WO2012041357A1

WO2012041357A1 - Method for producing a disinfectant based on hypochlorous acid or hypochlorite by electrochemical activation of a chloride solution

Info

Publication number: WO2012041357A1
Application number: PCT/EP2010/006007
Authority: WO
Inventors: Christian Fischer; Achim Wenner; Benjamin Pfeiffer; Frank Kandler
Original assignee: Actides Berlin Gmbh
Priority date: 2010-10-01
Filing date: 2010-10-01
Publication date: 2012-04-05

Abstract

A method is proposed for producing a disinfectant containing hypochlorous acid (HOC1) and/or hypochlorite (OC1^-)by electrochemical activation of a dilute water/chloride solution, in that water is added to a chloride solution and the dilute water/chloride solution obtained in this manner is exposed to an electric current in the anode chamber of an electrolysis reactor which comprises at least one cathode chamber having a cathode and at least one anode chamber, which is spatially separated therefrom by a membrane, and comprises an anode, by applying an electric voltage to the electrodes, in order to convert the chloride at least in part to hypochlorous acid and/or hypochlorite. In order to decrease the consumption of chloride, the invention provides that the water/chloride solution is only delivered to the anode chamber of the electrolysis reactor, whereas the cathode chamber of the electrolysis reactor is fed with water which has not been admixed with chloride ions.

Description

Process for the preparation of a disinfectant based on hypochlorous acid or hypochlorite by electrochemical activation of a chloride solution

The invention relates to a method for producing a hypochlorous acid (H0C1) and / or hypochlorite (0C1 ^~ ) containing disinfectant by electrochemical activation of a dilute acid / chloride solution by adding a chloride solution to water and the thus obtained dilute water / chloride solution in the anode compartment of a Elektrolysereaktors having at least one cathode compartment with a cathode and at least one, of which by a membrane spatially separated anode compartment with an anode, is applied by applying an electrical voltage to the electrodes with an electric current to the chloride at least partially in hypochlorous acid and / or to transfer hypochlorite.

The method of electrochemical activation is known in particular for the disinfection of water. Here, a dilute solution of a chloride, especially in the form of a neutral salt, such as sodium chloride (NaCl) or common salt, potassium chloride (KCl) or the like, in an electrolytic reactor by applying a voltage at the electrodes under anodic oxidation of a portion of the chloride ions primarily in hypochlorous . acid (H0C1) and / or their salts (hypochlorites, CIO ^") converted electrolytic reactor includes a cathode chamber with one or more cathodes and an anode compartment comprising one or more anodes, wherein the anode chamber and the cathode chamber by means of an electrically conducting - in particular a for ion conductive - diaphragm or by means of a membrane with the properties mentioned spatially separated

CO FIRMÄT10 COPY are to prevent mixing of the water / chloride solution in both rooms. While in electrolysis usually a substantially complete conversion of the reactants used - in the case of the use of a sodium chloride solution to chlorine gas (Cl ₂ ) and sodium hydroxide (NaOH), in the case of the use of a potassium chloride solution to chlorine gas and potassium hydroxide (KOH) - is sought with the use of highly concentrated electrolyte solutions, primarily to maximize the chlorine gas yield, the water / chloride solution in contrast to the electrochemical activation in much diluted form, usually in a concentration of not more than 20 g / 1, preferably not more than 10 g / 1, the electrolysis reactor and reacted to a low contrast predominantly to HOC1 and / or OC1 ^" reacted, in particular, the redox potential of the mixed with the chloride as electrolyte water is increased, whereby a very effective disinfecting effect is obtained Reaction conditions, such as pressure, temperature, electrode st rome, etc., in the electrochemical activation generally chosen to be more moderate than in the case of chlorine-alkali electrolysis. An advantage of such an electrochemical treatment, which is referred to in the context of the present application as "electrochemical activation", is in particular the good health and environmental compatibility of the substances produced during the electrochemical activation in their respective concentrations, which for example also according to the German Drinking Water Ordinance (TrinkwV) are permitted. As with electrolysis, oxidation also occurs at the anode (ie at the positively charged electrode) during electrochemical activation, while at the cathode (ie at the negatively charged electrode) there is oxidation takes place. When using a diluted neutral salt solution, such as a sodium chloride solution, primarily hydrogen is generated at the cathode according to the following reaction equation (1):

2 H ₂ O + 2 e ^" > H ₂ + 2 OH which, after outgassing from the solution, is removed from the cathode of the reactor, for example ,

At the anode, according to the following reaction equations (2) and (3), in particular the chemical oxidants oxygen (0 ₂ ) and chlorine (Cl ₂ ) are produced, which are known to be effective with respect to disinfecting water. It should also be noted that due to the formation of H ₃ O ⁺ ions, the dilute water / chloride solution in the anode compartment of the electrolysis reactor becomes acidic:

6 H ₂ 0> 0 ₂ + 4 H ₃ 0 ⁺ + 4 e (2),

2 Cl ^" > Cl ₂ + 2 e ^" (3). Chlorine in turn dissociates in water according to the following equilibrium reaction (4) in Hypochloritionen (0C1 ^~ ) and chloride ions (Cl ^~ ), which in turn depending on the pH with a suitable cation, eg Na ⁺ from the electrolyte, or with a proton or a H ₃ 0 ⁺ ion to the corresponding (sodium) salt or to the corresponding acid, ie hypochlorous acid (HC 10) and hydrogen chloride or dilute hydrochloric acid (HCl) can react: Cl ₂ + 3 H ₂ O <===> 2 H ₃ O ⁺ + OC1 (4).

Furthermore, from the abovementioned substances formed at the anode, secondary substances can be used to generate small amounts of other substances which are also known to be effective with respect to the disinfection of water. These are in particular small amounts of hydrogen peroxide (H ₂ 0 ₂ , reaction equation (5)) and ozone (0 ₃ , reaction equation (6)).

4 H ₂ 0> H ₂ 0 ₂ + 2 H ₃ 0 ⁺ + 2 e (5),

0 ₂ + 3 H ₂ 0> 0 ₃ + 2 H ₃ 0 ⁺ + 2 e (6),

A disadvantage of the method of electrochemical activation has hitherto been in many cases the lack of quality control, as required for a sufficient disinfection of the water, mostly empirically determined process parameters, such as amount of added electrolyte or chloride solution, adjusted electrode voltage or -ström and the like, not only of the electrolysis reactor used, such as its reaction volume, its anode and cathode surface, the residence time of the water to be disinfected in the reactor, etc., but in particular the composition of the respective water to be disinfected, in particular its conductivity and its redox potential, depend. In this case, for a given water - mostly empirically - determined process parameters, which lead to a satisfactory disinfecting effect in this water, lead in another water to a very poor disinfecting effect. Furthermore, it has been found, in particular, that the electrodes produced by means of electrochemical activation according to the prior art solutions are usually contaminated - sometimes highly - with undesirable products, which is often generated according to the above reaction equation (3) almost exclusively chlorine gas (Cl ₂ ), which is desirable in conventional electrolysis processes, however, in the electrochemical activation to produce a disinfectant is not desirable because it causes a pungent odor of the electrochemically activated solution and due to its volatility out of this relatively quickly outgassed, so that the life of a disinfectant thus produced is very limited. In this context, it should also be mentioned that, in principle, no reliable information is given regarding the composition of the electrochemically activated solution, which varies greatly depending on the abovementioned parameters

Durability or shelf life of the electrochemically activated solution made, so that practically only a production of the same locally comes into consideration. In practice, therefore, the method has - mainly due to its poor handling and the insufficiently possible guarantee of adequate disinfection - on the market can not prevail.

A generic method for producing a disinfectant by means of electrochemical activation is known for example from WO 2007/093395 A2, which is hereby expressly made the subject of the present disclosure. In order for the most extensive possible shift of the equilibrium of free chlorine in the disinfectant in the form of the dilute, electrochemically activated solution towards the hypochlorous acid with high disinfectivity and a high redox potential which is also favorable with regard to the disinfecting action to provide, the cited document proposes to control the pH of the anodically obtained disinfectant ("Anolyte") to a value between 2.5 and 3.5. If the value drops below about 2.5, the hypochlorous acid reacts with the above-mentioned disadvantages to elemental chlorine (Cl ₂ ), while at a pH above about 3.5, the redox potential of the electrochemically activated solution decreases and the hypochlorous acid dissociated from about a pH of 6 with elimination of their proton to hypochlorite, which is also disinfectant effective, but about 1 to 2 orders of magnitude lower than the hypochlorous acid itself. In that regard, this is from WO 2007/093395 A2 a very effective and reproducible method for generating a generic disinfectant means.

Moreover, as also mentioned in the abovementioned WO 2007/093395 A2, it has proved to be advantageous if the water used for the electrochemical activation - or the dilute water / chloride solution - has the highest possible purity, in particular should be substantially free of other halide ions than chloride ions, ie those from the group bromide (Br ^~ ), fluoride (F ^~ ) and iodide (I ^" ), but also oxohalide ions, such as hypochlorite (CIO ^" ), chlorite (C10 ₂ ^" ), Chlorate (C10 ₃ ^~ ),

Perchlorate (C10 ₄ ^~ ), bromate (Br0 ₃ ^~ ) etc. Furthermore, it should be substantially free of heavy metals, in particular those from the group antimony (Sb), arsenic (As), lead (Pb), cadmium (Cd) , Chromium (Cr), nickel (Ni), mercury (Hg), selenium (Se), iron (Fe) and manganese (Mn). For this reason, WO 2007/093395 A2 proposes that the specific electrical conductivity of the water to be activated electrochemically before adding the chloride solution to a Value of at most 350 pS / cm or preferably lower, which increases the reproducibility of the method with respect to the disinfecting and depot effect of the disinfectant produced, virtually independent of the water used. Such a "standardization" of the raw water used not only allows a particularly simple adjustment of the process parameters, such as electrode voltage or flow, residence time of the dilute water / chloride solution in the electrolysis reactor, amount of metered chloride solution, etc., but also makes a simple way Use of waters of practically any composition without any impairment of the resulting disinfectant possible, whereby a highly reliable and reproducible quality of the disinfectant is ensured. In addition, ions which may be present in the water used for the electrochemical activation and which are converted into harmful substances during the electrochemical activation, even if only in low concentrations, can be eliminated as far as possible. As an example, bromide ions may be mentioned, which - as in the case of ozonation which is frequently carried out in drinking water treatment - can be oxidized to bromate, which has a carcinogenic effect in higher concentrations. Finally, in this way, in particular, the content of divalent cations, such as the hardness formers calcium and magnesium, reduce, which can enforce the anode compartment of the cathode compartment separating membrane relatively easily, which is why the water used can also be additionally softened to the To increase the life of the electrolysis reactor and to extend its maintenance intervals. By "specific electrical conductivity" is in this context, moreover, the specific ionic conductivity, which is based on the conductivity of the water or the water / chloride solution due to the herein dissolved, mobile ions. In this case, however, has proved to be problematic in that the use of softened and demineralized in particular for the electrochemical activation of the control of the pH to a favorable disinfection value, such as between 2.5 and 6, in which the generated free chlorine mainly is in the form of hypochlorous acid, is relatively difficult, in particular, the amount of free chlorine generated limits are, as increased conversion of the dilute water / chloride solution in the electrolysis reactor (eg by longer residence time, higher electrode voltage or the like) accompanied by an increased production of H ₃ O ⁺ ions hydrochloric acid (see the above reaction equation (4)), so that the pH runs the risk of being lowered rapidly to values below about 2.5, where the free chlorine is practically complete in the form of elemental chlorine (CI2) is present and the disadvantages mentioned above are given.

To counter this, EP 2 191 721 A1 proposes, in a generic method, adding to the water / chloride solution before entry into the electrolysis reactor a proton acceptor in the form of a buffer or a base. In this way, even in the case of use of softened or also completely demineralized or distilled water, a significantly increased yield of free chlorine in the form of the desired products HOCl or OCl ^{"can be} ensured because the proton acceptor has a stoichiometric amount of anodically formed H ₃ 0 ⁺ ions according to the above reaction equation (2) can "catch" and thus the pH can be kept within the desired range of above about 2.5, even in the case of relatively high conversions of the added chloride solution, in which the equilibrium according to the above reaction equation (4) corresponds to the elemental chlorine (Cl ₂ ) in the direction of hypochlorous acid (HOC1) or hypochlorite (0C1 ^~ ) is shifted.

US Pat. No. 6,632,347 B1 likewise describes a generic process for producing a disinfectant which, for adjusting the pH of the chloride solution added to the electrolysis reactor, recirculates a portion of the solution containing electrochemical activation in the cathode compartment into the anode compartment of the reactor provides to compensate for either variations in the pH of the raw water used in each case or to increase the pH of the finished, anodically produced disinfectant as needed, while at the same time the proportion of accumulating catholyte should be reduced. In addition to significant control engineering problems (for example, depending on the composition of the dosed catholyte, which contains, in addition to hydroxide ions, for example, chloride ions and other ions, the conductivity of the chloride solution and consequently the electrolysis current changes in a manner which can not be predicted and the volumetric flow rate is affected a disadvantage of the known method is in particular that large amounts of dissolved hydrogen are introduced into the anode compartment (see also the above reaction equation (1)), which in the anode compartment with the Chloride ions or with the short time directly generated at the electrode chlorine atoms and in particular with the anodically generated desired Desin hypochlorous acid (H0C1) to hydrogen chloride (HCl) reacts:

H ₂ + 2 Cl-> 2 HCl (7)

H ₂ + HOC 1> HCl + H ₂ O (8)

In light of this latter procedure in respect of the objective of generating a mainly HOC1 or OC1 ^"containing disinfectant manufacturing counterproductive.

Another disadvantage of the electrochemical activation is the continuous consumption of relatively large amounts of chloride usually added in the form of sodium chloride (common salt), the chloride, as mentioned above, in the electrochemical activation in contrast to the chlor-alkali electrolysis only to a relatively small Part is reacted and thus largely unreacted passes both the anode and the cathode compartment, the electrolytic reactor.

The invention is therefore based on the object to develop a method of the type mentioned in that at least as far as possible avoid the aforementioned disadvantages of the chloride consumption can be reduced in a simple and cost-effective manner, without affecting the yield of hypochlorous acid or hypochlorite. According to the invention this object is achieved in a method of the type mentioned in that the water / chloride solution is fed only to the anode compartment of the electrolysis reactor, while the cathode compartment of the electrolysis Is fed lysereaktors with not mixed with chloride ions water.

The embodiment of the invention thus makes it possible to reduce the consumption of chloride solution, which is usually added to the water used, in the form of an alkali metal chloride solution, e.g. a potassium chloride or, in particular, a sodium chloride solution is added to reduce about half, whereby the electrochemical reaction in the anode compartment, where the hypochlorous acid-based and / or hypochlorite-based disinfectant is produced, is not impaired.

Surprisingly, the invention also offers in particular the possibility of using demineralized and / or distilled water or generally a "standardized" water for the water / chloride solution charged to the electrolysis reactor, wherein an advantageous embodiment of the method provides that the water used softens and / or demineralized. In this way, the reproducibility of the method with respect to the disinfecting and depot effect of the disinfectant produced is increased, virtually independent of the water used. As mentioned above, such "standardization" of the raw water used also not only ensures a particularly simple adjustment of the process parameters, such as electrode voltage or flow, residence time of the dilute water / chloride solution in the electrolysis reactor, amount of metered chloride solution, etc., but makes It also makes it possible to easily use waters of practically any composition without any impairment of the disinfectant obtained, thereby providing a highly reliable and reproducible zable quality of the disinfectant is guaranteed. In addition, in this way, in particular, the content of divalent cations, such as primarily the hardness formers calcium and magnesium, reduce, which can enforce the anode space of the cathode space separating membrane relatively easily.

For this reason, it is preferably provided that the anode compartment of the electrolysis reactor with the water / chloride solution of softened and / or demineralized water and the cathode compartment of the electrolysis reactor with softened and / or demineralized water are fed, i. both electrochemical half-cells of the electrolysis reactor are fed with softened or demineralized water. Also in this regard, it has surprisingly been found that the electrochemical reaction in the anode compartment is not affected by this, it being assumed that the cathodically produced hydroxide provide sufficient conductivity in the cathode compartment, so as not to adversely affect the electrochemical reaction in the anode compartment.

In particular, in the case of softening and / or demineralization of the water used, it may also be advantageous if a cation-permeable membrane, in particular a cation exchange membrane, is used to separate the anode space from the cathode space of the electrolysis reactor, wherein the anode space is separated from For example, a polymer electrolyte membrane commercially available under the trade name "Nafion ™" may be used in the cathode compartment of the electrolytic reactor. Such a membrane is largely permeable to monovalent cations, so that the cations from the Anode space added water / chloride solution, such as potassium or in particular sodium ions, the membrane can pass from the anode compartment in the cathode compartment and provide in the cathode compartment for improved conductivity and consequently for a faster electrochemical reaction.

In order to reduce the amount of cathodic waste water generated during the electrochemical reaction, it may also be advantageous if the cathode space of the electrolysis reactor is fed with a lower volume flow of water than the volume flow of dilute water / chloride solution through the anode space of the electrolysis reactor. A further advantage of such a procedure, in particular when using softened and / or demineralized water, is that the conductivity caused by electrochemically generated hydroxide ions (OH.sup.- ¹ ) and preferably also by the membrane permeating alkali metal ions (K.sup. ⁺ , Na.sup. ⁺ ) In the cathode compartment lower dilution is increased so that the anode space in the going electrochemical conversion of the chloride ions is not inhibited.

The volume flow through the anode chamber of the electrolysis reactor may in this case preferably amount to at least twice, in particular at least three times, preferably at least four times and for example also about ten times or more, the volume flow through the cathode space of the electrolysis reactor.

According to a development of the inventive method can be provided that contains a part of the volume flow of the exiting from the cathode compartment of the electrolysis reactor, hydroxide ions ^(OH-) water in the anode chamber of the electrolysis reactor or in the added this water / chloride solution. This can serve, in particular in the case of the use of softened and / or demineralized water, the purpose of ensuring an increased free chlorine yield in the form of the desired products HOCl or OC1 ^" up to a range of about 1000 mg / l of free chlorine, However, the invention offers the additional advantage that the partial recirculation of the cathodic - largely chloride-free - solution in the anode compartment of the electrolysis reactor the The chlorine content there does not change or remains constant, so that the control or regulation technically adjusted as a function of the chloride content parameters

Electrode current and voltage do not need to be changed. In addition, the conductivity of the water / chloride solution in the anode space is thereby at most increased to an extent which likewise does not require any control or regulatory changes. Of course, the invention also offers the possibility of adding a - also preferably substantially chloride-free - buffer, as is also known from EP 1 292 721 AI.

If a part of the cathodic solution is recirculated for the reasons mentioned in the anode compartment of the electrolysis reactor or in this added water / chloride solution, the hydrogen generated in the cathode compartment of the electrolysis reactor in the emerging from the cathode compartment water should preferably be removed before, not to according to the above reaction equation (8), a disintegration of the anodically produced, disinfectively active products HOC1 and / or to cause OC1 ^". The removal of hydrogen, for example, by means of conventional outgassing

Gas / liquid separator done.

As already mentioned, it can be provided according to a preferred embodiment of the method according to the invention that the pH of the disinfectant produced in the anode compartment of the electrolysis reactor to a value between 2.5 and 6, in particular between 2.5 and 5, preferably between 2.5 and 4, in particular, a pH range of from about 2.5 to about 3.5, or from about 2.7 to about 3.5, may be favorable to provide for substantially complete presence of the free chlorine in the form of hypochlorous Acid at a high redox potential of the disinfectant, eg in the range of about 1340 mV.

In a further preferred embodiment it can be provided that the used softened or demineralized water has a hardness between 0 and 4 dH, in particular between 0 and 2 dH. By "hardness" is in this context the concentration of divalent alkaline earth metal ions, ie calcium (Ca), magnesium (Mg), strontium (Sr) and barium (Ba), the latter two in practice usually play no role. l ° dH corresponds to a concentration of alkaline earth metal ions of 0.179 mmol / l, 2 ° dH of a concentration of 0.358 mmol / 1 etc. Such an adjustment of the hardness of the water used is expedient in particular for relatively hard, calcium- and / or magnesium-containing waters To increase the life of the electrolysis reactor or to extend its maintenance intervals. However, especially in the case of very conductive waters, ie those with a high total ion concentration, care should be taken to ensure that the water does not is only softened by means of an ion exchanger, since the ion exchanger ever replaced a divalent alkaline earth metal ion by two monovalent alkali metal ions and thus the conductivity is further increased overall. For this reason, it may be appropriate to first soften the water and then lower the conductivity by additional measures.

In this context, an advantageous embodiment of the inventive method provides that the specific electrical conductivity of the water used to a value of at most 350 yS / cm, in particular at most 150 yS / cm, preferably at most 100 S / cm, such as at most about 50 yS In particular, the method also allows advantageous use of standardized demineralized or deionized water, so-called demineralized water or "demineralised water," with a specific electrical conductivity of less than 25 yS / cm. For desalting and / or softening or demineralizing the water used, it is possible to use a membrane process, in particular reverse osmosis, micro-, nano- or ultrafiltration, whereby a further advantage of such membrane processes is that any impurities present in the raw water are removed , This applies on the one hand for organic impurities, so that, for example, the formation of organochlorine compounds during electrochemical activation is reliably avoided, on the other hand for inorganic impurities, such as metal ions, eg copper, iron, manganese, etc., which otherwise in the finished disinfectant undesirable degradation could favor catalytically the produced hypochlorous acid. Of course, however, come Other known as such method for softening and / or demineralization of the water used, such as distillation or - as already mentioned - contacting the water with ion exchange resins.

The chloride concentration, in particular in the form of sodium and / or potassium chloride, the dilute water / chloride solution added to the anode compartment of the electrolysis reactor can advantageously be at a value of at most 20 g / l, in particular between 0.1 and 10 g / l, preferably be controlled between 0.1 and 5 g / 1. In this way, in particular in the case of a partial recirculation of the cathodically obtained OH ^~ ions in the anode compartment or in the water-chloride solution added thereto also in the case of use of demineralized water or demineralized water, such as so-called "DI water", easily reach a concentration of free chlorine in the generated disinfectant in a desired range of about 10 mg / l to about 50 mg / l, preferably in the range of about 20 mg / l to about 40 mg / l, which at a pH A value of about 2.5 to 3.5 of the anodized disinfectant (anolyte) has a hypochlorous acid (HC10) concentration of about 7.4 mg / l to about 37 mg / l and about 14.8 mg / l to about about 29.6 mg / 1 corresponds.

As already indicated, in the case of a partial recirculation of the cathodic solution and / or an external addition of a buffer solution, the method according to the invention finally gives the possibility, as required, of a disinfectant having a free chlorine content in the form of HOC1 and / or OCl ^" in the range of about 20 mg / 1 to produce in the g / l range. Further features and advantages of the invention will become apparent from the following description of an embodiment of one with reference to the drawings. 1 is a schematic view of an electrolytic reactor including the charged starting materials and the products obtained, which can be used in a method according to the invention for producing a disinfectant based on hypochlorous acid and / or hypochlorite by electrochemical activation of a chloride solution; and a schematic process flow diagram of a process for preparing a hypochlorous acid-based hypochlorite-based disinfectant by electrochemical activation of a chloride solution using an electrolytic reactor shown in FIG. 1.

The illustrated schematically in Fig. 2, suitable for continuous or semi-continuous implementation of a method according to the invention for Desinfek tion of water by electrochemical activation (ECA) branches from a main water line 1 via a Abzweiglei device 2 from water, which as raw water for the electrochemical mixing activation is used. The main water line may for example be part of a public water supply system. The branch line 2 is connected to a valve 3, in particular in the form of a control valve, and preferably before with a valve 3 upstream or downstream Filter F, in particular in the form of a fine filter with a hole width of, for example, about 80 to 100 μπι, equipped and opens downstream of the valve 3 and the filter F in a softener 4, which is equipped for example with a suitable ion exchange resin and contained in the water divalent hardener calcium and magnesium ions replaced by monovalent ions, such as sodium ions. In order to increase the life of the electrolytic reactor 10 described in more detail below or to extend its maintenance intervals, the softener 4 keeps the hardness of the water, for example, at a value of at most 2 ° dH (corresponding to a concentration of alkaline earth metal ions of 0.358 mmol / l), preferably at most l ° dH (corresponding to a concentration of alkaline earth metal ions of 0.179 mmol / l). The effluent 5a of the water softener 4 opens into a desalination device 6 for reducing the specific electrical or ionic conductivity of the water, which may be formed in particular by a membrane system, such as a reverse osmosis plant or by a micro, nano or ultrafiltration plant and the specific electrical conductivity of the water, for example, to a value of at most about 100 S / cm or in particular also holds at most about 25 yS / cm, so that it is in the discharged via a line 7a from the desalting 6 water to substantially demineralized, so-called " VE water "is, which is thus standardized regardless of the water used in each case. In the drain 7a of the desalting device 6, a conductivity measuring device (not shown), such as a conductivity cell, electrode or the like, may be arranged to monitor compliance with the particular desired value of the specific electrical conductivity of the water. Of course, especially in the case of Use of relatively soft water alternatively, for example, only a desalination device 6 without one of these upstream softening system 4 may be provided. Furthermore, a discharge line 5b, 7b can lead from the softening plant 4 and / or from the desalting device 6, which discharge in the present embodiment into a common discharge line 8, via which the wastewater from the plants 4, 6 can be discarded. In addition, especially when the water to be disinfected has a relatively high organic carbon content, measures may be taken to lower the carbon content of the water. For this purpose, for example, additionally a UV oxidation system (not shown) may be provided which has the total organic carbon content (TOC) and / or the chemical oxygen demand (COD) to a value of, for example, at most about 25 ppb, in particular of at most about 20 ppb, or to a value of, for example, at most about 7 mg 0 ₂ / l, in particular of, for example, at most about 5 mg 0 ₂ / l, lowers. To measure and / or control the TOC or COD value - or other group parameters for detecting the organic carbon contained in the water, such as the dissolved organic carbon (DOC, dissolved organic carbon) - known from the prior art devices are provided be. Likewise, it is also conceivable in connection with the softener 4 and / or the desalination or membrane system 6, the partial flow of the water branched off via the branch line 2 from the main water line 1 and electrochemically activated only by the softener 4, the membrane system 6 or the UV oxidation plant, namely, when the respective limit value is exceeded, and the respective plant otherwise if by means of a bypass line (not shown) to bridge, which may be useful, for example, in strongly fluctuating quality of the raw water. The outlet 7a of the membrane unit 6 leads into a mixer Mi, which opens into an electrolysis reactor 10 explained in greater detail below with reference to FIG. Via the branch line 2 is thus controllable by means of the control valve 3, softened and deionized part of the funded in the main water line 1 water in the electrolysis reactor 10, for example, a partial flow of funded in the main water line 1 water in the order of 1/200 on the Branch line 2 is branched off. The mixer i is on the inlet side on the one hand - as already mentioned - with the outlet 7a of the membrane unit 6, on the other hand with a reservoir 11 for receiving a chloride solution, in particular in the form of a substantially saturated alkali metal chloride solution - in the present case, for example, a substantially saturated sodium chloride solution - , in which are mixed as homogeneously as possible in the mixer i and pass through a common, drain-side line 14 of the mixer Mi in the anode compartment 10a of the electrolysis reactor 10. The line 12 leading from the reservoir 11 into the mixer Mi is further equipped with a metering pump 13 to add to the softened and desalinated water a defined amount of sodium chloride solution, eg in the range of about 1 to about 10 g / 1 NaCl. The cathode chamber 10b of the electrolysis reactor 10, on the other hand, is fed directly with the softened and desalinated water leaving the membrane system 6, which takes place via a line 9 which branches off the outlet 7a of the membrane installation 6 upstream of the mixer Miaus. The via the line 9 to the cathode compartment 10b of the For the reasons mentioned above, the volumetric flow of softened and demineralized water supplied to the electrolysis reactor 10 can be set lower, for example by a factor of about 10, than the volume flow of softened and demineralized sodium chloride solution fed to the anode compartment 10a of the electrolysis reactor 10 via the conduit 14 a provided in the line 9 throttle valve 9a or by any other means for flow control and / or by appropriate (smaller) dimensioning of the cathode chamber 10b of the electrolysis reactor 10 can be done.

As can be seen in particular from FIG. 1, the electrolytic reactor 10 includes an anode 101, which is formed coated by a with catalytically active ruthenium dioxide (Ru0 ₂₎ when PRESENT embodiment, for example, carrier of titanium, to which the positive terminal 101a of an unspecified represented voltage source can be connected. Alternatively or in addition to ruthenium oxide, it is also possible, for example, to use a coating based on iridium dioxide (IrO ₂ ) or a mixture of both (RuO ₂ / IrO ₂ ) or other oxides, such as titanium dioxide (TiO ₂ ), lead dioxide (PbO ₂ ) and / or manganese dioxide (Mn0 ₂ ). The electrolytic reactor 10 further includes a cathode 102 which is conveniently made of stainless steel or similar materials such as nickel (Ni), platinum (Pt), etc. The cathode 102 is connectable to the negative pole 102a of the voltage source not further disclosed. Between the equipped with the anode 101 anode compartment 10 a and the cathode 102 equipped with the cathode chamber 10 b is the spatial

Separation of the same one (s) for cation permeable (s) diaphragm or membrane 104 is arranged. The membrane 104 prevents a mixing of the anode chamber 10a and the cathode. denraum 10b liquid and allows, however, a current flow, which is not a significant resistance in particular for the migration of cations. The membrane 104 is formed in the present embodiment, for example in the form of an electrically or ionically conductive, but substantially liquid-tight polymer electrolyte membrane.

The electrolysis reactor 10 further has two inlets 14, 9 (see also Fig. 2), via which on the one hand from the

Mixer Mi exiting line 14 with the demineralized and desalinated water / chloride solution in the anode chamber 10a of the reactor 10, on the other hand, the emerging from the membrane unit 6 line 9 is fed into the cathode chamber 10b of the reactor 10. As can be seen in particular from FIG. 1 and moreover from FIG. 2, the electrolysis reactor 10 also has two outlets 103a, 103b, via which the water / chloride solution or the water after the electrochemical activation from the anode chamber 10a or from the Cathode space 10b of the reactor 10 can be discharged. While the outlet 103a is for discharging the electrochemically activated solution containing hypochlorite generated from the anode space 10a of the reactor 10, ie for discharging the so-called "anolyte", the outlet 103b serves to discharge the electrochemically activated water with the hydroxide ions from the cathode space 10b of the reactor 10 - ie for discharging the so-called "catholyte". As already mentioned, the volume flow through the cathode space 10b of the reactor 10 can be selected to be smaller than that of the anode space 10a in order to minimize the amount of catholyte which is to be disposed of, at least for the most part, and also for good conductivity of the water to provide the cathode compartment 10b. As already For this, on the one hand, the cathodically produced hydroxide ions (OH ^" ) and, on the other hand, the sodium ions (Na ⁺ ), which can permeate the membrane 104 out of the anode space, provide the anode space 10a of the electrolysis reactor 10, for example with a throughput of 60 to

140 1 / h operated, of course, larger throughputs are possible by larger reactors 10th

and / or a plurality of reactors 10 connected in parallel. Preferably, the electrolysis reactor 10 always runs at full load, where it can be switched off as needed and peak loads can be intercepted via a storage tank for the electrochemically activated, anodic solution explained in more detail below. As can also be seen from FIGS. 1 and 2, it can be provided according to an advantageous embodiment of the method according to the invention that a portion of the cathodic solution with the cathodically generated hydroxide ions is recirculated into the anode space 10a of the reactor 10 in order to obtain a high yield ensure free chlorine in the form of the desired products HOC1 or 0C1 ^" in the anode compartment 10a, without the pH dropping below a value below about 2.5 at which the equilibrium of the hypochlorous acid is undesirable in the direction of the abovementioned reasons. th, elemental chlorine (in the form of chlorine gas, Cl ₂₎ towards would be moved. 2 it can be seen from FIG., the outlet 103b from the cathode compartment ends 10b of electrolytic reactor 10 for this purpose, initially in a gas separator 15 from which the exhaust gas , in particular hydrogen (H ₂ ), is discharged via an optionally provided exhaust pipe 16, while the catholyte itself, ie the cathode compartment of the electrolysis reactor 10 discharged basic water, via a line 17, for example, in the sewer K a municipal sewage system, is discharged. For example, exhaust line 16 may be fed with dilution air that is equipped with an explosion-proof low-pressure blower (not shown) to meet the safety requirements with respect to gaseous hydrogen. A portion of the costs incurred in the gas separator 15, hydrogen-free liquor is recirculated, however, a equipped with a dosing pump 18 line 19 into the mixer Mi to in the anode compartment 10a of the reactor 10 added to the desired proportion of OH ^~ ion water ser - / Chloride solution, which is able to prevent a decrease in the pH in the anode chamber 10a of the reactor 10 to a value of below about 2.5. The outlet 103a from the anode chamber 10a of the electrolysis reactor 10 opens via eg a control valve (not shown) and a line 20 into a storage tank 21, from which the anolyte or the disinfectant produced via a line 22 of the main water line 1 for the purpose of disinfection of the water carried herein. This is done in the present embodiment via a metering pump 23, which metered in the line 22 guided disinfectant via a mixer M _{2 of} the main water line 1. The metering pump 23 may in particular be operated depending on the volume flow of water determined by a flow meter 24 arranged in the main water line 1 in order to always add the required amount of disinfectant to the water. In order to control the parameters of the anodically produced disinfectant, such as its pH, its redox potential, its free chlorine content, etc., appropriate sensors 25 may also be provided in the conduit 20 connecting the anode compartment 10a of the reactor 10 to the storage tank 21. be seen. The measured values obtained can, of course, also be used in the control parameters, such as electrode current and voltage, amount of added chloride solution, volume flows through or residence times in the electrolysis reactor 10, etc.

As already mentioned, the device according to FIG. 2 further comprises a control (not shown in the drawing), as known for example from the prior art mentioned in WO 2007/093395 A2 and EP 2 191 72 A1 as such.

The disinfectant in the form of the anodically produced electrochemically activated solution (anolyte), which has been prepared in the manner described above from demineralised water as raw water, has e.g. at a pH in the range of 3.0 and a redox potential in the range of 1340 mV (vs. SHE vs. vs NHE, standard and / or normal hydrogen electrode), a free chlorine concentration in the range of about 25 mg / 1 to about 1000 mg / l, corresponding to a concentration of particularly effective hypochlorous acid (HC10) in the range of about 18.5 mg / l to about 706 mg / l.

Claims

Pa entansprüche

Process for the preparation of hypochlorous acid (H0C1) and / or hypochlorite (0C1 ^" ) containing disinfectant by electrochemical activation of a dilute water / chloride solution by adding a chloride solution to water and dilute water / chloride solution thus obtained in the anode compartment (10a) of an electrolytic reactor (10), which has at least one cathode space (10b) with a cathode (102) and at least one anode space (10a) spatially separated therefrom by a membrane (104) with an anode (101) by applying an electrical voltage to the electrodes (101, 102) is supplied with an electric current to at least partially convert the chloride into hypochlorous acid and / or hypochlorite, characterized in that the water / chloride solution is applied only to the anode space (10a) of the electrolysis reactor (10), while the cathode compartment (10b) of the electrolytic reactor (10) is treated with water not mixed with chloride ions r is fed.

Process according to Claim 1, characterized in that the water used is softened and / or demineralized.

A method according to claim 2, characterized in that the anode chamber (10a) of the electrolysis reactor (10) with the water / chloride solution of softened and / or demineralized water and the cathode compartment (10b) of the electrolytic reactor (10) with softened and / or demi- Neralized water to be fed.

Process according to one of Claims 1 to 3, characterized in that a cation-permeable membrane (104), in particular a cation-exchange membrane, is used to separate the anode space (10a) from the cathode space (10b) of the electrolysis reactor (10).

Method according to one of Claims 1 to 4, characterized in that a polymer electrolyte membrane (104) is used to separate the anode space (10a) from the cathode space (10b) of the electrolysis reactor (10)

Method according to one of claims 1 to 5, characterized in that the cathode space (10b) of the electrolysis reactor (10) is fed with a lower volume flow of water than the volume flow of dilute water / chloride solution through the anode space (10a) of the electrolysis reactor (10 ).

A method according to claim 6, characterized in that the volume flow through the anode space (10a) of the electrolysis reactor (10) is at least twice, in particular at least three times, preferably at least four times, the volume flow through the cathode space (10b) of the electrolysis reactor (10) ,

A method according to any one of claims 1 to 7, characterized in exiting (10) that a part of the volume flow of from the cathode chamber (10b) of the electrolytic reactor, hydroxide ions ^(OH-) containing water into the anode chamber (10a) of the electrolytic reactor (10) or into the water / chloride solution added to this is circulated.

Method according to claim 8, characterized in that the hydrogen generated in the cathode space (10b) of the electrolysis reactor (10) is removed in the water emerging from the cathode space (10b) before it enters the anode space (10a) of the electrolysis reactor (10). is recirculated in the added this water / chloride solution.

Method according to one of claims 1 to 9, characterized in that the pH of the disinfectant produced in the anode chamber (10a) of the electrolysis reactor (10) to a value between 2.5 and 6, in particular between 2.5 and 5, preferably between 2.5 and 4, is controlled.

Method according to one of claims 2 to 10, characterized in that the used softened and / or demineralized water has a hardness between 0 and 4 dH, in particular between 0 and 2 dH.

Method according to one of claims 2 to 11, characterized in that the specific electrical conductivity of the water used to a value of at most 350 pS / cm, in particular at most 150 S / cm, preferably at most 100 S / cm, is set.

Process according to one of Claims 2 to 12, characterized in that a membrane process, in particular reverse osmosis, micro, nano or ultrafiltration, is used for softening or demineralizing the water used. tration.

14. The method according to any one of claims 1 to 13, characterized in that the chloride concentration of the anode chamber (10 a) of the electrolysis reactor (10) added, dilute water / chloride solution to a value of at most 20 g / 1, in particular between 0.1 and

10 g / 1, preferably between 0.1 and 5 g / 1 is controlled.

15. The method according to any one of claims 1 to 14, characterized in that in the anode chamber (10a) of the electrolysis reactor (10) a disinfectant containing free chlorine in the form of hypochlorous acid and / or hypochlorite between 20 mg / 1 and 1000 mg / 1 is generated.