Application of magnetic alumina-ferric oxide nanocatalyst supported by KOH for in-situ transesterification of microalgae cultivated in wastewater medium

Nowadays, use of microalgae as a cheap feedstock and heterogeneous catalysts for biodiesel production has gained considerable interest as they mitigate environmental problems induced by the conventional process of biodiesel production using homogeneous alkali catalysts. However, separation of heterogeneous catalysts from tissues and carcass of microalgae is an important task. For this reason, a magnetic Fe2O3-Al2O3 nanocatalyst promoted by potassium groups was synthesized using a modified impregnation method and was profoundly studied and compared with nanocatalysts without ferric oxide using X-ray diffraction, Fourier-transform infrared, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda, scanning electron microscopy, transmission electron microscopy and energy-dispersive spectroscopy analyses. The results revealed that the magnetic nanocatalyst with a core-shell structure had suitable surface area, pore size, and particle size and also had no impurity on its structure. The nanocatalyst was used for biodiesel production from microalgae cultivated in a wastewater medium via in-situ transesterification reaction. The nanocatalyst converted 95.6% of microalgae lipids to esters at optimum conditions of 65 degrees C, 12 mL g(-1 )of methanol-to-dry biomass, 4 wt% of magnetic catalyst and 6 h of reaction time. The magnetic K/Fe2O3-Al2O3 core-shell nanocatalyst was reused for several times and presented high stability with less reduction in its activity until six runs.