Ultramafic Rock-Based Filters for CO2 Capture in Simulated Emission Streams: An Experimental Approach with Combustion Cells

Abstract This study explores the carbon capture and mineralization potential of ultramafic rock powders when exposed to flue gases generated from combustion of a crude oil and mesquite-derived charcoal. Three ultramafic rock samples—designated as Samples 20, 22, and 26—were characterized using Fourier Transform Infrared (FTIR) spectroscopy and thermogravimetric/differential scanning calorimetry (TGA/DSC) before and after exposure to flue gases. The samples were placed in stainless steel filter housings downstream of a heated combustion cell designed to simulate industrial CO2-emitting sources. Flue gas compositions were monitored in real-time using gas analyzers and gas chromatography, with bypass lines used as control conditions. FTIR analyses of post-exposure samples revealed the emergence of broad O–H stretching bands (~3300 cm-1), asymmetric CO2 vibrational modes (~2358–2332 cm-1), and a dominant carbonate peak at ~873 cm-1, indicating successful capture and partial mineral transformation of CO2. Despite extensive toluene washing and thermal drying at 50 °C, these spectral features persisted, suggesting chemisorption or irreversible physical adsorption of CO2 onto the rock surfaces. Notably, Sample 26, which was least exposed to condensable hydrocarbons, exhibited the clearest CO2 signatures. Following flue gas exposure, samples were subjected to TGA/DSC under air at 10 °C/min up to 900 °C. Post-heating FTIR spectra showed the disappearance of OH- and H2O-related bands and the preservation of the carbonate peak near 873 cm-1, indicating thermally stable amorphous carbonate formation. In contrast, OH-rich clay signals present in the initial samples disappeared after heating, suggesting dehydroxylation and phase transformation. Among the samples, Sample 22 exhibited the highest normalized mass gain and most robust carbonate signature, likely due to its mineralogy, which includes serpentine, olivine, dolomite, and talc. These findings confirm that ultramafic rocks can serve as both physical CO2 adsorbents and reactive mineral filters capable of capturing and stabilizing carbon in solid form under flue gas exposure.