Olivine dissolution from Indian dunite in saline water
2016
Agrawal, Amit Kumar | Mehra, Anurag
The rate and mechanism of olivine dissolution was studied using naturally weathered dunite FO₉₈.₂₁(Mg₁.₈₈₄Fe₀.₃₉₁SiO₄) from an Indian source, that also contains serpentine mineral lizardite. A series of batch dissolution experiments were carried out to check the influence of temperature (30–75 ∘C), initial dunite concentration (0.5 and 20 g/L), and salinity (0–35 g/L NaCl) under fixed head space CO₂ pressure (P[Formula: see text] = 1 barg) on dunite dissolution. Dissolved Mg, Si, and Fe concentrations were determined by inductive coupled plasma atomic emission spectroscopy. End-product solids were characterized by scanning electron microscopy and X-ray diffraction. Initially, rates of dissolution of Si and Mg were observed to be in stoichiometric proportion. After 8 h, the dissolution rate was observed to decline. At the end of the experiment (504 h), an amorphous silica-rich layer was observed over the dunite surface. This results in decay of the dissolution rate. The operating conditions (i.e., salinity, temperature, and mineral loading) affect the dissolution kinetics in a very complex manner because of which the observed experimental trends do not exhibit a direct trend.
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