Acidization III--The kinetics of the dissolution of sodium and potassium feldspar in HF/HCl acid mixtures

Abstract

The dissolution of a potassium and a sodium feldspar in hydrochloric-hydrofluoric acid mixtures was studied in a rotating disk system at 25 and 100[deg]C under a pressure of 40 psig. Under these conditions, the dissolution rate is limited by the rate of reaction of the acids with the solid surface.The rate of dissolution may be described by the following type of rate law: The parameters a and b for potassium feldspar have the values 0[middle dot]4 and 1[middle dot]2, respectively, whereas for sodium feldspar both have a value of 1[middle dot]0. A mechanism for the dissolution reaction is proposed which is consistent with experimental observation. The analysis suggests that the dissolution is limited by the rate at which the hydrofluoric acid reacts with the solid surface and that the strong influence of the hydrochloric acid on the dissolution rate is due to the adsorption of hydrogen ions on the mineral surface.