Evaluation of reaction spontaneity for acidic and reductive dissolutions of corrosion metal oxides using HyBRID chemical decontamination

Complete sets of reaction mechanisms are proposed in the acidic and reductive dissolution of magnetite, nickel ferrite, and chromite using the HyBRID (Hydrazine Based Reductive metal Ion Decontamination) process for the decontamination of a primary coolant system of nuclear power plant. Hydrazine participated in the reaction pathway of reducing ferric ions to ferrous ions and simultaneously regenerating oxidized cupric ions into cuprous ions. The data of the heat capacity, the heat of formation, the entropy of formation, and the Gibbs energy of formation for all chemical species and ions were collected from the HSC Chemistry 9 database. The enthalpy, entropy, and Gibbs energy changes of reactions were calculated in the temperature range of 298.15–373.15 K for individual reactions. The degree of spontaneity decreased with the increase of the temperature. The reaction spontaneity was significantly enhanced by addition of hydrazine and slightly increased by further addition of copper sulfate. (author)