A method for preparing calcium bromide and calcium bromate using electrodialysis

Abstract

This invention relates to a method for preparing calcium bromide and calcium bromate using electrodialysis. The method includes: reacting an alkaline bromine extraction absorbent with a calcium chloride solution using metathesis electrodialysis to obtain an overflow enriched with calcium bromide and calcium bromate; evaporating and crystallizing the overflow to obtain a mixed salt containing calcium bromide and calcium bromate; leaching the mixed salt with a leaching agent and performing solid-liquid separation to obtain calcium bromate and a calcium bromide-containing filtrate; distilling the obtained calcium bromide filtrate to obtain a distillate and calcium bromide; and recycling the distillate for the leaching process. The method provided by this invention achieves the simultaneous preparation of calcium bromide and calcium bromate using metathesis electrodialysis, and uses the alkaline bromine extraction absorbent as a raw material, reducing the preparation cost of calcium bromide. Furthermore, the raw materials and products are prepared in different compartments, overcoming the shortcomings of traditional methods that require complex separation and purification. This method has the advantages of an environmentally friendly synthesis process, high conversion rate, short synthesis route, high product purity, and low energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of calcium bromide preparation technology, and relates to a method for simultaneously preparing calcium bromide and calcium bromate, particularly a method for preparing calcium bromide and calcium bromate using electrodialysis. Background Technology

[0002] Calcium bromide, as a high-value bromide, has important applications in pharmaceutical synthesis and drilling engineering. In particular, it is widely used as a highly efficient mercury removal agent in mercury removal processes, and its demand is increasing with the increasing requirements for mercury emissions from coal-fired plants.

[0003] Traditional methods for preparing calcium bromide include direct extraction, ferrous bromide method, liquid ammonia method, urea reduction method, lime slurry method, and marble method. The ferrous bromide method is suitable for areas rich in bromine resources but not for underground brine with a bromine content as high as 200-300 mg / kg. Currently, the most commonly used methods for calcium bromide preparation in industrial production are the ferrous bromide method and the liquid ammonia method. The ferrous bromide method has a product conversion rate as low as 66.7%, and produces a lot of iron filings and oil pollution, resulting in high processing costs. The liquid ammonia method can achieve a conversion rate of up to 86%, but requires an excess of liquid ammonia. Furthermore, there are significant vaporization losses during production, leading to high storage costs and difficulties. The urea reduction method is simply an improvement on the liquid ammonia method, replacing liquid ammonia with urea. The lime slurry method and the marble method both use hydrobromic acid with a concentration not exceeding 40 wt% during synthesis, which suffers from high energy consumption during evaporation and concentration, and the quality of the hydrobromic acid directly affects the quality of the calcium bromide product. Additionally, the marble method is limited by raw material availability, making it difficult to meet quality requirements. Therefore, the lime slurry method and the marble method are not commonly used.

[0004] CN101618888A discloses a process in which a quantitative calcium bromide solution is first added, followed by quicklime, and hydrobromic acid is added dropwise until the reaction is complete. Then, slaked lime is added, and hydrobromic acid is added dropwise until the reaction is complete. CN101391748A discloses a method for preparing calcium bromide liquid using hydrobromic acid, a byproduct of bromine deep processing. CN106115761A discloses a method for preparing calcium bromide solution using waste hydrobromic acid, which has high production efficiency and low cost compared to the traditional lime slurry method. However, the hydrobromic acid requires pretreatment to remove organic matter and other impurities before use, making the process cumbersome. CN114031101A discloses a method for preparing calcium bromide using bromine-containing brine as raw material, employing a three-stage method with lime slurry to absorb bromine, resulting in high raw material utilization, but the process is lengthy. Furthermore, all of the above-mentioned existing technologies suffer from the problem of mixing of raw materials and products during the reaction process, leading to long purification processes and high costs, and failing to achieve efficient and environmentally friendly preparation of calcium bromide. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a highly efficient and environmentally friendly method for preparing calcium bromide and calcium bromate using electrodialysis, avoiding the mixing of products and raw materials during the preparation process. This method utilizes metathesis electrodialysis to achieve the simultaneous preparation of calcium bromide and calcium bromate, and uses alkaline bromine extraction absorbent as a raw material, reducing the preparation cost of calcium bromide. Furthermore, the raw materials and products are prepared in separate compartments, overcoming the drawbacks of traditional methods that require complex separation and purification. This method offers advantages such as an environmentally friendly synthesis process, high conversion rate, short synthesis route, high product purity, and low energy consumption.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing calcium bromide and calcium bromate using electrodialysis, the method comprising the following steps:

[0008] (1) The alkaline bromine extraction absorbent was reacted with calcium chloride solution by metathesis electrodialysis to obtain an overflow liquid enriched with calcium bromide and calcium bromate.

[0009] (2) The overflow obtained in the evaporation and crystallization step (1) yields a mixed salt containing calcium bromide and calcium bromate; the mixed salt is leached and separated into solid and liquid by using a leaching agent to obtain calcium bromate and calcium bromide-containing filtrate.

[0010] (3) The calcium bromide filtrate obtained in step (2) is distilled until all the solid precipitates out, and distillate and calcium bromide are obtained. The distillate is reused for the leaching in step (2).

[0011] One of the raw materials used in the method provided by this invention is an alkaline bromine extraction absorbent, which is the solution obtained after alkali absorption during the alkaline bromine extraction process in seawater, after the chemical removal of carbonate and bicarbonate ions. This invention uses the alkaline bromine extraction absorbent as a raw material for preparing calcium bromide, thus reducing the preparation cost of calcium bromide. Furthermore, this invention employs a metathesis electrodialysis-based method to prepare calcium bromide and calcium bromate, which has the advantages of an environmentally friendly synthesis process, high conversion rate, short synthesis route, high product purity, and low energy consumption. In other words, by selecting specific calcium bromide preparation raw materials and using metathesis electrodialysis, this invention significantly reduces the energy consumption for preparing calcium bromide solutions. The product solution prepared by electrodialysis has a low content of impurity ions, a shorter subsequent purification process, and high product purity.

[0012] Preferably, the alkaline bromine extraction absorbent in step (1) comprises 0.7-0.9 mol / L sodium bromide and 0.14-0.18 mol / L sodium bromate.

[0013] In the alkaline bromine extraction absorption solution described in step (1) of this invention, the concentration of sodium bromide is 0.7-0.9 mol / L, for example, it can be 0.7 mol / L, 0.8 mol / L or 0.9 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] In the alkaline bromine extraction absorption solution described in step (1) of this invention, the concentration of sodium bromate is 0.14-0.18 mol / L, for example, it can be 0.14 mol / L, 0.15 mol / L or 0.18 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the concentration of the calcium chloride solution in step (1) is 0.5-1.1 mol / L, for example, it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 1 mol / L or 1.1 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.5-0.7 mol / L.

[0016] Preferably, the concentration of calcium bromide in the overflow obtained in step (1) is 0.9-1.3 mol / L and the concentration of calcium bromate is 0.1-0.3 mol / L.

[0017] In step (1) of this invention, the concentration of calcium bromide in the overflow liquid is 0.9-1.3 mol / L, for example, it can be 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L or 1.3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In step (1) of this invention, the concentration of calcium bromate in the overflow liquid is 0.1-0.3 mol / L, for example, it can be 0.1 mol / L, 0.12 mol / L, 0.15 mol / L, 0.2 mol / L or 0.3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the evaporation and crystallization temperature in step (2) is 90-100℃, for example, it can be 90℃, 92℃, 95℃, 98℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] This invention does not specify the time for evaporation and crystallization, as long as the solid phase is completely precipitated.

[0021] Preferably, the leaching agent in step (2) includes any one or a combination of at least two of methanol, ethanol, ethylene glycol or isopropanol. Typical but non-limiting combinations include combinations of methanol and ethanol, ethanol and ethylene glycol, ethylene glycol and isopropanol, methanol, ethanol and ethylene glycol, ethanol, ethylene glycol and isopropanol, or methanol, ethanol, ethylene glycol and isopropanol.

[0022] Preferably, the solid-liquid mass ratio of the leaching in step (2) is 3:1-4.5:1, for example, it can be 3:1, 3.5:1, 4:1 or 4.5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the immersion temperature in step (2) is 30-50°C, for example, it can be 30°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the soaking time in step (2) is 6 hours or more, for example, 6 hours, 8 hours, 9 hours, 10 hours or 12 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] For example, the solid-liquid separation method in step (2) of the present invention includes pressure filtration; the filter cake obtained by pressure filtration is washed to obtain calcium bromate; the solute composition of the filtrate obtained by pressure filtration is more than 98.5 wt% calcium bromide and the remainder calcium bromate.

[0026] Preferably, the metathesis electrodialysis in step (1) is performed in a metathesis electrodialysis apparatus;

[0027] The metathesis electrodialysis device includes an electrode chamber, a first raw material chamber, a first product chamber, a second raw material chamber, a second product chamber, and at least one set of electrodialysis membrane stack assembly;

[0028] The electrodialysis membrane stack assembly includes a cathode plate, a first cation membrane, a first anion membrane, a second cation membrane, a second anion membrane, a third cation membrane, and an anode plate stacked sequentially.

[0029] The electrode liquid in the electrode liquid chamber circulates through the region between the cathode plate and the first cation membrane, and the region between the third cation membrane and the anode plate; the first raw material liquid in the first raw material chamber circulates through the region between the first cation membrane and the first anion membrane; the first product liquid in the first product chamber circulates through the region between the first anion membrane and the second cation membrane; the second raw material liquid in the second raw material chamber circulates through the region between the second cation membrane and the second anion membrane; and the second product liquid in the second product chamber circulates through the region between the second anion membrane and the third cation membrane.

[0030] This invention does not impose a specific limit on the number of electrodialysis membrane stacks in the metathesis electrodialysis apparatus. A higher number of electrodialysis membrane stacks results in a greater calcium bromide production, but also increases the volume of the metathesis electrodialysis apparatus. Those skilled in the art can select an appropriate number of electrodialysis membrane stacks by considering both production output and actual production conditions.

[0031] The first, second, and third cation exchange membranes are each independently a cation exchange membrane, allowing cations in the solution to pass through while retaining anions; the first and second anion exchange membranes are each independently anion exchange membranes, allowing anions in the solution to pass through while retaining cations. For example, in the metathesis electrodialysis device of the present invention, the areas of the first, second, and third cation exchange membranes, the first and second anion exchange membranes, and the second anion exchange membrane are each independently 200-250 cm². 2 For example, it could be 200cm 2 215cm 2 225cm 2 240cm 2 Or 250cm 2 However, this does not limit the listed values; any other unlisted values ​​within the range are also applicable.

[0032] During double electrodialysis in a double electrodialysis apparatus, anions in the first feed chamber pass through the first anion membrane into the first product chamber. Simultaneously, calcium ions in the second feed chamber pass through the second cation membrane into the first product chamber, chloride ions pass through the second anion membrane into the second product chamber, and sodium ions in the adjacent electrode chamber enter the second product chamber. This enriches calcium bromate and calcium bromide in the first product chamber, yielding an overflow solution enriched with calcium bromide and calcium bromate.

[0033] Preferably, before the metathesis electrodialysis in step (1) begins, water is added to the first product chamber and the second product chamber, the alkaline bromine extraction absorbent is added to the first raw material chamber, and the calcium chloride solution is added to the second raw material chamber;

[0034] Preferably, before the metathesis electrodialysis in step (1) begins, the amounts of water added to the first product chamber, the amount of water added to the second product chamber, the amount of bromine absorption liquid added to the first raw material chamber, and the amount of calcium chloride solution added to the second raw material chamber are equal.

[0035] Preferably, when the metathesis electrodialysis method described in step (1) is performed, the circulation flow rate of the first product chamber is 40-100 L / h, for example, it can be 40 L / h, 50 L / h, 60 L / h, 80 L / h or 100 L / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, when the metathesis electrodialysis method described in step (1) is performed, the circulation flow rate of the second product chamber is 40-100 L / h, for example, it can be 40 L / h, 50 L / h, 60 L / h, 80 L / h or 100 L / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, when the metathesis electrodialysis method described in step (1) is performed, the circulation flow rate of the first raw material chamber is 40-100 L / h, for example, it can be 40 L / h, 50 L / h, 60 L / h, 80 L / h or 100 L / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, during the metathesis electrodialysis described in this invention, the first product chamber and the second product chamber continuously overflow, and an overflow liquid enriched with calcium bromide and calcium bromate is obtained from the first product chamber. In order to replenish the raw material consumption in the first and second raw material chambers due to ion migration, it is necessary to continuously replenish the first and second raw material chambers with alkaline bromine extraction absorbent and calcium chloride solution of the same initial concentration. However, the feeding rate of the first and second raw material chambers should ensure that the overflow liquid concentrations of the first and second product chambers remain unchanged at electrodialysis equilibrium.

[0039] Preferably, when the metathesis electrodialysis method described in step (1) is performed, the circulation flow rate of the second raw material chamber is 40-100 L / h, for example, it can be 40 L / h, 50 L / h, 60 L / h, 80 L / h or 100 L / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the temperature during the double decomposition electrodialysis method in step (1) is 30-40℃, for example, it can be 30℃, 32℃, 34℃, 36℃, 38℃ or 40℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] For example, the power source used in the metathesis electrodialysis of the present invention is direct current.

[0042] Preferably, the current density during the metathesis electrodialysis method in step (1) is 250-500 A / m. 2 For example, it could be 250A / m 2 300A / m 2 350A / m 2 400A / m 2 450A / m 2 Or 500A / m 2 However, this does not limit the listed values; any other unlisted values ​​within the range are also applicable.

[0043] Preferably, the distillation temperature in step (3) is 90-100℃, for example, it can be 90℃, 92℃, 95℃, 98℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] As a preferred embodiment of the method provided by the present invention, the method includes the following steps:

[0045] (1) The temperature is 30-40℃ and the current density is 250-500A / m 2 The metathesis electrodialysis reacts the alkaline bromine extraction absorbent with a calcium chloride solution to obtain an overflow enriched with calcium bromide and calcium bromate.

[0046] The alkaline bromine extraction absorbent added to the first raw material chamber includes 0.7-0.9 mol / L sodium bromide and 0.14-0.18 mol / L sodium bromate, with a circulation flow rate of 40-100 L / h.

[0047] The concentration of calcium chloride solution added to the second raw material chamber is 0.5-1.1 mol / L, and its circulation flow rate is 40-100 L / h;

[0048] The electrode liquid in the electrode chamber is a sodium sulfate solution, and its circulation flow rate remains constant to satisfy the exchange process of sodium ions between the electrode chamber, the first raw material chamber, and the second product chamber.

[0049] Before the double decomposition electrodialysis begins, water is added to the first product chamber and the second product chamber, with each chamber having an independent circulation flow rate of 40-100 L / h.

[0050] Before the double decomposition electrodialysis begins, the amounts of water added to the first product chamber, the second product chamber, the first raw material chamber, and the second raw material chamber are equal.

[0051] When the metathesis electrodialysis method is performed, the feed rates of the first and second feed chambers should be such that the overflow concentrations of the first and second product chambers remain constant at electrodialysis equilibrium.

[0052] (2) Evaporation and crystallization at 90-100℃: The overflow obtained in step (1) allows the solid phase to precipitate completely, resulting in a mixed salt containing calcium bromide and calcium bromate; the mixed salt is then leached at 30-50℃ for more than 6 hours using an extractant, and the solid and liquid are separated to obtain calcium bromate and calcium bromide-containing filtrate.

[0053] The leaching agent includes any one or a combination of at least two of methanol, ethanol, ethylene glycol or isopropanol;

[0054] The solid-liquid mass ratio of the leaching is (3-4.5):1;

[0055] (3) The calcium bromide filtrate obtained in step (2) is distilled at 90-100℃ until all the solid is precipitated, and distillate and calcium bromide are obtained; the distillate is reused for the leaching in step (2).

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] One of the raw materials used in the method provided by this invention is an alkaline bromine extraction absorbent, which is the solution obtained after alkali absorption during the alkaline bromine extraction process in seawater, after the chemical removal of carbonate and bicarbonate ions. This invention uses the alkaline bromine extraction absorbent as a raw material for preparing calcium bromide, thus reducing the preparation cost of calcium bromide. Furthermore, this invention employs a metathesis electrodialysis-based method to prepare calcium bromide and calcium bromate, which has the advantages of an environmentally friendly synthesis process, high conversion rate, short synthesis route, high product purity, and low energy consumption. In other words, this invention significantly reduces the energy consumption for calcium bromide preparation by selecting specific raw materials for calcium bromide preparation and using metathesis electrodialysis. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the structure of the metathesis electrodialysis device used in a specific embodiment of the present invention.

[0059] Wherein: 101, cathode plate; 102, first cation film; 103, first anion film; 104, second cation film; 105, second anion film; 106, third cation film; 107, anode plate; 201, electrode liquid chamber; 202, first raw material chamber; 203, first product chamber; 204, second raw material chamber; 205, second product chamber. Detailed Implementation

[0060] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0061] A schematic diagram of the structure of the metathesis electrodialysis device used in the specific embodiments of the present invention is shown below. Figure 1As shown, the device includes five sets of electrodialysis membrane stack assemblies. Each electrodialysis membrane stack assembly includes a cathode plate 101, a first cation membrane 102, a first anion membrane 103, a second cation membrane 104, a second anion membrane 105, a third cation membrane 106, and an anode plate 107, stacked sequentially. The electrode liquid in the electrode liquid chamber 201 circulates through the area between the cathode plate 101 and the first cation membrane 102, and the area between the third cation membrane 106 and the anode plate 107. The first feed liquid in the first feed chamber 202 circulates through the area between the first cation membrane 102 and the anode plate 107. The area between the first anterior membrane 103; the area between the first product liquid in the first product chamber 203 and the second posterior membrane 104; the area between the second raw material liquid in the second raw material chamber 204 and the second posterior membrane 104; the area between the second product liquid in the second product chamber 205 and the second posterior membrane 106; and the membrane areas of the first posterior membrane 102, the second posterior membrane 104, and the third posterior membrane 106 are each independently 225 cm². 2 The membrane areas of the first anal membrane 103 and the second anal membrane 105 are each independently 225 cm². 2 .

[0062] During double electrodialysis in the double electrodialysis apparatus, anions in the first feed chamber 202 enter the first product chamber 203 through the first anion membrane 103. Simultaneously, calcium ions in the second feed chamber 204 enter the first product chamber 203 through the second cation membrane 104, chloride ions enter the second product chamber 205 through the second anion membrane 105, and sodium ions in the adjacent electrode chamber of the second product chamber 205 enter the second product chamber 205. This enriches calcium bromate and calcium bromide in the first product chamber 203, resulting in an overflow solution enriched with calcium bromide and calcium bromate.

[0063] The above description of the metathesis electrodialysis device is only for clearly illustrating the technical solution of the present invention and should not be regarded as a further limitation on the technical solution of the present invention.

[0064] Example 1

[0065] This embodiment provides a method for... Figure 1 The method for preparing calcium bromide and calcium bromate using electrodialysis in the illustrated double decomposition electrodialysis apparatus includes the following steps:

[0066] (1) The temperature is 30℃ and the current density is 250A / m 2 The metathesis electrodialysis reacts the alkaline bromine extraction absorbent with a calcium chloride solution to obtain an overflow enriched with calcium bromide and calcium bromate.

[0067] The alkaline bromine extraction absorbent added to the first raw material chamber includes 0.7 mol / L sodium bromide and 0.14 mol / L sodium bromate, with a circulation flow rate of 80 L / h.

[0068] The concentration of calcium chloride solution added to the second raw material chamber is 0.5 mol / L, and its circulation flow rate is 80 L / h;

[0069] The concentration of calcium bromide in the resulting overflow was 1.04 mol / L, and the concentration of calcium bromate was 0.14 mol / L.

[0070] The first and second raw material chambers are continuously fed with the same concentration as the initial solution concentration. The feeding rate ensures that the overflow concentration remains constant at electrodialysis equilibrium.

[0071] The electrode liquid in the electrode chamber is a sodium sulfate solution, and its circulation flow rate remains constant to satisfy the exchange process of sodium ions between the electrode chamber and the first raw material chamber and the second product chamber.

[0072] Before the double decomposition electrodialysis begins, deionized water is added to the first product chamber and the second product chamber, with each chamber having an independent circulation flow rate of 80 L / h.

[0073] Before the double decomposition electrodialysis begins, the amounts of water added to the first product chamber, the second product chamber, the first raw material chamber, and the second raw material chamber are equal.

[0074] After 8 hours of double decomposition electrodialysis, the solution reaches equilibrium. At this time, the overflow from the first product chamber is an overflow enriched with calcium bromide and calcium bromate.

[0075] (2) Evaporation crystallization at 100℃ The overflow obtained in step (1) completely precipitates the solid phase, resulting in a mixed salt containing calcium bromide and calcium bromate; the mixed salt is leached with methanol at 40℃ for 6 hours, and the solid and liquid are separated to obtain calcium bromate and calcium bromide filtrate.

[0076] The solid-liquid mass ratio of the leaching is 4:1;

[0077] (3) The calcium bromide filtrate obtained in step (2) is distilled at 100°C until all the solid is precipitated, and distillate and wet calcium bromide are obtained; the distillate is reused for the leaching in step (2); the wet calcium bromide is dried at 60°C for 12 hours to obtain calcium bromide.

[0078] Example 2

[0079] This embodiment provides a method for... Figure 1 The method for preparing calcium bromide and calcium bromate using electrodialysis in the illustrated double decomposition electrodialysis apparatus includes the following steps:

[0080] (1) The temperature is 30℃ and the current density is 250A / m 2 The metathesis electrodialysis reacts the alkaline bromine extraction absorbent with a calcium chloride solution to obtain an overflow enriched with calcium bromide and calcium bromate.

[0081] The alkaline bromine extraction absorbent added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, with a circulation flow rate of 80 L / h.

[0082] The concentration of calcium chloride solution added to the second raw material chamber is 0.7 mol / L, and its circulation flow rate is 80 L / h;

[0083] The concentration of calcium bromide in the resulting overflow was 1.26 mol / L, and the concentration of calcium bromate was 0.16 mol / L.

[0084] The first and second raw material chambers are continuously fed with the same concentration as the initial solution concentration. The feeding rate ensures that the overflow concentration remains constant at electrodialysis equilibrium.

[0085] The electrode liquid in the electrode chamber is a sodium sulfate solution, and its circulation flow rate remains constant to satisfy the exchange process of sodium ions between the electrode chamber and the first raw material chamber and the second product chamber.

[0086] Before the double decomposition electrodialysis begins, deionized water is added to the first product chamber and the second product chamber, with each chamber having an independent circulation flow rate of 80 L / h.

[0087] Before the double decomposition electrodialysis begins, the amounts of water added to the first product chamber, the second product chamber, the first raw material chamber, and the second raw material chamber are equal.

[0088] After 8 hours of double decomposition electrodialysis, the solution reaches equilibrium. At this time, the overflow from the first product chamber is an overflow enriched with calcium bromide and calcium bromate.

[0089] (2) Evaporation crystallization at 100℃ The overflow obtained in step (1) completely precipitates the solid phase, resulting in a mixed salt containing calcium bromide and calcium bromate; the mixed salt is leached with methanol at 40℃ for 6 hours, and the solid and liquid are separated to obtain calcium bromate and calcium bromide filtrate.

[0090] The solid-liquid mass ratio of the leaching is 4.5:1;

[0091] (3) The calcium bromide filtrate obtained in step (2) is distilled at 100°C until all the solid is precipitated, and distillate and wet calcium bromide are obtained; the distillate is reused for the leaching in step (2); the wet calcium bromide is dried at 60°C for 12 hours to obtain calcium bromide.

[0092] Example 3

[0093] This embodiment provides a method for... Figure 1 The method for preparing calcium bromide and calcium bromate using electrodialysis in the illustrated double decomposition electrodialysis apparatus includes the following steps:

[0094] (1) The temperature is 30℃ and the current density is 400A / m 2 The metathesis electrodialysis reacts the alkaline bromine extraction absorbent with a calcium chloride solution to obtain an overflow enriched with calcium bromide and calcium bromate.

[0095] The alkaline bromine extraction absorbent added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, with a circulation flow rate of 80 L / h.

[0096] The concentration of calcium chloride solution added to the second raw material chamber is 0.7 mol / L, and its circulation flow rate is 80 L / h;

[0097] The concentration of calcium bromide in the resulting overflow was 1.19 mol / L, and the concentration of calcium bromate was 0.22 mol / L.

[0098] The first and second raw material chambers are continuously fed with the same concentration as the initial solution concentration. The feeding rate ensures that the overflow concentration remains constant at electrodialysis equilibrium.

[0099] The electrode liquid in the electrode chamber is a sodium sulfate solution, and its circulation flow rate remains constant to satisfy the exchange process of sodium ions between the electrode chamber and the first raw material chamber and the second product chamber.

[0100] Before the double decomposition electrodialysis begins, deionized water is added to the first product chamber and the second product chamber, with each chamber having an independent circulation flow rate of 80 L / h.

[0101] Before the double decomposition electrodialysis begins, the amounts of water added to the first product chamber, the second product chamber, the first raw material chamber, and the second raw material chamber are equal.

[0102] After 8 hours of double decomposition electrodialysis, the solution reaches equilibrium. At this time, the overflow from the first product chamber is an overflow enriched with calcium bromide and calcium bromate.

[0103] (2) Evaporation crystallization at 100℃: The overflow liquid obtained in step (1) completely precipitates the solid phase, resulting in a mixed salt containing calcium bromide and calcium bromate; the mixed salt is leached with ethanol at 40℃ for 6 hours, and the solid and liquid are separated to obtain calcium bromate and calcium bromide filtrate.

[0104] The solid-liquid mass ratio of the leaching is 3:1;

[0105] (3) The calcium bromide filtrate obtained in step (2) is distilled at 100°C until all the solid is precipitated, and distillate and wet calcium bromide are obtained; the distillate is reused for the leaching in step (2); the wet calcium bromide is dried at 60°C for 12 hours to obtain calcium bromide.

[0106] Example 4

[0107] This embodiment provides a method for... Figure 1 The method for preparing calcium bromide and calcium bromate using electrodialysis in the illustrated double decomposition electrodialysis apparatus includes the following steps:

[0108] (1) The temperature is 30℃ and the current density is 300A / m 2 The metathesis electrodialysis reacts the alkaline bromine extraction absorbent with a calcium chloride solution to obtain an overflow enriched with calcium bromide and calcium bromate.

[0109] The alkaline bromine extraction absorbent added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, with a circulation flow rate of 60 L / h.

[0110] The concentration of calcium chloride solution added to the second raw material chamber is 0.7 mol / L, and its circulation flow rate is 60 L / h;

[0111] The concentration of calcium bromide in the resulting overflow was 1.30 mol / L, and the concentration of calcium bromate was 0.20 mol / L.

[0112] The first and second raw material chambers are continuously fed with the same concentration as the initial solution concentration. The feeding rate ensures that the overflow concentration remains constant at electrodialysis equilibrium.

[0113] The electrode liquid in the electrode chamber is a sodium sulfate solution, and its circulation flow rate remains constant to satisfy the exchange process of sodium ions between the electrode chamber and the first raw material chamber and the second product chamber.

[0114] Before the double decomposition electrodialysis begins, deionized water is added to the first product chamber and the second product chamber, with each chamber having an independent circulation flow rate of 60 L / h.

[0115] Before the double decomposition electrodialysis begins, the amounts of water added to the first product chamber, the second product chamber, the first raw material chamber, and the second raw material chamber are equal.

[0116] After 8 hours of double decomposition electrodialysis, the solution reaches equilibrium. At this time, the overflow from the first product chamber is an overflow enriched with calcium bromide and calcium bromate.

[0117] (2) Evaporation crystallization at 90℃: The overflow liquid obtained in step (1) completely precipitates the solid phase, resulting in a mixed salt containing calcium bromide and calcium bromate; the mixed salt is leached with methanol at 40℃ for 6 hours, and the solid and liquid are separated to obtain calcium bromate and calcium bromide filtrate.

[0118] The solid-liquid mass ratio of the leaching is 4:1;

[0119] (3) The calcium bromide filtrate obtained in step (2) is distilled at 90°C until all the solid is precipitated, and distillate and wet calcium bromide are obtained; the distillate is reused for the leaching in step (2); the wet calcium bromide is dried at 60°C for 12 hours to obtain calcium bromide.

[0120] Example 5

[0121] This embodiment provides a method for... Figure 1 The method for preparing calcium bromide and calcium bromate using electrodialysis in the illustrated double decomposition electrodialysis apparatus includes the following steps:

[0122] (1) The temperature is 40℃ and the current density is 500A / m 2 The metathesis electrodialysis reacts the alkaline bromine extraction absorbent with a calcium chloride solution to obtain an overflow enriched with calcium bromide and calcium bromate.

[0123] The alkaline bromine extraction absorbent added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, with a circulation flow rate of 100 L / h.

[0124] The concentration of calcium chloride solution added to the second raw material chamber is 1.1 mol / L, and its circulation flow rate is 100 L / h;

[0125] The concentration of calcium bromide in the resulting overflow was 1.12 mol / L, and the concentration of calcium bromate was 0.29 mol / L.

[0126] The first and second raw material chambers are continuously fed with the same concentration as the initial solution concentration. The feeding rate ensures that the overflow concentration remains constant at electrodialysis equilibrium.

[0127] The electrode liquid in the electrode chamber is a sodium sulfate solution, and its circulation flow rate remains constant to satisfy the exchange process of sodium ions between the electrode chamber and the first raw material chamber and the second product chamber.

[0128] Before the double decomposition electrodialysis begins, deionized water is added to the first product chamber and the second product chamber, with each chamber having an independent circulation flow rate of 100 L / h.

[0129] Before the double decomposition electrodialysis begins, the amounts of water added to the first product chamber, the second product chamber, the first raw material chamber, and the second raw material chamber are equal.

[0130] After 8 hours of double decomposition electrodialysis, the solution reaches equilibrium. At this time, the overflow from the first product chamber is an overflow enriched with calcium bromide and calcium bromate.

[0131] (2) The overflow obtained from the evaporation and crystallization step (1) yields a mixed salt containing calcium bromide and calcium bromate; the mixed salt is leached with methanol at 50°C for 6 hours, and the solid and liquid are separated to obtain calcium bromate and calcium bromide-containing filtrate.

[0132] (3) The calcium bromide filtrate obtained in step (2) is distilled to obtain distillate and wet calcium bromide; the distillate is reused for the leaching in step (2); the wet calcium bromide is dried at 60°C for 12 hours to obtain calcium bromide.

[0133] Example 6

[0134] This embodiment provides a method for... Figure 1 The method for preparing calcium bromide and calcium bromate using electrodialysis in the illustrated double decomposition electrodialysis apparatus includes the following steps:

[0135] (1) The temperature is 30℃ and the current density is 300A / m 2 The metathesis electrodialysis reacts the alkaline bromine extraction absorbent with a calcium chloride solution to obtain an overflow enriched with calcium bromide and calcium bromate.

[0136] The alkaline bromine extraction absorbent added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, with a circulation flow rate of 40 L / h.

[0137] The concentration of calcium chloride solution added to the second raw material chamber is 0.7 mol / L, and its circulation flow rate is 40 L / h;

[0138] The concentration of calcium bromide in the resulting overflow was 1.15 mol / L, and the concentration of calcium bromate was 0.16 mol / L.

[0139] The first and second raw material chambers are continuously fed with the same concentration as the initial solution concentration. The feeding rate ensures that the overflow concentration remains constant at electrodialysis equilibrium.

[0140] The electrode liquid in the electrode chamber is a sodium sulfate solution, and its circulation flow rate remains constant to satisfy the exchange process of sodium ions between the electrode chamber and the first raw material chamber and the second product chamber.

[0141] When the double decomposition electrodialysis begins, deionized water is added to the first product chamber and the second product chamber, and the circulation flow rate is 40L / h independently for each chamber.

[0142] When the double decomposition electrodialysis begins, the amounts of water added to the first product chamber, the second product chamber, the first raw material chamber, and the second raw material chamber are equal.

[0143] After 8 hours of double decomposition electrodialysis, the solution reaches equilibrium. At this time, the overflow from the first product chamber is an overflow enriched with calcium bromide and calcium bromate.

[0144] (2) Evaporation crystallization at 100℃ The overflow obtained in step (1) completely precipitates the solid phase, resulting in a mixed salt containing calcium bromide and calcium bromate; the mixed salt is leached with methanol at 30℃ for 6 hours, and the solid and liquid are separated to obtain calcium bromate and calcium bromide filtrate.

[0145] The solid-liquid mass ratio of the leaching is 4:1;

[0146] (3) The calcium bromide filtrate obtained in step (2) is distilled at 100°C until all the solid is precipitated, and distillate and wet calcium bromide are obtained; the distillate is reused for the leaching in step (2); the wet calcium bromide is dried at 60°C for 12 hours to obtain calcium bromide.

[0147] In the method provided in the above embodiments, the calcium bromide yield per unit area of ​​ion exchange membrane (Y, kg / (m²)) in metathesis electrodialysis 2 The energy consumption (E, kWh·t) and purity (P, wt%) of calcium bromide were calculated, and the results are shown in Table 1.

[0148]

[0149] =W+W

[0150] In the above formula, c is the concentration of calcium bromide in the overflow liquid at the equilibrium state of the metathesis electrodialysis system, in mol / L; V D The overflow volume (L) within 1 hour after the double decomposition electrodialysis operation reaches equilibrium; M is the molar mass of calcium bromide (g / mol); N is the number of electrodialysis membrane stack modules, denoted as 5; and S is the effective area of ​​a single membrane, denoted as 0.2255 m². 2 t represents the operation time, denoted as 1 hour;

[0151] U is the membrane stack voltage when the double decomposition electrodialysis system is in equilibrium; I is the membrane stack current when the double decomposition electrodialysis system is in equilibrium.

[0152] W + To achieve operational equilibrium during metathesis electrodialysis, the Ca content in the overflow solution... 2+ The content, wt%; W - To achieve operational equilibrium during metathesis electrodialysis, the Br content in the overflow solution... - The content, wt%.

[0153] The purity of the final obtained calcium bromide, the purity of the calcium bromate, and the recovery rate (e,%) of the leaching agent methanol in the method provided in the above embodiments were calculated, where e = V R / V A V A V represents the volume added during leaching, expressed in L; R L represents the volume of the leaching agent recovered through distillation.

[0154] Table 1

[0155]

[0156] In summary, one of the raw materials used in the method provided by this invention is an alkaline bromine extraction absorbent, which is the solution obtained after alkali absorption during the alkaline bromine extraction process in seawater, after the chemical removal of carbonate and bicarbonate ions. This invention uses the alkaline bromine extraction absorbent as a raw material for preparing calcium bromide, thus reducing the preparation cost of calcium bromide. Furthermore, this invention employs a metathesis electrodialysis-based method to prepare calcium bromide and calcium bromate, which has the advantages of an environmentally friendly synthesis process, high conversion rate, short synthesis route, high product purity, and low energy consumption. In other words, this invention significantly reduces the energy consumption for calcium bromide preparation by selecting specific raw materials for calcium bromide preparation and using metathesis electrodialysis.

[0157] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing calcium bromide and calcium bromate using electrodialysis, characterized in that, The method includes the following steps: (1) The alkaline bromine extraction absorbent was reacted with calcium chloride solution by metathesis electrodialysis to obtain an overflow liquid enriched with calcium bromide and calcium bromate. (2) The overflow obtained in the evaporation and crystallization step (1) yields a mixed salt containing calcium bromide and calcium bromate; the mixed salt is leached and separated into solid and liquid by using a leaching agent to obtain calcium bromate and calcium bromide-containing filtrate. (3) The calcium bromide filtrate obtained in step (2) is distilled until all the solid precipitates out, and the distillate and calcium bromide are obtained. The distillate is reused for the leaching in step (2). The alkaline bromine extraction absorption solution in step (1) comprises 0.7-0.9 mol / L sodium bromide and 0.14-0.18 mol / L sodium bromate; The metathesis electrodialysis described in step (1) is carried out in a metathesis electrodialysis apparatus; The metathesis electrodialysis device includes an electrode chamber, a first raw material chamber, a first product chamber, a second raw material chamber, a second product chamber, and at least one set of electrodialysis membrane stack assembly; The electrodialysis membrane stack assembly includes a cathode plate, a first cation membrane, a first anion membrane, a second cation membrane, a second anion membrane, a third cation membrane, and an anode plate stacked sequentially. The electrode liquid in the electrode liquid chamber circulates through the region between the cathode plate and the first cation membrane, and the region between the third cation membrane and the anode plate; the first raw material liquid in the first raw material chamber circulates through the region between the first cation membrane and the first anion membrane; the first product liquid in the first product chamber circulates through the region between the first anion membrane and the second cation membrane; the second raw material liquid in the second raw material chamber circulates through the region between the second cation membrane and the second anion membrane; the second product liquid in the second product chamber circulates through the region between the second anion membrane and the third cation membrane. Before the metathesis electrodialysis in step (1) begins, water is added to the first product chamber and the second product chamber, the alkaline bromine extraction absorbent is added to the first raw material chamber, and the calcium chloride solution is added to the second raw material chamber.

2. The method according to claim 1, characterized in that, The concentration of the calcium chloride solution in step (1) is 0.5-1.1 mol / L.

3. The method according to claim 1, characterized in that, The leaching agent in step (2) includes any one or a combination of at least two of methanol, ethanol, ethylene glycol or isopropanol.

4. The method according to claim 1, characterized in that, The immersion temperature in step (2) is 30-50℃.

5. The method according to claim 1, characterized in that, The soaking time in step (2) is more than 6 hours.

6. The method according to claim 1, characterized in that, Before the metathesis electrodialysis described in step (1) begins, the amounts of water added to the first product chamber, the second product chamber, the first raw material chamber, and the second raw material chamber are equal.

7. The method according to claim 1, characterized in that, When the metathesis electrodialysis described in step (1) is performed, the circulation flow rate of the first product chamber is 40-100 L / h.

8. The method according to claim 1, characterized in that, When the metathesis electrodialysis described in step (1) is performed, the circulation flow rate of the second product chamber is 40-100 L / h.

9. The method according to claim 1, characterized in that, When the metathesis electrodialysis described in step (1) is performed, the circulation flow rate of the first raw material chamber is 40-100 L / h.

10. The method according to claim 1, characterized in that, When the metathesis electrodialysis described in step (1) is performed, the circulation flow rate of the second raw material chamber is 40-100 L / h.

11. The method according to claim 1, characterized in that, When the metathesis electrodialysis described in step (1) is performed, the feed rates of the first and second raw material chambers should be such that the overflow concentrations of the first and second product chambers remain constant at electrodialysis equilibrium.

12. The method according to claim 1, characterized in that, The temperature during the metathesis electrodialysis in step (1) is 30-40℃.

13. The method according to claim 1, characterized in that, The current density during the metathesis electrodialysis in step (1) is 250-500 A / m. 2 .

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