Correlation between Pore Characteristics and High-Performance Carbon Dioxide Capture of Sustainable Porous Carbon Derived from Kraft Lignin and Potassium Carbonate

The development of cost-effective and efficient adsorbents for CO₂ capture has gained significant interest, with biomass-derived porous carbon materials emerging as promising candidates due to their outstanding textural properties, tunable porosity, and low production cost. This study introduces for the first time a sustainable fabrication of porous carbon from Kraft lignin using K₂CO₃ as an environment-friendly activator via a spray drying approach and carbonization process. K₂CO₃ offers a low-toxic, low-corrosive, and eco-friendly alternative to KOH, making it safer for long-term equipment use and more suitable for large-scale applications. Furthermore, K₂CO₃ effectively creates a microporous structure for CO₂ adsorption while simplifying waste management due to its benign and recyclable carbonate residues. Unlike conventional two-step activation, our approach integrates carbonization and activation into a single step, reducing production time and enhancing efficiency, making it suitable for practical applications. Porous carbon materials obtained through this novel process exhibited a CO₂ adsorption capacity of 4.54 mmol/g at 298 K, comparable to those activated with KOH and outperforming many previously reported adsorbents. Additionally, the effects of K₂CO₃ concentration and carbonization temperature were systematically studied to optimize CO₂ adsorption performance. A linear correlation analysis between pore structure parameters and CO₂ captures highlighted ultramicropores as key contributors to adsorption efficiency.