Effect of ozone on ruthenium species in alkaline medium – Part II: Oxidation of pentahydroxo nitrosyl ruthenate(II) ion RuNO(OH)52-

Abstract

SummaryOxidation of the nitrosyl ruthenium complex RuNO(OH)52-has been carried out in sodium hydroxide solutions in contact with a gas flow containing ozone. The RuNO(OH)52-complex is converted successively into ruthenate and perruthenate ions. An empirical kinetic rate law for the first step has been determined and was shown to depend on concentrations of (i) the ruthenium complex, (ii) the hydroxide ions and (iii) ozone concentration in the gas flow. The second step of the reaction, corresponding to the perruthenate ion formation, shows a complex mechanism and four competing reactions have been proposed to represent it. The influences on the second step kinetics of several parameters such as ozone or hydroxide concentrations or the conditions of the gas-liquid exchange area are also qualitatively discussed.