Nanocellulose-coated magnetite–strontium oxide as novel green catalyst for biodiesel production from waste cooking oil: Optimization using RSM

In this study, sustainable green heterogeneous catalysts were developed by combining locally available rice straw waste cellulose with SrO-Fe₃O₄ binary oxide to generate biodiesel. The catalyst was employed for the transesterification of waste cooking oil (WCO), and the biodiesel production process was fine-tuned using the response surface method based on central composite design. The biodiesel production reached 95.00 % under optimal conditions with a molar ratio of 7.5:1 between WCO and methanol, a catalyst weight of 2 %, a reaction time of 60 min, and a temperature of 62.50 °C. Kinetic studies revealed that the transesterification reaction for WCO conversion obeyed pseudo-first order kinetics, with an activation energy of 29.834 kJ/mol in the temperature range of 50–65 °C. These findings indicate that the reaction proceeds rapidly and requires minimal energy. Additionally, thermodynamic analysis of the transesterification process showed that the reaction was endothermic and did not occur spontaneously. The produced biodiesel was analyzed by gas chromatography-mass spectrometry and HNMR spectroscopy to determine its characteristics. The physicochemical characteristics of the produced biodiesel met the specifications of international standards, indicating its potential to replace diesel fuel. This study shows that the utilization of WCO using rice straw waste cellulose as sustainable catalyst in the production of biodiesel is a cost-efficient and promising method for oil recycling.