, Volume 47, Issue 4, pp 345–351 | Cite as

A Spectrophotometric Study of the Interaction of Uranyl Ions with Orthosilicic Acid and Polymeric Silicic Acids in Aqueous Solutions

  • A. B. Yusov
  • A. M. Fedoseev


The interaction of UO 2 2+ ions with orthosilicic acid Si(OH)4 and polymeric silicic acids (PSAs) was studied spectrophotometrically. The equilibrium constant of the reaction UO 2 2+ + Si(OH)4 = UO2OSi(OH) 3 + + H+ in solutions with the ionic strength I = 0.1–0.2 is log K = −2.56±0.09 (log K0 = −2.29±0.09 recalculated to I = 0); the stability constant of the complex UO2OSi(OH) 3 + (I = 0) is log β0 = 7.52±0.09. Formation of small oligomers (degree of polymerization n ≤ 4) has virtually no effect on the apparent constant K. When high polymers are formed (n > 100), the apparent equilibrium constant decreases by a factor of 2–3, and the “true” equilibrium constant recalculated to the actual concentration of silanol groups increases by a factor of 3–4. The absorption spectrum of the complex UO2OSi(OH) 3 + was obtained by treatment of the experimental spectra; it has an absorption maximum in the visible range at 422.5 nm, ɛ422.5 = 35±2 l mol−1 cm− 1. At pH higher than 5–6, complexes of UO 2 2+ with PSAs of the composition UO2(≡SiO)2(≡ SiOH)m − 2 are formed. The absorption spectrum of such a complex was obtained.


Absorption Spectrum Oligomer Uranyl Equilibrium Constant Actual Concentration 
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© MAIK “Nauka/Interperiodica” 2005

Authors and Affiliations

  • A. B. Yusov
    • 1
  • A. M. Fedoseev
    • 1
  1. 1.Institute of Physical ChemistryRussian Academy of SciencesMoscowRussia

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