CONTEXT

Hydrothermal treatments have been largely studied to destroy wastes. Some of these wastes like nitrite or sulphite in aqueous effluents as produced by acid attack of metals by sulphuric acid or nitric acid cannot be rejected in the environment without being previously treated. Some treatments like precipitation, bioprecipitation, crystallisation, ions exchange, electrolysis have been proposed but they are either not effective enough (crystallisation or precipitation) or too expensive (electrolysis) or produce nitric acid and/or NOx.