JPS5494498A - Manufacture of high purity phosphates - Google Patents

Abstract

PURPOSE: To manufacture high purity phosphates at lower cost by te procedure in which phosphoric acid by the wet process is desulfurized by using ground rock phosphate, then defluorinated by Na and K salts, then converted into acid phosphates by the addition of an alkali to remove insoluble components,then dearsenated by an alkali sulfide,and lastly crystallized by solvent after filteration through activated carbon.

CONSTITUTION: A 1 to 1.1 equivalent of ground rock phosphate is added to the sulfuric acid contained in phosphoric acid by the wet process for desulfurization treatment, and then the wet process phosphoric acid is deflurinated by using a Na salt or a K salt. Then, the phosphoric acid is regulated its pH to less than 8 by addition of an alkali and water to form primary phophate or secondary phosphate in order to remove insoluble components. Then, the arsenic present in the phosphate solution is precipitated by the addition of an alkali sulfide or H₂S as much as 10 to 500 times greater than AS (in mole) in the form of sulfide, where Pb, Cd, and Fe, basides As, are precipitated in the form of respective sulfide alike. After the treatment, air or an inert gas is blown into the liquor to remove H₂S and then the liquor is filtered by the addition of actibated carbon. And, the filtrate is mixed with a C₁ to C₃ alchole or acetone to crystallize high purity phosphates.

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