THE EFFECT OF MALONATE ON THE DISSOLUTION KINETICS OF ALBITE, QUARTZ,AND MICROCLINE AS A FUNCTION OF PH AT 70-DEGREES-C

The effect of malonate on the dissolution rate of the reservoir minera ls: albite, quartz, and microcline has been examined. The effect of pH on rate has been decoupled from the effect of the ligand by controlli ng pH using dilute buffer solutions at values of pH 4 through pH 10 at 70 degrees C. Any effect of the buffer ligands (acetate and berate) o r alkali cation (Na) on rate was accounted for by comparing the measur ed dissolution rates in buffer solutions with and without malonate. Fl owing reactors were used and malonate concentration was varied from 1 to 100 mmolal. As malonate anion concentration is increased, the disso lution rate of these minerals also increases. At moderately acidic to near neutral pH in the solutions containing the highest malonate conce ntration, malonate most significantly increases the dissolution rate o f the silicates over that expected due to simple hydrolysis. At alkali ne pH the effect of malonate on the dissolution rate of these silicate s is not significant, compared to the dissolution rate due to simple h ydrolysis alone.