Method for preparing calcium bromide and calcium bromate by electrodialysis

Abstract

The invention relates to a method for preparing calcium bromide and calcium bromate by electrodialysis, which comprises the following steps: reacting an alkali-process bromine extraction absorption liquid with a calcium chloride solution by double decomposition electrodialysis to obtain an overflow liquid enriched with calcium bromide and calcium bromate; evaporating and crystallizing the overflow liquid to obtain mixed salt containing calcium bromide and calcium bromate; leaching the obtained mixed salt by using a leaching agent, and carrying out solid-liquid separation to obtain calcium bromate and calcium bromide-containing filtrate; distilling the obtained calcium bromide filtrate to obtain distillate and calcium bromide; and reusing the distillate for leaching. According to the method provided by the invention, simultaneous preparation of calcium bromide and calcium bromate is realized by utilizing double decomposition electrodialysis, and the preparation cost of calcium bromide is reduced by utilizing the alkali-process bromine extraction absorption liquid as a raw material; meanwhile, raw materials and products in the preparation process are in different compartments, the defect that complex separation and purification are needed in a traditional method is overcome, and the method has the advantages of being environmentally friendly in synthesis process, high in conversion rate, short in synthesis route, high in product purity and low in energy consumption.

Description

Technical Field

[0001] The invention belongs to the technical field of calcium bromide preparation, and relates to a method for simultaneously preparing calcium bromide and calcium bromate, and in particular to a method for preparing calcium bromide and calcium bromate by utilizing electrodialysis. Background Art

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

[0003] Traditional preparation methods of calcium bromide include direct extraction, ferrous bromide, liquid ammonia, urea reduction, lime milk and marble. The ferrous bromide method is suitable for areas rich in bromine resources, but not for underground brine with a maximum bromine content of 200-300 mg / Kg. At present, the commonly used calcium bromide preparation methods in industrial production are ferrous bromide and liquid ammonia. The product conversion rate of the ferrous bromide method is as low as 66.7%, and there are more iron filings and oil pollution, and the processing cost is high; the conversion rate of the liquid ammonia method can reach 86%, but it is necessary to make the liquid ammonia excessive. At the same time, there is a large amount of gasification loss in the production process, and the storage cost is high and the difficulty is great; the urea reduction method is only improved on the basis of the liquid ammonia method, and the liquid ammonia is replaced by urea; the lime milk method and the marble method both use hydrobromic acid with a concentration of no more than 40wt% in the synthesis process, and there are problems such as high energy consumption for evaporation and concentration, and the quality of hydrobromic acid directly affects the quality of calcium bromide products, and the marble method is limited by raw materials, and the quality is not easy to meet the requirements, therefore, the lime milk method and the marble method are not commonly used.

[0004] CN101618888A discloses a process of first adding a quantitative calcium bromide solution product, then adding quicklime, dripping hydrobromic acid until the reaction is complete, then adding slaked lime, and dripping hydrobromic acid until the reaction is complete. CN101391748A discloses a method for preparing calcium bromide liquid by hydrobromic acid, a byproduct of the deep processing of bromine. CN106115761A discloses a method for preparing calcium bromide solution by waste hydrobromic acid, which has the characteristics of high production efficiency and low cost compared with the technology of preparing calcium bromide by traditional lime milk method, but hydrobromic acid needs to be pretreated before use to remove organic impurities such as organic matter, and the process is more complicated. CN114031101A discloses a method for preparing calcium bromide using brine containing bromine as raw material, using a three-stage method to absorb bromine with lime milk, and the utilization rate of raw materials is high, but the process flow is long. Moreover, the above-mentioned prior art all has the problem of mixing raw materials and products during the reaction process, and its purification process is long and the cost is high, and it is impossible to achieve efficient and environmentally friendly preparation of calcium bromide. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a method for preparing calcium bromide and calcium bromate by electrodialysis, which avoids mixing of products and raw materials during the preparation process and is efficient and environmentally friendly. The method utilizes double decomposition electrodialysis to achieve the simultaneous preparation of calcium bromide and calcium bromate, and utilizes alkaline bromine extraction absorption liquid as raw material, thereby reducing the preparation cost of calcium bromide; at the same time, the raw materials and products in the preparation process are in different compartments, which overcomes the defect that traditional methods require complex separation and purification, and has the advantages of environmentally friendly synthesis process, high conversion rate, short synthesis route, high product purity and low energy consumption.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

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

[0008] (1) using double decomposition electrodialysis to react the alkaline bromine extraction absorption liquid with a calcium chloride solution to obtain an overflow liquid enriched with calcium bromide and calcium bromate;

[0009] (2) evaporating the overflow liquid obtained in step (1) to obtain a mixed salt containing calcium bromide and calcium bromate; using a leaching agent to leach the obtained mixed salt and perform solid-liquid separation to obtain calcium bromate and a filtrate containing calcium bromide;

[0010] (3) The calcium bromide filtrate obtained in step (2) is distilled until all solids are precipitated to obtain a distillate and calcium bromide, and the distillate is reused in the leaching described in step (2).

[0011] One of the raw materials used in the method provided by the present invention is an alkaline bromine extraction absorption liquid, which is a solution after carbonate and bicarbonate are removed by chemical method and after alkali solution is absorbed in the process of seawater alkaline bromine extraction; the present invention adopts alkaline bromine extraction absorption liquid as a raw material for preparing calcium bromide, which reduces the preparation cost of calcium bromide; and the present invention adopts double decomposition electrodialysis as the main method to realize the preparation of calcium bromide and calcium bromate, which has the advantages of environmental protection in the synthesis process, high conversion rate, short synthesis route, high product purity and low energy consumption. That is to say, the present invention greatly reduces the energy consumption of preparing calcium bromide solution by selecting specific calcium bromide preparation raw materials and coordinating the use of double decomposition electrodialysis, the impurity ion content in the product solution prepared by electrodialysis is low, the subsequent purification process is short, and the product purity is high.

[0012] Preferably, the alkaline bromine extraction absorption liquid 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 liquid of step (1) of the present 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 it is not limited to the listed values, and the other values ​​not listed in the numerical range are also applicable.

[0014] In the alkaline bromine extraction absorption liquid of step (1) of the present 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, and the remaining values ​​within the numerical range not listed are also applicable.

[0015] Preferably, the concentration of the calcium chloride solution in step (1) is 0.5-1.1 mol / L, for example, 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, and other values ​​not listed within the numerical range are also applicable, preferably 0.5-0.7 mol / L.

[0016] Preferably, the concentration of calcium bromide in the overflow liquid 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 the overflow liquid of step (1) of the present invention, the concentration of calcium bromide 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, and other values ​​not listed within the numerical range are also applicable.

[0018] In the overflow liquid of step (1) of the present invention, the concentration of calcium bromate 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, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the temperature of the evaporation crystallization in step (2) is 90-100°C, for example, 90°C, 92°C, 95°C, 98°C or 100°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] The present invention does not impose any specific limitation on the time of evaporation and crystallization, as long as the solid phase is completely precipitated.

[0021] Preferably, the leaching agent in step (2) comprises any one of methanol, ethanol, ethylene glycol or isopropanol, or a combination of at least two of them. Typical but non-limiting combinations include a combination of methanol and ethanol, a combination of ethanol and ethylene glycol, a combination of ethylene glycol and isopropanol, a combination of methanol, ethanol and ethylene glycol, a combination of ethanol, ethylene glycol and isopropanol, or a combination of 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, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the leaching temperature in step (2) is 30-50°C, for example, 30°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] Preferably, the leaching time in step (2) is more than 6 hours, for example, it can be 6 hours, 8 hours, 9 hours, 10 hours or 12 hours, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

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

[0026] Preferably, the metathesis electrodialysis in step (1) is carried out in a metathesis electrodialysis device;

[0027] The double decomposition electrodialysis device comprises an extreme liquid 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 components;

[0028] The electrodialysis membrane stack assembly comprises a cathode plate, a first cation membrane, a first cathode membrane, a second cation membrane, a second cathode membrane, a third cation membrane and an anode plate which are stacked in sequence;

[0029] The cathode liquids in the cathode liquid chamber circulate through the area between the cathode plate and the first cation membrane, and the area between the third cation membrane and the anode plate respectively; the first raw material liquid in the first raw material chamber circulates through the area between the first cation membrane and the first cathode membrane; the first product liquid in the first product chamber circulates through the area between the first cathode membrane and the second cathode membrane; the second raw material liquid in the second raw material chamber circulates through the area between the second cation membrane and the second cathode mold; the second product liquid in the second product chamber circulates through the area between the second cathode mold and the third cation membrane.

[0030] The present invention does not specifically limit the number of electrodialysis membrane stack components in the double decomposition electrodialysis device. The more the number of electrodialysis membrane stack components, the greater the output of calcium bromide, but the volume of the double decomposition electrodialysis device will also increase. Those skilled in the art can select the appropriate number of electrodialysis membrane stack components based on the output and actual production conditions.

[0031] The first cation membrane, the second cation membrane and the third cation membrane are independently cation exchange membranes, allowing cations in the solution to pass through and retaining anions in the solution; the first anion membrane and the second anion membrane are independently anion exchange membranes, allowing anions in the solution to pass through and retaining cations in the solution. Exemplarily, in the double decomposition electrodialysis device of the present invention, the areas of the first cation membrane, the second cation membrane, the third cation membrane, the first anion membrane and the second anion membrane are independently 200-250cm 2 , for example, it can be 200cm 2 、215cm 2 、225cm 2 、240cm 2 or 250cm 2 , but not limited to the listed values, the remaining values ​​not listed in the numerical range are also applicable.

[0032] When performing double decomposition electrodialysis in a double decomposition electrodialysis device, anions in the first raw material chamber enter the first product chamber through the first anion membrane, and at the same time, calcium ions in the second raw material chamber enter the first product chamber through the second anion membrane, chloride ions enter the second product chamber through the second anion membrane, and sodium ions in the cathode chamber adjacent to the second product chamber enter the second product chamber. Thus, calcium bromate and calcium bromide in the first product chamber are enriched to obtain an overflow liquid enriched with calcium bromide and calcium bromate.

[0033] Preferably, before the double decomposition electrodialysis in step (1) is started, water is added to the first product chamber and the second product chamber, the alkaline bromine extraction absorption liquid 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 double decomposition electrodialysis in step (1) begins, the amount of water added to the first product chamber, the amount of water added to the second product chamber, the amount of alkaline bromine extraction 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 double decomposition electrodialysis method in step (1) is carried out, 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, and the remaining unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, when the double decomposition electrodialysis method in step (1) is carried out, 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, and the remaining unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, when the double decomposition electrodialysis method in step (1) is carried out, 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, and the remaining values ​​not listed within the numerical range are also applicable.

[0038] Preferably, when the double decomposition electrodialysis described in the present invention is carried out, the first product chamber and the second product chamber overflow continuously, 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 caused by ion migration in the first raw material chamber and the second raw material chamber, it is necessary to continuously replenish the first raw material chamber and the second raw material chamber with alkaline bromine extraction absorption liquid and calcium chloride solution with the same initial concentration, but the replenishment rate of the first raw material chamber and the second raw material chamber should be such that the concentration of the overflow liquid of the first product chamber and the second product chamber remains unchanged when the electrodialysis equilibrium is reached.

[0039] Preferably, when the double decomposition electrodialysis method in step (1) is carried out, 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, and the remaining values ​​not listed within the numerical range are also applicable.

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

[0041] Exemplarily, the power source used in the double decomposition electrodialysis of the present invention is direct current.

[0042] Preferably, the current density during the double decomposition electrodialysis in step (1) is 250-500 A / m 2 , for example, it can be 250A / m 2 、300A / m 2 、350A / m 2 , 400A / m 2 , 450A / m 2 or 500A / m 2 , but not limited to the listed values, the remaining values ​​not listed in the numerical range are also applicable.

[0043] Preferably, the distillation temperature in step (3) is 90-100°C, for example, 90°C, 92°C, 95°C, 98°C or 100°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] As a preferred technical solution of the method provided by the present invention, the method comprises the following steps:

[0045] (1) The temperature is 30-40℃ and the current density is 250-500A / m 2 The double decomposition electrodialysis makes the alkaline bromine extraction absorption liquid react with the calcium chloride solution to obtain an overflow liquid enriched with calcium bromide and calcium bromate;

[0046] The alkaline bromine extraction absorption liquid 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, and its circulation flow rate is 40-100 L / h;

[0047] The concentration of the 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 polar liquid in the polar liquid chamber is a sodium sulfate solution, and its circulation flow rate remains unchanged to meet the exchange process of sodium ions in the polar liquid 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, and the circulation flow rate thereof is independently 40-100 L / h;

[0050] Before the double decomposition electrodialysis begins, the amount of water added to the first product chamber, the amount of water added to the second product chamber, the amount of alkaline bromine extraction 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;

[0051] When the double decomposition electrodialysis method is carried out, the feed rate of the first raw material chamber and the second raw material chamber should be such that the overflow concentration of the first product chamber and the second product chamber remains unchanged at the electrodialysis equilibrium;

[0052] (2) evaporating and crystallizing the overflow liquid obtained in step (1) at 90-100° C. to completely precipitate the solid phase, thereby obtaining a mixed salt containing calcium bromide and calcium bromate; using a leaching agent to leaching the obtained mixed salt at 30-50° C. for more than 6 hours, and separating the solid from the liquid to obtain calcium bromate and a filtrate containing calcium bromide;

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

[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° C. until all solids are precipitated, thereby obtaining a distillate and calcium bromide; and the distillate is reused in the leaching described 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 the present invention is an alkaline bromine extraction absorption liquid, which is a solution after carbonate and bicarbonate are removed by chemical method and after alkali liquor is absorbed in the process of alkaline bromine extraction from seawater. The present invention uses alkaline bromine extraction absorption liquid as a raw material for preparing calcium bromide, which reduces the preparation cost of calcium bromide; moreover, the present invention adopts double decomposition electrodialysis as the main method to realize the preparation of calcium bromide and calcium bromate, which has the advantages of environmentally friendly synthesis process, high conversion rate, short synthesis route, high product purity and low energy consumption. In other words, the present invention greatly reduces the energy consumption of calcium bromide preparation by selecting specific calcium bromide preparation raw materials and coordinating the use of double decomposition electrodialysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic structural diagram of a double decomposition electrodialysis device used in a specific embodiment of the present invention.

[0059] Among them: 101, cathode plate; 102, first cation membrane; 103, first cathode membrane; 104, second cation membrane; 105, second cathode membrane; 106, third cation membrane; 107, anode plate; 201, polar liquid chamber; 202, first raw material chamber; 203, first product chamber; 204, second raw material chamber; 205, second product chamber. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0061] The structural schematic diagram of the double decomposition electrodialysis device used in the specific embodiment of the present invention is as follows Figure 1As shown, it includes 5 groups of electrodialysis membrane stack components; the electrodialysis membrane stack components include a cathode plate 101, a first cation membrane 102, a first cathode membrane 103, a second cation membrane 104, a second cathode, a third cation membrane 106 and an anode plate 107 stacked in sequence; the polar liquid in the polar 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 raw material liquid in the first raw material chamber 202 circulates through the first cation membrane 102 and the The first product liquid in the first product chamber 203 circulates through the area between the first negative film 103 and the second positive film 104; the second raw material liquid in the second raw material chamber 204 circulates through the area between the second positive film 104 and the second negative mold; the second product liquid in the second product chamber 205 circulates through the area between the second negative mold and the third positive film 106; and the membrane areas of the first positive film 102, the second positive film 104 and the third positive film 106 are independently 225cm 2 The membrane areas of the first and second anion membranes 103 and 105 are 225 cm 2 .

[0062] When performing double decomposition electrodialysis in the double decomposition electrodialysis device, anions in the first raw material chamber 202 enter the first product chamber 203 through the first anion membrane 103, and at the same time, calcium ions in the second raw material 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 electrode chamber adjacent to the second product chamber 205 enter the second product chamber 205. Thus, calcium bromate and calcium bromide in the first product chamber 203 are enriched, and an overflow liquid enriched with calcium bromide and calcium bromate is obtained.

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

[0064] Example 1

[0065] This embodiment provides a Figure 1 In the double decomposition electrodialysis device shown, a method for preparing calcium bromide and calcium bromate by electrodialysis comprises the following steps:

[0066] (1) The temperature is 30°C and the current density is 250A / m 2 The double decomposition electrodialysis makes the alkaline bromine extraction absorption liquid react with the calcium chloride solution to obtain an overflow liquid enriched with calcium bromide and calcium bromate;

[0067] The alkaline bromine extraction absorption liquid added to the first raw material chamber includes 0.7 mol / L sodium bromide and 0.14 mol / L sodium bromate, and its circulation flow rate is 80 L / h;

[0068] The concentration of the 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 liquid was 1.04 mol / L, and the concentration of calcium bromate was 0.14 mol / L;

[0070] The first raw material chamber and the second raw material chamber are continuously fed, the feed concentration is consistent with the initial solution concentration, and the feed rate makes the overflow liquid concentration remain unchanged when the electrodialysis equilibrium is reached;

[0071] The polar liquid in the polar liquid chamber is a sodium sulfate solution, and its circulation flow rate remains unchanged to meet the exchange process of sodium ions in the polar liquid 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, and the circulation flow rate thereof is independently 80 L / h;

[0073] Before the double decomposition electrodialysis begins, the amount of water added to the first product chamber, the amount of water added to the second product chamber, the amount of alkaline bromine extraction 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;

[0074] After 8 hours of double decomposition electrodialysis, the equilibrium state is reached, at which time the overflow liquid of the first product chamber is an overflow liquid enriched with calcium bromide and calcium bromate;

[0075] (2) evaporating and crystallizing the overflow liquid obtained in step (1) at 100° C. to completely precipitate the solid phase, thereby obtaining a mixed salt containing calcium bromide and calcium bromate; leaching the obtained mixed salt with methanol at 40° C. for 6 h, and separating the solid from the liquid to obtain calcium bromate and a filtrate containing calcium bromide;

[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 solids are precipitated, thereby obtaining a distillate and wet calcium bromide; the distillate is reused for the leaching in step (2); and the wet calcium bromide is dried at 60° C. for 12 h to obtain calcium bromide.

[0078] Example 2

[0079] This embodiment provides a Figure 1 In the double decomposition electrodialysis device shown, a method for preparing calcium bromide and calcium bromate by electrodialysis comprises the following steps:

[0080] (1) The temperature is 30°C and the current density is 250A / m 2 The double decomposition electrodialysis makes the alkaline bromine extraction absorption liquid react with the calcium chloride solution to obtain an overflow liquid enriched with calcium bromide and calcium bromate;

[0081] The alkaline bromine extraction absorption liquid added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, and its circulation flow rate is 80 L / h;

[0082] The concentration of the 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 liquid was 1.26 mol / L, and the concentration of calcium bromate was 0.16 mol / L;

[0084] The first raw material chamber and the second raw material chamber are continuously fed, the feed concentration is consistent with the initial solution concentration, and the feed rate makes the overflow liquid concentration remain unchanged when the electrodialysis equilibrium is reached;

[0085] The polar liquid in the polar liquid chamber is a sodium sulfate solution, and its circulation flow rate remains unchanged to meet the exchange process of sodium ions in the polar liquid 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, and the circulation flow rate thereof is independently 80 L / h;

[0087] Before the double decomposition electrodialysis begins, the amount of water added to the first product chamber, the amount of water added to the second product chamber, the amount of alkaline bromine extraction 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;

[0088] After 8 hours of double decomposition electrodialysis, the equilibrium state is reached, at which time the overflow liquid of the first product chamber is an overflow liquid enriched with calcium bromide and calcium bromate;

[0089] (2) evaporating and crystallizing the overflow liquid obtained in step (1) at 100° C. to completely precipitate the solid phase, thereby obtaining a mixed salt containing calcium bromide and calcium bromate; leaching the obtained mixed salt with methanol at 40° C. for 6 h, and separating the solid from the liquid to obtain calcium bromate and a filtrate containing calcium bromide;

[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 solids are precipitated, thereby obtaining a distillate and wet calcium bromide; the distillate is reused for the leaching in step (2); and the wet calcium bromide is dried at 60° C. for 12 h to obtain calcium bromide.

[0092] Example 3

[0093] This embodiment provides a Figure 1 In the double decomposition electrodialysis device shown, a method for preparing calcium bromide and calcium bromate by electrodialysis comprises the following steps:

[0094] (1) The temperature is 30°C and the current density is 400A / m 2 The double decomposition electrodialysis makes the alkaline bromine extraction absorption liquid react with the calcium chloride solution to obtain an overflow liquid enriched with calcium bromide and calcium bromate;

[0095] The alkaline bromine extraction absorption liquid added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, and its circulation flow rate is 80 L / h;

[0096] The concentration of the 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 liquid was 1.19 mol / L, and the concentration of calcium bromate was 0.22 mol / L;

[0098] The first raw material chamber and the second raw material chamber are continuously fed, the feed concentration is consistent with the initial solution concentration, and the feed rate makes the overflow liquid concentration remain unchanged when the electrodialysis equilibrium is reached;

[0099] The polar liquid in the polar liquid chamber is a sodium sulfate solution, and its circulation flow rate remains unchanged, which should satisfy the exchange process of sodium ions in the polar liquid 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, and the circulation flow rate thereof is independently 80 L / h;

[0101] Before the double decomposition electrodialysis begins, the amount of water added to the first product chamber, the amount of water added to the second product chamber, the amount of alkaline bromine extraction 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;

[0102] After 8 hours of double decomposition electrodialysis, the equilibrium state is reached, at which time the overflow liquid of the first product chamber is an overflow liquid enriched with calcium bromide and calcium bromate;

[0103] (2) evaporating and crystallizing the overflow liquid obtained in step (1) at 100° C. to completely precipitate the solid phase, thereby obtaining a mixed salt containing calcium bromide and calcium bromate; leaching the obtained mixed salt with ethanol at 40° C. for 6 h, and separating the solid from the liquid to obtain calcium bromate and a filtrate containing calcium bromide;

[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 solids are precipitated, thereby obtaining a distillate and wet calcium bromide; the distillate is reused for the leaching in step (2); and the wet calcium bromide is dried at 60° C. for 12 h to obtain calcium bromide.

[0106] Example 4

[0107] This embodiment provides a Figure 1 In the double decomposition electrodialysis device shown, a method for preparing calcium bromide and calcium bromate by electrodialysis comprises the following steps:

[0108] (1) The temperature is 30°C and the current density is 300A / m 2 The double decomposition electrodialysis makes the alkaline bromine extraction absorption liquid react with the calcium chloride solution to obtain an overflow liquid enriched with calcium bromide and calcium bromate;

[0109] The alkaline bromine extraction absorption liquid added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, and its circulation flow rate is 60 L / h;

[0110] The concentration of the 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 liquid was 1.30 mol / L, and the concentration of calcium bromate was 0.20 mol / L;

[0112] The first raw material chamber and the second raw material chamber are continuously fed, the feed concentration is consistent with the initial solution concentration, and the feed rate makes the overflow liquid concentration remain unchanged when the electrodialysis equilibrium is reached;

[0113] The polar liquid in the polar liquid chamber is a sodium sulfate solution, and its circulation flow rate remains unchanged, which should satisfy the exchange process of sodium ions in the polar liquid 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, and the circulation flow rate thereof is independently 60 L / h;

[0115] Before the double decomposition electrodialysis begins, the amount of water added to the first product chamber, the amount of water added to the second product chamber, the amount of alkaline bromine extraction 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;

[0116] After 8 hours of double decomposition electrodialysis, the equilibrium state is reached, at which time the overflow liquid of the first product chamber is an overflow liquid enriched with calcium bromide and calcium bromate;

[0117] (2) evaporating and crystallizing the overflow liquid obtained in step (1) at 90° C. to completely precipitate the solid phase, thereby obtaining a mixed salt containing calcium bromide and calcium bromate; leaching the obtained mixed salt at 40° C. for 6 h using methanol, and separating the solid from the liquid to obtain calcium bromate and a filtrate containing calcium bromide;

[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 solids are precipitated, thereby obtaining a distillate and wet calcium bromide; the distillate is reused in the leaching step (2); and the wet calcium bromide is dried at 60° C. for 12 h to obtain calcium bromide.

[0120] Example 5

[0121] This embodiment provides a Figure 1 In the double decomposition electrodialysis device shown, a method for preparing calcium bromide and calcium bromate by electrodialysis comprises the following steps:

[0122] (1) The temperature is 40°C and the current density is 500A / m 2 The double decomposition electrodialysis makes the alkaline bromine extraction absorption liquid react with the calcium chloride solution to obtain an overflow liquid enriched with calcium bromide and calcium bromate;

[0123] The alkaline bromine extraction absorption liquid added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, and its circulation flow rate is 100 L / h;

[0124] The concentration of the 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 liquid was 1.12 mol / L, and the concentration of calcium bromate was 0.29 mol / L;

[0126] The first raw material chamber and the second raw material chamber are continuously fed, the feed concentration is consistent with the initial solution concentration, and the feed rate makes the overflow liquid concentration remain unchanged when the electrodialysis equilibrium is reached;

[0127] The polar liquid in the polar liquid chamber is a sodium sulfate solution, and its circulation flow rate remains unchanged to meet the exchange process of sodium ions in the polar liquid 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, and the circulation flow rate thereof is independently 100 L / h;

[0129] Before the double decomposition electrodialysis begins, the amount of water added to the first product chamber, the amount of water added to the second product chamber, the amount of alkaline bromine extraction 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;

[0130] After 8 hours of double decomposition electrodialysis, the equilibrium state is reached, at which time the overflow liquid of the first product chamber is an overflow liquid enriched with calcium bromide and calcium bromate;

[0131] (2) evaporating the overflow liquid obtained in step (1) to obtain a mixed salt containing calcium bromide and calcium bromate; leaching the obtained mixed salt with methanol at 50° C. for 6 hours, and separating the solid from the liquid to obtain calcium bromate and a filtrate containing calcium bromide;

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

[0133] Example 6

[0134] This embodiment provides a Figure 1 In the double decomposition electrodialysis device shown, a method for preparing calcium bromide and calcium bromate by electrodialysis comprises the following steps:

[0135] (1) The temperature is 30°C and the current density is 300A / m 2 The double decomposition electrodialysis makes the alkaline bromine extraction absorption liquid react with the calcium chloride solution to obtain an overflow liquid enriched with calcium bromide and calcium bromate;

[0136] The alkaline bromine extraction absorption liquid added to the first raw material chamber includes 0.9 mol / L sodium bromide and 0.18 mol / L sodium bromate, and its circulation flow rate is 40 L / h;

[0137] The concentration of the 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 liquid was 1.15 mol / L, and the concentration of calcium bromate was 0.16 mol / L;

[0139] The first raw material chamber and the second raw material chamber are continuously fed, the feed concentration is consistent with the initial solution concentration, and the feed rate makes the overflow liquid concentration remain unchanged when the electrodialysis equilibrium is reached;

[0140] The polar liquid in the polar liquid chamber is a sodium sulfate solution, and its circulation flow rate remains unchanged to meet the exchange process of sodium ions in the polar liquid chamber and the first raw material chamber and the second product chamber;

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

[0142] When double decomposition electrodialysis begins, the amount of water added to the first product chamber, the amount of water added to the second product chamber, the amount of alkaline bromine extraction 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;

[0143] After 8 hours of double decomposition electrodialysis, the equilibrium state is reached, at which time the overflow liquid of the first product chamber is an overflow liquid enriched with calcium bromide and calcium bromate;

[0144] (2) evaporating and crystallizing the overflow liquid obtained in step (1) at 100° C. to completely precipitate the solid phase, thereby obtaining a mixed salt containing calcium bromide and calcium bromate; leaching the obtained mixed salt with methanol at 30° C. for 6 h, and separating the solid from the liquid to obtain calcium bromate and a filtrate containing calcium bromide;

[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 solids are precipitated, thereby obtaining a distillate and wet calcium bromide; the distillate is reused for the leaching in step (2); and the wet calcium bromide is dried at 60° C. for 12 h to obtain calcium bromide.

[0147] In the method provided in the above embodiment, the calcium bromide yield per unit area of ​​ion exchange membrane in double decomposition electrodialysis (Y, kg / (m 2 ·h)), calcium bromide energy consumption (E, kWh·t) and calcium bromide purity (P, wt%) were calculated, and the results are shown in Table 1, where:

[0148]

[0149] =W+W

[0150] In the above formula, c is the concentration of calcium bromide in the overflow liquid when the double decomposition electrodialysis is in equilibrium, mol / L; V D is the overflow volume within 1 h after the double decomposition electrodialysis operation is balanced, L; M is the molar mass of calcium bromide, g / mol; N is the number of electrodialysis membrane stack components, recorded as 5; S is the effective area of ​​a single membrane, recorded as 0.2255m 2 ; t is the operation time, recorded as 1h;

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

[0152] W + When the double decomposition electrodialysis is in equilibrium, the Ca in the overflow liquid 2+ Content, wt%; W - When the double decomposition electrodialysis is in equilibrium, the Br in the overflow liquid - Content, wt%.

[0153] The purity of the 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 embodiment are calculated, wherein e = V R / V A , V A is the volume added during leaching, L; V R is the volume of the extractant recovered by distillation, L.

[0154] Table 1

[0155]

[0156] In summary, one of the raw materials used in the method provided by the present invention is an alkaline bromine extraction absorption liquid, which is a solution after carbonate and bicarbonate are removed by chemical method and absorbed by alkali solution in the process of seawater alkaline bromine extraction. The present invention uses alkaline bromine extraction absorption liquid as a raw material for preparing calcium bromide, which reduces the preparation cost of calcium bromide; moreover, the present invention adopts double decomposition electrodialysis as the main method to realize the preparation of calcium bromide and calcium bromate, which has the advantages of environmental protection in the synthesis process, high conversion rate, short synthesis route, high product purity and low energy consumption. In other words, the present invention greatly reduces the energy consumption of calcium bromide preparation by selecting specific calcium bromide preparation raw materials and coordinating the use of double decomposition electrodialysis.

[0157] The above description is only a specific implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing calcium bromide and calcium bromate by electrodialysis, characterized in that: The method comprises the following steps: (1) using double decomposition electrodialysis to react the alkaline bromine extraction absorption liquid with a calcium chloride solution to obtain an overflow liquid enriched with calcium bromide and calcium bromate; (2) evaporating the overflow liquid obtained in step (1) to obtain a mixed salt containing calcium bromide and calcium bromate; using a leaching agent to leach the obtained mixed salt and perform solid-liquid separation to obtain calcium bromate and a filtrate containing calcium bromide; (3) The calcium bromide-containing filtrate obtained in step (2) is distilled until all solids are precipitated to obtain a distillate and calcium bromide, and the distillate is reused in the leaching described in step (2).

2. The method according to claim 1, characterized in that The alkaline bromine extraction absorption liquid in step (1) comprises 0.7-0.9 mol / L sodium bromide and 0.14-0.18 mol / L sodium bromate.

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

4. The method according to any one of claims 1 to 3, characterized in that: The leaching agent in step (2) includes any one of methanol, ethanol, ethylene glycol or isopropanol, or a combination of at least two thereof; Preferably, the leaching temperature in step (2) is 30-50°C; Preferably, the leaching time in step (2) is more than 6 hours.

5. The method according to any one of claims 1 to 4, characterized in that: The metathesis electrodialysis in step (1) is carried out in a metathesis electrodialysis device; The double decomposition electrodialysis device comprises an extreme liquid 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 components; The electrodialysis membrane stack assembly comprises a cathode plate, a first cation membrane, a first cathode membrane, a second cation membrane, a second cathode membrane, a third cation membrane and an anode plate which are stacked in sequence; The cathode liquids in the cathode liquid chamber circulate through the area between the cathode plate and the first cation membrane, and the area between the third cation membrane and the anode plate respectively; the first raw material liquid in the first raw material chamber circulates through the area between the first cation membrane and the first cathode membrane; the first product liquid in the first product chamber circulates through the area between the first cathode membrane and the second cathode membrane; the second raw material liquid in the second raw material chamber circulates through the area between the second cation membrane and the second cathode mold; the second product liquid in the second product chamber circulates through the area between the second cathode mold and the third cation membrane.

6. The method according to claim 5, characterized in that Before the double decomposition electrodialysis in step (1) is started, water is added to the first product chamber and the second product chamber, the alkaline bromine extraction absorption liquid is added to the first raw material chamber, and the calcium chloride solution is added to the second raw material chamber.

7. The method according to claim 6, characterized in that Before the double decomposition electrodialysis in step (1) is started, the amount of water added to the first product chamber, the amount of water added to the second product chamber, the amount of alkaline bromine extraction 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.

8. The method according to claim 6, characterized in that When the double decomposition electrodialysis method in step (1) is carried out, the circulation flow rate of the first product chamber is 40-100 L / h; Preferably, when the double decomposition electrodialysis method in step (1) is performed, the circulation flow rate of the second product chamber is 40-100 L / h; Preferably, when the double decomposition electrodialysis method in step (1) is performed, the circulation flow rate of the first raw material chamber is 40-100 L / h; Preferably, when the double decomposition electrodialysis method in step (1) is carried out, the circulation flow rate of the second raw material chamber is 40-100 L / h.

9. The method according to claim 6, characterized in that When the double decomposition electrodialysis method described in step (1) is carried out, the feed rates of the first raw material chamber and the second raw material chamber should be such that the overflow concentrations of the first product chamber and the second product chamber remain unchanged when the electrodialysis equilibrium is reached.

10. The method according to any one of claims 1 to 9, characterized in that: The temperature during the double decomposition electrodialysis in step (1) is 30-40° C. Preferably, the current density during the double decomposition electrodialysis in step (1) is 250-500 A / m 2 .

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