In this work, hydrothermal decomposition of [Fe(CN)₆]³⁻ in alkaline solution was conducted in a batch-type autoclave. The initial concentration of CN in [Fe(CN)₆]³⁻ in the sample solution was set to correspond to 1,000 mg CN/dm³. The experiments were conducted at temperatures of 403-443 K under O₂ atmosphere at 0.1-4 MPa pressure. Hydrogen peroxide (H₂O₂) was used as an oxidation agent to enhance oxidative decomposition of [Fe (CN)₆]³⁻. Moreover, the mechanism of this reaction was discussed.
Results show that the rate of hydrothermal decomposition of [Fe (CN)₆]³⁻ is independent of O₂ partial pressure. The rate is sufficiently described by first-order reaction Kinetics with respect to the [Fe(CN)₆]³⁻ concentration. The principal reaction products of cyanate (OCN⁻), formate (HCOO⁻), and ammonium (NH₄⁺) ions were detected using ion chromatography. When H₂O₂ was added to [Fe(CN)₆]³⁻ solution, the decomposition rate of CN in [Fe(CN)₆]³⁻ at the initial stage of the reaction (0.5-2 h) was found to be 1.2-1.3 times higher than that without H₂O₂. The reaction products of HCOO⁻, carbonate (CO₃²⁻) and NH₄⁺ ions were detected. Such different reaction products resulting from H₂O₂ addition suggest the formation of CO₃²⁻and N₂ during oxidative decomposition of [Fe(CN)₆]³⁻ by H₂O₂.

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