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 methodpure 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 pure water through the anode chamber; passing pure water containing at least one electrolyte which forms fluoride ions (F.sup.) through the cathode chamber; and applying an electrical voltage between the anode and the cathode so that the fluoride ions (F.sup.) are formed in the cathode chamber and 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.

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

3. The method as claimed in claim 1 wherein a concentration of the hydrofluoric acid produced is adjusted to a predetermined value by one or more of adjusting the concentration of the at least one electrolyte, and by adjusting the electrical current.

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

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

6. A method for handling dilute hydrofluoric acid, comprising mixing the dilute hydrofluoric with water containing cations of an electrolyte.

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

8. The method as claimed in claim 6 further comprising the steps of producing the dilute 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 pure water through the anode chamber; passing pure water containing at least one electrolyte which forms fluoride ions (F.sup.) through the cathode chamber; and applying an electrical voltage between the anode and the cathode so that the fluoride ions (F.sup.) are formed in the cathode chamber and 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, and wherein the mixing step is performed using the water withdrawn from the cathode chamber.

9. An apparatus for producing hydrofluoric acid, comprising: an anode chamber which has an anode; a cathode chamber which has a cathode, and wherein the anode chamber and the cathode chamber are separated from one another by an anion exchange membrane.

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.

Description

[0021] With the aid of the appended FIGURE, a working example of the present invention is elucidated in more detail hereinafter.

[0022] FIG. 1shows the schematic sectional representation through an apparatus for carrying out a method according to a first working example of the present invention.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.).

[0027] 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

[0028] 1Electrode arrangement [0029] 2Anode chamber [0030] 4Anode [0031] 6Cathode chamber [0032] 8Cathode [0033] 10Anion exchange membrane [0034] 12Anode chamber inlet [0035] 14Cathode chamber inlet [0036] 16Arrow [0037] 18Anode chamber outlet [0038] 20Cathode chamber outlet