CA1156599A - Process for purifying aqueous solution of alkali metal halide for electrolysis - Google Patents
Process for purifying aqueous solution of alkali metal halide for electrolysisInfo
- Publication number
- CA1156599A CA1156599A CA000310253A CA310253A CA1156599A CA 1156599 A CA1156599 A CA 1156599A CA 000310253 A CA000310253 A CA 000310253A CA 310253 A CA310253 A CA 310253A CA 1156599 A CA1156599 A CA 1156599A
- Authority
- CA
- Canada
- Prior art keywords
- alkali metal
- aqueous solution
- solution
- metal halide
- phosphate ion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/14—Purification
- C01D3/16—Purification by precipitation or adsorption
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B15/00—Operating or servicing cells
- C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Metallurgy (AREA)
- Inorganic Chemistry (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
- Removal Of Specific Substances (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to a process for purifying an aqueous solution of an alkali metal halide containing calcium ions for electrolysis which comprises adding phosphate ion to the solution with the amount of phosphate ion exceed-ing that which is consumed in the reaction of the phosphate ion with the calcium ions, adjusting the pH of the solution to the alkaline region to precipitate at least the calcium ions in the solution, and removing the precipitate.
This process purifies the aqueous solution to a high degree of purity.
This invention relates to a process for purifying an aqueous solution of an alkali metal halide containing calcium ions for electrolysis which comprises adding phosphate ion to the solution with the amount of phosphate ion exceed-ing that which is consumed in the reaction of the phosphate ion with the calcium ions, adjusting the pH of the solution to the alkaline region to precipitate at least the calcium ions in the solution, and removing the precipitate.
This process purifies the aqueous solution to a high degree of purity.
Description
1 1 5B59~3 1 BAC~GROUND OF THE INVENTION
1. Fie~d of the Invention This invention relates to a process for purifying an aqueous solution of an alkali metal halide for electrolysis, especially suitable for electrolysis of sodium chloride using an ion exchange membrane method, to a highly purity.
1. Fie~d of the Invention This invention relates to a process for purifying an aqueous solution of an alkali metal halide for electrolysis, especially suitable for electrolysis of sodium chloride using an ion exchange membrane method, to a highly purity.
2. Description of the Prior Art In the industrial production of alaklis and halogens by electrolysis of aqueous solutions of alkali metal halides, the starting solution, such as salt water to be fed into an electrolytic cell needs to be puriied to remove impurities (especially calcium and magnesium ions) to an extent that the electrolysis operation is not affected.
The tolerances of these impurities vary depending on the type of electrolysis method used. However, the tolerances for calcium and magnesium are usually considered as follows: -Method of Electrolysis ~ :
Ion Exchange ; ~ Diaphragm Membrane 20 Impurity Mercury Method Method Method Ca (ppm) ~ 20 < 10 < 1 Mg (ppm) < 1-2 < 10 < 1 In the prior art, calcium ion is removed by a method ~ which comprises adding Na2C03 to the aqueous solution of the ;~ alkali metal halide, and adding a flocculant to settle the calcium salt. Magnesium ion is removed by the same method as above except that NaOH is added to the aqueous solution of the alkali metal halide instead of Na2C03.
However, with these conventional purifying methods, the calcium ion and magnesium ion can merely be removed to a 1 15~599 1 level of only several ppm, e.g., about 5 to 10 ppm, and it is impossible to purify the aqueous solution of the alkali metal halide to the high purity that is required for the ion exchange membrane method (i.e., a calcium ion and magnesium ion content of less than 1 ppm each). Thus, to attain such a high level of purity, the aqueous solution of the alkali metal halide must be subjected to a secondary purification procedure using, for example, a chelate resin.
This secondary purification, of course, complicates the procedure and increases the cost.
A method is also known in which in an electrolytic cell partitioned into an anode compartment and a cathode compartment employing a cation exchange membrane is used and a compound such as a phosphate salt is added to an aqueous solution of an alkali metal halide in the anode compartment to precipitate polyvalent cations on the membrane as an insoluble gel, and the electrolysis is performed while avoiding a clogging of the membrane (as disclosed in U.S. Patent 3,793,163 corresponding to Japanese Patent Application (OPI~ No. 89895/73). This ;- 20 method utilizes the reaction between hydroxyl ions and the ; polyvalent cations and is based on the phenomenon occurring near the interface of the membrane during electrolysis. Hence, the electrolysis conditions must conform to the conditions for this reaction, and control of these conditions is not easy.
Moreover, the insoluble gel must be removed occasionally, and the method has various operational difficulties. With this method, also, sufficient effects cannot be achieved if the - concentrations of impurities in the electrolyte solution are high. In such a case, the polyvalent cation level must be decreased beforehand to less than about 1 ppm.
1 15~599 1 SUM~RY OF THE INVENTION
~ ccordin~l~, an object of this invention is to provide a process for purif~ing to a high degree of purity an aqueous solution of an alkali metal halide which is particularly applicable to electrolysis of sodium chloride using an ion exchange membrane method.
The above object is achieved in accordance with this invention by a process for purifying an aqueous solution of ; an alkali metal halide for electrolysis which comprises adding phosphate ion to an aqueous solution of an alkali metal halide containing polyvalent cations including calcium ions with the amount of the phosphate ion being in excess of the amount necessary for the reaction of the phosphate ion with calcium ions, adjusting the pH of the aqueous solution of the alkali metal halide to the alkaline region using an agent other than am-monia to precipitate at least calcium ions in the aqueous solution of the alkali metal halide, and removing the precipitate.
BRIEF DESCRIPTION OF THE DR~WINGS
Figure 1 is a graph showing the relationship between - the amounts of calcium and magnesium ions remaining in the aqueQus solution of the alkali metal halide and the excess amount of the phosphate ion.
Figure 2 is a graph showing the relationship between the amounts of calcium and magnesium ions remaining in the aqueous solution of the alkali metal halide and the pH of the aqueous solution of the alkali metal halide using sodium hydroxide to adjust the pH of a sodium chloride aqueous solution.
DETAILED DESCRIPTION OF THE INVENTION
In order to remove calcium ion to a level of less than --llS~99 1 1 ppm, the excess of thc phosphate ion must be ad~ sted to at least 1~ mg~lite.r (i.e., 10 mg (as P043 )/liter, hereinafter the same), and the pH of ~he aqueous solution of the alkali metal halide is preferably adjusted to a pH of 10 or more using an agent other than ammonia to precipitate at least the calcium ions and also any polyvalent cations capable of precipitating and re~ove them.
By this method, the calcium ion in the aqueous solution of the alkali metal halide can be removed to less than 1 ppm to-gether with magnesium ion, etc. Removal of the calcium ion in accordance with this invention does not require the addition of Na2C03, and the aqueous soiution of the alkali metal hal}de can be purified to a high purity without any additional treatment such as treatment with a chelate resin. The method of this invention is fully applicable to the purification of salt water for use in the electrolysis of sodium chloride by the ion exchange mem-~rane method~
The invention is described below in greater detail and with reference to the accompanyin~ drawin~s.
Phosphoric acid or phosphoric acid salts can be used to supply the phosphate ion which reacts with the polyvalent metal ions such as calcium ions, etc. to form a difficultly soluble precipitate in order to remove the polyvalent metal ions such as calcium ions, etc. as impurities in the starting alkali metal halide at the time of purifying the aqueous solution of the alkali metal halide to form a solution for electrolysis. The reaction mechanism for the formation of the precipitate is not at present completely clear. While not desiring to be bound, we assume, how-ever, that the polyvalent cations in the aqueous solution of the alkali metal halide react with the phosphate i~ns under alkaline conditions to form very difficulty .~. .-~
s 3 ` ` 115~S9g 1 soluble salts. The compound supplying the phosphate ion used to form this precipitate can be selected ~xm free phosphoric acid such as orthophosphoric acid and metaphosphoric acid, and phosphates such as alkali metal phosphates (e.g., orthophosphates such as Na3P04, metaphosphates such as NaP03 and other phosphates, for example, pyrophosphates such as Na4P207 and triphosphates such as Na5P3010 and the corresponding potassium and lithium phosphate salts to these sodium salts).
The phosphoric acid or the salt thereof must be added in excess of the amount required to react with at least the calcium ions of the polyvalent cations present at the time of purifying the aqueous solution of the alkali metal halide.
The amount will vary depending on the pH of the aqueous solution of the alkali metal halide. In order to reduce the calcium ion level to less than 1 ppm,the excess amount of P043 must be at least 10 mgjliter as shown in Figure 1. In usual operation, the excess amount of P043 may be achieved with a concentratlon of 15 to 100 mg/liter or even higher.
Sodium hydroxide is preferred as an alkaline compound when the aqueous solution of the alkali metal halide is a sodium halide and potassium hydroxide aqueous solution is suitable as the alkaline compound when the aqueous solution of the alkali metal halide is a potassium halide aqueous solution for adjusting the pH of the aqueous solution of the alkali metal halide to the alkaline region. As shown in Figure 2, the alkaline compound is added so that the pH of the aqueous solution of the alkali metal halide is adjusted to the alkaline region e.g., greater than 7, preferably to a pH of at least 10. This results in the precipitation of magnesium ion, etc. a~
in addition to the calcium ions, and the purifying effect in 115~iS9~
1 this invention can be fully achieved. The process of this invention can be conducted at a wide range of operational temperatures and while not limiting and merely exemplary, a suitable temperature is generally about 15C to about 90C.
The precipitation is quick and a suitable time for the reaction is about 10 minutes or more, preferably more than 1 hour to ensure complete precipitation.
The calcium- and magnesium-containing precipitate resulting from the treatment described above can be easily removed by sedimentation, and then by passing the aqueous solution through a sand filter, for example. When the content of poly-valent cations such as calcium ion and magnesium ion is low, sedimentation is not required, and the precipitate may be removed by direct filtration.
The process of the present invention can be used to achieve a higher purity at a lower cost than the conventional method which involves adding Na2C03 and further purifying the precipitate using a chelate resin. Thus, the cost required to purify the salt water and remove polyvalent cations (e.g., calcium ions, magnesium ions, etc.) to a content of less than 1 ppm is less than half of that involved in the conventional method.
The following Examples are given to illustrate the present invention in more detail. Unless otherwise indicated, all parts, percents, ratios and the like are by weight.
.
A starting salt was dissolved in water at room tem-perature (25-30C) to obtain a crude aqueous solution of sodium chloride having the following composition.
115~59g 1 NaCl 300 g/liter Ca+~ 211 ppm Mg+~ 52 ppm H3PO4 was added at an initial concentration of 200 mg/liter and the pH of the aqueous solution of sodium chloride was adjusted to 11.7 with sodium hydroxide. The aqueous solution of sodium chloride was allowed to stand for 16 to 20 hours, and the amounts of the phosphate ion and calcium and magnesium ions in the supernatant liquid were analyzed. It was found that the amount . 10 of the phosphate ion consumed was 190 mg/liter, and the excess amount of the phosphate ion was 10 g/liter. The supernatant liquid had a calcium ion content of 1.2 ppm and a magnesium ion content of 0.7 ppm.
~ EXAMPLE 2 - - The procedures of Example 1 were repeated except that the initial concentration of H3PO4 was changed to 400 mg/liter and the pH of the aqueous solution of sodium chloride was , - changed to 11.6. As a result, the amount of the phosphate ion consumed was 340 mg/liter, and the excess amount of the phosphate ion was 60 mg/liter. The supernatant liquid had a calcium ion content of 0.8 ppm and a magnesium ion content of 0.5 ppm.
A starting salt was dissolved in water to o~tain a crude aqueous solution of sodium chloride having the following composition:
NaCl 298 g/iiter Ca++ 165 ppm Mg + 48 ppm pH 7.0 Temperature 29C
1 15659g 1 An aqueous solution of Na3P04 was prepared by diluting 5 ml of a 70% H3P04 aqueous solution with water to 50 ml, then adding a 5~ NaOH aqueous solution to adjust the pH of the Na3P04 aqueous solution to 12Ø
2.2 ml of the thus-prepared Na3P04 aqueous solution was added to 500 ml of the crude aqueous solution of sodium chloride and mixed. The aqueous solution of sodium chloride became opaque, and the pH of the solution was 8.1.
Further, the pH of the aqueous solution of sodium chloride was adjusted to 11.8 by adding a 2% NaOH aqueous solution with mixing. Then, 3 mg/liter of a coagulating agent (sodium acrylate) was added to the aqueous solution of sodium chloride.
After mixing for 1 minute, the aqueous solution of sodium chloride was allowed to stand for 10 minutes.
Then, the solution was decanted and the supernatant was filtered through filter paper, and it was found by analysis that the amount of calcium ion remaining was 0.4 ppm, the - amount of magnesium ion remaining was 0.2 ppm, and the amount of P043 was 181 mg/liter.
An electrolytic cell for the electrolysis of sodium chloride using an ion exchange membrane method was operated under the following electrolyte purification conditions by using a continuous sedimentation separation device and a natural flow-type sand filter.
Composition of Starting Aqueous Solution of Sodium Chloride NaCl 280 - 310 g/liter Ca++ 20 - 80 mg/liter Mg 10 - 50 mg/liter 115~599 I Solution pH 10.2 - 12.0 Excess P043 11 - 115 mg/liter Temperature 30 - 42C
The electrolysis was continued without difficulty for more than 6 months while the concentrationsof calcium ions and that of magnesium ion were maintained at less than 1 ppm, and 0.1 to 0.3 ppm, respectively, even though Na2C03, as in the prior art, was not added.
~ While the invention has been described in detail and ~ t with reference to specific embodiments thereof, it will be ;~ apparent to one skilled in the art that various changes and :~ ~ - modifications can be made therein without departing from the ~ spLrit and scope thereof.
, :
.
.
:
:
20:
~ .
~ .
. ' .
_ 9 _
The tolerances of these impurities vary depending on the type of electrolysis method used. However, the tolerances for calcium and magnesium are usually considered as follows: -Method of Electrolysis ~ :
Ion Exchange ; ~ Diaphragm Membrane 20 Impurity Mercury Method Method Method Ca (ppm) ~ 20 < 10 < 1 Mg (ppm) < 1-2 < 10 < 1 In the prior art, calcium ion is removed by a method ~ which comprises adding Na2C03 to the aqueous solution of the ;~ alkali metal halide, and adding a flocculant to settle the calcium salt. Magnesium ion is removed by the same method as above except that NaOH is added to the aqueous solution of the alkali metal halide instead of Na2C03.
However, with these conventional purifying methods, the calcium ion and magnesium ion can merely be removed to a 1 15~599 1 level of only several ppm, e.g., about 5 to 10 ppm, and it is impossible to purify the aqueous solution of the alkali metal halide to the high purity that is required for the ion exchange membrane method (i.e., a calcium ion and magnesium ion content of less than 1 ppm each). Thus, to attain such a high level of purity, the aqueous solution of the alkali metal halide must be subjected to a secondary purification procedure using, for example, a chelate resin.
This secondary purification, of course, complicates the procedure and increases the cost.
A method is also known in which in an electrolytic cell partitioned into an anode compartment and a cathode compartment employing a cation exchange membrane is used and a compound such as a phosphate salt is added to an aqueous solution of an alkali metal halide in the anode compartment to precipitate polyvalent cations on the membrane as an insoluble gel, and the electrolysis is performed while avoiding a clogging of the membrane (as disclosed in U.S. Patent 3,793,163 corresponding to Japanese Patent Application (OPI~ No. 89895/73). This ;- 20 method utilizes the reaction between hydroxyl ions and the ; polyvalent cations and is based on the phenomenon occurring near the interface of the membrane during electrolysis. Hence, the electrolysis conditions must conform to the conditions for this reaction, and control of these conditions is not easy.
Moreover, the insoluble gel must be removed occasionally, and the method has various operational difficulties. With this method, also, sufficient effects cannot be achieved if the - concentrations of impurities in the electrolyte solution are high. In such a case, the polyvalent cation level must be decreased beforehand to less than about 1 ppm.
1 15~599 1 SUM~RY OF THE INVENTION
~ ccordin~l~, an object of this invention is to provide a process for purif~ing to a high degree of purity an aqueous solution of an alkali metal halide which is particularly applicable to electrolysis of sodium chloride using an ion exchange membrane method.
The above object is achieved in accordance with this invention by a process for purifying an aqueous solution of ; an alkali metal halide for electrolysis which comprises adding phosphate ion to an aqueous solution of an alkali metal halide containing polyvalent cations including calcium ions with the amount of the phosphate ion being in excess of the amount necessary for the reaction of the phosphate ion with calcium ions, adjusting the pH of the aqueous solution of the alkali metal halide to the alkaline region using an agent other than am-monia to precipitate at least calcium ions in the aqueous solution of the alkali metal halide, and removing the precipitate.
BRIEF DESCRIPTION OF THE DR~WINGS
Figure 1 is a graph showing the relationship between - the amounts of calcium and magnesium ions remaining in the aqueQus solution of the alkali metal halide and the excess amount of the phosphate ion.
Figure 2 is a graph showing the relationship between the amounts of calcium and magnesium ions remaining in the aqueous solution of the alkali metal halide and the pH of the aqueous solution of the alkali metal halide using sodium hydroxide to adjust the pH of a sodium chloride aqueous solution.
DETAILED DESCRIPTION OF THE INVENTION
In order to remove calcium ion to a level of less than --llS~99 1 1 ppm, the excess of thc phosphate ion must be ad~ sted to at least 1~ mg~lite.r (i.e., 10 mg (as P043 )/liter, hereinafter the same), and the pH of ~he aqueous solution of the alkali metal halide is preferably adjusted to a pH of 10 or more using an agent other than ammonia to precipitate at least the calcium ions and also any polyvalent cations capable of precipitating and re~ove them.
By this method, the calcium ion in the aqueous solution of the alkali metal halide can be removed to less than 1 ppm to-gether with magnesium ion, etc. Removal of the calcium ion in accordance with this invention does not require the addition of Na2C03, and the aqueous soiution of the alkali metal hal}de can be purified to a high purity without any additional treatment such as treatment with a chelate resin. The method of this invention is fully applicable to the purification of salt water for use in the electrolysis of sodium chloride by the ion exchange mem-~rane method~
The invention is described below in greater detail and with reference to the accompanyin~ drawin~s.
Phosphoric acid or phosphoric acid salts can be used to supply the phosphate ion which reacts with the polyvalent metal ions such as calcium ions, etc. to form a difficultly soluble precipitate in order to remove the polyvalent metal ions such as calcium ions, etc. as impurities in the starting alkali metal halide at the time of purifying the aqueous solution of the alkali metal halide to form a solution for electrolysis. The reaction mechanism for the formation of the precipitate is not at present completely clear. While not desiring to be bound, we assume, how-ever, that the polyvalent cations in the aqueous solution of the alkali metal halide react with the phosphate i~ns under alkaline conditions to form very difficulty .~. .-~
s 3 ` ` 115~S9g 1 soluble salts. The compound supplying the phosphate ion used to form this precipitate can be selected ~xm free phosphoric acid such as orthophosphoric acid and metaphosphoric acid, and phosphates such as alkali metal phosphates (e.g., orthophosphates such as Na3P04, metaphosphates such as NaP03 and other phosphates, for example, pyrophosphates such as Na4P207 and triphosphates such as Na5P3010 and the corresponding potassium and lithium phosphate salts to these sodium salts).
The phosphoric acid or the salt thereof must be added in excess of the amount required to react with at least the calcium ions of the polyvalent cations present at the time of purifying the aqueous solution of the alkali metal halide.
The amount will vary depending on the pH of the aqueous solution of the alkali metal halide. In order to reduce the calcium ion level to less than 1 ppm,the excess amount of P043 must be at least 10 mgjliter as shown in Figure 1. In usual operation, the excess amount of P043 may be achieved with a concentratlon of 15 to 100 mg/liter or even higher.
Sodium hydroxide is preferred as an alkaline compound when the aqueous solution of the alkali metal halide is a sodium halide and potassium hydroxide aqueous solution is suitable as the alkaline compound when the aqueous solution of the alkali metal halide is a potassium halide aqueous solution for adjusting the pH of the aqueous solution of the alkali metal halide to the alkaline region. As shown in Figure 2, the alkaline compound is added so that the pH of the aqueous solution of the alkali metal halide is adjusted to the alkaline region e.g., greater than 7, preferably to a pH of at least 10. This results in the precipitation of magnesium ion, etc. a~
in addition to the calcium ions, and the purifying effect in 115~iS9~
1 this invention can be fully achieved. The process of this invention can be conducted at a wide range of operational temperatures and while not limiting and merely exemplary, a suitable temperature is generally about 15C to about 90C.
The precipitation is quick and a suitable time for the reaction is about 10 minutes or more, preferably more than 1 hour to ensure complete precipitation.
The calcium- and magnesium-containing precipitate resulting from the treatment described above can be easily removed by sedimentation, and then by passing the aqueous solution through a sand filter, for example. When the content of poly-valent cations such as calcium ion and magnesium ion is low, sedimentation is not required, and the precipitate may be removed by direct filtration.
The process of the present invention can be used to achieve a higher purity at a lower cost than the conventional method which involves adding Na2C03 and further purifying the precipitate using a chelate resin. Thus, the cost required to purify the salt water and remove polyvalent cations (e.g., calcium ions, magnesium ions, etc.) to a content of less than 1 ppm is less than half of that involved in the conventional method.
The following Examples are given to illustrate the present invention in more detail. Unless otherwise indicated, all parts, percents, ratios and the like are by weight.
.
A starting salt was dissolved in water at room tem-perature (25-30C) to obtain a crude aqueous solution of sodium chloride having the following composition.
115~59g 1 NaCl 300 g/liter Ca+~ 211 ppm Mg+~ 52 ppm H3PO4 was added at an initial concentration of 200 mg/liter and the pH of the aqueous solution of sodium chloride was adjusted to 11.7 with sodium hydroxide. The aqueous solution of sodium chloride was allowed to stand for 16 to 20 hours, and the amounts of the phosphate ion and calcium and magnesium ions in the supernatant liquid were analyzed. It was found that the amount . 10 of the phosphate ion consumed was 190 mg/liter, and the excess amount of the phosphate ion was 10 g/liter. The supernatant liquid had a calcium ion content of 1.2 ppm and a magnesium ion content of 0.7 ppm.
~ EXAMPLE 2 - - The procedures of Example 1 were repeated except that the initial concentration of H3PO4 was changed to 400 mg/liter and the pH of the aqueous solution of sodium chloride was , - changed to 11.6. As a result, the amount of the phosphate ion consumed was 340 mg/liter, and the excess amount of the phosphate ion was 60 mg/liter. The supernatant liquid had a calcium ion content of 0.8 ppm and a magnesium ion content of 0.5 ppm.
A starting salt was dissolved in water to o~tain a crude aqueous solution of sodium chloride having the following composition:
NaCl 298 g/iiter Ca++ 165 ppm Mg + 48 ppm pH 7.0 Temperature 29C
1 15659g 1 An aqueous solution of Na3P04 was prepared by diluting 5 ml of a 70% H3P04 aqueous solution with water to 50 ml, then adding a 5~ NaOH aqueous solution to adjust the pH of the Na3P04 aqueous solution to 12Ø
2.2 ml of the thus-prepared Na3P04 aqueous solution was added to 500 ml of the crude aqueous solution of sodium chloride and mixed. The aqueous solution of sodium chloride became opaque, and the pH of the solution was 8.1.
Further, the pH of the aqueous solution of sodium chloride was adjusted to 11.8 by adding a 2% NaOH aqueous solution with mixing. Then, 3 mg/liter of a coagulating agent (sodium acrylate) was added to the aqueous solution of sodium chloride.
After mixing for 1 minute, the aqueous solution of sodium chloride was allowed to stand for 10 minutes.
Then, the solution was decanted and the supernatant was filtered through filter paper, and it was found by analysis that the amount of calcium ion remaining was 0.4 ppm, the - amount of magnesium ion remaining was 0.2 ppm, and the amount of P043 was 181 mg/liter.
An electrolytic cell for the electrolysis of sodium chloride using an ion exchange membrane method was operated under the following electrolyte purification conditions by using a continuous sedimentation separation device and a natural flow-type sand filter.
Composition of Starting Aqueous Solution of Sodium Chloride NaCl 280 - 310 g/liter Ca++ 20 - 80 mg/liter Mg 10 - 50 mg/liter 115~599 I Solution pH 10.2 - 12.0 Excess P043 11 - 115 mg/liter Temperature 30 - 42C
The electrolysis was continued without difficulty for more than 6 months while the concentrationsof calcium ions and that of magnesium ion were maintained at less than 1 ppm, and 0.1 to 0.3 ppm, respectively, even though Na2C03, as in the prior art, was not added.
~ While the invention has been described in detail and ~ t with reference to specific embodiments thereof, it will be ;~ apparent to one skilled in the art that various changes and :~ ~ - modifications can be made therein without departing from the ~ spLrit and scope thereof.
, :
.
.
:
:
20:
~ .
~ .
. ' .
_ 9 _
Claims (5)
1. A process for purifying an aqueous solution of an alkali metal halide containing calcium ions for electrolysis which comprises adding phosphate ion to said solution with the amount of phosphate ion exceeding that which is consumed in the reaction of the phosphate ion with the calcium ions, and with the excess amount of the phosphate ion being at least 10 mg/liter, to precipitate, at a pH of at least 10 in the ab-sence of ammonia, at least the calcium ions in said solution thereby reducing the calcium ion content in said solution to less than 1 ppm and removing the precipitate.
2. The process of claim 1, wherein said solution is an aqueous solution of sodium chloride.
3. A process as claimed in claim 1 wherein the adding of the phosphate ion is accomplished by adding a compound selected from the group consisting of free phosphoric acids and alkali metal phosphates.
4. A process as claimed in claim 3, wherein said alkali metal phosphates are selected from the group consisting of alkali metal metaphosphates, alkali metal orthophosphates, alkali metal pyrophosphates and alkali metal triphosphates.
5. A process as claimed in claim 1 including a step of sufficiently increasing the pH of the solution to establish a pH of at least 10.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP121848/77 | 1977-10-13 | ||
| JP52121848A JPS6055442B2 (en) | 1977-10-13 | 1977-10-13 | Method for purifying salt water for electrolysis |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1156599A true CA1156599A (en) | 1983-11-08 |
Family
ID=14821421
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000310253A Expired CA1156599A (en) | 1977-10-13 | 1978-08-29 | Process for purifying aqueous solution of alkali metal halide for electrolysis |
Country Status (19)
| Country | Link |
|---|---|
| JP (1) | JPS6055442B2 (en) |
| AT (1) | AT358068B (en) |
| AU (1) | AU514942B2 (en) |
| BE (1) | BE869949A (en) |
| BR (1) | BR7805611A (en) |
| CA (1) | CA1156599A (en) |
| CH (1) | CH637353A5 (en) |
| DE (1) | DE2837192B2 (en) |
| DK (1) | DK369678A (en) |
| ES (1) | ES472924A1 (en) |
| FI (1) | FI64401C (en) |
| FR (1) | FR2406004A1 (en) |
| GB (1) | GB2005645B (en) |
| IT (1) | IT1106279B (en) |
| NL (1) | NL7808794A (en) |
| NO (1) | NO151541C (en) |
| NZ (1) | NZ188254A (en) |
| PT (1) | PT68489A (en) |
| SE (1) | SE429979B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103449479A (en) * | 2013-09-12 | 2013-12-18 | 山东东岳氟硅材料有限公司 | Method for reducing content of calcium and magnesium ions in primary brine |
| CN105565342A (en) * | 2015-12-16 | 2016-05-11 | 攀枝花钢企欣宇化工有限公司 | Refining agent for refining primary brine in chlorine alkali industry and application of refining agent |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8321934D0 (en) * | 1983-08-15 | 1983-09-14 | Ici Plc | Electrolytic cell module |
| ZA852131B (en) * | 1984-04-17 | 1985-11-27 | Dampier Salt Ltd | Process for producing high grade sodium chloride |
| WO2012021033A2 (en) * | 2010-08-12 | 2012-02-16 | Research Institute Of Industrial Science & Technology | Method of extracting lithium with high purity from lithium bearing solution by electrolysis |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE55976C (en) * | M. M. MONSANTO in Hoboken, New-Jersey, V. St. A | Method for purifying Soole by sodium phosphate | ||
| GB199607A (en) * | 1922-06-28 | 1923-06-28 | Johann Theodor Westermann | Process for manufacturing pure sodium chloride |
| US2433601A (en) * | 1944-01-25 | 1947-12-30 | Bay Chemical Company Inc | Preparation of purified brine |
| US2624654A (en) * | 1949-06-03 | 1953-01-06 | Diamond Alkali Co | Method of making purified brine |
| US2906599A (en) * | 1953-11-16 | 1959-09-29 | Hagan Chemicals & Controls Inc | Method of preparing sodium chloride brines of high purity |
| US2906600A (en) * | 1954-10-22 | 1959-09-29 | Hagan Chemicals & Controls Inc | Method of preparing sodium chloride brine of high purity |
| US3140915A (en) * | 1962-08-13 | 1964-07-14 | Freeport Sulphur Co | Method of inhibiting dissolution of calcium sulfate |
| US3607688A (en) * | 1969-01-17 | 1971-09-21 | Seiichi Inoue | Treating sea water with production of chlorine and fertilizer |
| BE795460A (en) * | 1972-02-16 | 1973-08-16 | Diamond Shamrock Corp | PERFECTIONS RELATING TO ELECTROLYTIC TANKS |
| FR2244708B1 (en) * | 1973-09-25 | 1977-08-12 | Ugine Kuhlmann | |
| JPS551351B2 (en) * | 1974-03-07 | 1980-01-12 | ||
| US4040919A (en) * | 1974-10-29 | 1977-08-09 | Hooker Chemicals & Plastics Corporation | Voltage reduction of membrane cell for the electrolysis of brine |
| JPS5186100A (en) * | 1975-01-25 | 1976-07-28 | Asahi Chemical Ind | ENSUINO DENKAIHOHO |
| US4038365A (en) * | 1975-12-03 | 1977-07-26 | Basf Wyandotte Corporation | Removal of low level hardness impurities from brine feed to chlorine cells |
-
1977
- 1977-10-13 JP JP52121848A patent/JPS6055442B2/en not_active Expired
-
1978
- 1978-08-18 SE SE7808775A patent/SE429979B/en not_active IP Right Cessation
- 1978-08-21 DK DK369678A patent/DK369678A/en not_active Application Discontinuation
- 1978-08-22 NO NO782853A patent/NO151541C/en unknown
- 1978-08-24 NZ NZ188254A patent/NZ188254A/en unknown
- 1978-08-24 BE BE190051A patent/BE869949A/en not_active IP Right Cessation
- 1978-08-25 GB GB7834646A patent/GB2005645B/en not_active Expired
- 1978-08-25 NL NL7808794A patent/NL7808794A/en not_active Application Discontinuation
- 1978-08-25 AU AU39280/78A patent/AU514942B2/en not_active Expired
- 1978-08-25 DE DE2837192A patent/DE2837192B2/en not_active Ceased
- 1978-08-28 AT AT623378A patent/AT358068B/en not_active IP Right Cessation
- 1978-08-28 IT IT50868/78A patent/IT1106279B/en active
- 1978-08-28 FI FI782623A patent/FI64401C/en not_active IP Right Cessation
- 1978-08-29 CA CA000310253A patent/CA1156599A/en not_active Expired
- 1978-08-29 ES ES472924A patent/ES472924A1/en not_active Expired
- 1978-08-30 FR FR7825065A patent/FR2406004A1/en active Granted
- 1978-08-30 BR BR7805611A patent/BR7805611A/en unknown
- 1978-08-30 PT PT68489A patent/PT68489A/en unknown
- 1978-08-31 CH CH916778A patent/CH637353A5/en not_active IP Right Cessation
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103449479A (en) * | 2013-09-12 | 2013-12-18 | 山东东岳氟硅材料有限公司 | Method for reducing content of calcium and magnesium ions in primary brine |
| CN105565342A (en) * | 2015-12-16 | 2016-05-11 | 攀枝花钢企欣宇化工有限公司 | Refining agent for refining primary brine in chlorine alkali industry and application of refining agent |
| CN105565342B (en) * | 2015-12-16 | 2018-02-27 | 攀枝花钢企欣宇化工有限公司 | Refining agent and its application for primary refined brine in chlorine industry |
Also Published As
| Publication number | Publication date |
|---|---|
| ATA623378A (en) | 1980-01-15 |
| DE2837192A1 (en) | 1979-04-19 |
| NO151541B (en) | 1985-01-14 |
| IT7850868A0 (en) | 1978-08-28 |
| ES472924A1 (en) | 1979-02-16 |
| CH637353A5 (en) | 1983-07-29 |
| PT68489A (en) | 1978-09-01 |
| IT1106279B (en) | 1985-11-11 |
| NL7808794A (en) | 1979-04-18 |
| DE2837192B2 (en) | 1980-10-09 |
| FI64401B (en) | 1983-07-29 |
| AT358068B (en) | 1980-08-25 |
| GB2005645A (en) | 1979-04-25 |
| FR2406004A1 (en) | 1979-05-11 |
| BE869949A (en) | 1978-12-18 |
| FI782623A (en) | 1979-04-14 |
| BR7805611A (en) | 1979-06-05 |
| GB2005645B (en) | 1982-04-07 |
| FI64401C (en) | 1983-11-10 |
| FR2406004B1 (en) | 1981-03-06 |
| JPS5456079A (en) | 1979-05-04 |
| NZ188254A (en) | 1980-11-14 |
| NO151541C (en) | 1985-05-02 |
| NO782853L (en) | 1979-04-18 |
| DK369678A (en) | 1979-04-14 |
| SE7808775L (en) | 1979-04-13 |
| JPS6055442B2 (en) | 1985-12-05 |
| SE429979B (en) | 1983-10-10 |
| AU514942B2 (en) | 1981-03-05 |
| AU3928078A (en) | 1980-02-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4028237A (en) | Method and apparatus for treatment of fluorine-containing waste waters | |
| CA1090092A (en) | Purification of aqueous sodium chloride solution | |
| US5215632A (en) | Fluoride removal from aqueous streams | |
| CN111498940B (en) | Separation treatment method of phosphorus-containing and fluorine-containing phosphogypsum washing waste liquid | |
| US5282977A (en) | Separation of heavy metals from waste water of the titanium dioxide industry | |
| US4268486A (en) | Selective chromate removal from a chlorate solution | |
| CA1156599A (en) | Process for purifying aqueous solution of alkali metal halide for electrolysis | |
| US4259297A (en) | Chromate removal from concentrated chlorate solution by chemical precipitation | |
| CA1318880C (en) | Process of producing alkali hydroxide, chlorine and hydrogen by the electrolysis of an aqueous alkali chloride solution in a membrane cell | |
| JP2005193167A (en) | Drainage purification method and purification method | |
| CN105126937A (en) | Chelate resin tower regeneration prolongation process method | |
| CN112479416A (en) | Inorganic wastewater treatment process | |
| US4830837A (en) | Process for removing aluminum from concentrated alkali metal halide brines | |
| CN115321736A (en) | Treatment method of glyphosate production wastewater and high-value recycling of phosphorus-containing waste | |
| CN112607890B (en) | Zero-discharge water treatment process for high-salt-content water containing calcium and magnesium ions | |
| US2938770A (en) | Process for the purification of alkali metal hypophosphite solutions containing alkali metal phosphites | |
| JP2775550B2 (en) | Treatment of waste nitric acid containing aluminum | |
| US4379132A (en) | Process for sodium hypophosphite | |
| US3393233A (en) | Method for recovering ethylene diamine tetraacetic acid | |
| CN114735723B (en) | Potash coarse brine refining process | |
| US4200622A (en) | Purification of ammonium fluoride solutions | |
| JP2900406B2 (en) | Treatment of phosphate-containing wastewater | |
| CN108946688A (en) | A kind of method of chlorination oxygenated organophosphorus waste water preparing phosphoric acid disodium hydrogen | |
| SU1234365A1 (en) | Method of purifying sodium chloride solutions | |
| SU431099A1 (en) | METHOD OF OBTAINING SODIUM CHLORATE |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |