Direct Air Capture of Atmospheric CO₂ Using Iron Mining Waste-Based Geopolymers

This work investigates the use of iron mining waste-based geopolymers as a promising material for Direct Air Capture (DAC) applications. The proposed system consists of a geopolymer partially immersed in a sodium hydroxide solution, allowing capillary transport of the alkaline medium to the exposed surface, where interaction with atmospheric CO₂ favors carbonate formation. Geopolymers containing 50 wt.% iron mining waste were synthesized and characterized by XRF, XRD, SEM, and FTIR. Analyses performed after exposure to the proposed system provided evidence of carbonate phase formation, suggesting the operation of the proposed capture mechanism. These preliminary findings suggest that iron mining waste-based geopolymers are promising materials for DAC applications while simultaneously promoting the valorization of mining residues.