On the interpretation of closed system mineral dissolution experiments: comment on ''Mechanism of kaolinite dissolution at room temperature and pressure part II: kinetic study'' by Huertas et al. (1999)
Abstract
Huertas et al. (1999) reported the results of a series of constant-pH kaolinite dissolution experiments performed at 25°C in closed system reactors. The authors of this study chose to interpret these experiments assuming that the dissolution rates of kaolinite in their reactors, after a certain initial elapsed time, were time independent. The purposes of this comment are to (a) recall evidence available in the literature demonstrating that constant-pH kaolinite dissolution does not attain a constant rate in closed system reactors; (b) present a simple equation describing solution composition evolution during closed system multioxide mineral or glass dissolution experiments; and (c) demonstrate that Huertas et al.'s (1999) data are consistent with kaolinite rates that are proportional to cAlnAl where cAl refers to the concentration of aqueous aluminum, and nAl denotes a constant.