Influence of aquation and hydrolysis on substitution reactions in sulfate complexes of iridium and ruthenium

To extract ruthenium from sulfuric acid solutions of hydrometallurgy they are preliminarily trealed by NaCl to substitute chloride ions for sulfate ions. The chloride complex formation from sulfate complexes, prepared under mild conditions, proceeds much easier. The more aquated and hydrolyzed basic compounds appear to be, the faster and more complete substitution reaction in sulfate complexes proceeds. The interaction of Ru sulfate complexes with NaCl was studied, depending on the NaCl concentration, temperature (80, 98 and 110 deg) and period of heating. If the NaCl concentration is 0.4 to 1.0 mol/l, then the Ru (4) complexes, containing the [Ru2O2]4+ group, are formed on heating; at a higher NaCl concentration the [Ru2OCl10]4- group is formed. During further heating the substitution reaction is complicated by a redox process. In solutions where more hydrolyzed dioxochloride dimeric ruthenium (4) complexes form, Ru (4) reduction proceeds at the highest rate