Silica extracted from ragihusk as heterogeneous catalyst for synthesis of biodiesel from waste cooking oil

Abstract

Each year an estimated 1.3 billion tons of agricultural waste are produced worldwide, with staple crop residue forming a large bulk of the generated waste. This crop residue from cereal crops like Ragi husk is generally discarded despite being a rich silica source and is a widely used compound with an ever-increasing demand. In the present project, the process of extracting silica from agricultural waste has been studied, and the optimal conditions for the extraction of silica were reported. The extracted silica was used as a catalytic support for KOH and employed for the synthesis of biodiesel. The structural, morphological, and elemental characterizations of the silica sample were done using X-ray diffraction (XRD), DTA-TGA analysis, and Fourier transform infrared spectroscopy (FTIR). Scanning Electron Microscope (SEM) And Energy-Dispersive X-Ray Spectroscopy Analysis (EDS/EDX). The XRD study showed the presence of amorphous silica in the Ragi husk sample. The DTA curve for the Ragi husk silica sample indicated two distinct stages: all organic matter was decomposed in the first stage. The characteristic bands resulted from FTIR analysis were indicative of the presence of pure silica. SEM and EDS analysis also indicated the presence of high-purity silica. The physio-chemical characteristics of the catalyst were studied using XRD, TGA, and FTIR. The transesterification of reactants (waste cooking oil and methanol) was performed using a KOH-impregnated heterogeneous catalyst at reaction conditions with mole ratio 6:1, catalyst loading 3 w/w%, temperature 65 â¦C resulted in 83% yield of biodiesel. The present work proposes an economical pathway to valorize agricultural solid waste effectively.    Research Highlights

• Extraction of silica from Ragi husk through simple process.
• Impregnation of silica with potassium hydroxide.
• Characterisation of the synthesized catalyst.
• Synthesis of biodiesel from waste cooking oil using synthesized catalyst.
• It provides a sustainable path for the synthesis of biodiesel.