COMPOSITION FOR PRODUCING CHLORINE DIOXIDE, AND A METHOD FOR PRODUCING THE CHLORINE DIOXIDE AT A HIGH pH

Abstract

In one embodiment, the present invention relates to a composition for producing chlorine dioxide at a high pH. In another embodiment, the present invention relates to a method for producing chlorine dioxide at a high pH. In yet another embodiment, the present invention relates to use of the chlorine dioxide prepared as per the present invention.

Description

[0001] Title of the invention:

[0002] Composition for producing chlorine dioxide, and a method for producing the chlorine dioxide at a high pH.

[0003] Technical Field of the Invention:

[0004] Firstly, the present invention is not for the purpose of defence.

[0005] The present invention relates to a composition for producing chlorine dioxide, and a method for producing the chlorine dioxide at high pH.

[0006] Background of the invention:

[0007] Chlorine dioxide exists as a yellow-colored gas at room temperature (RT) and is sparingly soluble in water. It has wide application in use as biocide, disinfectant, textiles bleaching, etc. It is advantageous over other biocides such as bleach due to its ability to selectively oxidize microbes. Generally, the chlorine dioxide has been generated in situ in water by reaction of chlorite with HC1 acid (re Reaction scheme 1-1); or chlorate with oxalic acid in which the chlorate is reduced to CIO2.

[0008] It has also been generated using a chlorite (for example, sodium chlorite (NaCICh), and a hypochlorite (for example, sodium hypochlorite (NaOCT)) and an acid (for example, hydrochloric acid (HC1) (re Reaction scheme 1-2) giving similar results as ‘chlorite + acid’ route.

[0009] Reaction schemes-I:

[0010] Reaction scheme I- 1: 5NaC102+ 4HC1 4C1O2+ 5NaCl + 2H2O

[0011] Reaction scheme 1-2: 2NaC102+ NaOCl + 2HC1 2C1O2+ 3NaCl + H2O

[0012] However, generation of chlorine dioxide (C1O2) by the above-mentioned routes have a drawback because on addition of the acid, pH drops down below 7 pH, generally it drops down to 6 pH, or even down to 5 pH.

[0013] Furthermore, if the above-discussed composition comprising acid is to be transported, then there exists a risk of chlorine dioxide gas escaping from its mother solution which may lead to an explosion hazard.

[0014] Furthermore, this may result in depletion of active content of the C1O2which is detrimental to biocide activity, hence undesirable. To overcome the above-discussed industrial problems, the inventors had developed various compositions comprising the combination of the following ingredients which have been found to produce CIO2 without drop of pH below 7 pH, however, it has been found that such compositions as mentioned herein below either do not produce the CIO2 consistently, or CIO2 gets generated (produced) instantly, or CIO2 does not start getting generated (produced) after interval of about 4 hrs or more upon mixing or allowing to react the ingredients of the below-listed compositions, or the generation (production) of CIO2 does not continue until about 2 days to about 3 days. Furthermore, it has been found that the amount of the CIO2 produced by the below-discussed compositions is generally low, hence, the economics of the industrial process are not satisfactory:

[0015] Reaction schemes-II:

[0016] Reaction scheme II- 1: NaOCl and MgCh.6H2O;

[0017] Reaction scheme II-2: NaCICh, NaOCl and NaCl;

[0018] Reaction scheme II-3: NaC102, NaOCl and CaCh.2H2O;

[0019] Reaction scheme II-4: NaC102, NaOCl and MgCh.6H2O;

[0020] Reaction scheme II-5: NaC102, and Citric Acid;

[0021] Reaction scheme II-6: NaC102, MgCh.6H2O and Citric Acid;

[0022] Reaction scheme II-7: NaC102, NaOCl, MgCh.6H2O, and Citric Acid.

[0023] Need of the invention:

[0024] Therefore, there is still a need to develop an improved composition for producing chlorine dioxide (CIO2) on mixing or allowing to react its ingredients, or an improved composition for in- situ production of chlorine dioxide (CIO2), and a method for producing chlorine dioxide (CIO2) upon mixing or allowing to react its ingredients, and a method for in-situ production of chlorine dioxide (CIO2) upon mixing one ingredient of the composition in a media which already contains a second ingredient thereof, and a method of use of the composition for producing chlorine dioxide (CIO2), wherein the pH does not drop below 7 pH, and at the same time the CIO2 is produced consistently, and the CIO2 does not get generated (produced) instantly, but the CIO2 starts getting generated (produced) after interval of about 4 hrs or more upon mixing or allowing to react the ingredients of the compositions, and the generation (production) of CIO2 continues until about 2 days to about 3 days, or more, and the amount of the CIO2 produced is also high, hence, the economics of the industrial process are satisfactory, hence the above-discussed drawbacks are avoided.

[0025] Problem to be solved by the Invention:

[0026] Accordingly, the present invention aims to solve the above-discussed industrial problems by providing an improved composition for producing chlorine dioxide (CIO2), and an improved composition for in-situ production of chlorine dioxide (CIO2), and a method for producing the chlorine dioxide (CIO2), and a method for in-situ production of chlorine dioxide (CIO2), and a method of use of the composition for producing chlorine dioxide (CIO2), wherein the pH does not drop below 7 pH, hence the associated problems thereof, such as discussed herein above, including a risk of chlorine dioxide (CIO2) gas getting escape from its mother solution; an explosion hazard; depletion of active content of the CIO2 are avoided, and at the same time the economics of the industrial process are satisfied.

[0027] Description and Preferred Embodiments of the Invention:

[0028] As discussed herein, the Inventors have observed that the presently available compositions comprising acid including citric acid, and the compositions developed by the Inventors comprising NaOCl as one of the ingredients, and methods for producing chlorine dioxide (CIO2) from such compositions primarily suffer from the problem of the pH getting drop below 5 pH. Furthermore, as discussed herein, the Inventors have also observed that the compositions and the methods for producing chlorine dioxide (CIO2) developed earlier do not suffer from the problem of the pH getting drop below 7 pH, however, as discussed herein above, the economics of such compositions and the corresponding methods are not satisfactory.

[0029] To overcome the above-discussed industrial problems, the Inventors have found that if a chlorite selected from the group: sodium chlorite (NaCICh), potassium chlorite (KCIO2), calcium chlorite (Ca(C102)2) is combined with a magnesium (Mg) salt or a hydrate thereof, but without NaOCl and / or without an acid including the HC1 or citric acid, then the chlorine dioxide (CIO2), surprisingly and unexpectedly, get produced not only without drop of the pH below 7 pH, but also with substantially improved economics as the amount of the CIO2 produced is substantially improved, and production of the CIO2 is consistent, and it starts getting generated (produced) after about 4 to about 6 hrs of mixing the chlorite and the Mg salt, wherein the Mg salt may be added voluntarily or may be already present in the media, such as in sea-water, industrial brine, and production of the CIO2 continues until about 2 days to about 3 days. Accordingly, in first embodiment, the present invention relates to a composition for producing chlorine dioxide (CIO2), wherein the composition comprises:

[0030] (a) a chlorite essentially combined with a magnesium (Mg) salt.

[0031] Accordingly, in second embodiment, the present invention relates to a composition for in- situ production of chlorine dioxide (CIO2), wherein the composition comprises:

[0032] (a) a chlorite essentially combined (or mixed) with a medium containing magnesium (Mg) salt.

[0033] Accordingly, in third embodiment, the present invention relates to a method for producing chlorine dioxide (CIO2), wherein the method comprises a step of using the composition of the present invention to produce the chlorine dioxide (CIO2), wherein the composition comprises:

[0034] (a) a chlorite essentially combined with a magnesium (Mg) salt.

[0035] Accordingly, in fourth embodiment, the present invention relates to a method for in-situ production of chlorine dioxide (CIO2), wherein the method comprises a step of adding chlorite in a medium containing magnesium (Mg) salt for treating the medium with the chlorine dioxide (CIO2) so produced.

[0036] Accordingly, in fifth embodiment, the present invention relates to a method for treating or disinfecting a medium containing magnesium (Mg) salt, wherein the method comprises: a). a step of adding one or more chlorites in the medium containing magnesium (Mg) salt; wherein the medium containing magnesium (Mg) salt includes brine, industrial brine, and sea water.

[0037] Accordingly, in sixth embodiment, the present invention relates to a method of using one or more chlorites for treating or disinfecting a medium containing magnesium (Mg) salt, wherein the method comprises: a). a step of adding one or more chlorites in the medium containing magnesium (Mg) salt; wherein the medium containing magnesium (Mg) salt includes brine, industrial brine, and sea water.

[0038] As discussed herein above, the Inventors have found that when the presently provided composition essentially consists of a combination of: a chlorite, and a magnesium salt, which are mixed or allowed to react after dissolving in water, hence when the presently provided composition does not comprise: a) NaOCl; b) NaCl; c) CaCh; d) CaCl2.2H2O; e) Citric Acid; f) acid including HC1; and / or g) additional ingredient including water absorbing ingredient capable of releasing or slow releasing of water; then the presently provided composition, surprisingly and unexpectedly, produces CIO2 with the following technical advantages:

[0039] (1). with substantially improved economics as the amount of the CIO2 produced is substantially improved, and production of CIO2 is consistent, it releases after about 4 hrs to about 6 hrs of mixing the chlorite and the Mg salt, or allowing to react the chlorite and the Mg salt, and production of the CIO2 continues until about 2 days to about 3 days; and

[0040] (2). without dropping the pH of the reaction mixture of the chlorite and the Mg salt below 7 pH.

[0041] Therefore, in accordance with a preferred embodiment, the present invention relates to a composition for producing chlorine dioxide (CIO2), wherein the composition consists of:

[0042] (a) a chlorite essentially combined with a magnesium (Mg) salt.

[0043] Therefore, in accordance with another preferred embodiment, the present invention relates to a composition for in-situ production of chlorine dioxide (CIO2), wherein the composition consists of:

[0044] (a) a chlorite essentially combined with a medium containing magnesium (Mg) salt.

[0045] Therefore, in accordance with still another preferred embodiment, the present invention relates to a method for producing chlorine dioxide (CIO2), wherein the method comprises a step of using the composition of the present invention to produce the chlorine dioxide (CIO2), wherein the composition consists of: (a) a chlorite essentially combined with a magnesium (Mg) salt.

[0046] Therefore, in accordance with yet another preferred embodiment, the present invention relates to a method for in-situ production of chlorine dioxide (CIO2), wherein the method comprises a step of adding chlorite in a medium containing magnesium (Mg) salt for in-situ production of the chlorine dioxide (CIO2) and for in-situ treatment of the medium with the chlorine dioxide (CIO2) produced in-situ, wherein the method is performed without isolation of the chlorine dioxide (CIO2).

[0047] In accordance with a preferred embodiment of the present invention, the medium containing magnesium (Mg) salt includes brine, industrial brine, and sea water.

[0048] In accordance with a preferred embodiment of the present invention, the chlorite is selected from the group consisting of: sodium chlorite (NaCICh), potassium chlorite (KCIO2), calcium chlorite (Ca(C102)2). Preferably, the chlorite is sodium chlorite (NaCICh).

[0049] In accordance with a preferred embodiment of the present invention, the Mg salt includes magnesium chloride (MgCh), preferably the Mg salt includes hydrate of the Mg salt having a chemical formula MgCh.bFhO.

[0050] In accordance with one of the embodiments the present invention, the chlorite and the magnesium salt are mixed after separately dissolving in water (H2O), and the method comprises a step of mixing the chlorite and the magnesium salt after dissolving the chlorite in water (H2O), and separately after dissolving the magnesium salt in water (H2O).

[0051] In accordance with one of the embodiments the present invention, the amount of the chlorite may vary from about 1 ppm to about 1 ,00,000 ppm, preferably from about 1 ppm to about 75,000 ppm, more preferably from about 1 ppm to about 50,000 ppm, even more preferably from about 1 ppm to about 25,000 ppm, still more preferably from about 1 ppm to about 15,000 ppm.

[0052] In accordance with one of the embodiments the present invention, the amount of the chlorite may vary from about 0.1% w / w to about 30% w / w with respect to total composition, preferably from about 0.5% w / w to about 25% w / w with respect to total composition, more preferably from about 0.5% w / w to about 20% w / w with respect to total composition, even more preferably from about 0.5% w / w to about 15% w / w with respect to total composition. It may be noted that the scope of the present invention is not intended to be limited by the amount of the chlorite, because it would vary with volume of water, industrial water, brine, industrial brine, or sea water to be treated.

[0053] In accordance with one of the embodiments the present invention, the amount of the Mg salt may vary from about 1 ppm to about 3,00,000 ppm, preferably from about 1 ppm to about 2,25,000 ppm, more preferably from about 1 ppm to about 1,50,000 ppm, even more preferably from about 1 ppm to about 75,000 ppm, still more preferably from about 1 ppm to about 45,000 ppm. It may be noted that the scope of the present invention is not intended to be limited by the amount of the Mg salt, because it would vary with volume of the water, or the industrial water to be treated.

[0054] In accordance with one of the embodiments the present invention, the amount of the Mg salt may vary from about 0.1% w / w to about 60% w / w with respect to total composition, preferably from about 0.5% w / w to about 50% w / w with respect to total composition, more preferably from about 0.5% w / w to about 40% w / w with respect to total composition, even more preferably from about 0.5% w / w to about 30% w / w with respect to total composition

[0055] It may be noted that the scope of the present invention is not intended to be limited by the amount of the Mg salt, because it would vary with volume of water, industrial water, brine, industrial brine, or sea water to be treated.

[0056] Therefore, in accordance with one of the embodiments of the present invention, the presently provided composition does not comprise an acid including HC1 or citric acid.

[0057] Therefore, in accordance with one of the embodiments of the present invention, the presently provided composition is capable of producing the chlorine dioxide (CIO2) without drop of pH below 7 pH.

[0058] In accordance with one of the embodiments of the present invention, the presently provided composition is not only capable of producing the chlorine dioxide (CIO2) without drop of pH below 7 pH, but at the same time is also capable of producing the chlorine dioxide (CIO2) in substantially improved amount hence with improved economics.

[0059] In accordance with one of the embodiments of the present invention, the said step of adding the magnesium (Mg) salt does not comprise addition of an acid including HC1 or citric acid. In accordance with one of the embodiments of the present invention, the said method is not only capable of producing the chlorine dioxide (CIO2) without drop of pH below 7 pH, but at the same time is also capable of producing the chlorine dioxide (CIO2) in substantially improved amount hence with improved economics.

[0060] Accordingly, the present invention relates to an in-situ method of producing the chlorine dioxide (CIO2) at a pH of about 7 or more, preferably at a pH of about 7 to about 11.

[0061] In accordance with one of the embodiments of the present invention, the magnesium (Mg) salt and the chlorite are combined and allowed to react in an aqueous medium.

[0062] Without being bound by the theory, the mechanism of producing the CIO2 with improved stability on combining the chlorite with the magnesium (Mg) salt is believed to involve increase of the pH on account of generation of free proton at pH of more than about 7.

[0063] Accordingly, the presently provided composition for producing the CIO2 and the method for producing the CIO2 has following technical advantages

[0064] 1. Overcomes the existing problem of depletion of CIO2;

[0065] 2. Overcomes the existing problem of explosive hazard due to escape of CIO2 at a pH lower than 5.

[0066] In accordance with one of the preferred embodiments of the present invention, the CIO2 produced can be maintained even at a lowered active content of the CIO2.

[0067] In accordance with one of the preferred embodiments of the present invention, the presently provided method of producing CIO2 is capable of enhanced loading of the chlorite at a pH higher than7 pH, thereby having a technical advantage of resulting in increased capacity of the CIO2 production in the media, including aqueous media, water, industrial water, brine, industrial brine, and sea water.

[0068] In accordance with one of the preferred embodiments of the present invention, the presently provided method of producing CIO2 is capable of producing the CIO2 even having lowered active content of the CIO2 which in-turn has a technical advantage of allowing for a lowering of associated process safety risks.

[0069] In accordance with one of the embodiments of the present invention, the contents of the CIO2 produced may be measured or estimated by any method known in the art, including the iodometric titration analysis, hence, the scope of the present invention is not intended to be limited by a method of estimating or measuring contents of the CIO2 produced.

[0070] The present invention is now described with the help of the accompanying examples, which are not intended to limit scope of the present invention.

[0071] Examples of the Invention:

[0072] Compositions for producing chlorine dioxide:

[0073] The following comparative compositions and the present invention composition were used in the present experiments:

[0074] Example 1 (blank experiment):

[0075] The pH of the water used in the present experiments was measured and was found to be about 6.99 pH confirming that the water used was neutral.

[0076] Examples 2 and 3 (comparative experiment):

[0077] When only NaCICh was taken individually in water (H2O), then no amount of chlorine dioxide (CIO2) was produced confirming that the selected chlorite per se, that is, NaCICh per se is incapable of producing chlorine dioxide (CIO2).

[0078] Examples 4, 5 and 6 (comparative experiment):

[0079] When only MgCh.6H2O per se was taken individually in water (H2O), then no amount of chlorine dioxide (CIO2) was produced confirming that the selected Mg salt per se, that is, MgCh.6H2O per se is also incapable of producing chlorine dioxide (CIO2).

[0080] Examples 7 (present invention):

[0081] A weighed amount of NaCICh (about 4g) in aqueous medium (about 400mL of demineralized (DM) water (H2O)) so as to have about 1% w / w aqueous solution of NaCICh at room temperature (RT) is combined with weighed amount of MgCh.6H2O (about 5g) so as to have about 1.25% w / w aqueous solution of MgCh.6H2O with respect to (w.r.t.) H2O (or about 1.22% w / w aqueous solution of MgCh.6H2O with respect to (w.r.t.) total composition). The pH of the resulted composition of the aqueous solution of the NaCICh and the MgCh.6H2O was found to be about 9.89 pH. The active content of chlorine dioxide (CIO2) was found to be 50 ppm as measured by iodometric titration analysis. Example 8 (present invention):

[0082] A weighed amount of NaCICh (about 0.2g) in aqueous medium (about 200mL of demineralized (DM) water (H2O)) so as to have about 0.1% w / w aqueous solution of NaCICh at room temperature (RT) is combined with weighed amount of MgCh.bthO (about 60 gm) so as to have about 30% w / w aqueous solution of MgCh.bFhO with respect to (w.r.t.) H2O (or about 23.06% w / w aqueous solution of MgCh.6H2O with respect to (w.r.t.) total composition). The resulted aqueous solution is clear and has a slight yellow tinge. The pH of the resulted composition of the aqueous solution of the NaCICh and the MgCh.6H2O was found to be about 7.71 pH, and the active content of the chlorine dioxide (CIO2) was found to be 59 ppm as measured by iodometric titration analysis.

[0083] Example 9 (present experiment):

[0084] A weighed amount of NaCICh (about 1g) in aqueous medium (about lOOmL of demineralized (DM) water (H2O)) so as to have about 1% w / w aqueous solution of NaCICh at room temperature (RT) is combined with weighed amount of MgCh.6H2O (about 30 gm) so as to have about 30% w / w aqueous solution of MgCh.6H2O with respect to (w.r.t.) H2O (or about 22.90% w / w aqueous solution of MgCh.6H2O with respect to (w.r.t.) total composition). The resulted aqueous solution is clear and has a pale yellow colour. The pH of the resulted composition of the aqueous solution of the NaCICh and the MgCh.6H2O was found to be about 7.49 pH, and the active content of the chlorine dioxide (CIO2) was found to be 135 ppm as measured by iodometric titration analysis.

[0085] Example 10 (present invention):

[0086] A weighed amount of NaCICh (about 5g) in aqueous medium (about lOOmL of demineralized (DM) water (H2O)) so as to have about 5% w / w aqueous solution of NaCICh at room temperature (RT) is combined with weighed amount of MgCh.6H2O (about 5.6 gm) so as to have about 5.6% w / w aqueous solution of MgCh.6H2O with respect to (w.r.t.) H2O (or about 5.06% w / w aqueous solution of MgCh.6H2O with respect to (w.r.t.) total composition). The resulted aqueous solution is slightly hazy and has a pale yellow colour. On storing the solution at RT, colour becomes yellow within 2 days. The pH of the resulted composition of the aqueous solution of the NaC102 and of the MgCh.6H2O was found to be about 8.39 pH, and the active content of the chlorine dioxide (CIO2) produced was found to be 740 ppm as measured by iodometric titration analysis. Example 11 (present invention):

[0087] A weighed amount of NaCICh (about 5g) in aqueous medium (about lOOmL of demineralized (DM) water (H2O)) so as to have about 5% w / w aqueous solution of NaCICh at room temperature (RT) is combined with weighed amount of MgCh.bthO (about 30 gm) so as to have about 30% w / w aqueous solution of MgCh.bFhO with respect to (w.r.t.) H2O (or about 22.22% w / w aqueous solution of MgCh.bFhO with respect to (w.r.t.) total composition). The resulted aqueous solution is slightly hazy and has a pale yellow colour. On storing the solution at RT, colour becomes yellow within 2 days. The pH of the resulted composition of the aqueous solution of the NaC102 and the MgCh.6H2O was found to be about 8.11 pH, and the active content of the chlorine dioxide (CIO2) was found to be 1160 ppm as measured by iodometric titration analysis.

[0088] Method for producing chlorine dioxide:

[0089] The above-said comparative composition and the present invention compositions were used in the present experiments to produce the chlorine dioxide (CIO2) as follows:

[0090] The DM water was taken in a glass beaker of capacity of about IL (or 2L), the weight amount of the NaCICh was added in the beaker under stirring at room temperature. The resulted reaction mixture (mother solution) was stirred on a magnetic stirrer for about 5 min until a homogeneous solution is obtained followed by stepwise addition of weight amount of the magnesium chloride hexahydrate (MgCh.6H2O), over a period of about 45 minutes, and the pH is evaluated at different intervals. On complete addition of the MgCh.6H2O, the pH is measured, and the content of the active chlorine dioxide (CIO2) is measured by iodometric titration analysis after about 48 hrs to about 72 hrs from start of the reaction.

[0091] For the method of in-situ production of CIO2, and treatment (disinfection) of brine, industrial brine, and sea water by the in-situ produced CIO2, the inventors have conducted the experiments and found the treatment of the brine by the in-situ method a successful method without isolation of the CIO2. As in this method, the CIO2 was not isolated, hence, the active contents of the CIO2 were not estimated.

[0092] The results of the present experiments may be summarized in the following Table - 1. Table 1: Active content of CIO2 as measured by iodometric titration analysis for various compositions:

[0093] As can be observed from the foregoing examples and results thereof presented in Table - I, the presently provided composition of the Experiment Nos. 7, 8, 9, 10, and 11 demonstrate surprising and unexpected technical advantages of the additive composition comprising a combination of: the selected chlorite: NaCICh essentially combined with the selected magnesium (Mg) salt: MgCk.bfEO over the other comparative compositions at a pH of more than 7 pH, and active content of chlorine dioxide (CIO2) is also obtained over a wider range.

[0094] Therefore, the synergistic effect of the presently provided composition for production of chlorine dioxide (CIO2) and the method for producing the chlorine dioxide (CIO2), and method of using the present invention to produce the chlorine dioxide (CIO2) at a pH of more than 7 pH have been demonstrated.

Claims

CLAIMS:

1. A composition for producing chlorine dioxide (CIO2), wherein the composition consists of: (a) a chlorite essentially combined with a magnesium (Mg) salt.

2. A composition for in-situ production of chlorine dioxide (CIO2), wherein the composition consists of:(a) a chlorite essentially added to a medium containing magnesium (Mg) salt.

3. A method for producing chlorine dioxide (CIO2), wherein the method comprises a step of using the composition as claimed in Claim 1 to produce the chlorine dioxide (CIO2), wherein the composition consists of:(a) a chlorite essentially combined with a magnesium (Mg) salt.

4. A method for in-situ production of chlorine dioxide (CIO2), wherein the method comprises a step of adding chlorite in a medium containing magnesium (Mg) salt for in-situ production of the chlorine dioxide (CIO2) and for in-situ treatment of the medium with the chlorine dioxide (CIO2) produced in-situ, wherein the method is performed without isolation of the chlorine dioxide (CIO2).

5. A method for treating or disinfecting a medium containing magnesium (Mg) salt, wherein the method comprises: a). a step of adding one or more chlorites in the medium containing magnesium (Mg) salt.

6. A method of using chlorite for treating or disinfecting a medium containing magnesium (Mg) salt, wherein the method comprises: a). a step of adding one or more chlorites in the medium containing magnesium (Mg) salt.

7. The composition as claimed in claim 1 or 2, and the method as claimed in any one of the preceding claims 3 to 6, wherein the composition does not comprise: a) NaOCl; b) NaCl; c) CaCl2; d) CaCl2.2H2O; e) Citric Acid; f) acid including HC1; andg) additional ingredient including water absorbing ingredient capable of releasing or slow releasing of water.

8. The composition as claimed in claim 2, and the method as claimed in any one of the preceding claims 4 to 6, wherein the medium containing magnesium (Mg) salt includes brine, industrial brine, and sea water.

9. The composition as claimed in claim 1 or 2, and the method as claimed in any one of the preceding claims 3 to 6, wherein the chlorite is selected from the group consisting of: sodium chlorite (NaCICh), potassium chlorite (KCIO2), calcium chlorite (Ca(C102)2), preferably the chlorite is sodium chlorite (NaCICh).

10. The composition as claimed in claim 1 or 2, and the method as claimed in any one of the preceding claims 3 to 6, wherein the Mg salt includes magnesium chloride (MgCh), preferably hydrate of the Mg salt having a chemical formula MgCh.bFhO.

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