(557f) Combating Surface Passivation In the Mineralization of Carbon Dioxide

The accelerated weathering of ultramafic rocks is an environmentally benign route to a thermodynamically and kinetically stable form of carbon. The product, solid magnesium carbonate, can be produced with a range of properties depending on the final application. However, before this can be considered, the magnesium must be extracted from mineral particles at a reasonable rate. While mineral dissolution is thermodynamically favorable, the kinetics are prohibitively slow. The silica tends to accumulate on the particle surface creating a passivation layer, through which magnesium and protons must diffuse. In this work, we characterize the effect of silica passivation on the dissolution rate of serpentine minerals. The permeability and dissolution rate of this silica-based passivation layer are shown to ultimately limit the availability of magnesium for further reactions, and a number of silica specific chelating agents are evaluated for their ability to accelerate the removal of the passivation layer and increase the dissolution rate of magnesium.