Dissolution rates of alkaline rocks by carbonic acid: Influence of solid/liquid ratio, temperature, and CO2 pressure

Dissolution rates of alkaline rocks, including wollastonite (CaSiO3), olivine (Mg2SiO4), and phlogopite (KMg3AlSi3O10(OH)(2)), with high pressure aqueous CO2 solution were measured to examine the feasibility of CO2 fixation via carbonation. Influence of solid/liquid ratio (1.0-10 g/250 mL), temperature (303-353 K), and CO2 pressure (1.0-3.0 MPa) on the extraction rates of calcium or magnesium ions was investigated. Under the experimental conditions studied, the calcium ion extraction rate from wollastonite was the highest among the three rock samples studied. The calcium concentration reached about 120 mg/L, and about 12% of the calcium in wollastonite sample was extracted after 60 min at 353 K with 1.0 MPa CO2. The calcium and magnesium extraction ratios from the alkaline rocks were much lower than those from waste concrete powder. Increasing the extraction time and temperature would be an effective way to promote calcium extraction from wollastonite. (C) 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.