TREATMENT OF SPENT NITRIC ACID CONTAINING ALUMINUM

Japanese Patent JP2775550

B2

PURPOSE: To improve recovery efficiency by adding sulfuric acid to spent nitric acid contg. phosphoric acid and Al so as to have not less than the specified SO4/Al molar ratio before concentrating the mixture by distillation to the specified free sulfuric acid concentration to recover nitric acid.
CONSTITUTION: Sulfuric acid is added to spent nitric acid contg. phosphoric acid and Al so as to have ≥3 molar SO4/Al ratio to convert nitrate to nitric acid and the mixture is concentrated by distillation until the free sulfturic acid concentration becomes 25-50wt.% to recover nitric acid in the spent acid by ≥90%. Then, after warm water is added to the remained liquid to adjust it so that it may become supersatrated solution of Al2(SO4)3, a seed crystal is added to it to cool it and after a crystal of Al2(SO4)2 is deposited, it is separated from the mother liquor by filtration. In another treatment of the remained liquid after nitric acid recovery, after Fe content is added to the liquid by the specified quantity to make the ratio of free sulfuric acid to FeSO4 be <0.5, it is heat treated and brought into contact with air to oxidize it and the formed insoluble content is filtered and removed to prepare and use a solution essentially consisting of Al2(SO4)3, Fe2(SO4)3 and phosphoric acid.

JPS60204601

SEPARATION OF AQUEOUS SOLUTION OF INORGANIC ACID

MIKAMI YASUYA
YATOMI NOBUYOSHI
MORITA HIROYA

JP18625592A

July 16, 1998

June 19, 1992

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NITSUTETSU KOGYO KK

C01B21/46; C01F7/74; C02F1/04; (IPC1-7): C01B21/46; C02F1/04

JP62275018A

Kenichi Morita

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