The dissolution rates of gibbsite in the presence of chloride, nitrate, silica, sulfate, and citrate in open and closed systems at 20°C

Do clay mineral dissolution rates reach steady state?

“…Rate constants for plagioclase, K-feldspar, and hornblende were calculated to decrease by more than an order of magnitude over 3 million yr of weathering. This observation was also attributed by White et al (1995) to stem from a temporal decrease in the reactivity per unit of physical surface area due to a decrease in the density of reactive sites (Pokrovsky, 2004;Bickmore et al, 2001;Dietzel , 2004).…”

Comment on: “The dissolution rates of gibbsite in the presence of chloride, nitrate, silica, sulfate and citrate in open and closed systems at 20°C” by M. Dietzel and G. Böhme

“…Furthermore, their failure to adequately cite the recent literature detracts from their study. Figure 2 of Ridley et al (1997) shows linear aluminum release rates from dissolving gibbsite as a function of time in chloride and chloride + sulfate solutions with 0.01 m initial H + that are very similar to the pH 2 data in Figure 7 of Dietzel and Bö hme (2005). Minor differences can be attributed to the lower temperature and higher ionic strength used in our experiments.…”

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The recent paper by Dietzel and Bö hme (2005) reports the rate of dissolution of gibbsite under far-from equilibrium conditions and low pH at 20°C, indicating that the rates are about the same in chloride and nitrate solutions, faster in silica-bearing solutions, and fastest in sulfateand citrate-bearing solutions. This information is highly relevant to environmental geochemistry and soil science.

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An experimental study of the dissolution mechanism and rates of muscovite

“…Comparison of the 25°C far-from-equilibrium dissolution rates of quartz, gibbsite and d-Al 2 O 3 as a function of pH. Filled squares represent rates of quartz dissolution reported by Brady and Walther (1990), whereas open circles correspond to gibbsite and dAl 2 O 3 dissolution rates reported by Bloom (1983), Furrer and Stumm (1986), Bloom and Erich (1987), and Dietzel and Bohme (2004).…”