Molecular-level mechanisms of quartz dissolution under neutral and alkaline conditions in the presence of electrolytes

Copyright © 2014 by The Geochemical Society of Japan. Strandh et al., 1997), reactivity of different surface sites (e.g., Blum and Lasaga, 1988, 1991; Blum et al., 1990; Dove, 1994; Furrer and Stumm, 1986; Lasaga, 1992; Pelmenschikov et al., 2000; Raghavachari and Rohlfing, 1991; Bickmore et al., 2008; Wallace et al., 2010), the extent of undersaturation of the solution (e.g., Dove et al., 2005, 2008; Zhu, 2005; Zhu et al., 2006), and temperature (e.g., Brady and Walther, 1992; Casey and Sposito, 1992; Rimstidt, 1997; Rimstidt and Barnes, 1980). However, the molecular-level mechanisms for many of these driving forces remain elusive. Quartz is the simplest and an abundant silicate mineral in the earth’s crust. The study of its dissolution mechanism was expected to shed light on the dissolution mechanisms of other silicate minerals. However, it has been found that the dissolution mechanism of quartz is very different to that of other silicate minerals in several ways. For instance, the dissolution of most silicate minerals is insensitive in the presence of small amounts of electrolytes (NaCl, CaCl2). However, experimental data show that at near-neutral pH conditions, quartz will dissolve up to 100 times faster in the presence of small amounts of alkali and alkaline earth electrolytes (e.g., Berger et al., 1994; Dove and Crerar, 1990; Dove and Elston, 1992; Dove, 1994, 1999; Dove and Nix, 1997; Dove and Colin, Molecular-level mechanisms of quartz dissolution under neutral and alkaline conditions in the presence of electrolytes