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 c_Al^n_Al where c_Al refers to the concentration of aqueous aluminum, and n_Al denotes a constant.