Engineering structured solid amine sorbents from industrial slag-derived nanocomposites for CO2 capture

Abstract

The demand for shaped/structured sorbents that utilize inorganic support is steadily increasing, as many startups heavily use primary amine-functionalized ion exchange resins. Meanwhile, the cost of sorbents for direct CO2 capture from air is high, and the use of virgin raw materials remains expensive. Industrial byproducts, such as steel slags, which are readily available and cost-effective, can be explored as a potential support material for the development of solid amine-shaped sorbents for CO2 capture and removal applications. A blast furnace slag (BFS) contains various metals, including Al, Mg, Ca, and a significant proportion of Si. Porous nanocomposites were synthesized through controlled dissolution and precipitation processes, using CTAB and P123 surfactants as structural directing agents, and then shaped into three distinct pellet shapes (spherical, cylindrical, and hollow cylindrical) to evaluate their impact on CO2 adsorption capacity and kinetics. Among these, hollow cylindrical pellets were examined in detail for their long-term adsorption-desorption performance, demonstrating cyclic stability over 105 cycles with an average adsorption capacity of approximately 1 mmol/g. A more in-depth analysis of these cycles revealed changes in adsorption and desorption kinetics over repeated use.