EVOLUTION OF FUNCTIONALITIES AND STRUCTURE OF BIOCHAR IN PYROLYSIS OF COCONUT SHELL AT DIFFERENT TEMPERATURES

Journal: Acta Chemica Malaysia (ACMY)
Author: Chima Maximus Ejimadu, James M. Okuo, and Felix Ebhodaghe Okieimen
ISSN: 2576-6732
e-ISSN: 2576-6724

This is an open access journal distributed under the Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

DOI: 10.26480/acmy.02.2025.122.130

The aim of this study was to investigate the effect of pyrolysis temperature on the physicochemical properties and structures of coconut shell biochar. Biochar was produced by slow pyrolysis of coconut shell at different heat treatment temperatures (350, 400, 400, 500, 600 and 700°C) and were designated BC350, BC400, BC500, BC600 and BC700 respectively for heat treatment duration of 30mins. The biochar samples obtained were characterized in terms of physicochemical properties; quantitative surface oxygen groups, surface morphology/elemental composition (SEM/EDX), Brunauer-Emnett-Teller (BET) surface area and ultimate composition (%) C,O,H,N, and S. The physicochemical properties of the biochar sample; yield (wt %), bulk density (g.cm-3) decreased by about 40% with increase in heat treatment temperature, while the pH, cation exchange capacity (cmol.kg-1) and electrical conductivity (mS.cm-1) increased with heat treatment temperature and tended to attain maximum values at about heat treatment temperature 400 – 500° C. The total oxygen containing groups in the biochar samples decreased with increase in heat treatment temperature by up to 56%, from 4.94 mmol.g-1 for BC350 to 2.17 mmol.g-1 for BC700. Scanning electron micrograph of the biochar samples revealed largely mesoporous surface structures, that varied somewhat with the heat treatment temperature, while the energy dispersive X-ray (EDX) showed that the elemental content of the biochar samples decreased markedly with increase in heat treatment temperature and that carbon was the predominant element, contributing more than 60% of the total elements in the samples. The evolution of surface area of the biochar samples followed two patterns: an initial increase in surface area with heat treatment temperature from 282 m2.g-1 for BC350 to 712 m2.g-1 for BC450 followed by gradual decrease from 618 m2.g-1 for BC 500 and then to 220.7 m2.g-1 for BC 700. The changes in the pore volume (cm3.g-1) of the biochar samples with heat treatment temperature were found to be synchronous with the observed changes in BET surface area. The pore volume of the biochar samples increased almost two-fold with increase in heat treatment temperature, varying from 2.8nm for BC350 to 4.9nm for BC700 indicating that the biochar samples were mesoporous. These results suggest a range of potential benefits; agronomic, environmental, including carbon sequestration in soil remediation and wastewater treatment using coconut shell biochar.