PREPARATION

TECHNICAL FIELD

The present invention relates to oxides or oxyacids of halogens; biocides, pesticides or plant growth regulators which contain inorganic compounds; treatment of air, water, waste water or sewage; methods or apparatus for disinfecting or sterilizing materials or objects, sterilizing of packaging or its content.

In particular, the invention relates to a stable, aqueous composition comprising a high level of chlorine dioxide, a method for producing such chlorine dioxide composition and use thereof. BACKGROUND

From a historical point of view, chlorine dioxide was used mainly for bleaching in the paper and pulp industry, but it is also used as biocide or oxidant, for example for water purification and odour control. Chlorine dioxide has a relatively low oxidation potential compared with other oxidants, but nevertheless a high oxidation capacity. In addition, it forms in reaction less by-products in comparison with chlorine. Because of the well-known instability of this chemical compound, with the risk of explosion as a result, for a variety of applications, chlorine dioxide is not produced and distributed on an industrial scale, but generated on-site. Most of such generation methods include aqueous solutions of sodium chlorite or sodium chlorate which are treated with an oxidant, e.g. a peroxide, and/or acids or which undergo an electrochemical release of chlorine dioxide.

An important limitation of aqueous compositions of chlorine dioxide is their limited stability, storage capacity and purity on the one hand, and the relatively low levels of chlorine dioxide in water which can be obtained by known techniques.

Chlorine dioxide occurs at standard pressure and temperature as gas, and is for industrial use generally provided as a low concentrated solution in water. The preparation of such solutions is well known from the literature. For example, WO 2011/086579 discloses a two-component system comprising (i) sodium chlorite and (ii) sodium bisulphate (NaHS0 ₄ ) or sodium persulfate (Na ₂ S ₂ 0 ₈ ) for the production of chlorine dioxide as a stable and highly pure (>99%) solution with a concentration situated between 500 ppm and 50,000 ppm.

Although the literature offers several solutions to obtain stable, highly pure chlorine dioxide compositions, it is unclear how a very high purity and stability of an aqueous chlorine dioxide solution can be achieved. On the one hand, it is assumed that specific chemical contaminants in the solution result in reduced stability. Such contaminants are referred to as, for example, alkali and alkaline earth metal ions, such as, for example, sodium, magnesium and calcium, sodium chloride and free chlorine. It is further presumed that the purity and stability of the obtained chlorine dioxide solution is also determined by the specific method of preparation. WO 2010/151543 discloses to that effect aqueous solutions of chlorine dioxide. The solutions are essentially free of transition metal ions, transition metal oxides and particulate contaminants. The solutions are uniquely stable with respect to their chlorine dioxide concentration. The solutions contain chlorine dioxide in the concentration range of about 100 ppm or more to about 10,000 ppm, preferably about 1000 ppm or more to about 5000 ppm, and even more preferably about 2000 ppm or more to about 4000 ppm, and most preferably about 3000 ppm. Preferably, the solutions are substantially free of organic carbons and metal ions. Methods are described for the preparation of aqueous solutions of chlorine dioxide comprising (i) purification of water by at least two methods selected from the group comprising de-ionization, distillation, reverse osmosis (RO) filtration, carbon filtration, microporous filtration, ultrafiltration, hyperfiltration, ultraviolet oxidation and electrodialysis, and (ii) the dissolution of the filtered chlorine dioxide gas in the water. To protect people, animals or plants against infection by pathogens and/or against plague species, numerous biocides have been developed which can be used in a bio-secure and efficient manner. Examples of such biocides are alcohols such as, for example, ethanol and isopropanol; aldehydes such as formaldehyde, glutaraldehyde; (chloro)phenols; quaternary ammonium salts such as, for example, benzalkonium chloride; metals or metal alloys such as, for example, silver and copper alloys; and oxidizing agents. Oxidizing agents oxidize components of the cell membrane and of the cell content of microorganisms and plague species, which in turn results in the loss of the cell structure and/or functionality, and, consequently, the death of the organism or at least rendering it harmless. Such oxidizing agents can mainly be used beneficially with pathogens which are hard to combat and/or plague species with high resistance to more moderate disinfection methods. Known examples of oxidizing agents are sodium hypochlorite, chloramine, hydrogen peroxide and organic peracids, chlorine, iodine, ozone and chlorine dioxide. Chlorine dioxide is a specifically interesting biocide as it has a relatively low oxidizing strength compared with other oxidizing agents, but nevertheless a high oxidation capacity. However, as a result of the low oxidation strength relatively high concentrations of chlorine dioxide are necessary to obtain an effective impact of a chlorine dioxide treatment. A better efficiency of the chlorine dioxide treatment may possibly be obtained by the use of a higher concentration. Achieving high concentrations of chlorine dioxide, however, is limited by the instability of the chlorine dioxide molecule, as a result of which high concentrations, i .e. more than 3 grams of chlorine dioxide per liter, are difficult to obtain. To date, the literature shows no indication of a synthesis route for an aqueous chlorine dioxide composition which leads to chlorine dioxide having a concentration of more than 3 grams of chlorine dioxide per liter, or more than 4 grams per liter, or more than 5 grams per liter, or more than 6 grams per liter, or more than 7 grams per liter.

One of the applications of chlorine dioxide is the use as a disinfectant for instruments or buildings. For example, US 2008/286147 discloses a mobile, portable apparatus and a method for the remediation of products or environments contaminated with one or more pathogens. Methods and devices are described which can be used to disinfect an environment, for example, a room, building or objects contaminated with such pathogens.

One of the major drawbacks of known methods and systems for disinfecting equipment, instruments, packaging, and/or buildings is the relatively long period of time which is needed to adequately disinfect a space with the aid of chlorine dioxide. During the disinfection process, the space is unsuitable for access by persons and/or animals. This generally causes a problem in situations where the run time for the disinfection cycle is a critical factor, but particularly in the disinfection of hospital rooms, such as, for example, an operating theater or patient room, where the availability of the space is an important economic factor. One of the most important factors which contribute to a higher period of disuse is the relatively low concentration of chlorine dioxide in the gas after the stripping from an aqueous chlorine dioxide solution. Such low concentrations inevitably lead to the need for larger volumes of said aqueous solution, which on the one hand, entails a logistical cost and on the other hand, involves a lower process efficiency. Higher concentrations of chlorine dioxide in water are not feasible according to the state of the art, in view of the danger of explosion in concentrated solutions. Other systems use a chlorine dioxide generator, which produces chlorine dioxide on-site. In such way, potentially explosive chlorine dioxide solutions can be avoided. However, the use of such generators limits the employability and the mobility of such equipment for the disinfection of hard to reach spaces. In addition, such generators require a relatively long start-up time, so that the space to be treated is unsuitable for use for a longer period of time. Known methods often also lead to undesirable by-products, such as, for example, active chlorine, which together with the unreacted reagents, such as, for example, hypochlorite, hydrochloric acid, sodium chlorite, etc. can have a harmful impact on equipment, materials, and/or environment. Another important factor which contributes to the relatively long period of disuse, is the time needed to reduce the chlorine dioxide level in the space to below the limit of harmfulness for human, animal or plant. The state of the art provides for this in an activated carbon filter. Known filters work with a high removal efficiency, which, however, entails a low air flow and accordingly a longer period of time for the filtering. Alternative methods also lead to relatively strong increase in the duration of disuse and/or to risks for the safety of operators. For example, use is made of washing water with additives, for example, reducing agents, which (i) is a time- consuming process, and (ii) forms an additional liquid waste stream. The present invention aims to provide a solution to at least one of the aforementioned problems. In particular, the present invention aims to provide a method for disinfecting and/or combatting plague species with chlorine dioxide in a quick and effective way by means of mobile equipment. SUMMARY

To this aim, the invention provides in a first aspect an aqueous chlorine dioxide composition obtainable according to a process in which one or more chlorite and/or chlorate salts are mixed with one or more bisulphate and one or more persulphate salts in aqueous solution.

By providing a stable, highly concentrated and highly pure chlorine dioxide composition according to the present invention, a broader scope of application of the technology is possible. In this way, for example, it can be understood that, when stripping chlorine dioxide from an aqueous composition according to the invention, a concentrated gas stream can be obtained more rapidly.

In a second aspect, the present invention provides a method for disinfecting a space or object with chlorine dioxide gas, wherein said chlorine dioxide gas is stripped from an aqueous chlorine dioxide composition according to the first aspect of the invention, this is from a solution comprising chlorine dioxide obtained by reaction of (i) one or more chlorite and/or chlorate salts with (ii) a mixture comprising one or more bisulphate and one or more persulphate salts.

Such relatively simple procedure for obtaining chlorine dioxide allows the method and the stable and highly pure chlorine dioxide composition obtained therefrom to be used in a wide field of applications. In a third aspect, the present invention provides a use of an aqueous chlorine dioxide composition according to the first aspect of the invention, for the disinfection of water, air, spaces and/or objects, such as, e.g. food packaging, textiles, medical instruments, and/or buildings for medical, nursing or veterinary applications.

DESCRIPTION OF THE FIGURES

The explicit characteristics, advantages and objectives of the present invention will be further apparent to those skilled in the technical field of the invention after reading the following detailed description of the embodiment of the invention and of the figures enclosed herein. The figures serve to further illustrate the invention, without thereby limiting the scope of the invention. Figure 1 shows a system for the preparation of a stable chlorine dioxide composition according to a first method of preparation according to the invention . Figure 2 shows a system for the preparation of a stable chlorine dioxide composition according to a second method of preparation according to the invention.

Figure 3 is a schematic representation of a system according to the second aspect of the present invention with indication of decontamination apparatus 101, a container 105 with an aqueous solution comprising at least 5.0 g/L of chlorine dioxide and one or more fluid conduits 107 for guiding a gaseous effluent from said aqueous solution to a space 108 to be disinfected. DETAILED DESCRIPTION OF THE INVENTION

Unless defined otherwise, all terms used in the description of the invention, including technical and scientific terms, have the meaning as is commonly understood by the skilled person in the technical field of the invention . For a better assessment of the description of the invention, the following terms are explained explicitly.

"A", "an" and "the" refer in this document to both the singular and the plural, unless the context clearly implies otherwise. For example, "a segment" means one or more than one segment.

When "around" or "about" is used in this document with a measurable quantity, a parameter, a time period or moment in time, and the like, then variations are meant of +/-20% or less, preferably +/- 10% or less, more preferably +/-5% or less, even more preferably +/-1% or less, and even more preferably +/-0.1% or less than and of the cited value, to the extent that such variations apply in the described invention. It should, however, be understood that the value of the quantity in which the term "around" or "about" is used, is itself specifically disclosed.

The terms "comprise", "comprising", "consist of", "consisting of", "provided with", "include", "i ncluding", "contain", "containing", "encompass", "encompassing" are synonyms and are inclusive or open terms that indicate the presence of what follows, and which do not exclude or prevent the presence of other components, features, elements, members, steps, known from or described in the prior art.

Quoting numerical intervals by endpoints includes all integers, fractions and/or real numbers between the endpoints, these endpoints included.

1. Chlorine dioxide composition

The term "chlorine dioxide" or "CI0 ₂ " refers to a molecule identified by the CAS number 10049-04-4 and occurs as a gas at standard pressure and temperature. Chlorine dioxide has a greenish, yellow colour with a characteristic odour similar to chlorine, and is a highly effective biocide which quickly and efficiently destroys pathogens such as bacteria, viruses and parasites. Chlorine dioxide gas molecules can also destroy nebulized germs, and can also spread through cracks and crevices in an article or a building or space and thus reach any surface which is possibly a source of pathogens, microorganisms, vermin, such as e.g. fleas, worms, bedbugs, cockroaches, rodents, etc. Chlorine dioxide is very soluble in water but in contrast to chlorine, chlorine dioxide does not react with water. It exists in aqueous solution as a dissolved gas. Chlorine dioxide is recognized as oxidizing, possibly explosive, corrosive, toxic and environmentally hazardous.

In a first aspect, the present invention provides an aqueous chlorine dioxide composition obtainable according to a process in which one or more chlorite and/or chlorate salts are mixed with one or more bisulphate and one or more persulphate salts in aqueous solution. Preferably, the invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein (i) an aqueous solution comprising one or more chlorite and/or chlorate salts is mixed with (ii) an aqueous solution comprising one or more bisulphate and one or more persulphate salts; and even more specifically wherein (i) an aqueous solution comprising one or more chlorite salts is mixed with (ii) an aqueous solution comprising one or more bisulphate and one or more persulphate salts.

Preferably, said chlorine dioxide composition comprises chlorine dioxide in a concentration of at least 4 g of chlorine dioxide per liter, according to amperometric determination. By providing a stable, highly concentrated and highly pure chlorine dioxide composition according to the present invention, a broader scope of application of the technology is possible. In this way, for example, it can be understood that, when stripping chlorine dioxide from an aqueous composition according to the invention, a concentrated gas stream can be obtained more rapidly. Because a highly concentrated chlorine dioxide gas stream can be obtained more quickly and safely, the composition can be used in economically beneficial manner in multiple applications. One of the main reasons for this is that a highly effective dose of chlorine dioxide can be released from a solution more rapidly. High concentrations are usually desirable, because the concentration of chlorine dioxide is the driving force for the desired reaction. For example, the disinfection of a space with the aid of chlorine dioxide gas is more rapidly as the concentration of the introduced chlorine dioxide is higher. The amperometric titration of CI0 ₂ is an extension of the amperometric method for chlorine. By performing four titrations with phenylarsine oxide, free chlorine (including hypochlorite and hypochlorous acid), chloramines, chlorite and CI0 ₂ can be determined separately. The first titration step is the conversion of CI0 ₂ to chlorite and chlorate by adding sufficient NaOH to a pH of 12, followed by neutralization to a pH of 7 and titration of free chlorine. In the second titration, KI is added to a sample that was treated in a similar manner with alkali and was then adjusted to pH 7; titration provides free chlorine and monochloramine. The third titration relates to the addition of KI and adjustment to pH 7, followed by titration of free chlorine, monochloramine and one fifth of the available CI0 ₂ . In the fourth titration, H ₂ S0 ₄ is added to pH 2, which allows to determine all of the available CI0 ₂ and chlorite, as well as the total free chlorine level, by releasing an equivalent amount of iodine, and thus, by titrating. For further details, we refer to Haller, J.F. & Listek, S.S. 1948. Determination of chlorine dioxide and other active chlorine compounds in water. Anal. Chem. 20:639.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein said aqueous composition comprises one or more alkali and/or alkaline earth metals. Such alkali and/or alkaline earth metals usually originate from the method of preparation of chlorine dioxide according to the second aspect of the present invention. WO 2010/151543 mentions that, for example, such elements, such as, for example, sodium, may be a cause of increased instability of the obtained chlorine dioxide composition. Consequently, according to the state of the art, an additional separation step needs to be taken. The inventors found a method to achieve a stable chlorine dioxide composition without the need for such costly separation step.

In a preferred embodiment, said one or more alkali and/or alkaline earth metals are comprised in at least a stoichiometric amount relative to the amount of chlorine dioxide in said aqueous composition.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, with a concentration of at least 5 g of chlorine dioxide per liter, more preferably with a concentration of at least 6 g of chlorine dioxide per liter, and even more preferably with a concentration of chlorine dioxide situated between 5 g of chlorine dioxide per liter and 15 g of chlorine dioxide per liter, according to amperometric determination.

Most preferably, said aqueous solution comprises 7 g/L, 8 g/L, 9 g/L, 10 g/L, 11 g/L or 12 g/L of chlorine dioxide, or any quantity situated therein between. This offers the advantage that a very highly concentrated, stable, and highly pure chlorine dioxide composition is made available which can be used advantageously for various applications. In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, having a half-life time for decomposition of chlorine dioxide of at least 5 days, measured at a temperature of 25°C. The half-life time for decomposition can be determined by monitoring the concentration of chlorine dioxide in a chlorine dioxide composition obtained by the method according to the second aspect of the invention. The half-life time is then determined by the time which is required for the degradation of 50% of the chlorine dioxide present in the solution, wherein the concentration is determined amperometrically and wherein the solution is conditioned at a temperature of 25°C. Preferably, the half-life time for decomposition of chlorine dioxide in the aqueous composition according to the invention is at least 10 days, more preferably at least 20 days. This offers the advantage that a stock solution can be prepared and temporarily stored for use without adversely affecting the stability of the solution during storage. The increased stability of the solution also provides the advantage that a higher concentration of chlorine dioxide in the aqueous composition can be achieved.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, having a half-life time for decomposition of chlorine dioxide of at least 25 days, measured at a temperature of 25°C, more preferably of at least 50 days, and most preferably more than 100 days.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein said aqueous solution comprising chlorine dioxide has a purity of more than 99%.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein said aqueous solution comprising chlorine dioxide has a purity of more than 99.5%. In a more preferred embodiment, said aqueous solution comprising chlorine dioxide has a purity of more than 99.9%.

This offers the advantage that the aqueous solution exhibits a higher stability, and, optionally, less potentially harmful by-products end up in the environment or come into contact with the materials to be disinfected.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, essentially free of one or more transition metal ions, transition metal oxides, hydrocarbon compounds, and/or contaminating particles.

Transition metal ions, transition metal oxides and/or other can, even in small amounts, have a significant impact on the stability of chlorine dioxide in solution. Such components can be reduced from the solution, for example, by means of de- ionization processes, without thereby affecting other ingredients. Contaminating particles are to be understood as particles having an average particle size of less than 100 pm, more preferably less than 50 pm, and even more preferably less than 25 μιτι. The absence of one or more of afore-mentioned elements and/or compounds contributes in a positive way to the purity, stability, and high concentration of the obtained chlorine dioxide composition. Examples of the aforementioned impurities or contaminants are, but not limited to, calcium and/or calcium compounds, manganese and/or manganese compounds, chlorides and/or bromides, iron and/or iron compounds and/or iron particles, organic compounds and/or microorganisms.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein said aqueous solution was prepared with reagent-pure water. Reagent-pure water is preferably obtained by de-ionization, distillation and/or reverse osmosis, possibly supplemented with carbon filtration and/or adsorption, microporous filtration, ultrafiltration, hyperfiltration, ultraviolet oxidation, and/or electrodialysis. More preferably, said reagent-pure water meets ASTM standards for pure water types I, II, or III.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein said chlorine dioxide composition may be obtained by mixing (i) one or more chlorite and/or chlorate salts with (ii) one or more bisulphate and one or more persulphate salts in an aqueous solution; more specifically, by mixing (i) an aqueous solution comprising one or more chlorite and/or chlorate salts with (ii) an aqueous solution comprising one or more bisulphate and one or more persulphate salts; and even more specifically, by mixing (i) an aqueous solution comprising one or more chlorite salts with (ii) an aqueous solution comprising one or more bisulphate and one or more persulphate salts.

The inventors realized that the use of a mixture comprising one or more bisulphate and one or more persulphate salts for producing an aqueous solution of chlorine dioxide unexpectedly leads to an increased stability of the chlorine dioxide solution.

In this way, it was found that the obtained chlorine dioxide solution was stable during a period of more than 10 days, even more so more than 20 days and even for a period of more than 30 days. This offers the advantage that a very high purity of the chlorine dioxide gas can be obtained since by-products or unreacted reagents are not or only in a negligible amount present in the aqueous chlorine dioxide solution. Such method offers the advantage that a high stability and shelf-life of the obtained aqueous chlorine dioxide composition may be obtained. This method also offers the advantage that a good conversion is obtained of the reagents to the desired chlorine dioxide without relevant formation of any by-products. This contributes to a high purity of the solution. Because of the obtained high purity and stability of the chlorine dioxide composition, high concentrations of chlorine dioxide can be realized. Such relatively simple procedure for obtaining chlorine dioxide allows for the method and the chlorine dioxide composition obtained therefrom to be used in a wide field of applications.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein said one or more chlorite salts are provided in said aqueous solution in a concentration of between 0.1 to 20% by weight, relative to the total weight of the composition.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein said one or more bisulphate and one or more persulphate salts are provided in said aqueous solution in a concentration of at least 1% by weight, relative to the total weight of the composition.

In a more preferred embodiment, said aqueous chlorine dioxide composition is obtainable by the mixing of an aqueous composition comprising 0.1 to 20% by weight of chlorite and/or chlorate salts with an aqueous composition comprising more than 2% by weight of bisulphate salts and more than 2% by weight of persulphate salts. More preferably, said aqueous chlorine dioxide composition is obtainable by the mixing of an aqueous composition comprising 0.5 to 15% by weight of chlorite and/or chlorate salts with an aqueous composition comprising more than 5% by weight of bisulphate salts and more than 5% by weight of persulphate salts. Most preferably, said aqueous chlorine dioxide composition is obtainable by the mixing of an aqueous composition comprising from 1 to 10% by weight of chlorite and/or chlorate salts with an aqueous composition comprising more than 10% by weight of bisulphate salts and more than 10% by weight of persulphate salts. Preferably, said chlorite salt is provided as sodium chlorite; said bisulphate salt is provided as sodium bisulphate; and said persulphate salt is provided as such as sodium persulphate. In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein said one or more chlorite, one or more chlorate, one or more bisulphate and one or more persulphate salts are provided in a purity of more than 90% for dissolution into an aqueous solution, preferably more than 95%, more preferably more than 98% and even more preferably more than 99%. Most preferably, said salts are provided in a purity of 99.0%, 99.2%, 99.4%, 99.6%, 99.8%, 99.9%, or any value therein between. Such high purity of the reagents contributes in a positive way to the purity, stability and high concentration of the obtained chlorine dioxide composition.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein said chlorine dioxide composition is obtained after mixing (i) sodium chlorite, and (ii) one or more bisulphate and one or more persulphate salts in a ratio ranging between 5: 1 to 1 : 5.

In a more preferred embodiment, said chlorine dioxide composition is obtained after mixing (i) sodium chlorite, and (ii) one or more bisulphate and one or more persulphate salts in a ratio ranging between 2 : 1 to 1 :2. More preferably, said ratio is about 1 : 1, and most preferably said ratio is 1 : 1. This offers the advantage that the chlorine dioxide composition obtained by such method has a very high purity and a very high stability. Furthermore, relatively high concentrations of chlorine dioxide in the aqueous composition are feasible, i.e. concentrations higher than 4 g of chlorine dioxide per liter.

In a preferred embodiment, the present invention provides an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein an aqueous solution comprising sodium chlorite is mixed with an aqueous solution comprising sodium bisulphate and sodium persulphate.

The term "sodium chlorite" refers to a chemical molecule with brut formula NaCI0 ₂ and is identified by CAS number 7758-19-2. The term "sodium bisulphate" refers to a chemical molecule with brut formula NaHS0 ₄ and is identified by CAS number 7681-38-1. The term "sodium persulphate" refers to a chemical molecule with brut formula Na ₂ S ₂ 0 ₈ and is identified by CAS number 7775-27-1. In an alternative embodiment, lithium, potassium, rubidium, cesium and/or francium is used instead of sodium. This offers the advantage that the counterions minimally interfere with the active components in the aqueous compositions, and consequently, do not compromise the stability of the obtained chlorine dioxide composition.

The present invention also provides a method for producing an aqueous chlorine dioxide composition according to the first aspect of the invention, wherein an aqueous solution comprising one or more chlorite salts is mixed with an aqueous solution comprising one or more bisulphate and one or more persulphate salts. Preferably, said one or more chlorite salts are provided in said aqueous solution in a concentration of between 0.1 to 20% by weight, relative to the total weight of the composition. Preferably, said one or more bisulphate and one or more persulphate salts are provided in said aqueous solution in a concentration of at least 1% by weight, relative to the total weight of the composition. Preferably, afore-mentioned reagents are processed to an aqueous chlorine dioxide composition according to one or more of the aspects described in the preceding paragraphs.

The present invention also provides a kit for producing an aqueous chlorine dioxide composition according to the first aspect of the invention, comprising :

A. an aqueous solution comprising 0.1 to 20% by weight of one or more chlorite and/or chlorate salts; and

B. an aqueous solution comprising at least 1% by weight of one or more bisulphate salts and at least 1% by weight of one or more persulphate salts.

This offers the advantage that both compositions may be stored separately and/or transported without the quality of the composition being adversely affected thereby. Furthermore, an operator can easily produce the desired chlorine dioxide composition by combining both aqueous solutions and mixing them minimally. This may already be done with the aid of very simple equipment, and is illustrated schematically in Figure 1 and 2. Preferably, both aqueous solutions A and B of said kit are concentrated in such way that the mixing thereof in a ratio of between 20: 1 and 2: 1 yields the desired chlorine dioxide composition. More preferably, said ratio is between 15 : 1 and 5: 1, even more preferably between 12 : 1 and 7: 1 and most preferably about 9: 1. Preferably, said composition is produced by using said kit at least 1 hour prior to use, more preferably between 1 hour and 12 hours prior to use or any period of time situated therein between, such as for example, 2 hours, 4 hours, 8 hours or 12 hours prior to use, and even more preferably between 4 hours and 6 hours prior to use.

In a preferred embodiment, the present invention provides said kit, further provided with an instruction manual comprising instructions for the use of said kit.

This offers the advantage that the use of both components (A) and (B) can be explained unambiguously to an operator. This is important as the correct combining of both solutions contributes to the purity and the stability of the obtained chlorine dioxide composition. Preferably, said instruction manual also comprises information concerning potential risks and/or hazards of the various chemical components in the composition.

Said aqueous chlorine dioxide composition may be usefully applied in the oil and gas industry, for the treatment of water such as, for example, but not limited to, industrial waste water, household waste water, drinking water, groundwater, rain water, ultra-pure water, for controlling odours, and/or for disinfection of objects, food, goods, animals, and/or spaces of buildings. 2. Method for disinfecting a space with chlorine dioxide gas from chlorine dioxide composition

The term "disinfect" is to be understood as synonym for the term "decontaminate" or "purify" and refers to the at least partial elimination of one or more types of plague species, pathogens or germs. Preferably, at least 90% of said pathogens or germs are destroyed, more preferably at least 97% and most preferably 100%.

The term "plague species" is to be understood as synonym for the term "harmful organism" and refers to any organism which has an unwanted presence or a detrimental effect on humans, animals, plants and/or the environment. Examples of plague species are weeds, microorganisms, pathogens, fungi, larvae, insects, parasites, nematodes, algae, mites, rodents, bacteria, viruses, etc.

The term "pathogen" or "pathogens" is to be understood as synonym for the term "disease agent" or "infectious agent" and refers to various bacteria, viruses, fungi, yeasts and protozoa which may cause disease and/or death in humans, animals, plants or other biological organisms. Pathogenic spores are spores which are produced by a pathogen. Specific examples of pathogens which produce spores comprise, but are not limited to, members of the genera Bacillus, Clostridium, Desulfotomaculans, Sporolactobacillus, and Sporosarcina, members of the Phylum Apicomplexa (such as Plasmodium falciparum and Cryptosporidium parvum), and phytopathogenic fungi .

The term "stripping" refers to the physical separation process wherein one or more substances are removed from a liquid and are entrained in the gas or vapour stream which was brought into contact with said liquid. Preferably, said gas stream is brought into contact with said liquid stream in countercurrent.

In a second aspect, the present invention provides a method for disinfecting a space or object with chlorine dioxide gas, wherein said chlorine dioxide gas is stripped from an aqueous chlorine dioxide composition according to the first aspect of the invention, this is from a solution comprising chlorine dioxide obtained by reaction of (i) one or more chlorite and/or chlorate salts with (ii) a mixture comprising one or more bisulphate and one or more persulphate salts.

The inventors realized that the use of a mixture comprising one or more bisulphate and one or more persulphate salts for the production of an aqueous solution of chlorine dioxide unexpectedly leads to an increased stability of the chlorine dioxide solution. In this way, it was found that the obtained chlorine dioxide solution was stable during a period of more than 10 days, even more so, more than 20 days and even for a period of more than 30 days. This offers the advantage that a very high purity of the chlorine dioxide gas can be obtained as by-products or unreacted reagents are not or only in negligible amount present in the aqueous chlorine dioxide solution. The improved stability of the chlorine dioxide composition provides a better source of chlorine dioxide for stripping chlorine dioxide from solution. This offers the advantage that a stable chlorine dioxide can be used for disinfecting a space or an object.

In a preferred embodiment, said chlorine dioxide gas is stripped from an aqueous solution obtained by mixing an aqueous composition comprising 0.1 to 20% by weight of chlorite and/or chlorate salts with an aqueous composition comprising more than 2% by weight of bisulphate salts and more than 2% by weight of persulphate salts. More preferably, chlorine dioxide gas is stripped from an aqueous solution obtained by mixing an aqueous composition comprising 0.5 to 15% by weight of chlorite and/or chlorate salts with an aqueous composition comprising more than 5% by weight of bisulphate salts and more than 5% by weight of persulphate salts. Most preferably, chlorine dioxide gas is stripped from an aqueous solution obtained by mixing an aqueous composition comprising 1 to 10% by weight of chlorite and/or chlorate salts with an aqueous composition comprising more than 10% by weight of bisulphate salts and more than 10% by weight of persulphate salts. Preferably, said chlorite salt is provided as sodium chlorite; said bisulphate salt is provided as sodium bisulphate; and said persulphate salt is provided as sodium persulphate.

In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein one or more chlorite and/or chlorate salts are brought together with a mixture comprising one or more bisulphate and one or more persulphate salts in aqueous solution in a batch reactor, and wherein after reaction, this is in conversion of at least 90% to chlorine dioxide, preferably at least 95%, more preferably at least 99%, the obtained aqueous solution is stored in a storage container. This offers the advantage that a continuous system for stripping chlorine dioxide from the solution can be provided. In a more preferred embodiment, said chlorine dioxide is obtained by the activation of sodium chlorite by a mixture comprising a preferably equimolar amount of sodium bisulphate and sodium persulphate. Still preferably, said sodium chlorite is provided as a solution in water, preferably in an amount of 1 to 10% by weight. Still preferably, said sodium bisulphate and sodium persulphate are provided as a concentrated solution in water, preferably as a solution comprising more than 10% by weight.

This offers the advantage that in a relatively rapid manner a high concentration of chlorine dioxide may be introduced into the space to be disinfected. Obtaining a high concentration of chlorine dioxide allows the space to be disinfected in a rapid and effective way. The faster the disinfection process can be finalized, the shorter the period of time of disuse of the space to be disinfected and/or to the instruments or materials to be disinfected in said space. In addition, a shorter period of time increases the employability of the equipment which allows for the stripping of said chlorine dioxide gas from said solution. In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein said chlorine dioxide gas is stripped from an aqueous solution comprising at least 4.0 g/L of chlorine dioxide, according to amperometric determination.

In a more preferred embodiment, said aqueous solution comprises at least 5.0 g/L of chlorine dioxide, according to amperometric determination, more preferably at least 6.0 g/L of chlorine dioxide, even more preferably between 7 and 15 g/L of chlorine dioxide. Most preferably, said aqueous solution comprises 7 g/L, 8 g/L, 9 g/L, 10 g/L, 11 g/L or 12 g/L of chlorine dioxide, or any quantity therein between.

In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein said aqueous solution comprising chlorine dioxide has a purity of more than 99%.

In a more preferred embodiment, said aqueous solution comprising chlorine dioxide has a purity of more than 99.5%, more preferably more than 99.9%. This offers the advantage that the aqueous solution exhibits a higher stability, and, optionally, less potentially harmful by-products end up in the environment or come in contact with the materials to be disinfected.

In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein said space is partially or completely closed off prior to the disinfection.

This offers the advantage that no or only a limited amount of chlorine dioxide gas can leak into the environment, as a result of which the actual concentration of chlorine dioxide remains maximal in the space to be disinfected, and that there is no risk of undesired contact between said chlorine dioxide and adjacent or adjoining spaces and the equipment present therein. Avoiding or at least significantly reducing chlorine dioxide gas leaks to adjacent spaces contributes to the safety of both professional operators and persons in the vicinity of the space to be disinfected. Preferably, said space is sealed by means of a substantially gas-impermeable closure. A sealed space such as a sealed article, sealed space, or a sealed building is to be understood as an environment wherein substantially all fluid conduits with the environment are or have been sealed, for example, by means of plastic covers or other sheets, tape, insulation, sealing or combinations thereof, and wherein preferably said covers are gas-impermeable. In a further embodiment, said sealed space is formed by means of a 'glove bag', a 'gas bag', an 'air bag' or an 'atmosbag'. Said sealed space is, nevertheless, preferably provided with one or more in- and/or outlets which allow that specific agents can be moved into and/or out of the sealed space.

In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein afore-mentioned aqueous solution comprising chlorine dioxide is provided in said space to be disinfected, and wherein a stripping unit is also being arranged in said space in connection with said solution. Such system comprising said solution with stripper can be equipped with a module for remote control for remotely controlling said system; by this is meant, from a position outside of the space to be disinfected.

In a preferred embodiment, the present invention provides a method according to the first aspect of the invention, wherein one or more packages, devices and/or instruments are provided in said space.

In a preferred embodiment, the present invention provides a method according to the first aspect of the invention, wherein the concentration of chlorine dioxide in said space is determined during the disinfection. This offers the advantage that an estimation can be made of the efficiency of the chlorine dioxide gas production from the aqueous solution and, consequently, the efficiency of the disinfection process. More preferably, said concentration of chlorine dioxide in said space is monitored during the disinfection process. This offers the advantage that the consumption of chlorine dioxide gas during the process can be monitored. Thus, an estimation can be made of the time at which the further addition of chlorine dioxide to the space to be disinfected becomes less efficient.

In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein the required amount of chlorine dioxide is determined beforehand. This offers the advantage that only the maxinnum required amount of chlorine dioxide needs to be transported to the space to be disinfected. This is advantageous, as the transportation of the potentially explosive chlorine dioxide gas is preferably minimized.

In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein the temperature and/or relative humidity of the space to be disinfected is conditioned beforehand. This offers the main advantage that the cell walls of microorganisms, e.g. spores, are made more permeable to chlorine dioxide. In addition, a suitable humidity leads to an efficient and rapid decomposition of the chlorine dioxide in the space to be disinfected. Such decomposition initiates the disinfection process. Increasing the relative humidity can be done, for example, by means of an air humidifier, such as for example, but not limited to, an evaporative humidifier, a steam humidifier, and/or an ultrasonic humidifier. The air humidity can be measured using a hygrometer. Preferably, said space is humidified to a relative humidity level ranging between 35% and 100%, preferably between 50% and 95%, more preferably between 60% and 90%, and most preferably between 75% and 85%. Most preferably, said relative humidity is 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84% or 85%, or any value therein between.

In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein said chlorine dioxide is stripped from said solution by means of a carrier gas. In a more preferred embodiment, said carrier gas comprises air or nitrogen gas.

In a preferred embodiment, said carrier gas is circulated in a space with the aid of a fan. A fan is to be understood as a device which produces an air stream, and can be used to circulate the air in an environment.

In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein said aqueous solution comprising chlorine dioxide is generated in a mobile decontamination unit.

This offers the advantage that said decontamination device can easily be transported to the location of the space to be disinfected. In a specific embodiment, said decontamination device can be provided on a trolley. Preferably, a portable apparatus is an apparatus having a weight of less than 100 kg, preferably less than 50 kg, and more preferably, an apparatus with a weight of 10 kg to 25 kg. In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein said aqueous solution comprising chlorine dioxide is brought into fluid connection with the space to be disinfected.

In a preferred embodiment, the present invention provides a method according to the second aspect of the invention, wherein said chlorine dioxide is neutralized and/or removed after disinfecting said space.

The term "neutralize/neutralizing" refers to the chemically making neutral of a chemical substance, preferably by means of chemisorption, physisorption, and/or decomposition. As a result of the neutralization, the concentration of chlorine dioxide in said gas stream is significantly reduced. For example, said chlorine dioxide can be neutralized by means of, preferably intensive, contact with an aqueous solution comprising 10% by weight of NaOH and 10% by weight of sodium thiosulphate hydrate. Preferably, said chlorine dioxide is neutralized in a gas scrubber.

In an alternative or preferably additional embodiment, a filter with a fixed chlorine dioxide adsorbent, preferably activated carbon, is used for adsorbing remaining chlorine dioxide in the disinfected space. Such a filter may be provided with a reducing agent, such as, for example, but not limited to thiosulphate, which reduces the remaining chlorine dioxide to chlorite and/or chlorate. Preferably, said filter is suitable for treating an air flow rate greater than 1000 m ³ /hour, preferably between 2000 m ³ /hour and 10000 m ³ /hour, more preferably between 2500 m ³ /hour and 5000 m ³ /hour, and most preferably an air flow rate of 2500, 2750, 3000, 3250, 3500, 3750, or 4000 m ³ /hour or any value therein between. This offers the advantage that the space to be disinfected can more rapidly be discharged of the potentially harmful chlorine dioxide. Preferably, the neutralization of chlorine dioxide in said space takes less than 2 hours, more preferably less than 1 hour, even more preferably between 5 minutes and 30 minutes and most preferably 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes, or any value therein between. In a more preferred embodiment, the concentration of chlorine dioxide in the effluent gas is monitored after the neutralization of said chlorine dioxide. This offers the advantage that the efficiency of the neutralization can be monitored. The present invention further provides a disinfection system for the disinfection of a space with chlorine dioxide gas, comprising a decontamination device, a container with an aqueous solution comprising chlorine dioxide obtained by reaction of (i) one or more chlorite and/or chlorate salts with (ii) a mixture comprising one or more bisulphate and one or more persulphate salts, and one or more fluid conduits for guiding a gaseous effluent from said aqueous solution to a space to be disinfected.

In a preferred embodiment, the present invention provides the afore-mentioned disinfection system, wherein said aqueous solution comprises at least 4.0 g/L of chlorine dioxide. Figure 3 is a schematic representation of a disinfection system according to the present invention, with indication of a decontamination device 101 comprising a stock solution of sodium chlorite 102 and a stock solution comprising a mixture of sodium bisulphate and sodium persulphate 103, a batch reactor 104 for mixing both stock solutions 102, 103 for the production of an aqueous solution comprising at least 5.0 g/L of chlorine dioxide, a container and/or stripping reactor 105 for the temporary storage of an aqueous solution comprising at least 5.0 g/L of chlorine dioxide and/or stripping chlorine dioxide from said solution by means of a carrier gas, preferably supplied air 106, and one or more fluid conduits 107a for guiding a gaseous effluent from said aqueous solution to a space 108 to be disinfected. Finally, the remaining amount of chlorine dioxide can be evacuated after the treatment via one or more fluid conduits 107b to an absorption and/or adsorption unit 109 for reducing the chlorine dioxide level in the effluent gas 110 for disposing the effluent gas into the atmosphere.

In a preferred embodiment, the present invention provides the afore-mentioned disinfection system, further provided with an air pump and aeration compartments for the purging of air through said solution comprising chlorine dioxide.

In a preferred embodiment, the present invention provides the afore-mentioned disinfection system, comprising one or more storage vessels (12, 13) for the at least temporary storage of reagents, at least one reaction vessel (14), and at least one chlorine dioxide vessel (15); a network of conduits with one or more pumps for moving gases and/or liquids through said network of conduits, wherein said network of conduits is configured for transferring reagents to a reaction vessel, for transferring a mixture in said reaction vessel to a chlorine dioxide vessel and for dispensing chlorine dioxide. In this, the internal volume of said network of conduits is smaller than the total volume of said chlorine dioxide vessel . Preferably, the internal volume of said network of conduits is 50% smaller than the total volume of said chlorine dioxide vessel, and more preferably 80% smaller. Most preferably, said network of conduits volume is 90%, 92%, 94%, 96%, 98%, 99% smaller than the volume of said chlorine dioxide vessel . In a preferred embodiment, the present invention provides the afore-mentioned disinfection system, comprising a chlorine dioxide vessel with a fluid sensor for detecting the fluid level in said chlorine dioxide vessel . In this way, the residual volume of chlorine dioxide composition in said chlorine dioxide vessel can be monitored. Once the residual volume has dropped below a predetermined value, a new batch of chlorine dioxide composition according to the first aspect of the invention can be created by way of a management system .

In a preferred embodiment, the present invention provides the afore-mentioned disinfection system, wherein said aeration compartments for the purging of air through said solution comprising chlorine dioxide is provided as a stripping tower, wherein said stripping tower is preferably provided with an active height ranging between 25 cm and 200 cm, preferably between 75 cm and 150 cm, more preferably between 100 cm and 150 cm, and most preferably is equal to 100 cm, 110 cm, 120 cm, 130 cm, 140 cm, or 150 cm, or any value therein between. Still preferably, said stripping tower has a ratio of height to diameter greater than 2 : 1, preferably greater than 5 : 1, and most preferably greater than 10 : 1. Still preferably, said stripping tower has a carrier gas flow rate, preferably an air flow rate, ranging between 250 and 10000 I per minute, preferably between 400 and 4000 I per minute, even more preferably between 800 and 2000 I per minute, and most preferably a flow rate of 800, 1000, 1200, 1400, 1600, 1800, or 2000 I per minute or any value therein between. Still preferably, said stripping tower has a liquid recirculation flow rate of between 10 I per hour and 1000 I per hour, preferably between 20 I per hour and 500 I per hour. The professional specialist will appreciate that the optimum liquid recirculation flow rate will be dependent on the volume of the space to be disinfected, and for smaller spaces will be situated at approximately 20 I per hour, and for larger spaces will be situated between 150 and 500 I per hour, and more preferably between 200 and 400 I per hour. In a third aspect, the present invention provides a use of an aqueous chlorine dioxide composition according to the first aspect of the invention, for the disinfection of water, air, spaces and/or objects, such as e.g. food packaging, textiles, medical instruments, and/or buildings for medical, nursing or veterinary applications.

Furthermore, said aqueous chlorine dioxide composition according to the first aspect of the invention, can be used for the disinfection of spaces in care institutions, such as for example, but not limited to childcare or nursery facilities, elderly care or home, psychiatric care institution; for the disinfection of spaces in a production environment, such as for example, but not limited to, production spaces for food products, pharmaceuticals, cosmetics, etc. and/or packaging for food products, pharmaceuticals, cosmetics, etc. ; for the disinfection of a space in the public environment, such as for example, but not limited to tourist space such as for example, but not limited to amusement park, museum, movie theater, stadium, cafeteria, etc. or transport space, such as for example, but not limited to train, tram, bus, plane, boat, etc. or an industrial space or a general living environment.

EXAMPLES

The invention will now be further elucidated with reference to the following example, without being in any case limited thereto.

Example 1

Figure 1 shows a system for the preparation of a stable chlorine dioxide composition according to the invention. The system comprises a first 12 and a second 13 storage vessel for reagents, respectively a 0.75% NaCI0 ₂ solution and a 0.75% solution comprising sodium bisulphate and sodium persulphate. Reagent feed is controllable by means of shut-off valves 32 and 33, respectively, by means of pump 22. In this way, reagents can be transferred to a reaction vessel 14, where both reagents are brought into contact with each other during a reaction time of 5 hours. After this reaction time, the chlorine dioxide solution is ready for use, and it is transferred to a chlorine dioxide vessel 15.

Example 2 Figure 2 shows a system for the preparation of a stable chlorine dioxide composition according to the invention. The system comprises a first 12 and a second 13 storage vessel for reagents, respectively a 25% NaCI0 ₂ solution and a 0.75% solution comprising sodium bisulphate and sodium persulphate. These storage vessels are connected to the main conduit 42 via the fluid conduit 51-52 and 53-54. Reagent feed is controllable by means of shut-off valves 32 and 33, respectively. Although this is not indicated on the figure, shut-off valves 32 and 33 are preferably provided with a liquid pump connected in series in order to enhance the liquid transport of reagents in the storage vessels 12 and 13 to the main conduit 42. Alternatively, the storage vessels may be provided with a pressure mechanism for applying a pressure on the liquids in the storage vessels.

The main conduit 42 is connected to the supply side 41 to a water conduit 13 and water supply is controllable by means of the shut-off valve 31. At the discharge side, the main conduit 42 is provided with a flow meter 21 and a pump 22. The pump brings the liquid mixture to a pressure of 5 bar. Water and reagents in storage vessels 12 and 13 are guided via the conduit 43-44, flow meter 21 and liquid pump 22 to a reaction vessel 14, where the reagents are brought in contact with each other during a reaction time of about 6 hours.

In a practical methodology, chlorine dioxide is produced in a five-step process. In a first step, a first volume of water is transferred from the water conduit 11 to a reaction vessel 14. In a second step, sodium chlorite is transferred from a storage vessel 12 to said reaction vessel 14. In a third step, a second volume of water from the water conduit 11 is transferred to a reaction vessel 14. In a fourth step, an aqueous mixture of sodium bisulphate and sodium persulphate is transferred from a storage vessel 13 to said reaction vessel 14. In a final step, a third volume of water of the water conduit 11 is transferred to a reaction vessel 14. In doing this, the volumes of water and reagents are dosed in such a way that the total of said first, second and third volume of water accounts for approximately 85% of the volume in the reaction vessel; the volume of sodium chlorite solution about 5%; and the volume of sodium bisulphate and sodium persulphate solution about 10%.

Upon completion of reaction, the contents of the reaction vessel 14 is transferred to a chlorine dioxide vessel 15 via the transfer line 45-46, which is controlled by means of a shut-off valve 34 and is possibly provided with a liquid pump to enhance the liquid transfer.

The chlorine dioxide vessel 15 is provided with a fluid sensor 23 which is activated when the contents of the chlorine dioxide vessel 15 has dropped below a predetermined level. At a liquid level below a pre- determined value, for example, less than 8 liters, the fluid sensor 23 will transmit a signal to an operating system, which is configured for managing the controllable shut-off valves 31, 32 and 33 and the pump 22 to thus produce a new volume of chlorine dioxide composition. Furthermore, the chlorine dioxide vessel 15 is connected to a conduit 47 which leads to a chlorine dioxide pump 24 with injection valve 35, so that chlorine dioxide can be used for intended purposes.