Kinetic Parameters Using Non-Isothermal Method for Wasted Disposable Bamboo Chopsticks

The aim of this study was to define the kinetic parameters, including activation energy and pre-exponential factor, using the Coats-Redfern method. The wasted disposable bamboo chopsticks were used and then heated in a thermogravimetric analyzer (METTLER TOLEDO, TGA/DSC 3+) at various heating rates 5, 10 and 20°C/min using air as the carrier gas. The results of the experiment showed that multiple stages of thermal degradation occurred in rang of temperatures between 32 °C to 650 °C. In the early stage, moisture evaporation occurred at temperatures between 32 °C - 110 °C. Then, volatiles release and char combustion occurred at temperatures of 165 °C - 385 °C (stage A) and 350 °C -530 °C (stage B), respectively. The weight loss occurred by approximately 67 wt% in stage A due to the combustion of volatiles which had abundant in the wasted disposable bamboo chopsticks and released during this stage.

Coats-Redfern method was used to explain the reaction mechanisms: chemical reaction (first order), diffusion, and shrinking core, which were employed to investigate the oxidation stages A and B. The correlation coefficients between the models and experimental data were particularly high in range of 0.91 – 0.94 (stage A) and 0.85 – 0.92 (stage B) for chemical reaction, and 0.90 – 0.93 (stage A) and 0.98 – 0.99 (stage B) for diffusion reaction. The activation energy values for stages A and B were determined, ranging from 80.8 kJ/mol to 88.7 kJ/mol and 26.4 kJ/mol to 28.9 kJ/mol, with the highest values attributed to reaction mechanisms chemical reaction and diffusion reaction, respectively. Furthermore, the pre-exponential factor (A) displayed variability between 6 min^-1 and 22.8 min^-1 for stage A (chemical reaction, first order) and between 1.2 × 10^⁻⁷ min^-1 and 8.8 × 10^⁻⁶ min^-1 for stage B (diffusion reaction).