Experimental study of dissolution rates of actinolite in CaCl2-HCl-H2O up to 400 °C

Our results show that water properties vary strongly within the critical region, which affects the dissolution mechanism. Thus, the release rates for various elements at temperatures above 300 °C are different from those at temperatures below 300 °C. High resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) studies indicate that a Fe(Al)-rich, Si-deficient layer is formed on the surface at temperatures above 300 °C. X-ray photoelectron spectroscopy (XPS) analyses show that the surface layer that formed by reaction with aqueous HCl at 400 °C is a hydrated silicate, composed of Si-OH and Mi-OH, as well as Si-O and Mi-O bonds.