Interaction between copper(II) oxide and aqueous ammonia in the presence of ethylenediaminetetraacetic acid

The interaction of copper(II) oxide with aqueous ammonia containing ethylen ediaminetetraacetic acid (H4L) is analyzed in terms of formal heterogeneous kinetics and the fractal dimension of the dissolving space. It is shown ex perimentally that, in the presence of H4L, the dissolution rate of CuO grow s with increasing ammonia concentration. At a fixed ammonia concentration, the dissolution rate of CuO passes through a maximum at an H4L concentratio n of 8 x 10(-3) mol/l. Two mechanisms of dissolution are suggested. namely. an adsorption and a redox mechanism. The adsorption mechanism involves fou r intermediate species and implies that the dissolution rate is a fractiona l rational function of the EDTA concentration. The redox mechanism takes in to account the oxide/electrolyte interfacial potential. ne role of the CuOH L3- ion is elucidated. and the kinetic parameters of dissolution are derive d.