Aluminium Pechiney

Aluminum Pechiney

Pechiney

Francois Nicolas

Pierre Maurel

Bernard Bosca

Eric Lavalou

Jean Fabre

A process for purifying at least a fraction of a solution in the Bayer cycle, which is preferably taken off after decomposition of the sodium aluminate, before or after concentration thereof, by causing the precipitation of the sodium oxalate in solution by the introduction of an agent for destabilization of the state of supersaturation of the sodium oxalate, which is characterized in that the supersaturation destabilization agent introduced into the Bayer solution to cause precipitation of the sodium oxalate is selected from the group comprising calcium oxalate and barium oxalate and that, in the case of solutions charged with degraded organic materials which generally result from high-temperature attack on bauxites with high proportions of humic materials, an anionic synthetic polyelectrolyte of high molecular mass is previously introduced into said solutions in order to increase the efficiency of the purification effect.

Purification of solutions of sodium aluminate in the Bayer cycle by the

A process for the purification of solutions containing sodium or potassium carbonate, sulphate, hydroxide or hydrogen carbonate, and mainly at least one of the metals belonging to the group formed by vanadium, uranium or molybdenum, in the form of sodium or potassium salts, and inorganic and/or organic impurities, wherein the above-mentioned solutions are completely or partially caustified by the addition of an adequate amount of lime, whereby a first precipitate essentially containing calcium carbonate is separated, and the separated liquor is concentrated by evaporation until the hydroxide content is at most equal to 50%, to cause the production of a second precipitate which essentially comprises sodium or potassium sulphate, then, after separation thereof, a hydroxide-rich liquor is collected. This process is more particularly adapted for treatments of liquors resulting from the alkaline attach of vanadiferous and uraniferous ores.

Process for the purification of solutions containing a sodium or

Process for the purification of an aqueous solution containing alkali metal carbonate, sulphate, and hydroxide or hydrogen carbonate and primarily one at least of the metals belonging to the group formed by vanadium, uranium and molybdenum, in the form of alkali metal salts, and mineral and/or organic impurities, said solutions resulting from an ore attack cycle and being taken off after extraction of the metal being sought, which comprises treating said solutions by means of lime at a temperature which is at most equal to the boiling temperature, to convert the carbonate and hydrogen carbonate present into alkali metal hydroxide, then effecting separation and washing of a first precipitate of calcium carbonate and a liquor which is enriched in respect of alkali metal hydroxide, concentrating it by evaporation to cause production of a second precipitate which essentially comprises alkali metal sulphate, separating it from the hydroxide-rich liquid phase, re-dissolving it in an aqueous medium and treating the resulting alkali metal sulphate solution by means of barium aluminate and then carbon dioxide, and separating the resulting precipitate which is subjected to a heat treatment to regenerate the barium aluminate which is recycled.

Carbonate, sulphate and hydroxide or hydrogen carbonate

Process for extracting molybdenum from aqueous solutions containing alkali metal carbonate, sulphate, hydroxide or hydrogen carbonate and, primarily, one at least of the metals belonging to the group formed by vanadium, uranium and molybdenum, in the form of alkali metal salts, and mineral and/or organic impurities, said solutions resulting from an ore attack cycle and being taken off after extraction of the metal being sought, in the form of a concentrate, wherein said solutions are caustified by the addition of a suitable amount of lime, converting the carbonate present into alkali metal hydroxide, a first precipitate is separated from the alkali metal hydroxide-rich liquor, said liquor is concentrated until the alkali metal hydroxide content is at most equal to 50%, to cause the production of a second precipitate formed by alkali metal sulphate and molybdate, which is solubilized in an aqueous recycle liquor, said re-dissolution liquor then being treated with sulphide ions and then acidified to give a pH-value of lower than 4.5, in order quantitatively to precipitate the molybdenum which is separated from the mother liquor, washed and dried for use as a source of molybdenum.

Process for the purification of solutions containing alkali metal

The present invention concerns a continuous process for the oxidizing attack of a uraniferous ore by means of an aqueous recycling liquor which contains in a dissolved state alkaline carbonate and bicarbonate and uranium at a concentration close to the limit of solubility thereof at the temperature of the attack operation. The uranium which is precipitated in the course of the attack operation is collected within the solid phase which remains after attack. By redissolution in a suitable aqueous liquor and separation from the sterile materials, a uraniferous liquor is obtained.

Process for the hot oxidized attack on a uraniferous ore by a

A process for the oxidizing attack at high temperature of ores containing at least one metal belonging to the group formed by uranium, vanadium and molybdenum, by means of an aqueous liquor containing a majority of sodium bicarbonate and a minority of sodium carbonate according to a ratio by weight of sodium bicarbonate to sodium carbonate of at least 1.5, in the presence of free oxygen injected into the reaction medium, this medium being maintained at a temperature of between 160.degree. C. and 300.degree. C. for at most six hours.

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Aix-en-Provence, France

Francois Nicolas