Uptake of iodide by a mixture of metallic copper and cupric compounds

Ability of copper/cupric compound mixtures to remove iodide from solution was investigated to predict sorption of radioactive iodine in the environme- nt and to assess their use in a nuclear reprocessing method. Thermodynamic calculations were performed to study the stability of such mixtures in solution and to obtain equilibrium constants of Cu(O)/Cu(II)/Iand Cu(O)/Cu(II)/Cl- systems. Both calculations and experimental results showed that a Cu(0)/ Cu3(OH)2(CO3)2 (azurite) mixture selectively uptakes iodide ions (initial concentrations: 10-2 and 10-1 M) in the presence of 10-1 M chloride ions. Reaction of iodide with copper powder and azurite crystal or copper plate and azurite powder have also been investiga- ted, leading to precipitation of CuI onto massive copper phase. The different solids were separately analyzed by XPS and MEB-EDX, giving some insight in the uptake mechanism. It is proposed that soluble copper released by the cupric compound is reduced at the surface of metallic copper, leading to a preferential precipitation of CuI on copper surface.