Sustainable processing of methylene blue dye-adsorbed Zea mays peel ash biosorbent as a novel heterogeneous catalyst for biodiesel production

This study investigates the circular economy approach of Zea mays peel ash as an adsorbent for methylene blue (MB) dye and as a sustainable renewable heterogeneous green catalyst for the transesterification of waste cooking oil into biodiesel. The adsorption study shows that MB removal was maximum at pH 8 with 89.95% in 60 min. The functional groups and surface morphology of Zea mays peel ash were analysed using FTIR and SEM, respectively. The spent Zea mays peel dye-adsorbed ash was valorized into green catalyst by calcination process at 400 °C for 60 min. The optimization of transesterification reactions is achieved using the Taguchi method. A maximum yield of 95.77% FAME (fatty acid methyl ester) obtained at reaction time (240 min), temperature (65 °C), catalyst load (1.5 wt.%), and methanol-to-oil ratio (4:1). The FAME was purified and characterized through various analyses, including gas chromatography and nuclear magnetic resonance. Overall, this study shows that Zea mays peel ash can used as a promising biosorbent for dye sequestration and a sustainable catalyst for biodiesel production.

Graphical abstract