Production of monobasic potassium phosphate by electrodialysis

Claim 2

In the combined process for producing phosphoric acid by treating apatite with sulfuric acid, and aluminum from alunite ore with the production of by-product potassium sulfate, the improvement which comprises converting the phosphoric acid and potassium sulfate to monobasic potassium phosphate by electrodialysis.

Claim 3

The process of claim 1 performed continuously.

Claim 4

A continuous process for producing aluminum and monobasic potassium phosphate from alunite ore and apatite ore which comprises: (a) reacting apatite ore with sulfuric acid to produce phosphoric acid; (b) roasting and leaching the alunite ore to remove water and compounds of sulfur and alkali metals resulting in a residue containing aluminum values and a solution containing potassium sulfate; (c) digesting the residue from step (b) with at least one alkali metal hydroxide to convert substantially all of said aluminum values to soluble aluminate; (d) removing silica from the aluminate formed in step (c); (e) recovering aluminum values from the aluminate remaining from step (d); and (f) converting phosphoric acid from step (a) and potassium sulfate from step (b) to monobasic potassium phosphate by electrodialysis.

Claim 5

A continuous process for producing aluminum and monobasic potassium phosphate from alunite ore and apatite ore which comprises: (a) reacting apatite ore with sulfuric acid to produce phosphoric acid; (b) roasting and leaching the alunite ore to remove water and compounds of sulfur and alkali metals resulting in a residue containing aluminum values and a solution containing potassium sulfate; (c) digesting the residue from step (b) with at least one alkali metal hydroxide to convert substantially all of said aluminum values to soluble aluminate; (d) removing silica from the aluminate formed in step (c); (e) recovering aluminum values from the aluminate remaining from step (d); and (f) converting phosphoric acid from step (a) and potassium sulfate from step (b) to monobasic potassium phosphate by electrodialysis.

Claim 6

The process of claim 3 performed continuously.

Claim 7

The process of claim 3 in which in step (b) the roasted ore is subjected to a reducing roast followed by an oxidizing roast and leached with a solvent to remove compounds of sulfur and alkali metals.

Claim 8

The process of claim 3 in which the roasted ore in step (b) is subjected directly after roasting to a leach with ammonium hydroxide or an alkali metal hydroxide to remove compounds of sulfur and alkali metals.

Claim 9

A process for producing aluminum and monobasic potassium phosphate from alunite and apatite rock which comprises: (a) reacting apatite rock with sulfuric acid to produce phosphoric acid; (b) roasting and leaching the alunite ore to remove water and compounds of sulfur and alkali metals resulting in a residue containing aluminum values and a solution containing potassium sulfate; (c) digesting the residue from step (b) with at least one alkali metal hydroxide to dissolve substantially all of the aluminum values from said solid residue; (d) separating the liquid and solid portions of the slurry resulting from step (c); (e) removing silica from the liquid portion resulting from step (d) leaving a desilication product which is essentially sodium aluminum silicate; (f) separating the liquid and solid portions resulting from step (e); (g) precipitating aluminum hydroxide from the liquid portion resulting from step (e); (h) recovering aluminum values from the aluminum hydroxide precipitate of step (g); and (i) converting the phosphoric acid from step (a) and the potassium sulfate from step (b) by electrodialysis into monobasic potassium phosphate.

Claim 10

A process for producing aluminum and monobasic potassium phosphate from alunite and apatite rock which comprises: (a) reacting apatite rock with sulfuric acid to produce phosphoric acid; (b) roasting and leaching the alunite ore to remove water and compounds of sulfur and alkali metals resulting in a residue containing aluminum values and a solution containing potassium sulfate; (c) digesting the residue from step (b) with at least one alkali metal hydroxide to dissolve substantially all of the aluminum values from said solid residue; (d) separating the liquid and solid portions of the slurry resulting from step (c); (e) removing silica from the liquid portion resulting from step (d) leaving a desilication product which is essentially sodium aluminum silicate; (f) separating the liquid and solid portions resulting from step (e); (g) precipitating aluminum hydroxide from the liquid portion resulting from step (e); (h) recovering aluminum values from the aluminum hydroxide precipitate of step (g); and (i) converting the phosphoric acid from step (a) and the potassium sulfate from step (b) by electrodialysis into monobasic potassium phosphate.

Claim 11

The process of claim 7 performed continuously.

Claim 12

The process of claim 7 in which in step (b) the roasted ore is subjected to a reducing roast followed by an oxidizing roast or alternatively a high temperature decomposition roast, and leached with a solvent to remove compounds of sulfur and alkali metals.

Claim 13

The process of claim 7 in which in step (b) the roasted ore is subjected directly after roasting to a leach with ammonium hydroxide or an alkali metal hydroxide to remove compounds of sulfur and alkali metals.

Claim 14

The process for producing monobasic potassium phosphate from phosphoric acid and potassium sulfate by electrodialysis in a single frame electrodialysis cell, said unit comprising: in successive positions, an anion compartment, an intermediate compartment, a cation compartment; an anion permselective membrane between the anion and intermediate compartments, a cation permselective membrane between the intermediate and cation compartments; the arrangement forming anion and cation compartments and an intermediate compartment, which process comprises: adding water to the anion compartment, potassium sulfate to the intermediate compartment, phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the central compartment and monobasic Potassium Phosphate in the cathode compartment.

Claim 15

The process for producing monobasic potassium phosphate from phosphoric acid and potassium sulfate by electrodialysis in a single frame electrodialysis cell, said unit comprising: in successive positions, an anion compartment, an intermediate compartment, a cation compartment; an anion permselective membrane between the anion and intermediate compartments, a cation permselective membrane between the intermediate and cation compartments; the arrangement forming anion and cation compartments and an intermediate compartment, which process comprises: adding water to the anion compartment, potassium sulfate to the intermediate compartment, phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the central compartment and monobasic Potassium Phosphate in the cathode compartment.

Claim 16

The process of claim 11 in which the electrodialysis cell includes at least two of said frames and materials identical to those of claim 11 are added to like compartments.

Claim 17

The process of claim 1 in which the electrodialysis is performed in a single frame cell, said frame comprising, in successive positions, an anion compartment, an intermediate compartment, a cation compartment; an anion permselective membrane between the anion and intermediate compartments, a cation permselective membrane between the intermediate and cation compartments; the arrangement forming anion and cation compartments and an intermediate compartment; the process performed by adding water to the anode compartment, potassium sulfate solution to the intermediate compartment, phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the central compartment and monobasic potassium phosphate in the cation compartment.

Claim 18

The process of claim 13 in which the electrodialysis cell includes at least two of said frames and materials identical to those of claim 13 are added to like compartments.

Claim 19

The process of claim 13 in which the electrodialysis is performed in a single frame cell, said frame comprising, in successive positions, an anion compartment; an intermediate compartment, a cation compartment, an anion permselective membrane between the anion and intermediate compartments, a cation permselective membrane between the intermediate and cation compartments; the arrangement forming anion and cation compartments and an intermediate compartment; the process performed by adding water to the anion compartment, potassium sulfate solution to the intermediate compartment, phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the central compartment and monobasic potassium phosphate in the cation compartment.

Claim 20

The process of claim 15 in which the electrodialysis cell includes at least two of said frames and materials identical to those of claim 15 are added to like compartments.

Claim 21

The process of claim 7 in which the electrodialysis is performed in a single frame cell, said frame comprising, in successive positions, an anion compartment, an intermediate compartment, a cation compartment; an anion permselective membrane between the anion and intermediate compartments, a cation permselective membrane between the intermediate and cation compartments; the arrangement forming anion and cation compartments and an intermediate compartment; the process performed by adding water to the anion compartment, potassium sulfate solution to the intermediate compartment, phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the central compartment and monobasic potassium phosphate in the cation compartment.

Claim 22

The process of claim 17 in which the electrodialysis cell includes at least two of said frames.

Claim 23

A process for the manufacture of monobasic potassium phosphate from phosphoric acid and potassium sulfate which comprises, providing ionizable aqueous solutions in successive positions, said aqueous solutions comprising water, potassium sulfate and phosphoric acid, placing an anion permselective membrane between said water and potassium sulfate, placing a cation permselective membrane between said potassium sulfate and said phosphoric acid and, establishing a direct current electrical potential across said aqueous solutions.

Claim 24

A process for the manufacture of monobasic potassium phosphate from phosphoric acid and potassium sulfate which comprises, providing ionizable aqueous solutions in successive positions, said aqueous solutions comprising water, potassium sulfate and phosphoric acid, placing an anion permselective membrane between said water and potassium sulfate, placing a cation permselective membrane between said potassium sulfate and said phosphoric acid and, establishing a direct current electrical potential across said aqueous solutions.

Claim 25

An electrodialysis cell comprising, a single frame comprising in successive positions an anion compartment, an intermediate compartment, a cation compartment, an anion permselective membrane between said anion and intermediate compartments, a cation permselective membrane between said intermediate and cation compartments, and means for impressing a direct current electrical potential across aqueous solutions in said compartments.

Claim 26

An electrodialysis cell comprising, a single frame comprising in successive positions an anion compartment, an intermediate compartment, a cation compartment, an anion permselective membrane between said anion and intermediate compartments, a cation permselective membrane between said intermediate and cation compartments, and means for impressing a direct current electrical potential across aqueous solutions in said compartments.

Claim 27

The electrodialysis cell of claim 20 including at least two of said frames.

Claim 28

The process of claim 7 in which the conversion of phosphoric acid and potassium sulfate into monobasic potassium phosphate is performed in a single frame electrodialysis cell.

Claim 29

The process of claim 22 in which the electrodialysis cell includes at least two of said frames.

Claim 30

The process for producing monobasic potassium phosphate from phosphoric acid and potassium sulfate by electrodialysis in a single frame electrodialysis cell, said unit comprising: in successive positions, an anion compartment, a first intermediate compartment, a second intermediate compartment, and a cation compartment; an anion permselective membrane between the anion and first intermediate compartments, a cation permselective membrane between the intermediate compartments and an anion permselective membrane between the second intermediate and the cation compartments; the arrangement forming anion and cation compartments and two intermediate compartments; which process comprises: adding water to the anion compartment, potassium sulfate to the first intermediate compartment, water to the second intermediate compartment and phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the first intermediate compartment, monobasic potassium phosphate in the second intermediate compartment, and dilute phosphoric acid in the cation compartment.

Claim 31

The process for producing monobasic potassium phosphate from phosphoric acid and potassium sulfate by electrodialysis in a single frame electrodialysis cell, said unit comprising: in successive positions, an anion compartment, a first intermediate compartment, a second intermediate compartment, and a cation compartment; an anion permselective membrane between the anion and first intermediate compartments, a cation permselective membrane between the intermediate compartments and an anion permselective membrane between the second intermediate and the cation compartments; the arrangement forming anion and cation compartments and two intermediate compartments; which process comprises: adding water to the anion compartment, potassium sulfate to the first intermediate compartment, water to the second intermediate compartment and phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the first intermediate compartment, monobasic potassium phosphate in the second intermediate compartment, and dilute phosphoric acid in the cation compartment.

Claim 32

The process of claim 24 in which the electrodialysis cell includes at least two of said frames and materials identical to those of claim 24 are added to like compartments.

Claim 33

The process of claim 1 in which the electrodialysis is performed in a single frame cell, said frame comprising, in successive positions, an anion compartment, a first intermediate compartment, a second intermediate compartment, and a cation compartment; an anion permselective membrane between the anion and first intermediate compartments, a cation permselective membrane between the intermediate compartments and an anion permselective membrane between the second intermediate and cation compartments, the arrangement forming anion and cation compartments and two intermediate compartments; the process performed by adding water to the anode compartment, potassium sulfate solution to the first intermediate compartment, water to the second intermediate compartment and phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the first intermediate compartment, monobasic potassium phosphate in the second intermediate compartment, and dilute phosphoric acid in the cation compartment.

Claim 34

The process of claim 26 in which the electrodialysis cell includes at least two of said frames and materials identical to those of claim 26 are added in like compartments.

Claim 35

The process of claim 3 in which the electrodialysis is performed in a single frame cell, said frame comprising, in successive positions, an anion compartment, a first intermediate compartment, a second intermediate compartment, a cation compartment, an anion permselective membrane between the anion and intermediate compartments, a cation permselective membrane between the intermediate compartments and an anion permselective membrane between the second intermediate and cation compartments, the arrangement forming anion and cation compartments and two intermediate compartments; the process performed by adding water to the anion compartment, potassium sulfate solution to the first intermediate compartment, water to the second intermediate compartment and phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the first intermediate compartment, monobasic potassium phosphate in the second intermediate compartment, and dilute phosphoric acid in the cation compartment.

Claim 36

The process of claim 28 in which the electrodialysis cell includes at least two of said frames and materials identical to those of claim 28 are added to like compartments.

Claim 37

The process of claim 7 in which the electrodialysis is performed in a single frame cell, said frame comprising, in successive positions, an anion compartment, a first intermediate compartment, a second intermediate compartment, and a cation compartment, an anion permselective membrane between the anion and first intermediate compartments, a cation permselective membrane between the intermediate compartments, and an anion permselective membrane between the second intermediate compartment and the cathode compartment; the arrangement forming anion and cation compartments and two intermediate compartments; the process performed by adding water to the anion compartment, potassium sulfate solution to the first intermediate compartment, water to the second intermediate compartment, and phosphoric acid to the cation compartment, and applying a direct current electrical potential across the electrodes to produce sulfuric acid in the anion compartment, dilute potassium sulfate in the first intermediate compartment, monobasic potassium phosphate in the second intermediate compartment, and dilute phosphoric acid in the cation compartment.

Claim 38

The process of claim 30 in which the electrodialysis cell includes at least two of said frames and materials identical to those of claim 30 are added to like compartments.

Claim 39

A process for the manufacture of monobasic potassium phosphate from phosphoric acid and potassium sulfate which comprises, providing ionizable aqueous solutions in successive positions, said aqueous solutions comprising water (1), potassium sulfate, water (2) and phosphoric acid, placing an anion permselective membrane between said water (1) and potassium sulfate, placing a cation permselective membrane between said potassium sulfate and said water (2) and placing an anion permselective membrane between said water (2) and said phosphoric acid and, establishing a direct current electrical potential across said aqueous solutions.

Claim 40

A process for the manufacture of monobasic potassium phosphate from phosphoric acid and potassium sulfate which comprises, providing ionizable aqueous solutions in successive positions, said aqueous solutions comprising water (1), potassium sulfate, water (2) and phosphoric acid, placing an anion permselective membrane between said water (1) and potassium sulfate, placing a cation permselective membrane between said potassium sulfate and said water (2) and placing an anion permselective membrane between said water (2) and said phosphoric acid and, establishing a direct current electrical potential across said aqueous solutions.

Claim 41

An electrodialysis cell comprising, a single frame comprising in successive positions an anion compartment, a first intermediate compartment, a second intermediate compartment, a cation compartment, an anion permselective membrane between said anion and first intermediate compartments, a cation permselective membrane between said intermediate compartments, an anion permselective membrane between said second intermediate compartment and said cation compartment, and means for impressing a direct current electrical potential across aqueous solutions in said compartments.

Claim 42

An electrodialysis cell comprising, a single frame comprising in successive positions an anion compartment, a first intermediate compartment, a second intermediate compartment, a cation compartment, an anion permselective membrane between said anion and first intermediate compartments, a cation permselective membrane between said intermediate compartments, an anion permselective membrane between said second intermediate compartment and said cation compartment, and means for impressing a direct current electrical potential across aqueous solutions in said compartments.

Claim 43

The electrodialysis cell of claim 32 including at least two of said frames.