Chemical Stability of Coconut Shell Biochar Under Oxidative Conditions

Background and Objective: Biochar, a carbon-rich byproduct of biomass pyrolysis, holds promise for soil enhancement, water purification, and environmental remediation, largely due to its carbon sequestration potential. However, the stability of carbon within biochar varies, influencing its effectiveness. This study aimed to evaluate the relationship between pyrolysis temperature and the chemical oxidative stability of coconut shell-derived biochar. Materials and Methods: Coconut shell biomass was pyrolyzed at four different temperatures (400, 500, 600, and 700°C). The resulting biochar samples were subjected to chemical oxidation using potassium permanganate (KMnO₄) at neutral pH (7.2) to assess stability. Stability was quantified as a percentage and compared across treatments. Ultimate analysis and atomic ratios (H:C and O:C) were used to support interpretations of aromaticity and hydrophobicity. Results: Biochar stability increased with rising pyrolysis temperature, indicating enhanced oxidative resistance at higher heat treatments. These findings aligned with elemental data and decreasing H:C and O:C ratios, suggesting increased aromatic carbon content and hydrophobicity. Conclusion: Higher pyrolysis temperatures improved the oxidative stability of coconut shell biochar due to increased aromatic structure and reduced oxygen-containing groups. These findings support the use of high-temperature biochar in long-term environmental applications, although further field-based validation is recommended.