Kinetics and thermodynamic studies on biodiesel synthesis via Soxhlet extraction of Scenedesmus parvus algae oil

Abstract

In recent times, there has been a notable surge in interest regarding the utilization of microalgae for biodiesel production through wastewater treatment. This can be attributed to the versatile nature of microalgae to thrive in various water systems, including wastewater systems, and their ability to show a high rate of photosynthesis. This research aims to assess the viability of utilizing Scenedesmus parvus microalgae, commonly used in the treatment of wastewater, as a potential source of oil feedstock for biofuel production. To extract oil from microalgae, a Soxhlet extraction technique was employed, using methanol for both extraction and separation processes. The extraction process was carried out under differing experimental conditions, including variable extraction temperatures (40–80 °C), extraction period (3–12 h), and algae to solvent ratios (S/L) (1:05–1:10). The microalgae exhibited a maximum oil yield of about 24% when subjected to the extraction conditions of an 8-hour extraction period, an extraction temperature of 70 °C, and a methanol to algae ratio of 1:10. The extraction process of algae oil using the Soxhlet method was analyzed for its thermodynamic and kinetic properties using a second-order equation and Eyring's theory, respectively. In this process, biodiesel was successfully produced with an efficiency of approximately 92.2 ± 0.8% through an alkaline transesterification reaction. This reaction was conducted at a temperature of 65 °C, using a catalyst concentration of 1 wt% (KOH), with the ratio of algae oil to methanol set at 1:9, for 3 h. The biodiesel obtained from microalgae in this research conformed to the global biodiesel standards, specifically ASTM D6751 and EN 14214. The findings emphasize the viability of Scenedesmus parvus microalgae as a valuable resource for biodiesel production.