous research studies carried out on liquid-liquid extractions involving ternary systems containing only one aromatic component in each mixture. Therefore this study shows that ionic liquids are capable extraction solvents for simultaneous recovery of the aromatic components from any organic mixtures containing low to high BTEX concentrations. In addition, the outcomes of this project have proved that ionic liquids are economically viable as potential extraction solvents since they can be easily recycled and reusable many times without any noticeable degradation. The results of this study are envisaged to make significant contributions to the current research efforts aimed at achieving greener environments and minimization of global warming. The findings of this project are also geared to boost the economy of our country through job creation using economically viable methods.Item Separation of aromatic solvents from oil refinery reformates by a newly designed ionic liquid using gas chromatography with flame ionization detection(Wiley Online Library, 2015-02-26) Bahadur, Indra; Singh, Prashanth; Kumar, Sudharsan; Moodley, Kandasamy; Mabaso, Mbongeni Hezekia; Redhi, Gan G.The aim of this study was to determine whether the new ionic liquid, N,N-dimethyl-2-oxopyrrolidonium iodide, synthesized in our laboratory is a suitable solvent for the separation of aromatic components benzene, toluene, ethylbenzene, and xylenes from petroleum mixtures (reformates) in liquid–liquid extraction. In pursuance of the above aim, a method to extract all components of a mixture, containing four aromatic components simultaneously, was developed. A new ionic liquid and a previously used liquid were compared for their extraction abilities. These ionic liquids were, respectively, N,N-dimethyl-2-oxopyrrolidinium iodide and 1-ethyl-3-methyl imidazolium ethyl sulfate. The concentrations of each benzene, toluene, ethylbenzene, and xylenes component in the extract and raffinate phases were measured by gas chromatography with flame ionization detection as volume percent to determine the extraction ability of the ionic liquids. The results obtained for both the reformate samples and model mixtures indicated that the new ionic liquid was effective as an extracting solvent for the recovery of aromatic components from reformates. Also the analysis results, using gas chromatography with flame ionization detection, for the reformate samples were as good as the results obtained by a local oil refinery. The extraction results also show that the developed method is very suitable for the separation and analysis of aromatic components in reformates.