Central Glass Company, Limited

Soichi Asagao

Shinsuke Nakagawa

Naoki Okada

Yoshiyuki Takahara

Masaru Nakatani

Motoshige Ogura

Seizi Yoshikawa

Yoshishige Fujita

An economically advantageous method of recovering uranium from a wet process phosphoric acid solution through the steps of making hemihydrate gypsum contact with the acid solution thereby transferring uranium from the acid solution into the gypsum, dispersing the U-containing gypsum separated from the acid solution in water to convert the gypsum to dihydrate accompanied by the transfer of uranium into water, separating the obtained U-containing aqueous solution from the dihydrate gypsum, and adding precipitant such as an inorganic base to the aqueous solution to form a precipitate comprising an insoluble uranium compound. The contact of hemihydrate gypsum with the phosphoric acid solution is preferably preceded by reduction of hexavalent uranium in the acid solution to tetravalent uranium, and can be achieved either by adding hemihydrate gypsum to the acid solution or by converting dihydrate gypsum to hemihydrate within the acid solution preferably preceded by the addition of sulfuric acid.

Method of recovering uranium from wet process phosphoric acid

A process for preparing crystalline ammonium dihydrogen phosphate, comprises the steps of (a) adding a sequestering agent into ammonium hydrogen phosphate aqueous solution, the sequestering agent reacting with metallic ions contained in the aqueous solution to form water solouble compounds, (b) heat-treating the aqueous solution at a temperature of 70.degree. C. or more after addition of the sequestering agent, and (c) crystallizing ammonium dihydrogen phosphate out of the aqueous solution after the heat-treating, so that crystalline ammonium dihydrogen phosphate can be obtained in high whiteness and in the form of columnar crystals.

Process for preparing crystalline ammonium dihydrogen phosphate

A process for preparing crystalline ammonium dihydrogen phosphate, comprises the steps of (a) adding a sequestering agent into ammonium hydrogen phosphate aqueous solution, the sequestering agent reacting with metallic ions contained in the aqueous solution to form water soluble compounds, (b) heat-treating the aqueous solution at a temperature of 70.degree. C. or more after addition of the sequestering agent, and (c) crystallizing ammonium dihydrogen phosphate out of the aqueous solution after the heat-treating, so that crystalline ammonium dihydrogen phosphate can be obtained in high whiteness and in the form of columnar crystals.

Highly pure sodium ammonium hydrogenphosphate and ammonium chloride are prepared from wet process phosphoric acid. A mixture of phosphoric acid, ammonia and/or sodium chloride is added to a circulating mother liquor, to which is additionally added ammonia until the pH of the liquor reaches 5.5 to 9.0. The liquor is then cooled to cause sodium ammonium hydrogenphosphate to crystallize at 30.degree. to 60.degree. C. The resulting filtrate is added with an acidic compound to adjust its pH to 5.6 to 6.4 whereby the solubility of the hydrogenphosphate is increased while that of ammonium chloride is reduced to a minimum. The filtrate is cooled to 5.degree. to 50.degree. C to precipitate ammonium chloride as crystals without involving co-precipitation of the hydrogenphosphate. The filtrate from which the ammonium chloride crystals have been removed is recycled for use as a circulating mother liquor.

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Ube, Japan

Soichi Asagao