Adsorption of CO2 on agricultural waste biochar: synthesis, experimental and kinetic studies

Climate change is a pressing issue that requires immediate attention and action. A significant factor contributing to greenhouse gas emissions is CO₂. To mitigate the impacts of climate change, it is essential to explore strategies aimed at decreasing atmospheric CO₂ levels. The Rice Husk Biochar (RHB) synthesized in a pyrolysis furnace and its CO₂ sorption was investigated in a thermogravimetric analyzer. The CO₂ uptake capacities at atmospheric pressure on the non-commercial Rice Husk Biochar with a 38.12 m²/g specific surface area at 280, 300, and 320 K are 3.0, 2.0 and 1.25 mmol/g solid, respectively. Kinetic studies have also shown that the adsorption of CO₂ on biochar follows a diffusion, nucleation and growth, and geometrical contracting volume mechanism, indicating that the process is highly efficient and rapid; facilitating the rapid removal of CO₂ from the atmosphere. Knowing the adsorption kinetic is essential for the design of the scaling-up adsorption systems. Low mean activation energy (5.42 kJ mol⁻¹) estimated with a free model confirm a rapid reaction rate. The use of agricultural waste biochar for CO₂ adsorption offers a sustainable and effective alternative material to address the challenge of carbon dioxide emissions with further innovation in activation, surface area and texture improvements.