Dissolution of dehydroxylated lizardite at flue gas conditions: III. Near-equilibrium kinetics

• The kinetic model is updated for the dissolution of dehydroxylated lizardite.
• Experiments are performed in near-equilibrium solution compositions.
• The model describes the non-steady state dissolution behavior accurately.

The near-equilibrium dissolution kinetics of partially dehydroxylated lizardite was investigated at conditions relevant for ex situ CO2CO2 mineralization, namely 30°C⩽T⩽90°C and pCO2<1atm. Batch experiments were carefully designed to explore a wide range of operating conditions without precipitating any secondary phases, namely amorphous silica or magnesium carbonates. The operational range included solutions whose compositions were very close to solubility of the dissolving silicate species. Expressions for specific dissolution rates were developed in order to describe the experimentally measured near-equilibrium, non-steady state dissolution profiles. The near-equilibrium kinetic model was able to describe the evolution of the concentration profiles of Mg(aq)Mg(aq) and SiO2(aq)SiO2(aq) with good accuracy. A small enhancement in the dissolution rates of forsteritic silicate was observed in the presence of high concentrations of bicarbonate ions. The presence of Mg2+Mg2+ ions and SiO2(aq)SiO2(aq) in the solution were found to affect the specific dissolution rates of the different silicate species present in dehydroxylated lizardite.