Uranyl-catalyzed chemiluminescent reaction of U4+ oxidation by dioxygen in aqueous HClO4 solution

Article abstract of DOI:10.1007/BF02495151

Chemiluminescence (CL) accompanying the reaction of U⁴⁺ with O₂ in 0.0004-0.1 M HClO₄ was studied. It was found that the electron-excited uranyl ion (UO₂²⁺)* is the CL emitter. The fact that the reaction rate and the CL yield increase as the solution acidity decreases was explained by different reactivities of the U⁴⁺_aq aquaion and the products of its stepwise hydrolysis, UOH³⁺ and U(OH)₂²⁺, toward O₂. Based on the results of analysis of the chain-radical mechanism of the reaction between U⁴⁺ and O₂, it was concluded that transfer of an electron from the UO₂⁺ ion to the oxidizing agent (a OH radical) is the most plausible elementary step of the reaction of (UO₂²⁺)* formation. It was found that the reaction rate, as well as the CL yield, increase substantially in the presence of uranyl ion. Catalytic action of UO₂²⁺ was explained by the formation of a UO₂²⁺ · UO₂⁺ complex, which reduces the rate of the UO₂⁺ disproportionation reaction (UO₂⁺ is an intermediate of the reaction and is involved in chain propagation), and by regeneration of the active center, UO₂⁺, in the reaction of UO₂²⁺ with U⁴⁺.