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Soil Science Society of America Journal Abstract -

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


This article in SSSAJ

  1. Vol. 51 No. 4, p. 885-889
    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 organic anions were investigated with the intent of distinguishing mononuclear and polynuclear Al. Mononuclear Al solutions containing malate, glutarate, succinate, salicylate, formate, malonate, and fulvate with ligand/Al molar ratios ranging from 0.4 to 7.5, reacted rapidly with ferron and were modeled using a single second-order equation. Similarily, mononuclear Al solutions containing citrate, tartarate, and oxalate with ligand/Al molar ratios ⩽ 0.13, 0.08, and 0.38, respectively, also reacted rapidly with ferron and were modeled using a single second-order expression. Model fitted ka values (rate of Al-monomer reactions with ferron) for these organic-Al solutions were similar to ka values determined for uncomplexed mononuclear Al solutions without added organic ligands. Increasing concentrations of citrate, tartarate, and oxalate that cause the ligand/Al molar ratios to exceed the critical values of 0.13, 0.08, and 0.38, respectively, form complexes with Al that are not easily degraded by ferron, thus limiting the credibility of accurate distinction between monomeric and polymeric Al. The interaction of ferron with Al-polymers was not significantly affected by concentrations of organic anions whose ligand/Al molar ratio did not exceed these critical values. These conditions allowed the accurate distinction of mononuclear and polynuclear Al.

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