Abstract

The current investigation delved into biodiesel synthesis from castor oil (CO) employing a magnetic nanocatalyst contrived from waste Citrus limetta peel ash (CLPA@Fe3O4). SEM, TEM, EDAX, XRD, XPS, VSM, and FTIR were used meticulously to analyze the synthesized catalyst. The catalyst's core–shell arrangement kept its regulated size and shape and enhanced its surface properties, significantly increasing its stability. The optimal biodiesel yield of 97.92 % was accomplished utilizing CLPA@Fe3O4 catalyst through transesterification under the ideal reaction conditions of 30 wt% methanol concentration, the catalyst of 6 wt%, 60 °C temperature, and 3 h reaction time. The thermodynamics study advocated the transesterification process to be endothermic and nonspontaneous, while the kinetic tests were revealed to obey pseudo-first-order kinetics. The transesterification of CO employing the current catalyst was found to have an activation energy of 33.138 kJ mol−1. Nevertheless, an extraneous magnet could recover the prepared magnetic iron oxide-supported nanocatalyst from the reactor, as the catalyst showed a strong magnetization of 31.56 (emu/g). The catalyst showed excellent reusability up to 80 % for 6 consecutive cycles. The turnover frequency of the catalyst was ascertained to be 0.011 mol g−1.h−1, which measures the ability to drive biodiesel synthesis. The conversions from CO to biodiesel were validated via FTIR and GC–MS analysis. It is essential to highlight that biodiesel's key fuel properties align with the standards set by ASTM D6751, indicating promising prospects for its future industrial use. The life cycle cost analysis of the catalyst and biodiesel, i.e., USD 0.533/kg and USD 1.005/L, indicates excellent potential for commercialization. Lastly, using creative bibliometric analysis to identify the gaps in the literature, the study made recommendations for the synthesis of biodiesel utilizing nanocatalyst.