Gamma radiolysis of aqueous solutions of ferric-nitrilotriacetate chelates

Abstract

Radiolytic G values were determined for Fe(II), iminodiacetic acid (IDA) and glyoxalic acid in deoxygenated aqueous solution of Fe(III)NTA, Fe(III)(NTA) 2 and Fe(III)(NTA) 3 and in the presence of scavengers O 2, N 2O, HCOO − and t-butanol. The mode of reaction of the radicals was found to be similar irrespective of number of NTA ligands around the metal ion. The metal ion was reduced directly by e −(aq), H or secondary radicals HO 2, O 2 −, CO 2 − and (CH 3) 2COH while the OH radical did so indirectly through alpha hydrogen abstraction from ligand followed by intramolecular electron transfer. The rate constants determined by competition kinetic methods at pH 6.0 were k[OH + Fe( III)NTA] = 2.5 x 10 8, k[OH + Fe( III)(NTA) 2] = 7.8 x 10 8, k[e −(aq) + Fe( III)NTA] = 3.0 x 10 10 and k[e −(aq) + Fe( III)(NTA) 2] = 2.1 x 10 10 dm 3 mol −1 s −1 and at pH 2.0, k[OH + Fe( III)(NTA) 2] = 6.4 x 10 8 dm 3 mol −1 s −1.