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Experimental and Theoretical Study of the Lipid Extraction from Wet Microalgae for Biodiesel Production

Malekzadeh, Mohammad | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46025 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Rashtchian, Davood; Vossoughi, Manoochehr
  7. Abstract:
  8. In this study, different stages of biodiesel production from microalgae were investigated, specifically the extraction step.Various cultivation methods were also studied among which cultivation under stress was the best. Different carbon sources were also investigated to achieve highest growth. Sodium acetate with complete growth was achieved after 8 days with 6.22% fatty acid recovery. Different mixtures of solvents were compared with Blye and Dier method. Results showed that the mixture of hexane and methanol with crude lipid extraction of 15% and fatty acid recovery of 3.97% were chosen as the solvent mixture of equilibria experiments.Organic solvent composed of hexane (non-polar solvent) and methanol (polar solvent) was used for extraction of lipids from dry and wet biomass of Chlorella vulgaris. The effect of hexane/methanol ratio on the recovery of crude lipids and fatty acids was investigated. The results of extraction from lyophilized biomass indicated that the crude lipid extraction was enhanced by increasing the ratio of methanol in the solvent mixture. Nevertheless, the highest fatty acid recovery was attained by using hexane/methanol mixture with volumetric ratio of 1:1 and amount of it was 2.30. The presence of water in the algal biomass leaded to a decrease in the extracted crude lipids when the solvent was mostly composed of hexane. However, no significant change in crude lipid extraction was observed when methanol was dominant part of the solvent. The fatty acid extraction performance was also decreased at the presence of water in the biomass. Similar to the extraction from dry biomass, the maximum fatty acid recovery was attained by applying equivolume mixture of hexane and methanol. Therefore, it is concluded that the best performance of extraction belongs to 1:1 hexane/methanol ratio which was 2.2 and 0.95 for 70 and 85% moisture content of biomass, respectively.. The effect of temperature on the performance of extraction was also investigated and the results showed that the recovery of both crude lipids and fatty acids was improved by increase of temperature, in which the crude lipid and fatty acid recovery was increased by about 17 and 36% at 65 oC comparing to the 25 oC.
    Thermodynamic modeling was employed to investigate the effect of hexane/methanol ratio and moisture content on the extraction performance. The results indicated that the models can accurately estimate the fatty acid recovery with average absolute deviation (AAD %) inferior to 8.65
  9. Keywords:
  10. Microalgae ; Chlorelavulgaris ; Organic Solvent ; Lipids ; Extraction ; Thermodynamic Model ; Polar Solvent ; Nonpolar Solvent

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