EXPERIMENTAL STUDIES OF HALITE DISSOLUTION KINETICS .1. THE EFFECT OFSATURATION STATE AND THE PRESENCE OF TRACE-METALS

The comprehensive understanding of halite dissolution facilitates asse ssment of long-term radiogenic waste storage strategies, quantitative description of evaporite deposit formation and optimization of industr ial processes. To this end, the dissolution rate of compressed halite powders was measured using the rotating disk method as a function of t emperature, solute saturation state and the concentration of aqueous t race metals. The results of these experiments were used to generate di ssolution and transport rate constants, as well as activation energies for these processes at temperatures from 25 degrees to 80 degrees C. Results indicate that in the absence of trace metals, constant-tempera ture halite dissolution rates vary linearly with the overall mineral s aturation state. The presence of trace quantities of Fe and Zn were fo und 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 foun d to vary in the order: Fe approximate to Zn > Co > Cr > Pb > Cd. A co mbined transition state theory/Langmuir adsorption model was developed and demonstrated to effectively describe measured rates as a function of solution composition.