AU2021102286A4 - Cleaning Methods - Google Patents

Abstract

The present invention relates to cleaning or sanitizing methods using an aqueous hypochlorite concentrate wherein the concentrate contains very low levels of chlorates and perchlorates (harmful to human health). The concentrate is characterized by the lowest level of salt impurities defined by a "residual" ionic strength of between 0.2 and 1.7 gram moles per litre of concentrate. - 1/9 EXPERIMENTAL DEGRADATION OF NAOCL MADE BY NA2CO3 METATHESIS *Ca(Ocl)2 by Na process, 1=2.6231 E Ca(OCI)2 by Ca process, 1=1.945 140 120 100 . U : 80 z 60 40 20 0 0 10 20 30 40 50 60 DAYS Figure 1

Description

- 1/9

EXPERIMENTAL DEGRADATION OF NAOCL MADE BY NA2CO3 METATHESIS *Ca(Ocl)2 by Na process, 1=2.6231 E Ca(OCI)2 by Ca process, 1=1.945

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: 80 . U

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Figure 1

CLEANING METHODS

Reference The present innovation patent is a divisional of International Application No. PCT/AU2020/051038 filed 30 September 2020, the contents of which are incorporated by reference in its entirety.

Field The present invention relates to methods of surface sanitization, which may be a biological or non-biological surface. The main sanitisation /disinfectant material contemplated is an aqueous hypochlorite solution, prepared initially as a hypochlorite concentrate.

Background Abbreviations: OSG = On Site Generator by CAP process. CAP = ChlorAlkali Process HSLS= High Strength Low Salt sodium hypochlorite belonging to Powell Manufacturing. HRL = Highest Recommended Level HAL = Highest Allowable Level CAPEX = Capital Expenditure OPEX = Operating Expenditure RESIDUAL IONIC STRENGTH (RI)= RI = Total Ionic Strength (IT) - [Ionic strength of Hypochlorite species] SALT METATHESIS = a reaction between two inorganic salts where one product is insoluble in water. The reactants need not be highly soluble for the reaction to take place, but may take a longer time for the reaction to reach completion.

Hypochlorites are very effective, cheap sanitizers which provide a valuable disinfection service to humanity. The largest use for hypochlorite is for drinking water disinfection. Its use for this application however has been hindered due to its low strength; CAP sodium hypochlorite

(12.5%w/w) is mostly composed of water, and is thus expensive to transport at scale. Some plants have installed sodium hypochlorite OSGs to reduce the transport cost, and Powell has developed a HSLS process to make a more concentrated CAP sodium hypochlorite (30% w/w). At this time the HSLS process, in theory, can produce the most stable aqueous hypochlorite with the resultant lowest disproportionation rate to chlorate and perchlorate. The disadvantages of the HSLS process are: 1.1 The substantial OPEX and CAPEX required. 1.2 The need to locate the process adjacent to a chlorine plant or alternatively to continue transporting liquefied chlorine gas in bulk, drums or cylinders to the manufacturing site. 1.3 The continuing transport cost of 30%w/w sodium hypochlorite. (70% water, and a more Dangerous Good than CAP hypo; also more corrosive to road tankers).

All aqueous hypochlorites to some degree are unstable and disproportionate into undesirable chlorates and perchlorates. Instability increases with an increase in hypochlorite concentration. Upon heating, exposure to UV light or simply storage over time, hypochlorite will disproportionate to a mixture of chloride, oxygen, chlorates and perchlorates: 2 CIO- 2 Cl- + 02 3 ClO- 2 Cl-+ ClO-3 OCl- +C1032- -> C104- + Cl

Recently, as a result of improved analytical capability, perchlorates derived from hypochlorite have been shown to be a major human health issue. Perchlorate has been found to both interfere with brain development in children and present a dose -related risk to iodine uptake in healthy adults, as an endocrine disruptor of the human thyroid system. Perchlorate contamination of drinking water is a major global concern and the US EPA has recently proposed (in 2018) to regulate the perchlorate level in drinking water via a maximum contaminant level goal

[MCLG]. Currently the US EPA has levels for drinking water set at: HRL Chlorate: 210 ptg/L HAL Perchlorate: 15 ptg/L Whilst the limit set by the World Health Organization is 70 pg/L for chlorate (2016).

To partly ameliorate this issue, the current practice is focussed on better management techniques and guidelines for handling and storing hypochlorite to prevent disproportionation. For example, some of the key recommendations are to dilute hypochlorite solutions on delivery since halving the concentration decreases the disproportionation rate by a factor of 7, to store hypochlorite solutions at lower temperatures as reducing temperature by 5 C decreases disproportionation rate by a factor of 2, to keep the pH between 11 and 13 even after dilution, and importantly, to avoid extended storage times by, using fresh hypochlorite solutions when possible.

The most common aqueous hypochlorite is sodium hypochlorite which is made by the Chlor Alkali Process (CAP) shown by reaction (I)

Cl2 + 2NaOH = NaOCl + NaCl + H 2 0 (CAP) (I)

Another method for aqueous hypochlorite preparation is by salt metathesis reactions such as: Ca(OCl)2 + Na2 CO 3 = 2NaOCl + CaCO 3 (II)

Ca(OCl)2 + Na2 SO4 = 2NaOCl + CaSO 4 (III)

Although the preparation of aqueous hypochlorites by metathesis has been known for many decades, the process has never achieved commercial success. The lack of application is due to the fact that Chlor Alkali Plants (CAP) must produce aqueous hypochlorite as a by-product.

As the demand for chlorine has increased (eg PVC manufacture), in turn producing more CAP hypochlorite, aqueous hypochlorite produced by metathesis has not been required, and hence this process has never been developed or commercialized.

Also as bleaching activity increased, emphasis was placed upon the development of solid hypochlorites to avoid the costly transport of water which is the main component of sodium hypochlorite.

Only lithium hypochlorite, calcium hypochlorite and barium hypochlorite have been isolated as pure anhydrous solids.

Processes for the manufacture of solid calcium hypochlorite have been in development since the early 1950's, and today there are two main processes:

A) The sodium process based on the following reaction:

CaCl2 + 2NaOCl = 2NaCl + Ca(OCl)2 (IV)

B) The calcium process based on the reaction:

2C2 + 2Ca(OH) 2 = CaCl2 + Ca(OCl) 2 + 2H 20 (V)

Both processes are widely used, although product from the sodium process seems to be dominant in the market.

A major problem with the use of solid calcium hypochlorite is storage and handling of large quantities because of its self reactivity.

It is well known that if a single drop of organic liquid such as glycerin or brake fluid were to fall into a drum of solid calcium hypochlorite it can start an exothermic decomposition causing the whole contents to heat up and bubble like boiling porridge.

There have been numerous fatalities and fires on board ships which have been carrying large quantities of solid calcium hypochlorite in plastic lined steel drums.

The disproportionation reaction of solid by a hydration reaction is exothermic and in the case of concentrated solid hypochlorites, such as LiOCl and Ca(OCl) 2 , can lead to dangerous thermal runaway reactions and potentially explosions. As a result, solid hypochlorite is classified as a dangerous good by the criteria of the Australian Dangerous Goods Code (ADG Code) for Transport by Road and Rail. This makes it expensive to transport and store large quantities of solid hypochlorite as many safety precautions must be followed. To further mitigate the risk of fire caused by the self reactivity of calcium hypochlorite on ships, government authorities rely on standard tests performed under the UN Protocol or the US NFPA to classify into different risk categories, calcium hypochlorite depending on its strength, degree of hydration and diluent concentrations.

In addition to the production of excess CAP hypochlorite, restrictive regulations associated with the storage, transport and handling of calcium hypochlorite have increased the cost of its use for water treatment and these reasons have prevented the material from being used as a metathesis feedstock.

Considerable work has been done over the last 50 years to find a way to reduce the self reactivity of solid Ca(OCl) 2. The following methods have been investigated:

1 Maintaining a level of moisture in the Ca(OC) 2

2 Reducing the available chlorine level in the product 3 Adding non hydrated diluents to the product 4 Coating the product with hydroscopic materials

Accordingly, there is an urgent need to improve upon the current practices for both domestic and commercial applications of hypochlorites.

Summary The present discovery is important for human health since hypochlorites produced by a metathesis reaction can contain lower levels of chlorates and perchlorates than conventional CAP or the more expensive and capital intensive HSLS hypochlorites. Metathesised hypochlorite concentrates also exhibit superior stabilities and are therefore more efficacious than CAP or HSLS hypochlorite.

The present methods described herein have been found to have the following other advantageous properties: 1 Lower Chlorates and Perchlorates levels in metathesised hypochlorites make them more suitable for sanitising biological surfaces like fruit and vegetables.

2 Chlorination using the metathesis process described herein is also the cheapest method for drinking water treatment. (see Table 3). 3 Hypochlorites made via the present metathesis process have better high temperature stability than CAP and HSLS hypochlorites, resulting in a lower rate of gereration of Chlorates and Perchlorates in higher temperature applications. 4 Since metathesis hypochlorites are more stable than conventional hypochlorites, they have superior time based efficacy. 5 Potassium and sodium based metathesized hypochlorites containing exceedingly low caustic levels (which is only added to the hypochlorite as a stability booster) are environmentally friendly surface sanitisers. [Caustic levels in conventional hypochlorites prevent their use on some surfaces because of corrosion to said surfaces.].

Accordingly, the resultant aqueous sodium hypochlorite concentrates produced by metathesis as described herein can be formed easily and cheaply and are safe to store and handle, while also minimising the aqueous concentration of the chlorate and/or perchlorate by-products which are reduced to a previously un-achievable minimal level.

In one aspect the invention provides a method for sanitizing a non-biological surface using an aqueous hypochlorite concentrate of Li, K or Na, wherein the concentrate is characterized with a low level of salt impurities defined by a "residual" ionic strength of between 0.2 and 1.7 gram moles per litre of concentrate, wherein the method includes the step of applying said concentrate, or a diluted solution thereof, to said non-biological surface to provide an available chlorine level on said surface of between 10 and 10000 ppm (w/v), and wherein the hypochlorite is produced via Metathesis reaction.

In another aspect the invention provides a method for sanitizing a biological surface using an aqueous hypochlorite concentrate of Li, K or Na, wherein the concentrate is characterized with a low level of salt impurities defined by a "residual" ionic strength of between 0.2 and 1.7 gram moles per litre of concentrate, wherein the method includes the step of applying said concentrate, or a diluted solution thereof, to said biological surface to provide an available chlorine level on said surface of between 10 and 10000 ppm (w/v), and wherein the hypochlorite is produced via Metathesis reaction.

The Ca(OCl)2 feedstock used in the metathesis reaction to produce the hypochlorite concentrate as used herein is characterised with a high available chlorine content of from 65-80%, preferably about 70%,71%,72%,73%,74%,75%, or about76%.

In some embodiments, if the calcium hypochlorite feedstock is produced from a reaction of chlorine and calcium hydroxide (calcium process, reaction V), the sodium hypochlorite solution or hypochlorite solution can have a half-life about 20% to about 50% more than that of a hypochlorite solution produced from a reaction of calcium hypochlorite produced by reacting calcium chloride and sodium hypochlorite (sodium process, reaction IV).

In one embodiment the surface is a non-biological surface selected from selected from stainless steel and other ferrous alloys, copper and its alloys, nickel and its alloys, titanium and its alloys, aluminium and its alloys, plastics, rubbers, glass, wood, or ceramic.

In another embodiment the surface is a biological surface selected from fruit and vegetables, processed animal skin (eg chicken, beef or pork) and human skin.

Brief description of the drawings Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the drawings in which:

Figure 1 illustrates a comparison of NaOC stabilities made by metathesis reaction with two different calcium hypochlorites. (one made by Na process, the other by the Ca process). Figure 2 illustrates a comparison of stabilities of hypochlorite solution of the present invention compared to other methods. Figure 3 illustrates the degradation of sodium hypochlorite solutions of the present invention compared to the CAP process. Figure 4 illustrates the formation of chlorate from sodium hypochlorite solutions of the present invention compared to the CAP process. Figure 5 illustrates the formation of perchlorate from sodium hypochlorite solutions of the present invention compared to the CAP process. Figure 6 illustrates a comparison of degradation of sodium hypochlorite solutions at 52 C. Figure 7 illustrates a comparison of commercial and lithium hypochlorite solutions of the present invention, compared with simulation results of a high strength low salt (HSLS) sodium hypochlorite belonging to Powell Manufacturing. Figure 8 a table which compares hypochlorite solutions made using different processes. Figure 9 a table showing the economics associated with drinking water chlorination.

Detailed description In one aspect, the present invention is predicated on the discovery that aqueous hypochlorite concentrates of Li, K, or Na made by the metathesis reaction can be produced with low levels of salt impurities. As concentrates they are then mixed further with water, (i.e, required dilution) and such resultant hypochlorites are more stable than CAP and HSLS (by Powell) hypochlorites, and have, in a pre diluted state, a residual ionic concentration less than 1.7 g.mole/litre and as low as 0.2 g mole/litre.

To solve the problem of the safe transportation storage, and domestic use of Li, K or Na hypochlorites, the inventors have developed methods which allow for a new way to disinfect a surface.

Advantageously, the metathesis process can allow for the preparation of fresh hypochlorites (family includes Na, Li, and K) at the point of use.

In other embodiments, the hypochlorite concentrates have a lower chlorate concentration governed by the total ionic concentration but more particularly by a residual ionic concentration of less than 1.7 M, down to about 0.2 M.

The chlorate content will still be dependent upon time, temperature history, strength of the hypochlorite solution and starting chlorate concentration, but will always be less than CAP hypochlorite and, in some instances, HSLS hypochlorites because of the advantage of the lowest residual ionic strength.

In other embodiments the hypochlorite concentrates are characterised by a lower perchlorate concentration governed by the total ionic concentration but more particularly by the residual ionic concentration of less than 1.7 M, down to about 0.2 M

The perchlorate content will still be dependent upon time, temperature history, strength of the hypochlorite solution and starting perchlorate concentration, but will always be less than CAP hypochlorite and, in some instances, HSLS hypochlorites because of the advantage of the lowest residual ionic strength.

To solve the problem of high generation of chlorates and perchlorates in CAP hypochlorates, the inventors have discovered a new family of extremely stable aqueous hypochlorite products made by a salt metathesis process.

In an aspect, the present invention provides a family of extremely stable aqueous hypochlorite products including Na, K, and Li which have a residual ionic strength of less than 1.7 M.

The stability and rate of disproportionation of aqueous hypochlorites is markedly dependant on the concentration of the hypochlorite molecules in solution. In order to understand the impact of impurities upon hypochlorite stability it is necessary to devise a way of removing hypochlorite concentration from consideration. This was done by comparing hypochlorites based on their residual ionic strengths instead of the conventional total ionic strength. As a result, it was discovered that the stability of hypochlorites could be reliably indicated by calculating their residual ionic strengths (or calculating from experimental measurements). Furthermore, for the first time, it was found that residual ionic strength was a quantitative method of defining a family of hypochlorite products that are markedly different (greater stability) to standard CAP hypochlorite which has a residual ionic strength greater than about 1.7 M.

Residual ionic strength (RI) is first defined. Aqueous hypochlorites are difficult to describe as they have variable parameters such as: 1 Metallic parent, ( Ca, Ba, Mg, Na, K, and Li )

2 Strength, which may be measured as gpl of available chlorine 3 Method of preparation (CAP, HSLS, and Salt Metathesis) 4 Impurities, e.g. NaCl, CaCl2, LiCl salts etc.

An important parameter influencing the stability of an aqueous hypochlorite is its ionic strength. The Total Ionic strength for aqueous alkali metal hypochlorites is expressed as

IT =1/2miZi2 = 12(m1Zl2 + 2 m2Z2 +...+ mnZn 2) where (V1) n= total number of different ionic species in solution m= molal concentration, in this case molar. z= Charge on the ion of specific species i IT= Ionic Strength as defined by G.N. Lewis (Alkaline earth hypochlorites require a different expression for ionic strength to reflect complex multivalent ionic interactions.)

Because the Total Ionic strength represented by equation VI includes the concentrations of the anion and cation of the hypochlorite species, the total ionic strength is a function of the hypochlorite strength. If the ionic strength of the hypochlorite species is removed from the total ionic strength calculation then a new function called "residual ionic strength (RI)" is newly defined. RI = Total Ionic Strength (IT) - [Ionic strength of Hypochlorite species]

This new parameter "Residual Ionic Strength" is only dependent on 1) The purity of the reactants involved in its production 2) The type of anion bound to the alkali metal reactant, used in the salt metathesis reaction. 3) The solubility of the salt produced by the metathesis reaction. 4) The solubility of salts produced as by-products or impurities associated with the reactants of the metathesis reaction.

The term "Residual Ionic Strength" can therefore be used to define a new family of hypochlorite products, produced by metathesis, which have residual ionic strengths below 1.7 g mole/litre, which is the minimum residual ionic strength of traditional CAP hypochlorite.

The concentrates of the present invention provides a sodium hypochlorite solution that has a residual ionic concentration of less than about 1.7 molarity.

This embodiment defines a new family of aqueous hypochlorite products, including Li, Na, and K, defined by their exceedingly low residual ionic strengths, which contributes to improved stability and the associated lowest rate of disproportionation into chlorates and perchlorates. (See equations VII, and VIII)

The problem with the Chlor Alkali Process (CAP) for making hypochlorites Reaction (1) is product instability (due to amongst other things the co-generation of salt) and the associated generation of harmful by-products, such as chlorates and perchlorates. (see Figure 2).

To mitigate this problem, aqueous hypochlorite concentrates of the present invention are produced from a metathesis reaction. The hypochlorites produced by metathesis contain chlorate levels about 25% lower, and perchlorate levels about 50% lower than the equivalent CAP hypochlorite.

In some embodiments, the metathesized hypochlorite concentrates have a residual ionic concentration less than about 1.7 molarity, down to about 0.2 molarity. In other embodiments, the residual ionic concentration is from about 0.2 M (g mole/1) to about 1.7 M. In other embodiments, the residual ionic concentration is from about 0.2 M to about 1.5 M, about 0.2 M to about 1.4 M, about 0.2 M to about 1.3 M or about 0.2 M to about 1.0 M.

A feature of this family of very stable aqueous hypochlorite aqueous concentrates, which include LiOCl and KOC1, is their very low residual ionic concentrations. Residual Ionic concentrations as low as about 0.2 gm mole/litre, can be obtained by judicious choice of the KOC1, K2 C0 3 , K2 S0 4 , Li2 SO 4 , Li 2 CO 3 or 2(LiOH.H 20).

Hypochlorites made by using Ca(OC)2 (Ca) which has been made by the calcium process,( reaction (V)) are more stable than products made by using Ca(OCl)2 (Na) which has been made by the sodium process ( reaction (IV)). (see Figure 1).

Table 1: Common impurities in calcium hypochlorite produced by the sodium or calcium process, including the %w/w of available chlorine. Impurities Sodium Process Calcium Process Solubility

% w/w equation (IV) %w/w equation (V) (g/10gin H2 0 at 20 C)

Available chlorine 65-80 65 (minimum) Ca(OH)2 5 (typical) 6 (maximum) 0.165 CaCO3 1 (typical) 1 (typical) 0.0014 NaCl (soluble) 20 (max) 0 35.7 CaCl2 0 9 (maximum) 74.5 Ca(Cl0 3 )2 0 1 (maximum) (soluble) H2 0 10 (max) 4 (max)

MgCO 3 Trace Trace 0.01

Mg(OH)2 Trace Trace 0.0009 BaCO3 Trace Trace 0.0022

Ba(OH) 2 Trace Trace 1.67

It is believed that the increased stability of aqueous metathesis hypochlorites formed from Ca(OCl)2(Ca) made by the calcium process is due to a smaller quantity of CaCl2 in the product from the calcium process compared with the NaCl content of product from the sodium process. Further, the general insolubility of calcium impurities resulting in a purer aqueous hypochlorite and accordingly has a better aqueous stability as compared to the one made using the sodium process. A lower rate of formation of chlorate/perchlorate in the NaOCl made by Ca(OCl)2 (Ca) as compared to that made by using Ca(OCl)2 (Na), was also found.

Advantageously, this further improves the purity of the resultant sodium hypochlorite solution, which has better stability with respect to lower disproportionation rates into chlorate and/or perchlorate.

In some embodiments, the aqueous hypochlorite concentrate has a concentration of greater than % w/w, greater than 10 % w/w, greater than 15 % w/w, or greater than 20 % w/w of the hypochlorite species.

The disproportionation products of hypochlorites are chlorates and perchlorates. The inventors have further investigated the hypochlorite, chlorate, perchlorate and 02 content of the solution and determined that these concentrations are dependent on several factors such as temperature, starting chlorate, hypochlorite and ionic strengths. By regulating these factors, the disproportionation products of the composition can be controlled to a minimum.

In some embodiments, the calcium hypochlorite is produced from a reaction of chlorine and calcium hydroxide (calcium process). The sodium hypochlorite solution or hypochlorite solution can have a half-life about 20% to about 50% more than that of a hypochlorite solution produced from a reaction of calcium hypochlorite produced by the reaction of calcium chloride and sodium hypochlorite (sodium process).

In other embodiments, to ensure stability, the hypochlorite concentrate further comprises a soluble alkali of about 0.1 g/L to about 0.5 g/L, and optionally an alkaline buffer selected from carbonate, bicarbonate or a mixture thereof; and wherein the hypochlorite concentrate is produced via a metathesis reaction.

In another embodiment, the composition is substantially free of impurities. This is especially so if the calcium hypochlorite made by calcium process is used.

In another aspect, the present methods utilise an aqueous concentrate comprising: a) calcium hypochlorite having an available chlorine content of from 65-80% and a water content of about 4% to about 10% w/w; and b) an alkali metal salt; wherein the mix of the alkali metal salt and calcium hypochlorite is in approximately stoichiometric proportions; and wherein a) and b) is react-able in water to form a hypochlorite concentrate and a filterable salt.

The alkali metal can be selected from Na, Li or K.

In other embodiments, the anion associated with the alkali metal salt is selected from C0 32 S04 2 , P0 4 3 , HP0 4 2 , H 2 PO4, OH-, S0 3 2 , HS0 4 , HS3 and S2032 -

In certain embodiments the biological surface is treated with the concentrate to provide an available chlorine level in the treated water of between 1 and 20 ppm (w/v), such as about 2, 4, 6, 8, 10, 12, 14, 16, 18 ppm (w/v) or any range in between. For sanitizing a biological surface the present invention contemplates using aqueous hypochlorites of Li, K or Na, and preferably K or Na.

In certain embodiments this method includes the step of applying said concentrate, or a diluted solution thereof, to said non-biological surface to provide an available chlorine level on said surface of between 10 and 10000 ppm (w/v), and wherein the hypochlorite is produced via Metathesis reaction.

For sanitizing a non-biological surface the present invention contemplates using aqueous hypochlorites of Li, K or Na, and preferably Na or K.

In an embodiment the concentrate is used neat.

In another embodiment the concentration is diluted prior to use.

In certain embodiments the surface is treated with the concentrate to provide an available chlorine level in the treated water of between 0.1 and 20 ppm (w/v), such as about 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, about 19 ppm (w/v), or any range in between.

In another aspect, the present invention provides a method for preparing an aqueous hypochlorite concentrate (to be used in the methods described herein), including mixing an alkali metal salt (family includes Na, Li and K) with calcium hypochlorite having an available chlorine content of from 65-80% and a water content of about 4% to about 10% w/w; wherein the alkali metal salt and the calcium hypochlorite are in approximately stoichiometric proportions; and wherein the alkali metal salt and calcium hypochlorite is react-able in water to form a hypochlorite concentrate.

In an embodiment, the process further comprises adding a soluble alkali. The soluble alkali can be sodium hydroxide. Other alkali can be potassium hydroxide, calcium hydroxide or lithium hydroxide.

In another embodiment, the soluble alkali is present in an amount of about 0.1 g/L to about 0.5 g/L. In other embodiments, the concentration is about 0.1 g/L to about 0.4 g/L, about 0.1 g/L to about 0.3 g/L or about 0.1 g/L to about 0.2 g/L. Advantageously, the soluble alkali acts to further stabilise the hypochlorite solution.

In another embodiment, the process further comprises a step of adding an alkaline buffer to the sodium hypochlorite, wherein the alkaline buffer is selected from carbonate, bicarbonate or a mixture thereof.

In another embodiment, the metathesis reaction is performed at room temperature, or at about 1°C to about 35°C.

The metathesized based metal hypochlorite concentrate, as used herein is characterised by the metal hypochlorite concentrate having an residual ionic concentration less than 1.7 molarity, the metal hypochlorite solution having an available chlorine content of about 90 g/L to about 160 g/L; and wherein the metal is selected from Na, K or Li.

In some embodiments, the metathesized hypochlorite concentrate has a residual ionic concentration less than about 1.7 molarity. In other embodiments, the residual ionic concentration is from about 0.2 M (g.mole/L) to about 1.7 M. In other embodiments, the residual ionic concentration is from about 0.2 M to about 1.6 M, about 0.2 M to about 1.5 M, about 0.2 M to about 1.4 M or about 0.2 M to about 1.2 M. In some embodiments, the hypochlorite solution has a residual ionic concentration of about 0.2 M to about 1 M.

Advantageously, the metathesized metal hypochlorite concentrate has approximately 50% reduction of perchlorate when compared with CAP hypochlorite exposed to the same conditions and at the same concentrations.

In other embodiments, the metathesized alkali metal hypochlorite concentrate comprises a soluble alkali of about 0.lg/l to about 0.5 g/l. In other embodiments, the concentration is of about 0.lg/l to about 0.4 g/l or about 0.2g/l to about 0.4 g/l.

In other embodiments, the metathesized alkali metal hypochlorite concentrate comprises an alkaline buffer selected from a carbonate/bicarbonate mixture.

In other embodiments, the metathesized hypochlorite concentrate has a half-life of at least 1.4 times greater than that of Chlor Alkali Plant (CAP) hypochlorites. Preferably, the half-life is at least 1.7 time greater than that of CAP hypochlorites.

In other embodiments, the metathesized hypochlorite concentrate is produced from an alkali metal salt or its corresponding hydrated form.

In other embodiments, the anion associated with the alkali metal salt or its corresponding hydrated form is selected from C0 32 -,S0 4 2-, P043-, HP04 2 -, H2PO4-, OH-, S032-, HSO4-, HSO3 and S2032

It will be appreciated that many further modifications and permutations of various aspects of the described embodiments are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Examples

Example 1

Li 2 SO 4 + Ca(OCl)2 -- 2LiOCl + CaSO 4

A solution of Ca(OCl) 2 was prepared using HY-CLOR Super-Shock granular pool chlorine containing 700 g/kg of chlorine as Ca(OCl)2, by dissolving 72.0 g in 400 ml of distilled water at 20 °C. The dissolution process was achieved by mixing with a Heidolph RZR 2041 variable speed, polyurethane coated, steel, four blade, anchor style, 120 mm diameter, agitator at 305 rpm for 0.5 hours. 38.7 g of Aldrich AR grade Li 2 SO4 was slowly added to the previously prepared unfiltered Ca(OC) 2 solution with constant stirring for a period of 1 hour. The mixture was then filtered using a Buchner funnel under vacuum through a polypropylene cloth filter. The LiOCl solution was clean and bright and had an available chlorine content of 113.01 g/l. A small quantity of LiOH was added to the product to impart stability. After washing with distilled water, the CaSO4 was removed from the filter cloth, dried at 1500 °C for 8 hours and weighed on a Sartorius electronic balance. The weight of CaSO4 was determined to be 47 g. Yield is 98 % based on Li 2 SO 4 . The reaction essentially goes to completion in stoichiometric quantities.

Ionic strength of solution= 1.6503, pH=11

Example 2

2(LiOH.H 20) + Ca(OCl)2= 2LiOCl + Ca(OH)2 +2H 20

A solution of Ca(OCl) 2 was prepared using HY-CLOR Super-Shock granular pool chlorine containing 700 g/kg of chlorine as Ca(OCl)2 , by dissolving 72.0 g in 400 ml of distilled water at 20 °C. The dissolution process was achieved by mixing with a Heidolph RZR 2041 variable speed, polyurethane coated, steel, four blade, anchor style, 120 mm diameter, agitator at 305 rpm for 0.5 hours. 26.05 g of Helm AR grade LiOH.H20 was slowly added to the previously prepared unfiltered Ca(OC) 2 solution with constant stirring for a period of 3 hour. The mixture was then filtered using a Buchner funnel under vacuum through a polypropylene cloth filter. The LiOCl solution was clean and bright and had an available chlorine content of 110 g/l. After washing with distilled water, the Ca(OH) 2 was removed from the filter cloth, dried at 800°C for 8 hours and weighed on a Sartorius electronic balance. The weight of Ca(OH) 2 was determined to be 25 g. Yield is 95 % based on LiOH.H 2 0. The reaction essentially goes to completion in stoichiometric quantities.

Ionic strength of solution = 1.5978, pH=12

K2 S04 + Ca(OCl)2 -- 2KOCl + CaSO4

A solution of Ca(OC) 2 was prepared using HY-CLOR Super-Shock granular pool chlorine containing 700 g/kg of chlorine as Ca(OCl) 2, by dissolving 72.0 g in 400 mL of distilled water at 20 °C. The dissolution process was achieved by mixing with a Heidolph RZR 2041 variable speed, polyurethane coated, steel, four blade, anchor style, 120 mm diameter, agitator at 320 rpm for 0.5 hours. 61.4 g of Merck AR grade K2 SO4 was slowly added to the previously prepared unfiltered Ca(OC) 2 solution with constant stirring for a period of 1 hour. The mixture was then filtered using a Buchner funnel under vacuum through a polypropylene cloth filter. The KOCl solution was clean and bright and had an available chlorine content of 123.4 g/L. After washing with distilled water, the CaSO4 was removed from the filter cloth, dried at 150 °C for 8 hours and weighed on a Sartorius electronic balance. The weight of CaSO4 was determined to be 46.1 g. Yield = 96% based on CaSO4. The reaction essentially goes to completion in stoichiometric quantities.

Example 4

K2 C03 + Ca(OCl)2 -- 2KOCl + CaCO3

As in example 1, a solution of Ca(OC) 2 was prepared using HY-CLOR Super-Shock granular pool chlorine containing 700 g/kg of chlorine as Ca(OCl)2, by dissolving 72.0 g in 400 ml of distilled water at 20 °C. The dissolution process was achieved by mixing with a Heidolph RZR 2041 variable speed, polyurethane coated, steel, four blade, anchor style, 120 mm diameter, agitator at 305 rpm for 0.5 hours. 48.6 g of Mallinckrodt AR grade K2 CO3 (anhydrous) was slowly added to the previously prepared unfiltered Ca(OCl) 2 solution with constant stirring for a period of 1 hour. The mixture was then filtered using a Buchner funnel under vacuum through a polypropylene cloth filter. The KOCl solution was clean and bright and had an available chlorine content of 120.5 g/L. It was found that the hypochlorite formed by this reaction lacked stability and it was necessary to add a small quantity of KOH to the product to impart stability. After washing with distilled water, the CaCO3 was removed from the filter cloth, dried at 1500 °C for 8 hours and weighed on a Sartorius electronic balance. The weight of CaCO 3 was determined to be 34.8 g. Yield is 98.8 % based on CaCO 3. The reaction essentially goes to completion in stoichiometric quantities.

Example 5

2KOH + Ca(OCl) 2 -- 2KOCl + Ca(OH) 2

As in example 2, a solution of Ca(OC) 2 was prepared using HY-CLOR Super-Shock granular pool chlorine containing 700 g/kg of chlorine as Ca(OCl)2, by dissolving 72.0 g in 400 mL of distilled water at 20 °C. The dissolution process was achieved by mixing with a Heidolph RZR 2041 variable speed, polyurethane coated, steel, four blade, anchor style, 120 mm diameter, agitator at 305 rpm for 0.5 hours. 39.6 g of Merck AR grade KOH (anhydrous) was slowly added to the previously prepared unfiltered Ca(OC) 2 solution with constant stirring for a period of 1 hour. The mixture was then filtered using a Buchner funnel under vacuum through a polypropylene cloth filter. The KOCl solution was clean and bright and had an available chlorine content of 144 g/L. After washing with distilled water, the Ca(OH)2 was removed from the filter cloth, dried at 150 °C for 8 hours and weighed on a Sartorius electronic balance. The weight of Ca(OH) 2 was determined to be 24.2 g. Yield is 92.6 % based on Ca(OH) 2. Again the reaction essentially goes to completion in stoichiometric quantities.

Example 6

CIP (Cleaning-In-Place) Cleaning and Sterilisation of a Fruit Juice Plant.

1 Pre-Rinse Rinse the pipework and equipment with clean water. Ensure that the flow through pipes and valves is in the turbulent regime (3 m/s) Direct first flush to drain. The pre-rinse will remove particulates and product residues. 2 Caustic Wash Dilute concentrated caustic to approximately 1.5% (w/v) and heat to 80 deg C. Circulate hot caustic solution for 15 minutes and return to feed tank following filtration. 3 Water Wash Heat the wash water to 75 deg C. Direct the first flush which will contain residual caustic to drain. Continue recirculation for 15 minutes. 4 Sterilisation Dilute the metathesised NaOCl concentrate (125 gpl available chlorine [125000 ppm w/v]) to 5000 ppm (w/v). Recirculate the diluted concentrate for 15 minutes. Check the available chlorine before capturing the recycled sterilant for the next CIP clean. Post Rinse Do not heat this post rinse water before circulation. The purpose of this rinse is to remove the residual NaOCl, so continue flushing to drain until Starch Iodide paper shows that all the NaOCl has been flushed from the system. 6 Acid Rinse This step may or not be required depending on the ability of the Post Rinse to remove any alkaline residue from the Caustic Wash and the Sterilisation steps. Because Metathesised hypochlorite contains much less caustic for stability control compared with CAP and HSLS hypochlorites, the Post Rinse should be sufficient to remove final traces of caustic.

The Chlorate and Perchlorate analysis of a typical plant operation using CAP and Metathesised NaOCl are compared below based on the authors simulation package.

Assumptions: Typically NaOCl (125 gpl available chlorine) ex a chloralkali plant (CAP) is 3 days old. NaOCl from the CAP plant may be stored at the Fruit Juice Processor for 2 weeks. (There being a natural desire to reduce delivery frequencies) Assume the NaOCl is stored at 25 deg C and the initial Chlorate concentration is 1 gpl.

Results:-

Analysis at 0 days old Source of Hypo Temp Total Ionic OCl' C103' C104' DegC Conc Cone Cone Cone gmoles/l gpl gpl gpl CAP NaOCI 25 4.494 131.25 1.0 0 Metathised NaOCl 25 1.65 131.25 1.0 0

Analysis at Analysis at 17 days old Source of Hypo Temp Total Ionic OCl' C103' C104' Deg C Conc Cone Cone Cone gmoles/l gpl gpl gpl CAP NaOCI 25 4.494 121.43 4.508 6.416*10-4 Metathised NaOCl 25 1.65 127.06 2.387 2.398*10-4

Conclusion: There is a significant reduction of Chlorate and Perchlorate concentrations in the Metathesised sterilising concentrate, with a lower potential contamination, of the fruit juice, with these degradation products which are harmful to human health.

Claims (5)

1. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

   1 A method for sanitizing a biological or non-biological surface using an aqueous hypochlorite concentrate of Li, K or Na, wherein the concentrate is characterized with a low level of salt impurities defined by a "residual" ionic strength of between 0.2 and 1.7 gram moles per litre of concentrate, wherein the method includes the step of applying said concentrate, or a diluted solution thereof, to said non-biological surface to provide an available chlorine level on said surface of between 10 and 10000 ppm (w/v), and wherein the hypochlorite is produced via Metathesis reaction.
2. 2 A method of claim 1 wherein the hypochlorite concentrate contains between 2 and 150 g/l of available chlorine, and the aqueous hypochlorite concentrate is a Na or K hypochlorite concentrate.
3. 3 A method of claims 1 to 2 wherein it includes the step of applying the K or Na concentrate, or diluted solution thereof, to said biological surface to provide an available chlorine level on said surface of between 0.1 and 20 ppm (w/v) and wherein the hypochlorite is produced via Metathesis reaction.
4. 4 A method of anyone of claims 1 to 3 wherein the surface is a non-biological surface is selected from stainless steel and other ferrous alloys, copper and its alloys, nickel and its alloys, titanium and its alloys, aluminium and its alloys, plastics, rubbers, glass, wood, concrete, stone or ceramic.
5. 5. A method of any one of the claims 1-4 wherein the hypochlorite concentrate has a half life about 1.4 to 1.7 times that of a CAP produced hypochlorite under the same conditions of concentration, temperature profile, exposure to light, storage time and container material, the concentration of the hypochlorite species at any time being expressed by the rate expression d(ClO')/dt =-3K2(OCl')2; or, wherein the hypochlorite concentrate has a chlorate concentration at least 25% less than that of CAP produced hypochlorite under the same conditions of concentration, temperature profile, exposure to light, storage time and container material, the concentration of the chlorate species at any time being determined by the rate expression d(Cl03')dt = 3K2[1/(3K2t +(OCl')-1]2 K3(Cl03')[1/(3K2t+(OCl')-1]; or wherein the hypochlorite concentrate has a perchlorate concentration of at least 50% less than that of CAP produced hypochlorite under the same conditions of concentration, temperature profile, exposure to light, storage time and container material, the concentration of the perchlorate species at any time being determined by the rate expression d(Cl04')dt= K3(Cl03')(OCl').

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   Figure 1

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   Figure 2

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   Figure 6

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   Figure 7

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   Figure 8 Comparison between hypochlorite solutions made using different processes

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   Figure 9 The economics associate with drinking water chlorination