Speciation Method for Partitioning Mononuclear and Polynuclear Aluminum Using Ferron

摘要

The kinetic reactions of ferron with unneutralized and partially neutralized Al solutions in the presence of various inorganic and organic anions were investigated with the intent of distinguishing mononuclear and polynuclear Al. Mononuclear Al solutions containing ClO sub 4- , Cl sup - , NO sub 3- , SO sub 42- , H sub 2 PO sub 4- , and F sup - with anion to Al molar ratios of 13, 21, 15, 5, 0.75, and 0.08, respectively, expressed similar reactions with ferron which conformed to a single second-order reaction. Mononuclear Al solutions containing malate, glutarate, succinate, salicylate, formate, malonate, and fulvate with ligand/Al molar ratios ranging from 0.4 to 7.5, also 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 less than or equal to 0.13, 0.08, and 0.38, respectively, also were modeled using a single second-order expression. Ferron interactions with partially neutralized Al-anion solutions were described by two simultaneous second-order reactions which provided the rate of Al polymer interactions with ferron, k/sub b/, and the mole fraction of mononuclear Al species present, f/sub a/. Model-fitted f/sub a/'s are based on the differential kinetic reactions of ferron with Al, thus arbitrary separation times for determining mononuclear and polynuclear Al are avoided. Increasing concentrations of H sub 2 PO sub 4- , F sup - , citrate, tartarate, and oxalate which cause the ligand/Al molar ratios to exceed the critical values of 0.75, 0.08, 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. 11 figs., 5 tabs. (ERA citation 13:016182)