Evaluation of reaction variables in the dissolution of serpentine for mineral carbonation

The sequestration of CO₂ through the employment of magnesium silicates, olivine and serpentine, is beyond the proof of concept stage. Serpentine has been chosen as the feedstock mineral due to its abundance and availability. Although the reactivity of olivine is greater than that of serpentine, physical and chemical treatments have been shown to greatly increase the reactivity of serpentine. A sulfuric acid leaching stage has been shown to alleviate the rate limiting step of magnesium removal, thereby accelerating the overall carbonation process. Varying reaction conditions can significantly influence the results for the dissolution process with an extreme reaction environment providing desirable results. However, a more careful assessment of the reaction variables under milder conditions is needed for a better understanding of the reaction processes and potential pathways for high extraction yields under more modest conditions. Accordingly in this work, a statistical design of experiments was conducted to ascertain the effect of acid concentration, particle size and reaction time and temperature on the leaching of magnesium from serpentine using sulfuric acid. Results demonstrated that acid concentration provided primary control on the dissolution via the removal of water, which is closely correlated with the extraction of magnesium from serpentine. Particle comminution to a median size less than 163 μm remained an important consideration in increasing reactivity and liberating magnetite. Single variable experimentation demonstrated dissolution enhancements with increased reaction time and temperature. An increase in magnesium dissolution of 46% and 70%, over a baseline test, occurred for increased reaction time and temperature, respectively.