Kinetic studies of the oxidation of L-ascorbic acid by tris(oxalate) cobaltate in the presence of CDTA metal ion complexes

Abstract

It was investigated the kinetic of the reduction reaction of tris(oxalate)cobaltate by L-ascorbic acid, H2A, at different acidity. The Co(III) complex was monitored at 600 nm, under pseudofirst-order conditions: [H2A] = 3.0 × 10-2 mol L-1, [Co(C2O4)3]3- = 3.0 × 10 -3 mol L-1, in the presence of CDTA (3.0 × 10 -3 mol L-1) and ionic strength 1.0 mol L-1, (NaCl) at 25.0±0.1 °C. The catalytic activity of CDTA metal ion complexes of Fe(III), Ni(II), Cu(II), Cr(III) and Mn(II) was also examined. The pseudo-first-order rate constant was proportional to the concentration of Fe(III)/CDTA, which is the best catalyst, in the range of (1-10) × 10 -5 mol L-1. © 2006 Sociedade Brasileira de Química.