Mechanical activation of olivine

This paper investigates how mechanical activation of olivine can increase the mineral’s surface reactivity, and illustrates how such technology can give rise to new or improved olivine products. The olivine material used in this study consisted of pure olivine crystals (Mg1.860Fe0.134Ni0.006SiO4) originating from North Cape Minerals dunite deposit at Åheim in Western Norway. Following activation in a planetary mono mill, the activated olivine products were visually inspected using scanning electron microscopy (SEM) and characterised with respect to particle size, specific surface area (BET) and X-ray diffraction (XRD) signature. The surface reactivity of the activated olivine products was determined through simple acid leaching experiments in which the initial acid consumption rates were determined. The initial phase of olivine dissolution could be modelled using first order kinetics. Prolonged dry milling of pure olivine crystals resulted in highly aggregated products that were more reactive with respect to dissolution in acid than their respective BET surface areas would suggest. Relative to olivine that had been milled for 1 min, 60 min of milling increased the initial reaction rate by a factor of 9.0, whereas the corresponding increase in specific surface area was 1.8. The results from both the leaching experiments and the XRD analysis suggest that the observed over-proportional increase in reactivity with respect to surface area is largely due to structural disordering (i.e. mechanical activation) of the olivine surfaces.