Synthesis and characterization of high-performance activated carbon from walnut shell biomass for CO₂ capture

An increasing level of carbon dioxide (CO₂) in the atmosphere has ultimately resulted in global warming and climate change. The high-performance activated carbon (AC-WL) was synthesized from walnut shell, a low-cost biomass by-product, by physical activation using a tube furnace. The adsorption behavior of CO₂ from the CO₂/N₂ mixture was investigated using a fixed bed. The surface and morphological characterizations of the produced activated carbons were measured using a BET analyzer and a scanning electron microscope (SEM). The effect of temperature, flow rate, CO₂ level, and partial pressure on breakthrough behavior was analyzed, and the adsorption response presented in terms of breakthrough point and adsorption capacity. The breakthrough and saturation periods vary significantly with change in temperature. The steepness of the breakthrough curves signifies good utilization of adsorbent capacity at breakthrough point. The increase in temperatures and flow rates lead to an increase in the length of mass transfer zone. The adsorption capacity of 1.58 mmol/g was obtained at 1.30 bars and 293 K with higher capacity utilization factor of 0.8492.These results suggest that the walnut-based activated carbon is favorable for capturing CO₂.