Biomass-based adsorbents for post-combustion CO₂ capture: Preparation, performances, modeling, and assessment

The adsorbents are critical carriers in the process of adsorption-based post-combustion CO₂ capture. Biomass-based adsorbents (BAs) are considered to have great potential because of their high efficiency, low cost, and good sustainability. To understand the methods, theories, and technologies of BAs-based CO₂ capture, this work analyzes their preparation and activation/modification, influencing factors, mechanisms, thermodynamics/kinetics, regeneration and cycle performances, and the pathway to application. It is found that BAs prepared by pyrolysis, chemical activation, and modification with dual heteroatoms are more conducive to improving adsorption sites. CO₂ adsorption capacity positively correlates with elemental C and fixed carbon of feedstocks, but negatively with moisture. The BAs prepared at 550-600 °C have high performance. The specific surface area (SSA) increases as the preparation time increases by 9.4%-93.4%. The adsorption capacity is positively correlated to the SSA (R = 0.880) and microporous volume (R = 0.773). Moreover, it decreases linearly with increasing operating temperature with the slope of -0.6 mmol/(g·°C) but increases exponentially with increasing operating pressure and CO₂ concentration with the power of 0.824. The adsorption process includes physical and/or physicochemical adsorption. Freundlich isotherm equation and pseudo-second-order model characterize the adsorption thermodynamics and kinetics more effectively with R² = 0.985-1.000 and R² = 0.894-1.000. The quantum chemistry indicates that most BAs modified with non-metallic belong to physisorption. The regeneration of BAs has low energy consumption (<3.44 MJ/kg CO₂) and loss rate (<8%). Furthermore, the technical pathway is proposed for application. Finally, the challenges are also presented to facilitate the development of BAs-CO₂ capture.