In this investigation, optimization experiments were carried on lipid extraction and biodiesel production parameters from Ulva fasciata as a potential feed stock. This study was carried by running one to one optimization model. The results showed that, the highest yield and the best quality of biodiesel was achieved at the optimum condition of <0.16 mm algal particle size, 55 o C extraction temperature, 25:1 v/w solvent to solid ratio, 60 min extraction time and 250 rpm shaking speed, using chloroform: methanol: H 2 O (2: 2: 1) solvent mixture. The recorded lipid yield was 28.84 mg g-1 with total fatty acids ΣTFAs content 1148.94 µg g-1 , saturated fatty acids ΣSFAs=979.43 µg g-1 , monounsaturated ΣMUFAs=136.98 µg g-1 and polyunsaturated ΣPUFAs fatty acids =32.53 µg g-1. The quality of the produced biodiesel at these optimum conditions was determined by its physicochemical properties which showed a very high quality. Cetane number (CN) was 73.21, while kinematic viscosity (υ), density (ρ), higher heating value (HHV) and iodine value (IV) were 4.68 mm 2 s-1 , 0.87 g cm-3 , 39.85 MJ kg-1 and 18.48 gI 2 100g-1 fat, respectively. Other properties such as degree of unsaturation (DU), saponification value (SV) and long chain saturation factor (LCSF) recorded 17.58, 200.66mg KOHg-1 and 23.06, respectively. On the other hand, Linolenic acid (C18:3) % and Polyunsaturated fatty acid methyl esters containing ≥ 4 double bonds % recorded 0.68% and 0.98%, respectively. The initial extraction rate (h) was 6.169 ml g-1 min-1 ; the extraction capacity (Cs) was 31.036 g ml-1 ; the second order extraction constant (k) was 0.0064 ml g-1 min-1 and the coefficient of determination (R 2
Chemical pretreatment of Ulva fasciata cell wall for enhancing biodiesel yield _________________________________________________________________________________________
The green algae Ulva faciata was subjected to different physical pretreatments comprising thermal and mechanical techniques at different experimental conditions to state the most appropriate method of cell disruption for increasing the quantity of the extracted lipid and hence improve the quality of the produced biodiesel with low cost. Thermal pretreatment was autoclaving of either wet or dry algal biomass, while mechanical pretreatments include microwave and ultrasonication at different time intervals. The control was the alga without pretreatment extracted at optimum conditions: 60 min, 55oC, shaking speed at 250 rpm, < 0.16 mm particle size with 25:1 v/w solvent to solid ratio. The results showed that the quantity of extracted lipids in case of using all physical pretreatments increased the Total fatty acids yield significantly by about 2-folds of the control for wet algae in hydrothermal treatment with optimum time of treatment 40 minutes, and 1.4 folds for dry algae in thermal pretreatment of the dried alga for 60minutes autoclaving period. The sharp increase by 2.2 folds of extracted lipids was recorded by microwave pretreatment for radiation period (5 min), while ultrasonication showed 2.1-fold increase in lipid yield at 15minutes ultrasound exposure time. Concerning the physical properties of the produced biodiesel after all physical pretreatments, the results indicated that the produced biodiesel had very high quality as all its properties are almost complied with the ASTM D6751 and EN14214 standards. These results were confirmed statistically where all physical pretreatments had high significant effect on fatty acids yield and Biodiesel properties.
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