Record details

Title
    Formation of colloidal silica and alumina during experimental granodiorite weathering
Statement of responsibility
    Jiří Faimon
Author
    Faimon, Jiří, 1950-
Language
    anglicky
Source title - serial
    Aquatic geochemistry
Vol./nr.
    Vol. 9, no. 4
Pages
    p. 305-341
Year
    2003
Notes
    13 diagr., 1 sch.
    Bibliografie na s. 336-341
    il.
    Zkr. název ser.: Aquatic Geochem.
Classfication no.
    552
Conspectus category
    552
Subject group
    brněnský masiv
    fylosilikáty
    granodiorit
    hliník
    koloid
    křemík
    přesycení
    rozpouštění
    studie experimentální
    zvětrávání
Geographical name
    Brno-Řečkovice
    ČR-Morava
Keyword
    Alumina
    Colloidal
    During
    Experimental
    Formation
    Granodiorite
    Silica
    Weathering
Abstract (in english)
   The role of aluminum and silica in the formation of colloids during granodiorite weathering was studied on the basis of long-term experiments in batch reactors. Rock samples were dissolved in un-buffered solutions of initial pH "proportionall" 3.2, 5.4, and 9.9 at ambient conditions for 500 days. During weathering, extremely high supersaturation with respect to various secondary solids was attained in the solutions. Consequently, new solids, part of which was conserved in solutions as colloids, condensed. The mean concentrations of colloidal Si reached values of 70, 50, and 48 mímol 1-1 in the alkaline, neutral, and acid solutions, respectively. The mean concentrations of colloidal AI, reached values of 34, 22, and 12mímol 1-1 in the alkaline, neutral, and acid solutions, respectively. The concentration of colloids gradually decreased after 200-400 days of experiment. This phenomenon was interpreted as being due to the competition between homogeneous nucleation and crystal growth.
   At the initial stages of the experiments, the colloidal species (predominantly colloidal AI) comprised a large proportion of the total amounts of aqueous species. Their share, however, decreased with time. The molar Al/Si-ratios of colloids were as high as 2-2.5 at the early stages of the experiment. After 250-300 days of experiments, on the other hand, these ratios decreased to values of about 0.5 in both the neutral and alkaline solutions and to a value of 0.15 in the acid solution. The evolution of colloids was consistent with the evolution of secondary solids in the sequence Al-hydroxides - clay minerals (illite, chlorite), in both the neutral and alkaline solutions. In acid solutions, the evolution of Al/Si-colloids was influenced by the presence of sulfate ion and Al-sulfate precipitation. Besides AI and Si, other elements, in particular Ca or Mg as a major component and Na, K, P, S, and Cl as minor components, readily participated in the formation of colloids
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    31. 3. 2006
Import date
    8. 8. 2012