Synthesis and characterization of potassium hydroxide impregnated cassava leaves heterogeneous catalyst for biodiesel production from waste cooking oil

This study introduces, for the first time, a novel heterogeneous catalyst synthesized from potassium hydroxide (KOH)-impregnated calcined cassava leaves (KICCL) for the production of biodiesel from waste cooking oil (WCO). While cassava leaves have been largely overlooked as a catalyst precursor, this work demonstrates their potential when impregnated with varying KOH concentrations (10–50 wt%) to enhance basicity and catalytic activity. The raw and modified materials were characterized using Fourier-transform infrared spectroscopy (FT–IR), X-ray fluorescence (XRF), scanning electron microscopy (SEM), Brunauer–Emmett–Teller surface area analysis (BET), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. Among the catalysts, the 30 wt% KICCL, calcined at 700 °C for 2 h, exhibited the highest basicity of 5.78 mmol HCl/g. This catalyst delivered a maximum biodiesel yield of 92.9 wt% with 97.4 % purity under optimized transesterification conditions: a 9:1 methanol-to-oil molar ratio, 3 wt% catalyst loading, 2 h reaction time, 62 °C reaction temperature, and 500 rpm stirring speed. The WCO and resulting biodiesel were further analyzed through FT–IR, Nuclear Magnetic Resonance (NMR), and fuel property testing to confirm compliance with standard specifications. Catalyst reusability tests confirmed the stability and effectiveness of the developed catalyst over multiple cycles. This work demonstrates a sustainable and efficient pathway for biodiesel production using an innovative bio-based catalyst derived from cassava leaves.