Dissolution Process of Phlogopite in Acid Solutions

Abstract

Abstract--The alteration experiments of phlogopite with 0.01 N HC1 solution containing 0.1 M NaC1 at 50*, 80* and 120"C have been carried out to aid in the understanding of the dissolution process of mica and the formation of secondary phases such as vermiculite and interstratified mica/vermiculite. Twenty milligrams of phlogopite samples were suspended in 20 ml or 100 ml of leaching solution.In these experiments, the dissolution ofphlogopite occurred incongruently, where the preferential release of K occurred in almost all stages of the alteration reaction. In the 100 ml experiments, the priority in dissolution in the initial stage was in the order; K > Fe > Mg, Al > Si. This supports that phlogopite leaching is controlled by the mineral structure. At 80* and 50"C in the 20 ml experiments, the release of all elements except for K was nearly congruent. At 120"(2 in the 20 ml experiments, the dissolution was outwardly incongruent, which Fe decreased remarkably after six days and A1 was released most slowly compared with all other elements in phlogopite. This is probably due to the precipitation of secondary phases such as aluminum and iron oxides and/or hydroxides.Vermiculite and Rl-type interstratified mica/vermiculite, containing 70 -50% mica, were formed in the alteration process of phlogopite. The following two processes were confirmed for the formation of interstratified structure: Interstratified structure was formed (1) directly from phlogopite or (2) from vermiculite which was produced earlier from phlogopite by regaining of K from the ambient solution. It may depend on the release rate of K from phlogopite whether mica-vermiculite layer sequences develop or vermiculite-vermiculite sequences do.

Effects of Salinity and the Extent of Water on Supercritical CO2-Induced Phlogopite Dissolution and Secondary Mineral Formation

“…Kuwahara and Aoki reported that phlogopite dissolved preferentially in the order of K > Mg ≈ Al > Si within 96 h in 0.01 M HCl þ 0.1 M NaCl solution at elevated temperature (323-393 K). 15 Another study of phlogopite in water at 1 atm CO 2 and room temperature reported that Mg dissolution was preferred over Si dissolution, 16 while the present work shows similar dissolution rates of Mg and Si. The different behavior of phlogopite at low CO 2 pressure (1 atm) or in acid solution, and under GCS conditions (this work), suggests that the reaction mechanisms between rock minerals and CO 2 -saturated saline water could differ from changes in ambient conditions.…”

Biotite dissolution processes and mechanisms in the laboratory and in nature: Early stage weathering environment and vermiculitization

“…This study for 1, 4, 10, and 56 day dissolution of biotite, respectively, 5 = this study for 5.5 day dissolution of phlogopite, 6 = Malmström and Banwart (1997), and 7 = Kuwahara and Aoki (1995). Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 7/1/15 6:47 PM sibly a kaolin polymorph) were also observed.…”

“…Similar observations also have been made using lattice-imaging techniques (Reichenbach et al 1988;Veblen et al 1993;Aoudjit et al 1996;Dong et al 1998). Vermiculitization and/or kaolinitization are found for some biotite dissolution experiments (Kuwahara and Aoki 1995;Kalinowski and Schweda 1996;Malmström and Banwart 1997), but are not observed or reported for others Clemency and Lin 1981;Acker and Bricker 1992;Turpault and Trotignon 1994).…”

“…The thermodynamic calculations by EQ3NR/6 revealed that the solutions after a 56 day dissolution of biotite and a 5.5 day dissolution of phlogopite were not supersaturated with respect to any montmorillonites or saponites. Malmström and Banwart (1997) and Kuwahara and Aoki (1995) also observed vermiculite after their dissolution experiments, although their solutions were not supersaturated with respect to any montmorillonites or saponites ( Table 1). The samples in which vermiculite is observed are richer in Mg [more than 0.8 Mg per O 10 (OH) 2 in the octahedral sheet, Table 1].…”

Stoichiometry of a dissolution reaction of a trioctahedral vermiculite at pH 2.7

“…Kalinowski and Schweda (1996) found a continuous preferential leaching of interlayer K without any significant modification to the cationic composition of the 2:1 layer. Kuwahara and Aoki (1995) studied the dissolution of phlogopite in 0.01 N HCl/0.1 M NaCl solutions at pH 2 from 50 to 120°C. They observed nearly congruent dissolution at 50°and 80°C.…”