Process for recovery of columbium

Claim 2

A process as defined in claim 2 wherein step (b) is carried out in at least two separate stages, the first to solubilize impurities and to separate them, and the second and subsequent stages to solubilize the columbium values.

Claim 3

A process as defined in claim 3 wherein step (c) comprises cooling the aqueous solution of columbium values of step (b) until precipitation of the columbium values is substantially complete and separating said precipitated columbium values.

Claim 4

A process as defined in claim 4 including the step of leaching the precipitate with mineral acid to remove occluded impurities.

Claim 5

A process as defined in claim 4 including the step of adding an excess of alkali metal hydroxide or an excess of mineral acid to assist in the precipitation of the columbium values.

Claim 6

A process as defined in claim 1 comprising: a. heating a columbium concentrate with an excess of an alkali metal hydroxide at a temperature of from about 650* to about 750* C. until the formation of an alkali metal-columbium complex salt is substantially complete; b. aqueously leaching the product of step (a) with enough water to dissolve impurities but not enough water to dissolve a substantial amount of said complex and separating an aqueous solution of said impurities; c. aqueously leaching the product of step (b) to provide an aqueous solution of said complex; d. adding an alkali metal hydroxide to the solution of step (c), cooling until precipitation of the columbium values is substantially complete and recovering said precipitate; e. treating the precipitate of step (d) with mineral acid to remove occluded impurities; and f. calcining the final product of step (e) to obtain the final product.

Claim 7

A process for the recovery of columbium values from a columbium concentrate comprising: a. heating a columbium concentrate with an excess of an alkali metal hydroxide at a temperature of above 400* C. until the columbium values therein are fixed; b. leaching the product of step (a) in at least two separate stages, with water, the first to solubilize impurities and to separate them, and the second and subsequent stages to solubilize the columbium values; c. recovering the columbium values from the resulting solution of step (b).

Claim 8

A process comprising: a. heating a columbium concentrate with from 0.5 to 3 parts of alkali metal hydroxide per part of Cb2O5 in the concentrate at a temperature of from about 550* to about 750* C.; b. aqueously leaching the product of step (a) in at least two separate stages, the first to solubilize impurities and separate them, and the second and subsequent stages to solubilize the columbium values; and c. recovering the columbium values from the solution of step (b).

Claim 9

A process as defined in claim 9 wherein step (c) comprises cooling the aqueous solution of columbium values of step (b) until precipitation of the columbium values is substantially complete and separating said precipitated columbium values.

Claim 10

A process as defined in claim 9 including the step of leaching the precIpitate with mineral acid to remove occluded impurities.

Claim 11

A process as defined in claim 9 including the step of adding an excess of alkali metal hydroxide or an excess of mineral acid to assist in the precipitation of the columbium values.

Claim 12

A process as defined in claim 9 comprising: a. heating a columbium concentrate with an excess of an alkali metal hydroxide at a temperature of from about 650* to about 750* C. until the formation of an alkali metal-columbium complex salt is substantially complete; b. aqueously leaching the product of step (a) with enough water to dissolve impurities but not enough water to dissolve a substantial amount of said complex and separating an aqueous solution of said impurities; c. aqueously leaching the product of step (b) to provide an aqueous solution of said complex; d. adding an alkali metal hydroxide to the solution of step (c), cooling until precipitation of the columbium values is substantially complete and recovering said precipitate; e. treating the precipitate of step (d) with mineral acid to remove occluded impurities; and f. calcining the final product of step (e) to obtain the final product.