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Soil Science Society of America Journal Abstract -

Influence of Inorganic Anions on the Speciation of Mononuclear and Polynuclear Aluminum by Ferron1


This article in SSSAJ

  1. Vol. 51 No. 4, p. 889-892
    Received: Sept 17, 1986

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  1. P. M. Jardine and
  2. L. W. Zelazny2



The kinetic reactions of ferron (8-hydroxy-7-iodo-5-quinoline-sulfonic acid) with unneutralized and partially neutralized Al solutions in the presence of various inorganic anions were investigated for the purpose of differentiating mononuclear and polynuclear Al. Development of a general order reaction function indicated that ferron interactions with Al were modeled best by second-order rate expressions. Mononuclear Al solutions containing ClO-4, Cl-, NO-3, SO2-4, H2PO-4, and F- with anion to Al molar ratios of 13, 21, 15, 5, 0.75, and 0.08, respectively, expressed similar reactions with ferron that conformed to a single second-order reaction. Ferron interactions with partially neutralized Al-anion solutions were described by two simultaneous second-order reactions that provided the rate of Al-polymer interactions with ferron, kb, and the mole fraction of mononuclear Al species present, fa. Distinction of mononuclear and polynuclear Al in partially neutralized solutions with various anions is possible using ferron if the H2PO-4/Al and F-/Al molar ratios do not exceed ≈ 0.75 and 0.08, respectively. Phosphate and F- concentrations that reduce these ratios and SO2-4/Al ratios of ≈ 5 still form complexes with Al, but are easily degraded by ferron and react identically to uncomplexed mononuclear Al solutions. Such complexes must be accounted for if an estimate of toxic mononuclear Al [Al(H2O)3+6, AlOH(H2O)2+5, Al(OH)2(H2O)+4] is desired.

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