Abstract: A metallurgical processing system for economically recovering metal values, such as columbium, tantalum, thorium, and uranium from dilute source solids, such as digestion sludges, by a series of steps including:1) slurrying the source solids with dilute hydrofluoric acid to produce a solid phase and a liquid phase containing dissolved tantalum and columbium, then extracting tantalum and/or columbium from the liquid phase by means of a liquid ion-exchange process and then, additionally;2) roasting the solid phase with sulfuric acid to recover and recycle hydrofluoric acid, leaching the roasted solids with dilute sulfuric acid to produce a disposable solid phase and a liquid phase containing thorium and uranium, and extracting thorium and uranium from the liquid phase by means of a liquid-liquid amine extraction process.

Abstract: An electrolytic process for the recovery of copper and regeneration of nitric acid from a waste liquor containing the same comprising adjusting the nitrate and hydronium ion concentrations in the liquor to between about 2 to 12 moles per liter and between about 0.5 to 6 moles per liter, respectively, and subjecting the liquor to electrolysis at a temperature of between about 0.degree. to 55.degree. C. using anodes resistant to oxidation.