WO2013064694A2

WO2013064694A2 - Process for producing an electrolyte

Info

Publication number: WO2013064694A2
Application number: PCT/EP2012/071854
Authority: WO
Inventors: Kurt Kaehn; Dieter Krause; Manfred Hoehn
Original assignee: Lohas Products Gmbh
Priority date: 2011-11-04
Filing date: 2012-11-05
Publication date: 2013-05-10
Also published as: WO2013064694A3

Abstract

The present invention relates to a process for producing an electrolyte comprising the steps of (a) providing an aqueous solution comprising one or more alkaline earth or alkali metal chloride salts in a concentration of 0.2 to 12 g/l; (b) passing the solution through a first cathode chamber and subsequently through at least a second cathode chamber to obtain a catholyte; (c) passing at least part of the catholyte through a first anode chamber and subsequently through at least a second anode chamber to obtain an anolyte, wherein the anode in at least one of the anode chambers is shaped in the form of a rod.

Description

Process for producing an electrolyte

The present invention relates to a process for producing an electrolyte, such as an electrochemically activated water- based solution, and in particular an anolyte solution as well as to the use of such anolyte.

Electrolysis of aqueous liquids comprising one or more alkaline earth or alkali metal chloride salts, usually sodium chloride, carried out in electrolysis cells comprising a separation between anode and cathode, such as a diaphragm, to produce an anolyte and a catholyte liquid have been described in numerous publications, like US 5,635,040 and WO 98/13304, and respective electrolysis cells are commercially available.

Anolyte liquids have been used for numerous applications, including the use as an oxidizing agent, a purification agent, disinfectant, etc.

The prior art uses of electrolyte solutions, and in particular anolyte solutions, have been limited by the fact that the electrolyte is not stable in aqueous liquids. A further use limitation is caused by the high salt content required by most electrolysis cells to generate an anolyte with a high oxidation reduction potential and a high oxidizing power.

There is thus a need to improve the stability of the electrolyte, in particular the stability of an anolyte. Moreover, it would be desirable to improve at the same time the performance and efficiency of the obtained water solutions, such as the biocidal activity or oxidation- reduction potential of anolyte solutions.

These objects are solved by a process according to claims 1 to 9. The invention also relates to an apparatus for carrying out electrolysis according to claim 10, an anolyte solution according to claim 11, the use of the anolyte according to claim 13 as well as to product comprising the anolyte according to claims 14 and 15.

In a first aspect, the invention relates to a process for producing an electrolyte comprising the following steps:

(a) providing an aqueous solution comprising one or more alkaline earth or alkali metal chloride salts in a concentration of 0.2 to 12 g/1;

(b) passing the solution through a first cathode chamber and subsequently through at least a second cathode chamber to obtain a catholyte;

(c) passing at least part of the catholyte through a first anode chamber and subsequently through at least a second anode chamber to obtain an anolyte, wherein the anode in at least one of the anode chambers is shaped in the form of a rod.

As used herein, the term "electrolyte" refers to an aqueous solution comprising free ions and/or free radicals. In particular, the term refers to an electrochemically activated water-based solution, such as a catholyte and/or anolyte solution obtained by an electrochemical treatment of water. Preferably, the electrolyte is an anolyte solution and, therefore, the present invention particular relates to a process for preparing an anolyte solution.

Moreover, the term "anolyte" as used herein refers to an aqueous liquid generated by electrolysis in the anode chamber of an electrolysis cell comprising separated anode and cathode chambers .

In step (a) of the process an aqueous solution comprising one or more alkaline earth or alkali metal chloride salts is provided. In the most preferred embodiment of the present invention, the solution provided in step (a) comprises sodium chloride . One of the advantages of the present invention resides in using a low concentration of the alkaline earth or alkali metal chloride salt, preferably sodium chloride. The concentration is in the range of 0.2 to 12 g/1, preferably in the range of 1 to 8 g/1, more preferably in the range of 2 to 6 g/1, wherein a concentration of 3.5 to 4.5 g/1 is particularly preferred. It has surprisingly been found that even such low amounts of chloride salts are sufficient to yield effective electrolytes such as effective anolyte solutions having high activity and good stability. Due to the rather low amount of chlorides in the starting solution undesired corrosive properties of the obtained solutions are avoided .

In step (b) , the solution is passed through a first cathode chamber and subsequently through at least a second cathode chamber to obtain a catholyte. For example, the solution of step (a) is fed into the at least one cathode chamber by a supply means such as a peristaltic pump. The solution leaving the at least one cathode chamber is referred to the catholyte. In a preferred embodiment, the number of cathode chambers through which the solution is passed is identical with the number of anode chambers used in step (c) . In accordance with the present invention at least two cathode chambers are connected in series.

In step (c) at least part of the catholyte is passed through a first anode chamber and subsequently through at least a second anode chamber to obtain an anolyte, wherein the anode in at least one of the anode chambers is shaped in the form of a rod. Thus, at least two anode chambers are connected hydraulically in series. It will be appreciated that any convenient number of anode chambers may be connected together in series .

The anode in at least one, preferably in all of the anode chambers is shaped in the form of a rod. The rod may contain openings or one or more boreholes, but does not have a tubular form.

The cathode chamber and anode chamber can be separated by at least one separator, such as diaphragm or membrane like a semi-permeable or ion-selective membrane, preferably a zirconium-aluminum ceramic membrane. Thus, it is preferred that the cathode chambers used in step (b) are separated from the anode chambers used in step (c) by at least one separator, such as diaphragm or membrane like a semi-permeable or ion- selective membrane, preferably a zirconium-aluminum ceramic membrane .

In a related embodiment, the present invention provides an apparatus, for carrying out electrolysis comprising at least one electrolysis cell, in particular at least two electrolysis cells, wherein each electrolysis cell comprises a cathode chamber and an anode chamber, wherein the cathode and anode chambers are separated by a membrane or a semi-permeable or ion-selective separator and the apparatus comprises means for carrying out process for producing an electrolyte as described above, including an anode in at least one, preferably in all of the anode chambers that is shaped in the form of a rod.

Thus, it is preferred that the apparatus comprises

a fluid inlet,

a fluid outlet in fluid communication with said fluid inlet,

at least two electrolysis cells arranged in fluid communication between said fluid inlet and said fluid outlet, wherein each electrolysis cell has an anode chamber, a cathode chamber, and at least one separating element separating said anode chamber from said cathode chamber, and

a pipe system forming a fluid connection between said electrolysis cells and both said fluid inlet and said fluid outlet in order to pass a fluid from said fluid inlet through said electrolysis cells to said fluid outlet .

It is further preferred that said pipe system forms a fluid connection between separate electrolysis cells,

so that the aqueous solution provided in step (a) of the above-described process is passed from said fluid inlet through the cathode chamber of one of said electrolysis cells, then through the cathode chamber (s) of at least another one of said electrolysis cells, then through the anode chamber of one of said electrolysis cells, then through the anode chamber (s) of at least another one of the electrolysis cells, and then to the fluid outlet.

In a preferred alternative, the apparatus comprises at least 2 to 6 electrolysis cells. In the most preferred alternative, the apparatus comprises 6 electrolysis cells and means for passing the aqueous solution through the electrolysis cells such that the solution is first passed through 6 cathode chambers and subsequently through 6 anode chambers.

The cathode chamber and anode chamber are separated by at least one separator, such as diaphragm or membrane like a semi-permeable or ion-selective membrane, preferably a zirconium-aluminum ceramic membrane. Moreover, the apparatus may also provide an electric current source for the electrodes of the anode and cathode chambers.

Respective electrolytic cells for producing an electrolyte are known in general and for example described in US 5,635,040. Preferably, the at least one cathode chamber and at least one of the anode chambers cells used in the process according to the invention form an electrolytic cell comprising co-axial cylindrical and rod electrodes separated by the separator, such as a semi-permeable or ion-selective membrane like a zirconium-aluminum ceramic membrane. Preferably, the internal electrode is used as anode, while the external electrode is used as cathode. Figures 1 to 7 illustrate apparatuses for carrying out the present invention. In particular:

Figure 1 shows an anode;

Figure 2 shows a cathode;

Figure 3 shows an adaptor;

Figures 4 to 6 show the electrolysis cell;

Figure 7 shows an apparatus comprising several electrolysis cells.

In one embodiment, the electrodes used in the anode chambers comprise platinum or titanium coated with an electrocatalytic coating, preferably selected from platinum, platinum oxide, ruthenium oxide, iridium oxide and mixtures thereof.

In a particularly preferred embodiment, the processes for producing an electrolyte of the present invention are characterized in that the solution is serially passed through 6 cathode chambers and subsequently through 6 anode chambers, and wherein the electrodes of the fifth and sixth anode chambers are made of platinum or titanium coated with platinum .

In a further preferred embodiment of the process, the catholyte solution obtained in step (b) is degassed prior to passing it into the first anode chamber in step (c) . Thus, gases such as hydrogen formed in the at least one cathode chamber are removed by common degassing means such as a commonly used gas separator.

According to a particularly preferred embodiment, the process of the invention further comprises

(d) adding a metal salt to the anolyte obtained in step (c) .

The metal salt may be added in liquid or solid form. The metal salt is preferably a metal sulfate. More preferably, the metal salt is selected from the group consisting of sodium sulfate, magnesium sulfate, aluminum sulfate, sodium carbonate, calcium carbonate and mixtures thereof.

Preferably, the metal salt is added to the anolyte solution in amounts suitable for stabilization of the anolyte. The amount of the metal salt in the anolyte solution obtained in step (d) generally ranges from 1 to 50 g/liter, preferably from 5 to 20 g/liter or from 7 to 15 g/liter.

As a further stabilizer, the anolyte of the present invention may comprise a carbonate, preferably in a concentration of 300 to 1200 mg/1 sodium carbonate or 300 to 1200 mg/1 calcium carbonate .

The anolyte solution obtained by the process according to the invention is preferably characterized in that it has a pH between 6 and 8. In a preferred embodiment, the pH of the anolyte is between 6.5 and 7.5.

Moreover, the anolyte solution obtained by the process according to the invention is preferably characterized in that it has an oxidation-reduction potential (ORP) of about 250 mV to about 1500 mV, preferably 650 mV to about 1200 mV such as 750 mV to 900 mV. The oxidation-reduction (or redox) potential can be determined using commercially available devices and standard conditions.

Without any limitation to a particular theory, it was surprisingly found that the anolyte obtained in the process of the present invention has an improved stability and activity and can therefore be stored for prolonged periods without suffering a substantial loss of activity such as biocidal activity .

Thus, in another aspect the invention is also directed to an anolyte solution obtained by the process according to the invention . The anolyte solution is preferably characterized by one or more of the following features:

(i) a pH between 6 and 8 ;

(ii) an oxidizing power of between 500 ppm and 1500 ppm free chlorine equivalents; and/or

(iii) an oxidation reduction potential (ORP) of about

650 mV to about 1500 mV.

In a further embodiment, the anolyte of the present invention is characterized by a particular stability. Upon storage for a period of more than 12 months, the anolyte will still contain more then 50% of the oxidizing power of between 500 ppm and 1500 ppm free chlorine equivalents; and/or more than 50% of the oxidation reduction potential (ORP) of about 650 mV to about 1500 mV.

The electrolyte solutions of the present invention can be used as a cleaning agent, a detergent, an oxidizing agent, a disinfection agent or a plant protecting agent. Consequently, the present invention also provides a cleaning agent, a detergent, an oxidizing agent, a disinfection agent or a plant protecting agent that comprises an electrolyte as described above .

In a related embodiment, the present invention provides the use of the electrolytes, and in particular anolytes, as described above as a cleaning agent, detergent, oxidizing agent, disinfection agent or plant protecting agent.

In particular, the anolytes can be used for the cleaning of surfaces in restaurants, hospitals, chemical production plants, production lines for the preparation of foods, beverages, animal feed and/or pharmaceutical production plants, etc. For example, the anolyte solutions of the present invention may be sprayed onto surfaces using techniques for spraying liquid compositions on surfaces that are generally available in the art.

In one embodiment, the electrolytes, i.e. the catholyte solution and/or the anolyte solution, are directly produced prior to their use for the above purposes. Hence, the electrolytes a produced shortly before their use, such as less than 2 hours, preferably less than 1 hour, more preferably less than 30 minutes before their use. Thus, the process according to the invention is according to this embodiment performed directly at the place where the electrolyte is need to be used, such as in a hospital, by means of a portable or hand apparatus .

Alternatively, the electrolytes like the anolyte solutions of the present invention can directly be used for human or animal consumption or the preparation of pharmaceutical products and can be incorporated into respective products to be used for this purpose. The invention therefore also provides food, beverages, animal feed and pharmaceutical compositions comprising an electrolyte such as an anolyte solution as described above, as well as the use of the electrolytes for the preparation of these products. As used in the present application, the term pharmaceutical composition comprises orally applied forms (such as tablets, liquids) , intramuscularly or intravenously applied forms (for example liquids) as well as topically applied forms (such as creams, gels, liquids, plaster) . According to a preferred aspect of the pharmaceutical use the electrolytes such as anolytes of the present invention are used for the treatment of wounds, including treatment of wounds by disinfection.

If used for human or animal consumption, the electrolytes of the invention will not contain any compounds that are unsuitable for this purpose, such as chlorine dioxide or other strong oxidizing agents. EXAMPLE

Microbial Test of the Anolyte of the Present Invention:

The processes of the present invention (6 cathode chambers and 6 anode chambers in series) were used to generate a pH neutral anolyte .

The antimicrobial activity of CIO₂ and this anolyte against biofilms was compared (Figure 8) . CIO₂ was chosen for comparison because it has a very good antimicrobial activity against biofilms.

Material and Methods

Na-hypochlorite was obtained from Alfar Aesar (concentration of Na-hypochlorite w=13%; density = 1.207 kg/L) .

Anolyte was generated using a process comprising 6 serial cathode and subsequently 6 serial anode chambers; NaCl concentration: 6 g/L; conversion rate during electrochemical processing of 20%.

Based on the amount of chlorine equivalent concentrations of ECA and Na-hypochlorite were compared in microbial tests. The yeast Saccharomyces cerevisiae and the bacterium Pseudomonase aerogenosa in concentrations of 10⁵ CFU/ml were chosen as test organisms. All tests were conducted in duplicates.

Results

Equimolar concentration of total chlorine (20 mg/1 = 0.57 mmol/L) of the produced anolyte and the Na-hypchlorite solution were found to inactivate both test strains in a concentration of 10⁵ CFU/ml within 60sec.

Figure 8 shows a comparison of the antimicrobial activity of the anolyte and the Na-hypchlorite over time. Because of the conversion rate of 20%, a lower concentration of activated chlorine is present in the anolyte.

Concentration of active chlorine in Na-hypochlorite: 570 ymol/L .

Concentration of active chlorine in anolyte: 114 ymol/L.

Respecting the conversion rate of chlorine ions during the anolyte production process of 20% the antimicrobial activity of the anolyte is five times higher than the Na-hypochlorite because only the activated form of chlorine and not chlorine ions (Cl^~) inactivate the microorganisms.

Conclusion

Compared to other processes for producing an anolyte and the control Na-hypochlorite the tested anolyte offers several benefits :

5 times higher antimicrobial activity compared at the level of activated chlorine than Na-hypochlorite.

The anolyte removes existing biofilms much better than

CIO₂ (based on literature) .

The anolyte has a neutral pH value.

Claims

1. Process for producing an electrolyte comprising the following steps:

2. Process for producing an electrolyte according to claim 1, wherein the solution is serially passed through 2 to 6 cathode chambers and subsequently through 2 to 6 anode chambers .

3. Process for producing an electrolyte according to claim 1 or 2, wherein each anode in each anode chamber is a rod.

4. Process for producing an electrolyte according to one of claims 1 to 3, wherein gas is removed from the part of the catholyte that is subsequently passed through the at least two anode chambers .

5. Process for producing an electrolyte according to one of claims 1 to 4, wherein anolyte obtained has:

(i) a pH between 6 and 8 ;

(iii) an oxidation reduction potential (ORP) of about

650 mV to about 1500 mV.

6. Process for producing an electrolyte according to any one of claims 1 to 5, wherein a metal salt is added to the anolyte in a concentration of 1 to 50 g/liter of anolyte, wherein the metal salt is preferably sodium sulfate, magnesium sulfate, aluminum sulfate or a mixture thereof..

7. Process for producing an electrolyte according to any one of claims 1 to 6, wherein a carbonate is added to the anolyte, preferably 300 to 1200 mg/1 sodium carbonate or 300 to 1200 mg/1 calcium carbonate is added to the anolyte .

8. Process for producing an electrolyte according to any one of claims 1 to 7, wherein the electrodes of the first and at least second anode chambers comprise platinum or titanium coated with an electrocatalytic coating, preferably selected from platinum, platinum oxide, ruthenium oxide, iridium oxide and mixtures thereof.

9. Process for producing an electrolyte according to any one of claims 1 to 7, wherein the solution is serially passed through 6 cathode chambers and subsequently through 6 anode chambers, and wherein the electrodes of the fifth and sixth anode chambers are made of platinum or titanium coated with platinum.

10. Apparatus for carrying out electrolysis comprising at least one electrolysis cell, which electrolysis cell comprises a cathode chamber and an anode chamber, wherein the cathode and anode chambers are separated by a membrane or a semi-permeable or ion-selective separator and the apparatus comprises means for:

(a) providing an aqueous solution comprising one or more alkaline earth or alkali metal chloride salts in a concentration of 0.2 to 12 g/1; (b) passing the solution through a first cathode chamber and subsequently through at least a second cathode chamber to obtain a catholyte;

11. An anolyte solution obtainable by a process according to any one of claims 1 to 9 or obtainable in an apparatus according to claim 10.

12. Anolyte solution according to claim 11, characterized by:

(i) a pH between 6 and 8 ;

(iii) an oxidation reduction potential (ORP) of about

650 mV to about 1500 mV.

13. Use of an anolyte solution according to claim 11 as a cleaning agent, detergent, oxidizing agent, disinfection agent or plant protecting agent, preferably as a cleaning and disinfection agent for the cleaning of surfaces in restaurants, hospitals, chemical production plants, production plants for foods and beverages and pharmaceutical production plants.

14. Cleaning agent, detergent, oxidizing agent, disinfection agent or plant protecting agent comprising an anolyte solution according to claim 11.

15. Food, beverage, animal feed or pharmaceutical composition comprising an anolyte solution according to claim 11.