Experimental studies of halite dissolution kinetics:: II.: The effect of the presence of aqueous trace anions and K3Fe(CN)6

The dissolution rates of compressed halite powders were measured using rotating disk techniques at constant halite saturation states and in the presence of trace concentrations of aqueous F-, Br-, and I-. All experiments were performed at 25 degrees C. The presence of each trace anion decreased the overall halite dissolution rate and the degree of inhibition increases with increasing anion concentration. The order of constant concentration effectiveness in inhibiting rates is I- > Br- > F-. Dissolution inhibition by these anions is interpreted to result from their adsorption on the halite surface. Application of a combined transition state theory/Langmuir adsorption model to these experimental results allows both the description of measured rates and their extrapolation to other solution compositions. In contrast, work on aqueous K3Fe(CN)(6) indicates that trace quantities of this electrolyte has little effect on halite dissolution rates, except at relatively high electrolyte concentration or high halite saturation state where Na3Fe(CN)(6) precipitation occurs on the halite surface. (C) 1997 Elsevier Science B.V.