Title of Invention	"A PROCESS FOR THE PREPARATION OF HIGHLY PURE MANGANESE SULPHATE ELECTROLYTE USEFUL FOR ELECTRODEPOSITION OF HIGHLY PURE ELECTROLYTIC MANGANESE DIOXIDE (HPEMD")
Abstract	The invention relates to a process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD). In the process of the present invention the manganese sulphate solution containing monovalent cations, in particular K and Na are removed as a complex, viz. jarosite, which is highly crystalline and insoluble from manganese sulphate under optimum conditions. This has been done by digesting the manganese sulphate solution containing monovalent cations with ferric sulphate, at a pH of 1.5 to 3.0, for a duration of 15 to 180 minutes. The temperature being maintained between 80 to 100°C. Bringing about precipitation with suitable addition of seeding. Allowing to cool, followed by filtration. Subsequently treating either with CaO or calcine to raise the pH. The present invention thus provides a process for the preparation of highly pure manganese sulphate electrolyte by the removal of monovalent metal ions from manganese sulphate solution, which is a precursor for the electrodeposition of highly pure electrolytic manganese dioxide (HPEMD).

Title of Invention

"A PROCESS FOR THE PREPARATION OF HIGHLY PURE MANGANESE SULPHATE ELECTROLYTE USEFUL FOR ELECTRODEPOSITION OF HIGHLY PURE ELECTROLYTIC MANGANESE DIOXIDE (HPEMD")

Abstract

The invention relates to a process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD). In the process of the present invention the manganese sulphate solution containing monovalent cations, in particular K and Na are removed as a complex, viz. jarosite, which is highly crystalline and insoluble from manganese sulphate under optimum conditions. This has been done by digesting the manganese sulphate solution containing monovalent cations with ferric sulphate, at a pH of 1.5 to 3.0, for a duration of 15 to 180 minutes. The temperature being maintained between 80 to 100°C. Bringing about precipitation with suitable addition of seeding. Allowing to cool, followed by filtration. Subsequently treating either with CaO or calcine to raise the pH. The present invention thus provides a process for the preparation of highly pure manganese sulphate electrolyte by the removal of monovalent metal ions from manganese sulphate solution, which is a precursor for the electrodeposition of highly pure electrolytic manganese dioxide (HPEMD).

Full Text	The present invention relates to a process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD). The present invention particularly relates to a process for the removal of monovalent metal ions from manganese sulphate solution, which is suitable for electrodeposition of highly pure manganese dioxide (HPEMD). Preparation of manganese sulphate electrolyte is one of the important steps for the preparation of electrolytic manganese dioxide (EMD). Electrolytic manganese dioxide (EMD) is synthetically manufactured with naturally occuring manganese ore as the starting material. It is usually carried out after suitably converting the manganese ore into soluble oxide and dissolving in sulphuric acid. As the ore contains many metallic impurities like Fe, Al and other heavy metal impurities such as Co, Cu, these are to be removed from the solution. Traditionally, the heavy metal impurities are removed by passing hydrogen sulphide under acidic pH range and then the solution is neutralized by the addition of either calcine itself or calcium hydroxide or oxide. Under this condition iron and aluminium are removed as insoluble hydroxides. The solution thus purified is subjected to electrolysis under suitable conditions employing titanium anode and graphite or lead cathode. The EMD thus obtained is used as cathode mix in dry cells. Though the electrolyte prepared in the 1st cycle contains impurities of monovalent metal ions within limits, while repeatedly using the electrolyte the concentration of the monovalent metal ions gradually increase and hence affects the quality of the EMD produced. The conventional way of handling such electrolyte is to bleed partially the same and mix with freshly prepared electrolyte so that the impurities are controlled within limits in the electrolytic cell. This causes additional work and consumption of chemical. Conventionally, zinc sulphate containing iron was freed from the latter by the addition of sodium sulphate to form a highly crystalline and insoluble sodium jarosite. This type of removal is being adopted successfully in zinc industries for well over two decades. Further it has been the practice to exclude potassium ions from manganese sulphate solution prepared from potassium bearing minerals by way of adopting any one of the following methods: 1. Extraction of monvalent salt present in the reduced oxide minerals with hot water before digesting with sulphuric acid. 2. By allowing ferric hydroxide to form which adsorb the metal ion during leaching operation 3. Oxidising ferrous to ferric and allowing time to form jarosite. Large proportion of available manganese ores contain high proportions of potassium. Electrolytic manganese dioxide (EMD) is manufactured from manganous sulphate obtained from naturally occuring manganese ores. Crystallographically EMD has to be essentially gamma phase and other phases, alpha and beta should be the bare minimum. High potassium content is, however, an obstruction in the way of getting gamma phase EMD. In US patent no. 6,527,941 titled: "High discharge capacity electrolytic manganese dioxide and methods of producing the same', the invention provides improved cathode material comprised of electrolytic manganese dioxide having high discharge capacity at high discharge rates and methods of producing such electrolytic manganese dioxide by electrolysis in an electrolytic cell. The methods are basically comprised of maintaining a heated high purity aqueous electrolyte solution comprising specific amounts of sulfuric acid and manganese sulfate in the electrolytic cell and maintaining the amounts of the sulfuric acid and manganese ion in the solution at a ratio of sulfuric acid to manganese ion greater than 2. An electric current is applied to the electrodes of the electrolytic cell whereby the anodic electrode current density is in the range of from about 2.5 to about 6 amperes per square foot and the high discharge capacity EMD produced is deposited on the anodic electrode. In patent nos. US 4,285,913, EP 0037863 and GB 2051023 there is disclosed a method of making manganous sulphate solution with low level impurity of potassium from high potassium ores comprises adding the reduced ore to spent electrolyte containing ferric ions and digesting same at pH 1-2 and temperature of 60- 90 DEG C for 1-4 hours, and if desired thereafter again adding reduced ore to the digested product till pH is raised to 4-6 before separating the MnS04 solution from the precipitated material. The drawbacks observed in the above methods are, partial removal potassium is possible and hence the solution will be containing potassium above tolerable limit. Complete removal is possible only in the case of large excess of ferric. The main object of the present invention is to provide a process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD), which obviates the drawbacks of the hitherto known prior art processes. Another object of the present invention is to provide a process for the removal of monovalent metal ions from manganese sulphate solution, which is suitable for electrodeposition of high pure manganese dioxide (HPEMD). Still another object of the present invention is to control the soluble monovalent metal ions, in particular K and Na by removing them as a complex, viz. jarosite, which is highly crystalline and insoluble from manganese sulphate under optimum conditions. Yet another object of the present invention to introduce a purification step, utilizing the complex forming property of ferric iron in precipitating jarosite leading to the removal of potassium, in between the sulphide precipitation, and iron & aluminium precipitation. In the process of the present invention the manganese sulphate solution containing monovalent cations, in particular K and Na are removed as a complex, viz. jarosite, which is highly crystalline and insoluble from manganese sulphate under optimum conditions. This has been done by digesting the manganese sulphate solution containing monovalent cations with ferric sulphate, at a pH of 1.5 to 3.0, for a duration of 15 to 180 minutes. The temperature being maintained between 80 to 100°C. Bringing about precipitation with suitable addition of seeding-jarosite (a basic hydrous sulfate of potassium and iron with a chemical formula of KFe(MI)3(OH)6(S04)2.). Allowing to cool, followed by filtration. Subsequently treating either with CaO or calcine to raise the pH. The present invention thus provides a process for the preparation of highly pure manganese sulphate electrolyte by the removal of monovalent metal ions from manganese sulphate solution, which is a precursor for the electrodeposition of highly pure electrolytic manganese dioxide (HPEMD). Accordingly, the present invention provides a process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD), which comprises; subjecting manganese sulphate solution containing monovalent cations, potassium and sodium to digestion with ferric iron at a temperature in the range of 80 to 100°C, for a period in the range of 15 to 180 minutes, at a pH in the range of 1.5 to 3.0, effecting precipitation by the addition of seeding, cooling and filtering to obtain pure manganese sulfate, optionally treating with CaO or calcine to raise the pH. In an embodiment of the present invention, the ferric iron added is in the form of ferric sulphate. In another embodiment of the present invention, the quantity of ferric iron added in the form of ferric sulphate is in the range of 1 to 6 times the weight of the monvalent metal ion. In yet another embodiment of the present invention, the quantity of ferric iron added in the form of ferric sulphate is in the range of 1 to 6 times, preferably 3 times, the weight of the monvalent metal ion such as potassium. In still another embodiment of the present invention, the reaction is carried out at a temperature between 80 and 100°C, preferably at 100°C. In still yet another embodiment of the present invention, the precipitation reaction is carried out for a period of 15 min. to 180 minutes, preferably for 60 minutes. In a further embodiment of the present invention, the precipitation is effected by addition of synthetically prepared jarosite as seeding. In a yet further embodiment of the present invention, the quantity of seed added is in the range 1 to 5 g/l, preferably 2 g/l. The novelty of the process of the present invention resides in the preparation of highly pure manganese sulphate electrolyte by the removal of monovalent metal ions from manganese sulphate solution, which is a precursor for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD). It has been possible to achieve the novelty of the present invention by the non-obvious inventive step to control the soluble monovalent metal ions, in particular K and Na by removing them as a complex, viz. jarosite, which is highly crystalline and insoluble from manganese sulphate under optimum conditions. This has been particularly achieved by the introduction of a purification step, utilizing the complex forming property of ferric iron in precipitating jarosite leading to the removal of potassium, in between the sulphide precipitation, and iron & aluminium precipitation. The process steps of the present invention are: 1. Adding ferric sulphate to the manganese sulphate solution containing monovalent cations, wherein ferric iron to the monvalent metal ion, such as potassium, is in the range of 1 to 6 times the weight of the monvalent metal ion. 2. Maintaining the reaction temperature in the range of 80 to 100°C, for a period in the range of 15 to 180 minutes. 3. Adjusting the pH in the range of 1.5 to 3.0. 4. Effecting precipitation with addition of synthetically prepared jarosite as seeding in the range 1 to 5 g/l. 5. Allowing to cool and filtering. 6. Subsequently treating either with CaO or calcine, if required, to raise the PH. The following examples are given for further illustration of the process of the present invention in actual practice. However, the examples should not be construed to limit the scope of the invention. Example 1 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 1.5. Calculated amount of ferric iron in the form of ferric sulphate, so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. It was cooled and filtered. Potassium present in the solution was analysed. 56.5% of potassium was removed. Example 2 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. It was cooled and filtered. Potassium present in the solution was analysed. 61% of potassium was removed. Example 3 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 3.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. It was cooled and filtered. Potassium present in the solution was analysed. 56% of potassium was removed. Example 4 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 200 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 56% of potassium was removed. Example 5 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 57.5% of potassium was removed. Example 6 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 600 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 57% of potassium was removed. Example 7 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 1000 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 73% of potassium was removed. Example 8 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 90°C and maintained at the same temperature for 30 min. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 32% of potassium was removed. Example 9 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.5. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 15 min. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 60% of potassium was removed. Example 10 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 1.5. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 80°C and maintained at the same temperature for 1 hr. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 22% of potassium was removed. Example 11 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 6 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 99.5% of potassium was removed. Example 12 200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amunt of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 1 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 29% of potassium was removed. The main advantages of the present invention are: 1. Provides high pure electrolyte useful for electrodeposition of high pure manganese dioxide (HPEMD). 2. Controls the soluble monovalent metal ions, in particular K and Na by removing them as a complex, viz. jarosite, which is highly crystalline and insoluble from manganese sulphate under optimum conditions. We claim: 1. A process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD), which comprises; subjecting manganese sulphate solution containing monovalent cations, potassium and sodium to digestion with ferric iron at a temperature in the range of 80 to 100°C, for a period in the range of 15 to 180 minutes, at a pH in the range of 1.5 to 3.0, effecting precipitation by the addition of seeding, cooling and filtering to obtain pure manganese sulfate, optionally treating with CaO or calcine to raise the pH. 2. A process as claimed in claim 1, wherein the ferric iron added is in the form of ferric sulphate. 3. A process as claimed in claims 1-2, wherein the quantity of ferric iron added in the form of ferric sulphate is in the range of 1 to 6 times the weight of the monvalent metal ion. 4. A process as claimed in claims 1-3, wherein the quantity of ferric iron added in the form of ferric sulphate is preferably 3 times, the weight of the monvalent metal ion such as potassium. 5. A process as claimed in claims 1-4, wherein the reaction is carried out at a temperature preferably at 100°C. 6. A process as claimed in claims 1-5, wherein the precipitation reaction is carried out for a preferable period of 60 minutes. 7. A process as claimed in claims 1-6, wherein the precipitation is effected by addition of synthetically prepared jarosite as seeding. 8. A process as claimed in claims 1-7, wherein the quantity of seed added is in the range 1 to 5 g/l, preferably 2 g/l. 9. A process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD), substantially as herein described with reference to the examples.

Full Text

The present invention relates to a process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD). The present invention particularly relates to a process for the removal of monovalent metal ions from manganese sulphate solution, which is suitable for electrodeposition of highly pure manganese dioxide (HPEMD).
Preparation of manganese sulphate electrolyte is one of the important steps for the preparation of electrolytic manganese dioxide (EMD). Electrolytic manganese dioxide (EMD) is synthetically manufactured with naturally occuring manganese ore as the starting material. It is usually carried out after suitably converting the manganese ore into soluble oxide and dissolving in sulphuric acid. As the ore contains many metallic impurities like Fe, Al and other heavy metal impurities such as Co, Cu, these are to be removed from the solution.
Traditionally, the heavy metal impurities are removed by passing hydrogen sulphide under acidic pH range and then the solution is neutralized by the addition of either calcine itself or calcium hydroxide or oxide. Under this condition iron and aluminium are removed as insoluble hydroxides.
The solution thus purified is subjected to electrolysis under suitable conditions employing titanium anode and graphite or lead cathode. The EMD thus obtained is used as cathode mix in dry cells. Though the electrolyte prepared in the 1st cycle contains impurities of monovalent metal ions within limits, while repeatedly using the electrolyte the concentration of the monovalent metal ions gradually increase and hence affects the quality of the EMD produced. The conventional way of handling such electrolyte is to bleed partially the same and mix with freshly prepared electrolyte so that the impurities are controlled within limits in the electrolytic cell. This causes additional work and consumption of chemical.
Conventionally, zinc sulphate containing iron was freed from the latter by the addition of sodium sulphate to form a highly crystalline and insoluble sodium jarosite. This type of removal is being adopted successfully in zinc industries for well over two decades.
Further it has been the practice to exclude potassium ions from manganese sulphate solution prepared from potassium bearing minerals by way of adopting any one of the following methods:
1. Extraction of monvalent salt present in the reduced oxide minerals with hot
water before digesting with sulphuric acid.
2. By allowing ferric hydroxide to form which adsorb the metal ion during
leaching operation
3. Oxidising ferrous to ferric and allowing time to form jarosite.
Large proportion of available manganese ores contain high proportions of potassium. Electrolytic manganese dioxide (EMD) is manufactured from manganous sulphate obtained from naturally occuring manganese ores. Crystallographically EMD has to be essentially gamma phase and other phases, alpha and beta should be the bare minimum. High potassium content is, however, an obstruction in the way of getting gamma phase EMD.
In US patent no. 6,527,941 titled: "High discharge capacity electrolytic manganese dioxide and methods of producing the same', the invention provides improved cathode material comprised of electrolytic manganese dioxide having high discharge capacity at high discharge rates and methods of producing such electrolytic manganese dioxide by electrolysis in an electrolytic cell. The methods are basically comprised of maintaining a heated high purity aqueous electrolyte
solution comprising specific amounts of sulfuric acid and manganese sulfate in the electrolytic cell and maintaining the amounts of the sulfuric acid and manganese ion in the solution at a ratio of sulfuric acid to manganese ion greater than 2. An electric current is applied to the electrodes of the electrolytic cell whereby the anodic electrode current density is in the range of from about 2.5 to about 6 amperes per square foot and the high discharge capacity EMD produced is deposited on the anodic electrode.
In patent nos. US 4,285,913, EP 0037863 and GB 2051023 there is disclosed a method of making manganous sulphate solution with low level impurity of potassium from high potassium ores comprises adding the reduced ore to spent electrolyte containing ferric ions and digesting same at pH 1-2 and temperature of 60- 90 DEG C for 1-4 hours, and if desired thereafter again adding reduced ore to the digested product till pH is raised to 4-6 before separating the MnS04 solution from the precipitated material.
The drawbacks observed in the above methods are, partial removal potassium is possible and hence the solution will be containing potassium above tolerable limit. Complete removal is possible only in the case of large excess of ferric.
The main object of the present invention is to provide a process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD), which obviates the drawbacks of the hitherto known prior art processes.
Another object of the present invention is to provide a process for the removal of monovalent metal ions from manganese sulphate solution, which is suitable for electrodeposition of high pure manganese dioxide (HPEMD). Still another object of the present invention is to control the soluble monovalent metal ions, in particular K and Na by removing them as a complex, viz. jarosite, which is highly crystalline and insoluble from manganese sulphate under optimum conditions.
Yet another object of the present invention to introduce a purification step, utilizing the complex forming property of ferric iron in precipitating jarosite leading to the removal of potassium, in between the sulphide precipitation, and iron & aluminium precipitation.
In the process of the present invention the manganese sulphate solution containing monovalent cations, in particular K and Na are removed as a complex, viz. jarosite, which is highly crystalline and insoluble from manganese sulphate under optimum conditions. This has been done by digesting the manganese sulphate solution containing monovalent cations with ferric sulphate, at a pH of 1.5 to 3.0, for a duration of 15 to 180 minutes. The temperature being maintained between 80 to 100°C. Bringing about precipitation with suitable addition of seeding-jarosite (a basic hydrous sulfate of potassium and iron with a chemical formula of KFe(MI)3(OH)6(S04)2.). Allowing to cool, followed by filtration. Subsequently treating either with CaO or calcine to raise the pH. The present invention thus provides a process for the preparation of highly pure manganese sulphate electrolyte by the removal of monovalent metal ions from manganese sulphate solution, which is a precursor for the electrodeposition of highly pure electrolytic manganese dioxide (HPEMD).
Accordingly, the present invention provides a process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD), which comprises; subjecting manganese sulphate solution containing monovalent cations, potassium and sodium to digestion with ferric iron at a temperature in the range of 80 to 100°C, for a period in the range of 15 to 180 minutes, at a pH in the range of 1.5 to 3.0,

effecting precipitation by the addition of seeding, cooling and filtering to obtain pure manganese sulfate, optionally treating with CaO or calcine to raise the pH. In an embodiment of the present invention, the ferric iron added is in the form of ferric sulphate.
In another embodiment of the present invention, the quantity of ferric iron added in the form of ferric sulphate is in the range of 1 to 6 times the weight of the monvalent metal ion.
In yet another embodiment of the present invention, the quantity of ferric iron added in the form of ferric sulphate is in the range of 1 to 6 times, preferably 3 times, the weight of the monvalent metal ion such as potassium.
In still another embodiment of the present invention, the reaction is carried out at a temperature between 80 and 100°C, preferably at 100°C.
In still yet another embodiment of the present invention, the precipitation reaction is carried out for a period of 15 min. to 180 minutes, preferably for 60 minutes.
In a further embodiment of the present invention, the precipitation is effected by addition of synthetically prepared jarosite as seeding.
In a yet further embodiment of the present invention, the quantity of seed added is in the range 1 to 5 g/l, preferably 2 g/l.
The novelty of the process of the present invention resides in the preparation of highly pure manganese sulphate electrolyte by the removal of monovalent metal ions from manganese sulphate solution, which is a precursor for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD).
It has been possible to achieve the novelty of the present invention by the non-obvious inventive step to control the soluble monovalent metal ions, in particular K and Na by removing them as a complex, viz. jarosite, which is highly crystalline
and insoluble from manganese sulphate under optimum conditions. This has been particularly achieved by the introduction of a purification step, utilizing the complex forming property of ferric iron in precipitating jarosite leading to the removal of potassium, in between the sulphide precipitation, and iron & aluminium precipitation.
The process steps of the present invention are:
1. Adding ferric sulphate to the manganese sulphate solution containing
monovalent cations, wherein ferric iron to the monvalent metal ion, such
as potassium, is in the range of 1 to 6 times the weight of the monvalent
metal ion.
2. Maintaining the reaction temperature in the range of 80 to 100°C, for a
period in the range of 15 to 180 minutes.
3. Adjusting the pH in the range of 1.5 to 3.0.
4. Effecting precipitation with addition of synthetically prepared jarosite as
seeding in the range 1 to 5 g/l.
5. Allowing to cool and filtering.
6. Subsequently treating either with CaO or calcine, if required, to raise the
PH.
The following examples are given for further illustration of the process of the present invention in actual practice. However, the examples should not be construed to limit the scope of the invention.
Example 1
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 1.5. Calculated amount of ferric iron in the form of ferric sulphate, so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. It was cooled and filtered. Potassium present in the solution was analysed. 56.5% of potassium was removed.
Example 2
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. It was cooled and filtered. Potassium present in the solution was analysed. 61% of potassium was removed.
Example 3
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 3.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. It was cooled and filtered.
Potassium present in the solution was analysed. 56% of potassium was removed.
Example 4
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 200 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 56% of potassium was removed.
Example 5
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 57.5% of potassium was removed.
Example 6
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and
maintained at the same temperature for 1 hr. 600 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 57% of potassium was removed.
Example 7
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 1000 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 73% of potassium was removed.
Example 8
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 90°C and maintained at the same temperature for 30 min. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 32% of potassium was removed.
Example 9
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted
to 2.5. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 100°C and maintained at the same temperature for 15 min. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 60% of potassium was removed.
Example 10
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 1.5. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 3 was added, the solution was heated to 80°C and maintained at the same temperature for 1 hr. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 22% of potassium was removed.
Example 11
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amount of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 6 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 99.5% of potassium was removed.
Example 12
200 mg of potassium in the form of AR potassium sulphate was dissolved in 200 ml of pure AR manganese sulphate solution. The pH of the solution was adjusted to 2.0. Calculated amunt of ferric iron in the form of ferric sulphate so as to have ferric to potassium ratio = 1 was added, the solution was heated to 100°C and maintained at the same temperature for 1 hr. 400 mg of synthetically prepared jarosite was added as seed during precipitation. It was cooled and filtered. Potassium present in the solution was analysed. 29% of potassium was removed.
The main advantages of the present invention are:
1. Provides high pure electrolyte useful for electrodeposition of high pure
manganese dioxide (HPEMD).
2. Controls the soluble monovalent metal ions, in particular K and Na by
removing them as a complex, viz. jarosite, which is highly crystalline and
insoluble from manganese sulphate under optimum conditions.

We claim:
1. A process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD), which comprises; subjecting manganese sulphate solution containing monovalent cations, potassium and sodium to digestion with ferric iron at a temperature in the range of 80 to 100°C, for a period in the range of 15 to 180 minutes, at a pH in the range of 1.5 to 3.0, effecting precipitation by the addition of seeding, cooling and filtering to obtain pure manganese sulfate, optionally treating with CaO or calcine to raise the pH.
2. A process as claimed in claim 1, wherein the ferric iron added is in the form of ferric sulphate.
3. A process as claimed in claims 1-2, wherein the quantity of ferric iron added in the form of ferric sulphate is in the range of 1 to 6 times the weight of the monvalent metal ion.
4. A process as claimed in claims 1-3, wherein the quantity of ferric iron added in the form of ferric sulphate is preferably 3 times, the weight of the monvalent metal ion such as potassium.
5. A process as claimed in claims 1-4, wherein the reaction is carried out at a temperature preferably at 100°C.
6. A process as claimed in claims 1-5, wherein the precipitation reaction is carried out for a preferable period of 60 minutes.
7. A process as claimed in claims 1-6, wherein the precipitation is effected by addition of synthetically prepared jarosite as seeding.
8. A process as claimed in claims 1-7, wherein the quantity of seed added is in the range 1 to 5 g/l, preferably 2 g/l.
9. A process for the preparation of highly pure manganese sulphate electrolyte useful for electrodeposition of highly pure electrolytic manganese dioxide (HPEMD), substantially as herein described with reference to the examples.

Documents:

1186-DEL-2003-Abstract-(31-08-2010).pdf

1186-del-2003-abstract.pdf

1186-DEL-2003-Claims-(31-08-2010).pdf

1186-del-2003-claims.pdf

1186-DEL-2003-Correspondence-Others-(31-08-2010).pdf

1186-del-2003-correspondence-others.pdf

1186-del-2003-correspondence-po.pdf

1186-DEL-2003-Description (Complete)-(31-08-2010).pdf

1186-del-2003-description (complete).pdf

1186-del-2003-form-1.pdf

1186-del-2003-form-18.pdf

1186-del-2003-form-2.pdf

1186-DEL-2003-Form-3-(31-08-2010).pdf

1186-del-2003-form-3.pdf

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Patent Number

243686

Indian Patent Application Number

1186/DEL/2003

PG Journal Number

45/2010

Publication Date

05-Nov-2010

Grant Date

29-Oct-2010

Date of Filing

19-Sep-2003

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001. INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	J. PRABHAKAR RETHINARAJ	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, TAMIL NADU, INDIA
2	S. KULANDAISAMY	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, TAMIL NADU, INDIA
3	K.V. VENKATESHARAN	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, TAMIL NADU, INDIA

PCT International Classification Number

N/A

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA