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The Kinetics of Gibbsite Dissolution in Nitric Acid
Author(s) -
Bloom P. R.
Publication year - 1983
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1983.03615995004700010032x
Subject(s) - gibbsite , dissolution , chemistry , nitric acid , kinetics , diffusion , protonation , inorganic chemistry , reaction rate , nuclear chemistry , mineralogy , kaolinite , catalysis , organic chemistry , ion , thermodynamics , physics , quantum mechanics
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.