“Precipitating knowledge on fluid-mineral interactions. ”
PhD project title:
Elucidating mineral dissolution and precipitation mechanisms.
Dissolution and precipitation of minerals plays a key role in many processes on the Earth’s surface and subsurface, including ore mineral deposition, changes in porosity, CO¬¬2 sequestration, weathering, nutrient availability, geothermal energy generation, and the mobility of contaminants in soils. Assessing the effect of dissolution/precipitation reactions on these processes, not only requires knowledge of thermodynamics, but also of the kinetics of these reaction. Although there is a growing database of mineral dissolution and precipitation rate studies performed in the lab, many of them only consider far from equilibrium conditions. In nature however, the system is often close to equilibrium, affecting the rate by which minerals dissolve or precipitate and leading to discrepancies in rates observed in the lab and observations made in natural systems.
My thesis will focus on the mechanisms by which minerals dissolve and precipitate as a function of the system’s distance from equilibrium. To formulate a general law by which dissolution and precipitation reaction mechanisms and rates behave at near to equilibrium conditions, two completely different minerals will be precipitated and dissolved in the lab: sepiolite, a Mg-silicate, and siderite, an Fe-carbonate. The latter is of particular interest as it is unstable in oxygen rich environments and will therefore dissolve and potentially re-precipitate as a new phase in oxygenated soils. In doing so it may incorporate contaminants or nutrients in its structure, therefore directly affecting the groundwater chemistry. Similarly, it can form in the subsurface and act as a trap for CO2 during CO2 sequestration operations.