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This article in SSSAJ

  1. Vol. 47 No. 1, p. 164-168
    Received: Aug 3, 1981
    Accepted: July 23, 1982

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The Kinetics of Gibbsite Dissolution in Nitric Acid1

  1. P. R. Bloom2



The kinetics of dissolution of two synthetic gibbsite preparations was studied in nitric acid solutions with pH values that ranged from 1.5 to 3.3. Dissolution rates were determined at 298 K for both gibbsites and additional rate experiments were conducted at 313 K and 328 K with one of the gibbsites. Dissolution was controlled by reactions at the solid-solution interface and not by diffusion. The rate of reaction did not increase monotonically with H+ activity; rather, there was a minimum rate of about pH = 2.25. Two different mechanisms with different rate-controlling steps were suggested. At pH < 2.1 the rate-controlling step was probably protonation of positively charged surface sites while at pH > 2.4 the rate-controlling step was probably water attack of surface Al.

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