Optimization of Physical Parameters of Pearl Millet (Pennisetum glaucum) Husk for Microwave-Assisted Production of Adsorbent Biochar

This study evaluates the potential of Pearl Millet Husk (PMH) (Pennisetum glaucum) as a sustainable feedstock for producing high-quality biochar through high-power, short-duration Microwave-Assisted Pyrolysis (MAP). The effects of particle size and moisture content (MC) on biochar properties were examined to optimize its adsorption performance. PMH samples with three particle sizes and three moisture levels were pyrolyzed at 1400 W microwave power for 5 minutes. The influence of these parameters on biochar characteristics was analyzed using ANOVA and Response Surface Methodology (RSM), with iodine value selected as the primary indicator of adsorption efficiency. Biochar produced at a pyrolysis temperature of 500°C from smaller-sized PMH with 10% moisture content showed a Brunauer–Emmett–Teller (BET) specific surface area (SSA) of 17.05 m² g^-1. This biochar also exhibited an iodine value of 52.13 mg g^-1, a yield of 46.10%, an electrical conductivity (EC) of 8.26 mS cm^-1, a pH of 9.08, and a cation exchange capacity (CEC) of 149.24 mg g^-1, all at a 95% confidence level. Micropore development was strongly influenced by particle size in the initial stages, a key factor contributing to surface area enhancement. Additionally, iodine value showed a positive correlation with EC, CEC, SSA, and micropore distribution. Results indicated that PMH with 10% moisture content and smaller particle size (< 3 mm) enhances the adsorption properties of biochar, highlighting its potential for environmental remediation and sustainable adsorptive applications.