Optimization of Biodiesel Production from Waste Cooking Oil over a Magnetic Fe–Zr Nanocatalyst

Abstract

The increasing demand for sustainable and low-cost biodiesel production has driven interest in waste cooking oil (WCO) as an alternative feedstock. In this study, a mesoporous magnetic Fe–Zr nanocatalyst with a specific surface area of 203.12 m²/g was synthesized via co-precipitation followed by incipient wetness impregnation and evaluated for the transesterification of WCO. The effects of reaction temperature, reaction time, and catalyst loading were investigated and optimized using Response Surface Methodology (RSM) based on a Central Composite Design (CCD), with a fixed methanol-to-oil molar ratio of 9:1. The fitted quadratic model showed a strong agreement with the experimental data, with an R² of 0.9894. The model predicted a maximum biodiesel yield of 81.992 % at a reaction temperature of 80 °C, reaction time of 4 h, and catalyst loading of 5 wt.%. Following transesterification, the acid value of the WCO-derived biodiesel decreased from 3.228 to 0.865 mg KOH/g. The Fe–Zr nanocatalyst demonstrated effective catalytic performance and facile magnetic separation, indicating its potential as a heterogeneous catalyst for biodiesel production from WCO under the investigated conditions. Copyright © 2026 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).