EXPERIMENTAL STUDIES OF HALITE DISSOLUTION KINETICS, 1 THE EFFECT OF SATURATION STATE AND THE PRESENCE OF TRACE METALS

Abstract

The comprehensive understanding of halite dissolution facilitates assessment of long-term radiogenic waste storage strategies, quantitative description of evaporite deposit formation and optimization of industrial processes. To this end, the dissolution rate of compressed halite powders was measured using the rotating disk method as a function of temperature, solute saturation state and the concentration of aqueous trace metals. The results of these experiments were used to generate dissolution and transport rate constants, as well as activation energies for these processes at temperatures from 25° to 80°C. Results indicate that in the absence of trace metals, constant-temperature halite dissolution rates vary linearly with the overall mineral saturation state. The presence of trace quantities of Fe and Zn were found to negligibly affect halite dissolution, while trace quantities of Co, Cr, Cd and Pb significantly lowered halite dissolution rates. At constant trace-metal concentration, halite dissolution rates were found to vary in the order: Fe ~ Zn > Co > Cr > Pb > Cd. A combined transition state theory/Langmuir adsorption model was developed and demonstrated to effectively describe measured rates as a function of solution composition.