Method for producing diluted hydrofluoric acid

Abstract

The invention relates to a method and a device for producing diluted hydrofluoric acid using an electrode arrangement (1), which has an anode chamber (2) with an anode (4) and a cathode chamber (6) with a cathode (8), which are separated from one another by an anion exchange membrane (10), wherein in the method—pure water is guided through the anode chamber (2), —pure water, which includes at least one electrolyte which forms fluoride ions (F−), is guided through the cathode chamber (6), —and an electrical voltage is applied between the anode (4) and the cathode (8) such that the fluoride ions (F−) are moved through the anion exchange membrane (10) into the anode chamber (2), and an electrical current flows.

Claims

1. A method for producing hydrofluoric acid with an electrode arrangement which comprises an anode chamber having an anode and a cathode chamber having a cathode wherein the anode and the cathode are separated from one another by an anion exchange membrane, comprising the steps of: passing distilled water through the anode chamber; passing an electrolyte that forms fluoride ions (F.sup.−) through the cathode chamber; applying an electrical voltage between the anode and the cathode so that hydronium ions are formed within the distilled water of the anode chamber, and the fluoride ions (F.sup.−) in the cathode chamber are moved through the anion exchange membrane into the anode chamber to form the hydrofluoric acid therein and an electrical current flows between the anode and the cathode, wherein the only cations in the anode chamber are the hydronium ions; and controlling a concentration of the hydrofluoric acid produced by controlling one or more of the concentration of the at least one electrolyte, and the electrical current.

2. The method as claimed in claim 1 wherein the at least one electrolyte comprises ammonium fluoride.

3. The method as claimed in claim 1 wherein the applying step also forms ozone in the anode chamber.

4. The method as claimed in claim 3 wherein a concentration of the ozone is adjusted by adjusting the electrical current.

5. The method as claimed in claim 1, further comprising adjusting a concentration of the hydronium ions.

6. A method for handling hydrofluoric acid, comprising the steps of producing the hydrofluoric acid with an electrode arrangement which comprises an anode chamber having an anode and a cathode chamber having a cathode wherein the anode and the cathode are separated from one another by an anion exchange membrane, the step of producing comprising the steps of: passing distilled water through the anode chamber; passing an electrolyte that forms fluoride ions (F.sup.−) through the cathode chamber; and applying an electrical voltage between the anode and the cathode so that hydronium ions are formed within the distilled water of the anode chamber, and the fluoride ions (F.sup.−) in the cathode chamber are moved through the anion exchange membrane into the anode chamber to form the hydrofluoric acid therein and an electrical current flows between the anode and the cathode, wherein the only cations in the anode chamber are the hydronium ions; and mixing the hydrofluoric acid with water containing cations of another electrolyte, wherein the mixing step is performed using water withdrawn from the cathode chamber.

7. The method as claimed in claim 6, wherein the cations of the mixing step comprise ammonium ions.

8. The method as claimed in claim 6, further comprising adjusting a concentration of the hydronium ions.

9. An apparatus for producing hydrofluoric acid, comprising: an anode chamber which has an anode; a cathode chamber which has a cathode; an anion exchange membrane, wherein the anode chamber and the cathode chamber are separated from one another by the anion exchange membrane; and an electrical control configured to pass distilled water through the anode chamber; pass an electrolyte that forms fluoride ions (F.sup.−) through the cathode chamber; and apply an electrical voltage between the anode and the cathode so that hydronium ions are formed within the distilled water of the anode chamber, and the fluoride ions (F.sup.−) in the cathode chamber are moved through the anion exchange membrane into the anode chamber to form the hydrofluoric acid therein and an electrical current flows between the anode and the cathode, wherein the only cations in the anode chamber are the hydronium ions.

10. The apparatus as claimed in claim 9, further comprising at least one sensor for determining a concentration of an electrolyte and/or at least one sensor for determining the electrical current, wherein the electrical control is configured to regulate one or more of the electrical voltage and a concentration of the at least one electrolyte on the basis of measurements from the at least one sensor.

Description

(1) With the aid of the appended FIGURE, a working example of the present invention is elucidated in more detail hereinafter.

(2) FIG. 1—shows the schematic sectional representation through an apparatus for carrying out a method according to a first working example of the present invention.

(3) FIG. 1 shows an electrode arrangement 1 which comprises an anode chamber 2, in which there is an anode 4, and a cathode chamber 6, in which there is a cathode 8. Located between the anode chamber 2 and the cathode chamber 6 is an anion exchange membrane 10, which separates the anode chamber 2 from the cathode chamber 6. In the case of the method according to one working example of the present invention, pure water, distilled water or ultrapure water is introduced through an anode chamber inlet 12 into the anode chamber 2. At the same time, pure water, ultrapure water or distilled water containing an electrolyte which forms fluoride ions is passed through a cathode chamber inlet 14 into the cathode chamber 6. The fact that the cathode chamber 6 now contains not only water (H.sub.2O) but also ammonium ions (MH.sub.4.sup.+) and fluoride ions (F.sup.−) is represented schematically in FIG. 1.

(4) An electrical voltage is applied between the anode 4 and the cathode 8. This causes the fluoride ions (F.sup.−) to be accelerated along the arrow 16 in the direction of the anode 4. They are able to pass through the anion exchange membrane 10 and are then located in the anode chamber 2.

(5) Through an anode chamber outlet 18, the constituents represented in FIG. 1 leave the anode chamber 2. These constituents are water, fluoride ions (F.sup.−), and hydronium ions (H.sup.+), which are produced by the electrical voltage between anode 4 and cathode 8. At the same time, ozone (O.sub.3) is formed in the anode chamber 2, and likewise leaves the anode chamber 2 through the anode chamber outlet 18. The mixture present is therefore a mixture of dilute hydrofluoric acid, whose concentration can be adjusted very precisely even to low and very low levels, and ozone. This mixture is used in numerous applications in different sectors of industry.

(6) Leaving the cathode chamber 8 from a cathode chamber outlet 20 are not only the water but also the ammonium ions (NH.sub.4.sup.+) and also hydroxide ions (OH.sup.−).

(7) In a further embodiment of this method, which is not depicted, the mixture of ozone and dilute hydrofluoric acid is supplied to its desired intention. It is subsequently mixed with the liquid withdrawn from the cathode chamber outlet 20. As a result, again, a mixture of water and electrolyte is produced, the health risk of this mixture being reduced significantly.

LIST OF REFERENCE NUMERALS

(8) 1—Electrode arrangement 2—Anode chamber 4—Anode 6—Cathode chamber 8—Cathode 10—Anion exchange membrane 12—Anode chamber inlet 14—Cathode chamber inlet 16—Arrow 18—Anode chamber outlet 20—Cathode chamber outlet