Optimization of process parameters of self-purging microwave pyrolysis of corn cob for biochar production

Abstract

Microwave pyrolysis offers rapid and low-cost technology to upgrade agro-forestry residues to high-value products. I-optimal experimental design was used to determine the optimal combination of microwave power and exposure time to maximize biochar yield from corn cob. A validation experiment at optimal conditions of 600 W and 6.9 min produced an average yield of 56.98% on a dry and ash-free basis, agrees with the predicted value (3.43% error) and confirms the adequacy of the model yield equation. Characterization of biochar product revealed an organized mesoporous structure with a carbon content of 62.68%, surface area of 3.05 m2/g, pore volume of 0.003 cm3/g, capacitance range of 27.14–53.99 μF/g, energy density range of 6.0 × 10−7 - 1.2 × 10−6 Wh/kg, and power density range of 9.4 × 10−4 – 2.49 × 10−3 W/kg. The biochar produced would require further process to be considered for various industrial applications.

Keywords

• Corn cob
• Biochar
• Microwave pyrolysis
• Self-purging
• Optimization
• I-optimal design