An investigation on purity enhancement through hydrofluoric acid treatment in graphite powder derived from coconut shell

Abstract

The present research emphasizes a novel approach for synthesizing graphite powder derived from coconut shell (CS) as a precursor, particularly focusing on investigating the effects of hydrofluoric acid (HF) in removing silica and other impurities. The cost-effective pyrolysis technique employed in synthesizing graphite powder entails heating CS to 900 °C, followed by treatment with HF at varying sample-to-acid ratios. Several characterization methods are used to validate the successful synthesis of graphite powder, such as X-ray Diffraction (XRD), Raman Spectroscopy, Fourier-transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). XRD analysis shows a distinctive graphitic structure, with Gr14 (graphite prepared with a CSCP to HF ratio of 1:4) exhibiting a high graphitization degree of 93.02 %, indicative of excellent crystal structure and high-quality graphite. FTIR analysis of coconut shell charcoal powder (CSCP) reveals the presence of various oxygen-related functional groups, effectively removed by HF washing, leading to graphite with minimal impurities. The Raman spectra of Gr14 demonstrate fewer defects and a more organized structure than other samples. SEM image of CSCP reveals particles with non-uniform morphologies, while the EDX spectra indicate that Gr14 consists of 97.84 % carbon. Treating CSCP with HF enhances the electrical conductivity of the graphite, with Gr14 exhibiting a higher conductivity value. TGA results reveal the improved thermal stability of the graphite. The residual weight of Gr14 is maximum, confirming its exceptional thermal stability and purity. The findings suggest that HF has a significant influence on improving the purity of CS-derived graphite. The study concludes that, among the prepared samples, Gr14 exhibits favorable characteristics, such as minimal impurities, superior crystal structure, higher carbon content, good electrical conductivity, high thermal stability, and fewer defects, comparable to pure graphite. Future research in this study aims to use CS-derived graphite powder for synthesizing nanomaterials like graphene oxide (GO) and reduced graphene oxide (rGO).