Optimized flocculation of microalgae for fuel oil and antioxidant production

The key technologies for producing microalgae biofuels include identification of preferable culture conditions for high oil productivity, development of effective and economical microalgae cultivation system, as separation and harvesting of microalgae biomass and oil. Microcyst,sp. biomass harvesting by flocculation was studied using inorganic coagulants (FeCl3.6H2O, Al 2 (SO4)3 18H2O , liquid Bittern rich in Ca2+ and Mg2+ ions). The results show that FeCl3.6H2O proved the best algae removed efficiency when used alone as coagulent. The only drawback is yellow color in the clarified water besides the pollution with elements such as Fe ions. Algae removal efficiency increased remarkably when the culture water was pretreated with Na-ferrate and followed by [Al2 (SO4)3 .18H2O] and pH adjusted to 7.1. The addition of Na-ferrate reduced the optimum dose to one half. As well as the use of sonication significantly enhanced the reduction of algae cells in culture water and reduced the optimum dose down to one third. Coagulation efficiency depends strongly on the coagulant dose and sonication conditions. The optional sonication time (50- 60 sec.), the most effective sonication intensity was 2.5 w/cm3 and the high removal ratio was 99% by the sonication-coagulation with alum reduced dose. The dried micro algae flocks were collected and subjected for lipids extraction using less toxic solvents. Identification of lipids was studied by Gas Chromatography and the antioxidant activity was determined (IC50= 39.3%) by 2,2diphenylpicryl-hydrazyl (DPPH) free radical using DR- 2000 spectrophotometer.

Author(s): Guzine I. El Diwani, ShadiaA. El Rafei , Salwa I. Hawash, Sanaa A. El Enin

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