Record details

    Dissolution kinetics of natural kaolinites at low pH sulfuric acid solutions - an example from Stráž pod Ralskem mineral deposit
Statement of responsibility
    David Hradil, Jiří Hostomský
    Hostomský, Jiří
    Hradil, David
Source title - serial
    Acta Universitatis Carolinae. Geologica
    Vol. 43, no. 1
    p. 537-543
    4 obr., 5 tab., 2 s.bibl.
    Zkr. název ser.: Acta Univ. Carol., Geol.
Subject group
    česká křídová pánev
    kyselina sírová
    lužický faciální vývoj
    rudy U
    těžba loužením
    voda kontaminovaná
Geographical name
    Stráž pod Ralskem (Česká Lípa)
Abstract (in english)
   Kaolinite is the major reactant with acid solutions in the Cenomanian aquifer and the major source of aluminium pollution in groundwaters. Three samples separated from the Stráž block sediments supplied by the mining company (treated to grain fraction <63um) were used in kinetic experiments. The content of impurities was always lower than 25 wt.% (up to 1.5 wt.% of illite, up to 3 wt.% of quartz, up to 11 wt.% of crandallite group minerals, up to 11 wt.% of anatase and up to 2.5 wt.% of hydrozircon). Surface area of the well-ordered kaolinites (Hincley index in the range 1.00 - 1.13) varied from 8/.7 to 19.7 m2/g (when measured by gas adsorption methods). Six dissolution experiments were carried out at room temperature. Samples of kaolinites were suspended in the solid: liquid ratio = 1:100 with solution of sulfuric acid in concentrations of 5 and 50 g/l. The progress of dissolution reaction was measured during 356-532 hours.
   Kaolinite dissolution rates were calculated from the concentration of dissolved Si in the solution. Preferential removal of Al in the steady-state stage of dissolution is caused by parallel dissolution of the crandallite group minerals. At the end of experiments the equilibrium has not been reached. Dissolution rate is constant in the steady-state stage of dissolution (at constant pH), kinetics is "zero-order" with respect to the concentration of products (Si, Al) in the solution. No significant change of the total surface area was found when the leaching residues had been measured by Nelsen-Eggertsen method. No secondary mineral phases were determined by X-ray diffraction method. Calculated constant reaction rates are as follows: LogR(Si) = -15.95 (R = 1.12 x 10 -16 mol/cm2) on the average and logR (Si) = -15.39 (R = 4.07 x 10 -16 mol/cm2s) on the average in lower (5g/l, pH = 0.7) concentrated acid solutions, respectively.
   Measured values vary from logR(Si) = -16.16 to -15.83 in 5g/l of the acid and from logR(Si) = -15.70 to - 15.26 in 50g/l of the acid.
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    14. 1. 2008
Import date
    8. 8. 2012