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Factors affecting carbon dioxide fixation in chrysotile mining residues (CMR) under environmental conditions were studied by reproducing mineral dissolution and carbonation in laboratory columns packed with CMR particles. Carbonation is very sensitive to water saturation and watering frequency of the CMR porous media. CO₂ uptake by dry residues subjected to dry CO₂ flow for several days at ambient temperature was below 0.02%. However, an increase by a factor of 20 in CO₂ uptake was achieved by periodic addition of small amounts of water with respect to a moistened CO₂ stream over dry CMR samples. The highest MgCO₃ conversion resulted in nearly 22 mg of CO₂ captured per gram of residue, revealing that up to 93% of Mg remained noncarbonated because of surface obstructing processes. Magnesium leaching from CMR was hindered by two concomitant passivation phenomena limiting the …