Kinetic of Cobalt and Copper Oxides Dissolution in Acidic Media Containing EDTA

We studied the dependence of the rate of dissolution of d-elements oxides (cobalt and copper oxides) in acidic media with EDTA additives from different factors. Increase in EDTA concentration enhances the cobalt and copper oxides dissolution, while the copper oxide dissolution is inhibited. Within the research we determined the orders by hydrogen ions and EDTA: for cobalt oxide it is 0.5 ± 0.1; for copper oxide it is 0.6 and by EDTA it is ≈ −0.6. The peculiarity of the studied kinetics in EDTA is that the rate of cobalt oxides dissolution passes through a maximum at pH = --1, for copper oxide in the presence of chelating agent EDTA the dissolution rate first decreases, and then it increases at pH from 5 to 8. The activation energy of the process is E_a(H₂SO₄) = 70 kJ/mol, E_a(EDTA) = 60 kJ/mol, for copper oxide the activation energy is 73 ± 0.5 kJ/mol. The simulation of the processes showed that the surface particle, which determines the rate of dissolution is МеOH⁺ in mineral acids, and in the chelating agent it is МеHY^-

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