Sustainable Development of Sawdust Biochar as a Green and Promising Material for CO₂ Capture Technologies

The study investigates the synthesis of highly porous ZnCl2-activated biochars derived from sawdust via controlled pyrolysis at 300 °C and 500 °C, aimed at enhancing CO2 adsorption performance. The effects of pyrolysis temperature and chemical activation on particle size distribution, surface area, and pore structure are systematically analyzed. Particle size analysis has revealed that higher pyrolysis temperature and ZnCl2 activation significantly reduced both median and mean particle sizes, resulting in finer and more uniform biochar morphology. BET analysis has demonstrated a substantial increase in specific surface area and micropore volume upon ZnCl2 activation, particularly at 500 °C, where the activated biochar (S500ZC) has exhibited a high surface area of 717.60 m2/g and a micropore area of 616.60 m2/g. CO2 adsorption isotherms are recorded at 25 °C confirmed that both thermal treatment and activation markedly enhanced adsorption capacity, with the highest uptake of 35.34 cm3/g achieved by S500ZC. The adsorption performance has followed the order: S300NZC < S300ZC < S500NZC < S500ZC, closely correlating with microporosity and surface textural development. The findings highlight the potential of ZnCl2-activated biochars as cost-effective, environmentally friendly, and efficient sorbents for scalable CO2 mitigation technologies.