Kinetics of the dehydroxylation of serpentine

Abstract

There has been increasing interest in carbon dioxide sequestration in mineral form, because there are large deposits of silicate minerals in peridotite and basalt that have the potential for this option. We examined the dehydroxylation of natural serpentine ore, considered to be a candidate for mineralization of CO₂. In this study, serpentine and dehydroxylated serpentine have been characterized using different techniques and the dehydroxylation kinetics of serpentine has been investigated by non-isothermal thermogravimetry. The results indicated that the thermal decomposition of magnesium serpentine [Mg₃Si₂O₅(OH)₄] proceeds via the removal of physisorbed water and, subsequently, the hydroxyl group. Kinetic modeling of the dehydroxylation shows that the reaction follows a three-dimensional diffusion-controlled mechanism in the particles. The effect of the heating rate and particle size on the dehydroxylation reaction has been investigated, and the results are found to be consistent with diffusion-controlled kinetics. The gas-solid heat-transfer resistance is shown to influence the results at a high heating rate and large particle size.