Hamzah, Mohammad Hafiz (2015) The study of surface physico-chemical properties of alcohol-water mixtures using reverse-flow gas chromatography / Mohammad Hafiz Bin Hamzah. Masters thesis, University of Malaya.
Abstract
Spillage of volatile chemicals such as organic solvents into aquatic environment via various industrial activities has been a growing major worldwide concern. These volatile chemicals may spread into the atmosphere via evaporation and diffusion. Evaporation is a process where a substance in liquid phase is converted into the vapor phase. Reversed– flow gas chromatography (RF-GC) technique which is one of the perturbation gas chromatography techniques was used to determine the rate coefficient for evaporation and diffusion coefficients (D) of selected alcohols. The main objectives of this study are to determine the effect of water on the evaporation of alcohols from water-alcohol mixture, to study the influence of temperature, concentration of alcohol and carbon number on the evaporation of alcohols from water-alcohol mixture, and to study the effect of surfactant concentration and the types of surfactant (nonionic, cationic and anionic surfactant) on the evaporation of selected alcohols. With the presence of water, the KG values of methanol and ethanol were largely reduced and it was due to the formation of hydrogen bond between water and alcohol molecules. As most of the evaporation process, the rate of evaporation of selected alcohols from alcohol-water mixtures was also found to increase with temperature. In addition, ethanol and 1-propanol were found to be more volatile than methanol and 1- butanol for the pure alcohol liquid and even with the presence of 5% water. With the presence of 10% water, 1-propanol showed the highest KG as compared to methanol, ethanol and 1-butanol. The KG values pure methanol and ethanol were largely reduced by the addition of Triton X-100 which is a nonionic surfactant. This result was due to the formation of insoluble surfactant layer that covered the surface of the alcohols and reduced the rate of iii alcohols evaporation. The effect of nonionic surfactant, anionic surfactant and cationic surfactant on the evaporation of methanol from 24% methanol in water were evaluated using Triton X-100, SDS and CTAB, respectively. The result showed that Triton X-100 and CTAB can be used to reduce the methanol evaporation. However, the addition of SDS into the 24% methanol in water was found to enhance the methanol evaporation from the methanol-water mixture. In conclusion, RF-GC can be a good method and instrumentation for the measurement of the rate of evaporation for alcohols. RF-GC is unique because of its simplicity in the measurement of KG since the time taken to acquire the data is less than 3 hours. Furthermore, this method enables the measurement of KG and D for the volatile liquids simultaneously. In addition, this study also showed that nonionic and cationic surfactant can be a good candidate to reduce the evaporation of hazardous methanol from methanolic wastes.
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