Biodiesel production from waste cooking oil using (modified Iranian clinoptilolite + KOH)/biochar prepared from rapeseed meal: A low‐cost and eco‐friendly catalyst

This study proposes an environmentally friendly and low‐cost catalyst for producing biodiesel. This catalyst comprises 5% potassium hydroxide (KOH), 35% modified Iranian clinoptilolite (MIC), and 60% synthesized biochar from rapeseed meal. The synthesis was confirmed by SEM, XRD, and FTIR analyses. Different operating parameters such as acetone as co‐solvent (0–20 wt%), catalyst concentration (4–10 wt%), reaction time (60–120 min), and oil‐to‐methanol volume ratio (1–3 v/v) on biodiesel purity were tested. There was 99% fatty acid methyl ester (FAME) content in the biodiesel produced at the co‐solvent concentration of 12.4 wt%, the catalyst concentration of 8.5 wt%, the reaction time of 113 min, and the oil‐to‐methanol volume ratio of 2.6 v/v.