Dissolution of natural serpentinite in mineral and organic acids

Abundant resources of magnesium silicates make an interesting prospect for long-term storage of CO2 by mineral carbonation. Several carbonation processes proposed in literature for CO2 storage employ extraction of silicate minerals using a liquid solvent. In this study, the dissolution of natural serpentinite in respective solutions of acids, bases and ammonium salts has been investigated. Experiments performed at room temperature showed that H2SO4 was most efficient at extracting magnesium from serpentinite, followed by HCl, HNO3, HCOOH and CH3COOH. Experiments for determining the dissolution kinetics was performed at temperatures of 30, 50 and 70 degrees C in 2 M solutions of H2SO4, HCl, and HNO3. At 70 degrees C temperatures all magnesium was extracted from serpentinite in each of the three acid solutions tested during 1-2 h. Also a large part of iron in serpentinite was extracted, while very little silicon dissolved (< 4%). The dissolution rate seemed to be limited by product layer diffusion for serpentinite particles with a size distribution of 74-125 mu m. The apparent activation energies were 68 kJ mol(-1) for dissolution in H2SO4, 70 kJ mol(-1) for dissolution in HCl, and 74 kJ mol(-1) for dissolution in HNO3. (c) 2007 Elsevier B.V. All rights reserved.