NZ776421A - Methods and uses for hypochlorite concentrates - Google Patents

Abstract

The present invention relates to methods of sanitising and/or disinfecting a water source, which may be a potable water source or a body of water such as a pool or spa. The present invention also 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. he main sanitisation /disinfectant material contemplated is an aqueous hypochlorite solution, prepared initially as a hypochlorite concentrate.

Description

The present ion relates to methods of sanitising and/or ecting a water source, which may be a potable water source or a body of water such as a pool or spa. The present invention also 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.

NZ 776421 METHODS AND USES FOR HYPOCHLORITE CONCENTRATES Field The present invention s to methods of sanitising and/or disinfecting a water source, which may be a potable water source or a body of water such as a pool or spa. The present invention also relates to s of e sanitization, which may be a biological or non-biological surface. The main sation /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 ble 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.

Drinking water disinfecting has traditionally been achieved using chlorination via liquefied ne gas delivered in bulk, drums, or cylinders. Transporting and handling large volumes of liquefied ne gas is an g safety issue, and to solve this problem water treatment plants have been transitioning to using bulk CAP aqueous sodium hypochlorite (12.5 % w/w).

Hypochlorites are very effective, cheap sanitizers which provide a valuable ection 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 ed 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 s, in , can produce the most stable aqueous hypochlorite with the resultant lowest disproportionation rate to te and perchlorate. The disadvantages of the HSLS process are:- 1.1 The ntial OPEX and CAPEX required. 1.2 The need to locate the process adjacent to a ne plant or alternatively to continue transporting liquefied chlorine gas in bulk, drums or ers 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 portionate to a mixture of chloride, oxygen, chlorates and perchlorates: 2 ClO- → 2 Cl- + O2 3 ClO- → 2 Cl- + ClO-3 OCl- +ClO32- → ClO4- + Cl- Recently, as a result of improved analytical capability, orates 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 ination 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 µg/L HAL Perchlorate: 15 µg/L Whilst the limit set by the World Health Organization is 70 µg/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 t 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 lorite which is made by the Chlor Alkali Process (CAP) shown by on (I) Cl2 + 2NaOH = NaOCl + NaCl + H2O (CAP) (I) Another method for aqueous hypochlorite preparation is by salt metathesis reactions such as:- Ca(OCl)2 + Na2CO3 = 2NaOCl + CaCO3 (II) )2 + Na2SO4 = 2NaOCl + CaSO4 (III) Although the ation 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 sed (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 sed, 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 cture of solid calcium lorite 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:- 2Cl2 + 2Ca(OH)2 = CaCl2 + Ca(OCl)2 + 2H2O (V) Both processes are widely used, gh 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 c lined steel drums.

The disproportionation reaction of solid hypochlorite by a hydration reaction is rmic and in the case of concentrated solid hypochlorites, such as LiOCl and Ca(OCl)2, can lead to ous 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 ort 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, m hypochlorite depending on its strength, degree of hydration and t concentrations.

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 esis 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(OCl)2 2 Reducing the available chlorine level in the product 3 Adding non hydrated ts to the product 4 Coating the product with hydroscopic materials ingly, there is an urgent need to improve upon the current practices for both domestic and commercial ations of hypochlorites.

Summary The present disclosure is predicated on the discovery that bodies of water can be more efficiently sanitised and/or disinfected with aqueous hypochlorite concentrates differentiated from previously used concentrates by low level salt impurities. In particular, and without being bound by theory, the inventors have fied methods of using aqueous hypochlorite concentrates of Li, K, or Na differentiated by low levels of salt ties. These hypochlorite concentrates exhibit superior stabilities and generate less Chlorates and Perchlorates than hypochlorite concentrates made by the conventional CAP process, and are similar to and in some cases superior to hypochlorite concentrates produced by the more ive and capital ive HSLS process. The above applications also extend to the use of said concentrates in sanitising surfaces.

In particular, when you make hypochlorite by the CAP and the HSLS process, the reaction forms an equimolar quantity of NaCl and NaOCl. The formed NaCl which is highly soluble and though somewhat ult to remove, is easily avoided by using the esis process as highlighted in the present invention. For instance, in the HSLS process, the methods currently adopted uses refrigeration and fugation to remove the NaCl which adds an extra burden in on to CAPEX and OPEX. In contrast, the residue CaSO4 or CaCO3 uct from the hypochlorite produced in the present invention can be d by simple filtration processes. The inventors have realised that these reactions already produce products having very low solubility anyway and so as a result the concentrate can be produced with very pure hypochlorite (ie with very low levels of e salt impurities) compared with a CAP or HSLS product.

The present methods described herein have been found to have the following advantageous properties: 1 Lower Chlorates and Perchlorates make metathesized based hypochlorites safer to use for pools and spas (hot tubs). 2 Lower Chlorates and Perchlorates are also an advantage for drinking water chlorination fecting). Chlorination using the metathesis process described herein is also the cheapest method for drinking water ent. (see Table 3). 3 Hypochlorites made via the present metathesis process have better high temperature stability than other comparable hypochlorites, making them especially suitable for use in spas (hot tubs). 4 Since metathesis hypochlorites are more stable than conventional hypochlorites, they have or time based efficacy.

Potassium and sodium based metathesized hypochlorites containing exceedingly low c levels (which is only added to the hypochlorite as a stability booster) are environmentally ly spa sanitisers. [High c concentrations in conventional hypochlorites presents a disadvantage to their use in spas (hot tubs) because of corrosion to spa (hot tub) surfaces.]. 6 Lower Chlorates and Perchlorates levels in metathesised hypochlorites make them more suitable for sanitising biological surfaces like fruit and vegetables. 7 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 tration of the chlorate and/or perchlorate by-products which are reduced to a previously un-achievable minimal level.

Accordingly, in one aspect the present invention es a method for sanitizing a body of water (including pools and spas) 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, n the method includes the step of administering said concentrate to the body of water to provide an available chlorine level in the treated water of between 1 and 20 ppm (w/v), and wherein the hypochlorite is produced via Metathesis reaction.

In a r second aspect the ion also provides a method for disinfecting a potable water source using an aqueous hypochlorite concentrate of K or Na, wherein the concentrate is characterized with a low level of salt impurities defined by a ual” ionic strength of between 0.2 and 1.7 gram moles per litre of concentrate, wherein the method es the step of administering said concentrate to the potable water source to provide an available chlorine level in the treated water of between 0.1 and 10 ppm (w/v), and wherein the hypochlorite is produced via Metathesis on.

In one aspect the ion 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 f, 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 zing 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 ng said concentrate, or a d on 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 esis reaction to produce the lorite trate as used herein is characterised with a high available chlorine content of from 65-80%, preferably about 70%, 71%, 72%, 73%, 74%, 75%, or about 76%.

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 lorite solution produced from a reaction of calcium hypochlorite produced by reacting m chloride and sodium hypochlorite (sodium process, reaction IV).

In one embodiment the surface is a ological surface selected from selected from stainless steel and other ferrous alloys, copper and its alloys, nickel and its , 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 NaOCl 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 ion 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 rates a comparison of ation of sodium hypochlorite solutions at 52 ˚C.

Figure 7 illustrates a comparison of commercial and lithium hypochlorite ons of the present invention, compared with simulation results of a high th 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 , the present invention is predicated on the discovery that aqueous hypochlorite trates of Li, K, or Na made by the metathesis reaction are produced with low levels of salt ties. As concentrates they are then mixed further with water, (i.e, required dilution) and such resultant lorites 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 based on aqueous trates which allow for a new way to disinfect a portable water source or sanitize a pool or spa, or a e.

Advantageously, the metathesis process can allow for the preparation of fresh hypochlorites y 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 on and starting chlorate concentration, but will always be less than CAP hypochlorite and, in some instances, HSLS hypochlorites because of the age 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 al 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 e 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 ered a new family of extremely stable aqueous hypochlorite ts made by a salt metathesis process.

In an aspect, the present invention provides a family of extremely stable aqueous hypochlorite products ing Na, K, and Li which have a al 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 al ionic strengths (or calculating from experimental measurements).

Furthermore, for the first time, it was found that al ionic th was a quantitative method of defining a family of hypochlorite products that are markedly different (greater stability) to standard CAP lorite which has a residual ionic strength greater than about 1.7 M.

Residual ionic strength (RI) is first d.

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 and Salt Metathesis) 4 Impurities, e.g. NaCl, CaCl2, LiCl salts etc.

An important ter influencing the stability of an aqueous hypochlorite is its ionic strength. The Total Ionic strength for s alkali metal hypochlorites is expressed as IT =1/2∑mizi2 = ½(m1z12 + m2z22 +.......+ mnzn2) where (V1) n = total number of different ionic species in solution m = molal tration, in this case molar. z = Charge on the ion of specific species i IT = Ionic Strength as defined by G.N. Lewis ine earth hypochlorites require a different expression for ionic strength to reflect complex multivalent ionic interactions.) e the Total Ionic strength represented by on VI es the concentrations of the anion and cation of the hypochlorite s, 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 ual 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 ional CAP lorite.

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, d by their exceedingly low residual ionic strengths, which contributes to improved stability and the associated lowest rate of disproportionation into chlorates and orates.

(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 m, aqueous hypochlorite concentrates of the present invention are produced from a esis on. 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 ty. 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 1.5 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, NaOCl and KOCl, is their very low residual ionic concentrations. Residual Ionic trations as low as about 0.2 gm mole/litre, can be obtained by judicious choice of reactants and their levels of contaminant impurities.

Hypochlorites made by using Ca(OCl)2 (Ca) which has been made by the calcium process, ( reaction (V)) are more stable than ts 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 ne.

Impurities Sodium Process Calcium Process Solubility % w/w on (IV) %w/w equation (V) (g/100g in H2O at °C) ble 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(ClO3)2 0 1 (maximum) (soluble) H2O 10 (max) 4 (max) MgCO3 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 m process is due to a smaller quantity of CaCl2 in the t 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 ingly 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. ageously, 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 trate has a tration of greater than % w/w, greater than 10 % w/w, r 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, te, perchlorate and O2 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 ments, 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 ed by the reaction of calcium de 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 ed from carbonate, onate or a mixture thereof; and wherein the hypochlorite concentrate is produced via a metathesis reaction.

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

In another aspect, the present s 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 lorite concentrate and a able 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 CO32-, SO42-, PO43-, , H2PO4-, OH-, SO32-, HSO4-, HSO3- and S2O32-.

It will be appreciated the method described herein provides pool or water sanitisation by applying the concentrate.

In certain ments the body of water is treated with the concentrate to provide an ble 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 producing a zed pool or spa (i.e., body of water) the present invention plates using aqueous hypochlorites of Li, K or Na, and preferably Li.

In certain embodiments the potable water source 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. For producing a ected potable water source the present invention only contemplates using aqueous hypochlorites of K or Na.

In another aspect, the present invention provides a method for preparing an aqueous hypochlorite trate (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 certain ments 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 ng said concentrate, or a d solution thereof, to said non-biological surface to provide an available ne level on said surface of n 10 and 10000 ppm (w/v), and wherein the hypochlorite is produced via Metathesis on.

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 tration 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 trate (to be used in the surface sanitising methods described herein), including mixing an alkali metal salt y 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 % 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 ment, the soluble alkali is t in an amount of about 0.1 g/L to about 0.5 g/L. In other embodiments, the tration 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 e alkali acts to further stabilise the hypochlorite solution.

In r embodiment, the process further comprises a step of adding an alkaline buffer to the sodium hypochlorite, wherein the alkaline buffer is selected from ate, onate 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 lorite 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 ments, 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 0.1g/l to about 0.5 g/l. In other embodiments, the concentration is of about 0.1g/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 ate/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 ife is at least 1.7 time greater than that of CAP hypochlorites.

In other embodiments, the metathesized hypochlorite solution 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 ed from CO32-, SO42-, PO43-, HPO42-, H2PO4-, OH-, SO32-, HSO4-, HSO3- and .

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

The nce 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 tion 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 Li2SO4 + Ca(OCl)2 → 2LiOCl + CaSO4 A solution of Ca(OCl)2 was prepared using HY-CLOR Super-Shock ar 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 , steel, four blade, anchor style, 120 mm diameter, agitator at 305 rpm for 0.5 hours. 38.7 g of h AR grade Li2SO4 was slowly added to the previously prepared unfiltered Ca(OCl)2 solution with nt ng for a period of 1 hour. The mixture was then filtered using a Buchner funnel under vacuum h a polypropylene cloth filter.

The LiOCl solution was clean and bright and had an available ne 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 Li2SO4. The reaction ially goes to completion in stoichiometric quantities.

Ionic strength of solution = 1.6503, pH=11 Example 2 2(LiOH.H2O) + Ca(OCl)2 = 2LiOCl + Ca(OH)2 +2H2O 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.H2O was slowly added to the previously prepared unfiltered )2 solution with constant ng for a period of 3 hour. The e 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.H2O. The reaction essentially goes to completion in stoichiometric quantities.

Ionic strength of on = 1.5978, pH=12 Example 3 K2SO4 + Ca(OCl)2 → 2KOCl + CaSO4 A solution of Ca(OCl)2 was ed using HY-CLOR Super-Shock ar 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, ethane coated, steel, four blade, anchor style, 120 mm diameter, agitator at 320 rpm for 0.5 hours. 61.4 g of Merck AR grade K2SO4 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 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 ties.

Example 4 K2CO3 + )2 → 2KOCl + CaCO3 As in example 1, 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 led 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 er, agitator at 305 rpm for 0.5 hours. 48.6 g of Mallinckrodt AR grade K2CO3 (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 opylene 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 ity and it was necessary to add a small quantity of KOH to the product to impart ity.

After g 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 CaCO3 was determined to be 34.8 g. Yield is 98.8 % based on CaCO3. 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(OCl)2 was prepared using R 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(OCl)2 solution with constant stirring for a period of 1 hour. The mixture was then filtered using a Buchner funnel under vacuum h 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 ius 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 ially goes to completion in iometric quantities.

Example 6 Use of LiOCl from Example 2 for Spa Sanitising.

A fibreglass spa of 1300 litres was emptied, rinsed and filled with fresh Melbourne water. 180 mls of LiOCl concentrate from Example 2 which ned 110 g/litre of available chlorine was added to the Spa and the temperature set to 25 deg C.

The available chlorine was measured before heat was applied and a reading of 14 mg/litre of available chlorine was determined. (Shock Treatment) The Spa was left for two days to reach equilibrium and the temperature was measured at 26 deg C. The available chlorine at this time read 0.5 mg/litre.

The Spa was then dosed with 22 mls of LiOCl concentrate and the available chlorine measured 2 mg/litre.

Two days later, the Spa having not been used, the temperature was at 25 deg C and the ble chlorine analysed at 1.5 mg/litre.

The Spa displayed excellent ature control and the LiOCl displayed excellent ity.

Example 7 Use of KOCl from Example 3 for potable water disinfection.

In this example we will disinfect a 20,000 litre tank of rne rain water.

The tank filled with rain water is constructed of polyethylene. The tank fittings are also made of PVC or hylene.

A petrol driven Honda ‘trash” pump is connected to allow the tank to be recycled using a layflat discharge hose and a wire reinforced spiral wound suction hose, both being of c construction. 970 mls of KOCl from Example 3, containing 123.4 g/litre of available chlorine were added to the rain water tank.

The tank water was recirculated by using the Honda pump which ran for 3 hours.

A sample of rain water taken from the tank, analysed and found to contain 5 mg/litre of available ne. This is an appropriate level of available chlorine to achieve potable water disinfection.

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 trated c to approximately 1.5% (w/v) and heat to 80 deg C. Circulate hot caustic solution for 15 minutes and return to feed tank ing 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 s. 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 ant 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 ue 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 is of a typical plant operation using CAP and Metathesised NaOCl are compared below based on the authors simulation package.

Assumptions:- Typically NaOCl (125 gpl ble 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 te concentration is 1 gpl.

Analysis at 0 days old Source of Hypo Temp Total Ionic OCl’ ClO3’ ClO4’ Deg C Conc Conc Conc Conc g moles/l gpl gpl gpl CAP NaOCl 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’ ClO3’ ClO4’ Deg C Conc Conc Conc Conc g moles/l gpl gpl gpl CAP NaOCl 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 ial contamination, of the fruit juice, with these degradation products which are harmful to human health.

Claims (10)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for sanitizing a body of water (including pools and spas) 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 ual” ionic strength of between 0.2 and 1.7 gram moles per litre of concentrate, wherein the method es the step of administering said concentrate to the body of water to provide an available chlorine level in the treated water of between 1 and 20 ppm (w/v), and wherein the lorite is produced via Metathesis reaction.

2. A method for disinfecting a potable water source using an aqueous hypochlorite concentrate of 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 administering said concentrate to the potable water source to provide an available chlorine level in the treated water of between 0.1 and 10 ppm (w/v), and wherein the hypochlorite is produced via Metathesis reaction.

3. A method of claim 1 or claim 2 wherein the hypochlorite trate contains between 2 and 150 g/l of ble chlorine.

4. A method of anyone of claims 1 and 3 wherein the aqueous hypochlorite trate is a Li hypochlorite concentrate.

5. A method of any one of the claims 1-4 wherein the lorite 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 OCl’)2 ; or n 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(ClO3’)dt = 3K2[1/(3K2t +(OCl’)-1]2-K3(ClO3’)[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 e, exposure to light, storage time and ner material, the concentration of the perchlorate species at any time being determined by the rate expression d(ClO4’)dt = K3(ClO3’)(OCl’).

6. 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 n 10 and 10000 ppm (w/v), and wherein the lorite is produced via Metathesis reaction.

7. A method of claim 6 n the hypochlorite concentrate contains between 2 and 150 g/l of available chlorine, and the aqueous hypochlorite concentrate is a Na or K hypochlorite trate.

8. A method of claims 6 to 7 wherein it includes the step of ng the K or Na concentrate, or d 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 n the lorite is produced via Metathesis reaction.

9. A method of anyone of claims 6 to 8 wherein the surface is a non-biological surface is selected from stainless steel and other s 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.

10. A method of any one of the claims 6 to 9 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, ature profile, exposure to light, storage time and container material, the tration 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, re to light, storage time and container material, the concentration of the chlorate species at any time being determined by the rate expression ’)dt = 3K2[1/(3K2t +(OCl’)-1]2- K3(ClO3’)[1/(3K2t+(OCl’)-1]; or wherein the hypochlorite trate has a perchlorate tration 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(ClO4’)dt = K3(ClO3’)(OCl’). -