Chemical activation of castor stalk-derived porous carbon for highly efficient CO ₂ adsorption in sustainable carbon capture applications

Abstract Greenhouse gas emissions have become a pressing concern in recent times, with CO 2 emerging as the primary culprit behind global warming, rising sea levels, and disruptions to ecosystems. Of all the greenhouse gases, CO 2 ’s impact on global warming stands out as the most significant. To address this issue, activated carbon (AC) has gained prominence as an effective CO 2 adsorption agent, owing to its porous structure, expansive surface area, cost-effectiveness, and environmentally friendly properties. In this current research, activated carbon was produced from castor stalk biomass through a single-stage chemical activation process known as pyrolysis. This method is lauded for its cost-efficiency, simplicity, and minimal environmental impact. Potassium hydroxide (KOH) and aluminum sulfate (ALUM) were employed as the activating agents. Subsequently, the synthesized activated carbon was subjected to Methylene Blue adsorption testing to evaluate its CO 2 adsorption capacity, among other potential applications. The characterization of the activated carbon derived from castor stalk involved a series of techniques, including CHNS analysis, proximate analysis, SEM, FTIR, XRD, and BET surface area analysis. These analyses unveiled the impressive attributes of the castor stalk-derived activated carbon, featuring an exceptionally high surface area of 1,687 m 2 /g, a substantial pore volume of 1.015 cm 3 /g, and a pore diameter of 2.71 nm. Furthermore, the Methylene Blue adsorption test yielded a remarkable value of 447.72 mg/g with 89.5 % adsorption efficiency. High CO 2 adsorption capacity (2.46 mmol/g) was observed over castor stalk-derived activated carbon. The comparative study shows higher CO 2 adsorption capacity in comparison to activated carbon derived from various biomasses using KOH as the activating agent. So, the present study shows activated carbon derived from Castor stalk using KOH and Alum as activating agent can be a promising method for CO 2 adsorption.