Method for resourceful value-added utilization of high-concentration sodium sulfate wastewater

Abstract

The application provides a method for resourceful and value-added utilization of high-concentration sodium sulfate wastewater, comprising the following steps: (1) purifying sodium sulfate wastewater; (2) adding the purified sodium sulfate solution and a carbonic acid solution into a separation device for electrolysis regeneration to obtain a sodium hydroxide solution, a sodium bicarbonate solution and a sulfuric acid solution; and (3) evaporating and crystallizing the sodium bicarbonate solution to obtain sodium bicarbonate solid, and returning the sodium hydroxide solution to step (1) for use and / or evaporating and crystallizing the sodium hydroxide solution to obtain sodium hydroxide solid. The method uses sodium sulfate wastewater and carbonic acid as raw materials, removes impurities through precipitation and performs specific separation, and is converted into high-value products, i.e. sulfuric acid, sodium bicarbonate and sodium hydroxide, thereby successfully realizing resourceful and value-added utilization of the sodium sulfate wastewater. Compared with a traditional evaporation and concentration process for preparing low-value sodium sulfate, the additional value of the products is obviously increased. The treatment method has the characteristics of simple operation, high product value and good economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment and resource utilization technology and recycling, and specifically relates to a method for the resource-based value-added utilization of high-concentration sodium sulfate wastewater. Background Technology

[0002] In recent years, industries such as metallurgy, power plants, steel mills, and coking plants have been generating large amounts of high-concentration saline wastewater daily, especially sodium sulfate wastewater, with both production and discharge volumes continuously increasing. The production of sodium sulfate in industrial processes is substantial. If a highly efficient sodium sulfate wastewater recovery technology can be developed and its products transformed into high-value products, it will not only achieve the goal of wastewater treatment but also realize the resource-based value-added utilization of sodium sulfate.

[0003] Currently, the main technology for treating high-concentration sodium sulfate wastewater is thermal treatment, which uses steam as a heat source to evaporate and crystallize sodium sulfate. Although this process can achieve freshwater reuse and sodium sulfate regeneration, it consumes too much energy when treating large-scale wastewater, and sodium sulfate has low commercial value, resulting in poor economic benefits. Summary of the Invention

[0004] To address the above problems, this invention provides a method for the resource-based value-added utilization of high-concentration sodium sulfate wastewater.

[0005] To achieve the above objectives, the present invention proposes the following solution:

[0006] A method for the resource-based value-added utilization of high-concentration sodium sulfate wastewater includes:

[0007] (1) Add sodium hydroxide or sodium hydroxide solution to sodium sulfate wastewater, and after the reaction, separate the solid and liquid to obtain purified sodium sulfate solution;

[0008] (2) The purified sodium sulfate solution and carbonic acid solution are added to the separation device for electrolytic regeneration to obtain sodium hydroxide solution, sodium bicarbonate solution and sulfuric acid solution;

[0009] (3) Evaporate the sodium bicarbonate solution to obtain sodium bicarbonate solid, and return the sodium hydroxide solution to step (1) for use and / or evaporate and crystallize to obtain sodium hydroxide solid.

[0010] Preferably, the separation device includes: a separation chamber and a first cation exchange membrane, a first anion exchange membrane, a second cation exchange membrane, a second anion exchange membrane, and a third cation exchange membrane arranged sequentially and at intervals within the separation chamber, wherein the first cation exchange membrane, the first anion exchange membrane, the second cation exchange membrane, the second anion exchange membrane, and the third cation exchange membrane divide the separation chamber into a sequentially arranged chamber 1 for containing sodium sulfate solution, a chamber 2 for containing sodium bicarbonate solution, a chamber 3 for containing carbonic acid solution, a chamber 4 for containing sulfuric acid solution, a chamber 5 for containing sodium sulfate solution, and a chamber 6 for containing sodium hydroxide solution.

[0011] Preferably, in step (2), the purified sodium sulfate solution is added to chamber one and chamber five, and the initial sodium bicarbonate solution, carbonic acid solution, sulfuric acid solution and sodium hydroxide solution are added to chamber two, chamber three, chamber four and chamber six respectively. Then, electrolysis is performed to obtain sodium bicarbonate solution, sulfuric acid solution and sodium hydroxide solution in chamber two, chamber four and chamber six respectively.

[0012] Preferably, in step (2), the concentration of the sodium sulfate solution is 5~100 g / L.

[0013] Preferably, in step (1), the amount of sodium hydroxide added is controlled to maintain the pH value of the reaction system at 8-12; and the mass fraction of the sodium hydroxide solution is 10-40%.

[0014] Preferably, in step (2), the current density of the electrolytic regeneration is 2–20 mA / cm². 2 .

[0015] Preferably, in step (2), the reaction temperature of the electrolytic regeneration is 30~80℃.

[0016] Preferably, in step (2), the initial molar concentration of the sodium bicarbonate solution is 0.01~0.2 mol / L.

[0017] Preferably, in step (2), the initial molar concentration of sulfuric acid is 0.01~0.2 mol / L.

[0018] Preferably, in step (2), the initial molar concentration of the sodium hydroxide solution is 0.01~0.2 mol / L.

[0019] Preferably, in step (2), the molar concentration of carbonic acid in chamber three is 0.1~3 mol / L; more preferably, during the electrolysis process, carbon dioxide is introduced into chamber three to maintain the concentration of carbonic acid in the solution.

[0020] Preferably, the first cation exchange membrane, the first anion exchange membrane, the second cation exchange membrane, the second anion exchange membrane, and the third cation exchange membrane are made of any one of polyethylene, polypropylene, and polyvinyl chloride.

[0021] The active groups on the first and second anion exchange membranes are any one of quaternary phosphorus, amino, and aromatic amino groups.

[0022] Preferably, the active groups on the first cation exchange membrane, the second cation exchange membrane, and the third cation exchange membrane are any one of sulfonic acid groups, phosphate groups, and carboxylic acid groups.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention uses sodium sulfate wastewater and carbonic acid as raw materials. Through precipitation, impurity removal, and specific separation, the wastewater is transformed into high-value products: sulfuric acid, sodium bicarbonate, and sodium hydroxide. This successfully realizes the resource-based value-added utilization of sodium sulfate wastewater. Compared with the traditional process of evaporation and concentration to prepare low-value sodium sulfate, the added value of the products is significantly increased. The treatment method of this invention has the characteristics of simple operation, high product value, and good economic benefits. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the separation device provided by the present invention.

[0027] 1. First cation exchange membrane; 2. First anion exchange membrane; 3. Second cation exchange membrane; 4. Second anion exchange membrane; 5. Third cation exchange membrane; 6. Current collector; 7. Chamber 1; 8. Chamber 2; 9. Chamber 3; 10. Chamber 4; 11. Chamber 5; 12. Chamber 6. Detailed Implementation

[0028] A method for the resource-based value-added utilization of high-concentration sodium sulfate wastewater includes:

[0029] (1) Add sodium hydroxide or sodium hydroxide solution to sodium sulfate wastewater, and after the reaction, remove impurity elements such as nickel, cobalt and manganese through solid-liquid separation to obtain purified sodium sulfate solution.

[0030] (2) The purified sodium sulfate solution and carbonic acid solution are added to the separation device for electrolytic regeneration to obtain sodium hydroxide solution, sodium bicarbonate solution and sulfuric acid solution;

[0031] (3) Evaporate the sodium bicarbonate solution to obtain sodium bicarbonate solid, and return the sodium hydroxide solution to step (1) for use and / or evaporate and crystallize to obtain sodium hydroxide solid.

[0032] Preferably, the separation device includes: a separation chamber and a first cation exchange membrane, a first anion exchange membrane, a second cation exchange membrane, a second anion exchange membrane, and a third cation exchange membrane arranged sequentially and at intervals within the separation chamber, wherein the first cation exchange membrane, the first anion exchange membrane, the second cation exchange membrane, the second anion exchange membrane, and the third cation exchange membrane divide the separation chamber into a sequentially arranged chamber 1 for containing sodium sulfate solution, a chamber 2 for containing sodium bicarbonate solution, a chamber 3 for containing carbonic acid solution, a chamber 4 for containing sulfuric acid solution, a chamber 5 for containing sodium sulfate solution, and a chamber 6 for containing sodium hydroxide solution.

[0033] Preferably, in step (2), purified sodium sulfate solution is added to chambers one and five, and initial sodium bicarbonate solution, carbonic acid solution, sulfuric acid solution, and sodium hydroxide solution are added to chambers two, three, four, and six, respectively. Electrolysis is then performed to obtain sodium bicarbonate solution, sulfuric acid solution, and sodium hydroxide solution in chambers two, four, and six, respectively. Chambers one and five yield sulfuric acid solutions containing low concentrations of sodium ions, which can be used as acidic leaching agents (e.g., for resource recovery), pH adjusters, etc., in industrial production.

[0034] Preferably, in step (2), the concentration of the sodium sulfate solution is 5~100 g / L.

[0035] Preferably, in step (1), the amount of sodium hydroxide added is such that the pH value of the reaction system is controlled at 8-12, more preferably 10-12; and the mass fraction of the sodium hydroxide solution is 10-40%, more preferably 10-30%.

[0036] Preferably, in step (2), the current density of the electrolytic regeneration is 2–20 mA / cm². 2 More preferably 5~15 mA / cm 2 .

[0037] Preferably, in step (2), the reaction temperature of the electrolytic regeneration is 30~80℃, and more preferably 50~80℃.

[0038] Preferably, in step (2), the molar concentration of carbonic acid in chamber three is 0.1~3 mol / L, more preferably 0.1~1 mol / L. During subsequent electrolysis, the carbonic acid concentration in chamber three is maintained by introducing carbon dioxide.

[0039] In this invention, in order to facilitate the smooth progress of electrolysis, the solutions in each chamber must be able to conduct electricity. To achieve this, low concentrations of the target product are added to chambers two, four and six, namely, low concentrations of sodium bicarbonate solution, sulfuric acid solution and sodium hydroxide solution are added to chambers two, four and six respectively.

[0040] Preferably, in step (2), the initial molar concentration of the sodium bicarbonate solution is 0.01~0.2 mol / L, and more preferably 0.1~0.2 mol / L.

[0041] Preferably, in step (2), the initial molar concentration of sulfuric acid is 0.01~0.2 mol / L, and more preferably 0.1~0.2 mol / L;

[0042] Preferably, in step (2), the initial molar concentration of the sodium hydroxide solution is 0.01~0.2 mol / L, and more preferably 0.1~0.2 mol / L.

[0043] Preferably, the first cation exchange membrane, the first anion exchange membrane, the second cation exchange membrane, the second anion exchange membrane, and the third cation exchange membrane are made of any one of polyethylene, polypropylene, and polyvinyl chloride, with polyvinyl chloride being more preferred.

[0044] Preferably, the active groups on the first and second anion exchange membranes are any one of quaternary phosphorus groups, amino groups, and aromatic amino groups, with quaternary phosphorus groups being more preferred.

[0045] The active groups on the first, second, and third cation exchange membranes are any one of sulfonic acid groups, phosphate groups, and carboxylic acid groups, and are more preferably phosphate groups.

[0046] Preferably, the bottoms of chamber one and chamber five of the sodium sulfate wastewater are connected by a pipe;

[0047] Preferably, each containment chamber has an inlet at the bottom and an outlet at the top.

[0048] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0049] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0050] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0051] Example 1

[0052] The electrolytic separation device used in this embodiment is as follows: Figure 1 As shown, it includes: a separation chamber and a first cation exchange membrane 1, a first anion exchange membrane 2, a second cation exchange membrane 3, a second anion exchange membrane 4, and a third cation exchange membrane 5 arranged sequentially and at intervals within the separation chamber. The first cation exchange membrane 1, the first anion exchange membrane 2, the second cation exchange membrane 3, the second anion exchange membrane 4, and the third cation exchange membrane 5 divide the separation chamber into a sodium sulfate wastewater chamber 1 7, a sodium bicarbonate solution chamber 2 8, a carbonic acid solution chamber 3 9, a sulfuric acid solution chamber 4 10, a sodium sulfate wastewater chamber 5 11, and a sodium hydroxide solution chamber 6 12 arranged sequentially.

[0053] Among them, the first cation exchange membrane 1, the first anion exchange membrane 2, the second cation exchange membrane 3, the second anion exchange membrane 4 and the third cation exchange membrane 5 are made of polyvinyl chloride;

[0054] The active groups on the first anion exchange membrane 2 and the second anion exchange membrane 4 are quaternary phosphorus groups;

[0055] Among them, the active groups on the first cation exchange membrane 1, the second cation exchange membrane 3 and the third cation exchange membrane 5 are phosphate groups;

[0056] Among them, the bottom of sodium sulfate wastewater chamber 7 and chamber 511 are connected by a pipe;

[0057] The casing of the separation device is made of polyethylene.

[0058] Methods for the resource-based value-added utilization of sodium sulfate wastewater include:

[0059] First, a 30% sodium hydroxide solution was added to 10L of sodium sulfate wastewater (sodium sulfate concentration 25.0 g / L) to adjust the pH to 10.0. After reacting for a period of time, the mixture was filtered to obtain a sodium sulfate solution. Then, 5L of sodium sulfate solution, 5L of 0.1mol / L sodium bicarbonate solution, 5L of 0.1mol / L carbonic acid solution, 5L of 0.1mol / L sulfuric acid solution, 5L of sodium sulfate solution, and 5L of 0.1mol / L sodium hydroxide solution were sequentially added to chambers one, two, three, four, five, and six, at a concentration of 10 mA / cm². 2 Electrolysis was started at a current density of 50°C, and carbon dioxide was introduced into chamber three during electrolysis to maintain the concentration of carbonic acid. After electrolysis, sulfuric acid solution, sodium bicarbonate solution, and sodium hydroxide solution were obtained in chambers four, two, and six, respectively, and sulfuric acid solution containing low concentration of sodium ions was obtained in chambers one and five. The sodium bicarbonate solution and sodium hydroxide solution were evaporated and crystallized to obtain 188.1 g of sodium bicarbonate (purity >99%) and 89.5 g of sodium hydroxide (purity >99%). The overall recovery rate of sodium sulfate was 98.3%.

[0060] Example 2

[0061] This embodiment uses the same electrolytic separation device as in Embodiment 1.

[0062] Methods for the resource-based value-added utilization of sodium sulfate wastewater include:

[0063] First, a 15% sodium hydroxide solution was added to 15L of sodium sulfate wastewater (sodium sulfate concentration 5.0g / L) to adjust the pH to 11.0. After reacting for a period of time, the mixture was filtered to obtain a sodium sulfate solution. Then, 7.5L of sodium sulfate solution, 7.5L of 0.2mol / L sodium bicarbonate solution, 7.5L of 0.1mol / L carbonic acid solution, 7.5L of 0.2mol / L sulfuric acid solution, 7.5L of sodium sulfate solution, and 7.5L of 0.2mol / L sodium hydroxide solution were sequentially added to chambers one, two, three, four, five, and six, at a rate of 5mA / cm². 2 Electrolysis was started at a current density of 60°C, and carbon dioxide was introduced into chamber three during electrolysis to maintain the concentration of carbonic acid. After electrolysis, sulfuric acid solution, sodium bicarbonate solution, and sodium hydroxide solution were obtained. The sodium bicarbonate solution and sodium hydroxide solution were evaporated and crystallized to obtain 170.2 g of sodium bicarbonate (purity >99%) and 81.1 g of sodium hydroxide (purity >99%). The overall recovery rate of sodium sulfate was 99.3%.

[0064] Example 3

[0065] This embodiment uses the same electrolytic separation device as in Embodiment 1.

[0066] Methods for the resource-based value-added utilization of sodium sulfate wastewater include:

[0067] First, a 30% sodium hydroxide solution was added to 10L of sodium sulfate wastewater (sodium sulfate concentration 100.0g / L) to adjust the pH to 12.0. After reacting for a period of time, the mixture was filtered to obtain a sodium sulfate solution. Then, 5L of sodium sulfate solution, 5L of 0.2mol / L sodium bicarbonate solution, 5L of 0.1mol / L carbonic acid solution, 5L of 0.2mol / L sulfuric acid solution, 5L of sodium sulfate solution, and 5L of 0.2mol / L sodium hydroxide solution were sequentially added to chambers one, two, three, four, five, and six, at a concentration of 15mA / cm². 2 Electrolysis was started at a current density of 80°C, and the temperature inside the separation device was maintained at 80°C. During electrolysis, carbon dioxide was introduced into chamber three to maintain the concentration of carbonic acid. After electrolysis, sulfuric acid solution, sodium bicarbonate solution, and sodium hydroxide solution were obtained. The sodium bicarbonate solution and sodium hydroxide solution were evaporated and crystallized to obtain 664.6 g of sodium bicarbonate (purity >99%) and 316.5 g of sodium hydroxide (purity >99%). The overall recovery rate of sodium sulfate was 98.0%.

[0068] Comparative Example 1

[0069] First, a 30% sodium hydroxide solution was added to 10 L of sodium sulfate wastewater (sodium sulfate concentration 25.0 g / L) to adjust the pH to 10.0. After reacting for a period of time, the solution was filtered and separated to obtain a sodium sulfate solution. Then, the sodium sulfate solution was evaporated and crystallized at a high temperature of 90℃ to obtain sodium sulfate crystals (the overall recovery rate was 85.6% and the purity was 92.3%).

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for the resource-based value-added utilization of high-concentration sodium sulfate wastewater, characterized in that, include: (1) Add sodium hydroxide or sodium hydroxide solution to sodium sulfate wastewater, and after the reaction, separate the solid and liquid to obtain purified sodium sulfate solution; (2) The purified sodium sulfate solution and carbonic acid solution are added to the separation device for electrolytic regeneration to obtain sodium hydroxide solution, sodium bicarbonate solution and sulfuric acid solution; The separation device includes: a separation chamber and a first cation exchange membrane, a first anion exchange membrane, a second cation exchange membrane, a second anion exchange membrane, and a third cation exchange membrane arranged sequentially and at intervals within the separation chamber. The first cation exchange membrane, the first anion exchange membrane, the second cation exchange membrane, the second anion exchange membrane, and the third cation exchange membrane divide the separation chamber into a sequentially arranged chamber 1 for containing sodium sulfate solution, a chamber 2 for containing sodium bicarbonate solution, a chamber 3 for containing carbonic acid solution, a chamber 4 for containing sulfuric acid solution, a chamber 5 for containing sodium sulfate solution, and a chamber 6 for containing sodium hydroxide solution. The bottoms of the sodium sulfate wastewater chambers 1 and 5 are connected by a pipe. (3) Evaporate the sodium bicarbonate solution to obtain sodium bicarbonate solid, and return the sodium hydroxide solution to step (1) for use and / or evaporate and crystallize to obtain sodium hydroxide solid.

2. The method for resource-based value-added utilization of high-concentration sodium sulfate wastewater as described in claim 1, characterized in that, In step (2), the purified sodium sulfate solution is added to chamber one and chamber five, and the initial sodium bicarbonate solution, carbonic acid solution, sulfuric acid solution and sodium hydroxide solution are added to chamber two, chamber three, chamber four and chamber six respectively. Then electrolysis is performed to obtain sodium bicarbonate solution, sulfuric acid solution and sodium hydroxide solution in chamber two, chamber four and chamber six respectively.

3. The method for resource-based value-added utilization of high-concentration sodium sulfate wastewater as described in claim 1, characterized in that, In step (2), the concentration of the sodium sulfate solution is 5~100 g / L.

4. The method for resource-based value-added utilization of high-concentration sodium sulfate wastewater as described in claim 1, characterized in that, In step (1), the amount of sodium hydroxide added is determined according to controlling the pH value of the reaction system at 8 to 12; the mass fraction of the sodium hydroxide solution is 10 to 40%.

5. The method for resource-based value-added utilization of high-concentration sodium sulfate wastewater as described in claim 1, characterized in that, In step (2), the current density of the electrolytic regeneration is 2–20 mA / cm². 2 .

6. The method for resource-based value-added utilization of high-concentration sodium sulfate wastewater as described in claim 1, characterized in that, In step (2), the reaction temperature of the electrolytic regeneration is 30~80℃.

7. The method for resource-based value-added utilization of high-concentration sodium sulfate wastewater as described in claim 2, characterized in that, In step (2), the initial molar concentration of sodium bicarbonate solution is 0.01~0.2 mol / L; In step (2), the initial molar concentration of sulfuric acid is 0.01~0.2 mol / L; In step (2), the initial molar concentration of sodium hydroxide solution is 0.01~0.2 mol / L.

8. The method for resource-based value-added utilization of high-concentration sodium sulfate wastewater as described in claim 1, characterized in that, In step (2), the molar concentration of carbonic acid in chamber 3 is 0.1~3 mol / L; during electrolysis, carbon dioxide is introduced into chamber 3 to maintain the concentration of carbonic acid in the solution.

9. The method for resource-based value-added utilization of high-concentration sodium sulfate wastewater as described in claim 1, characterized in that, The first cation exchange membrane, the first anion exchange membrane, the second cation exchange membrane, the second anion exchange membrane, and the third cation exchange membrane are made of any one of polyethylene, polypropylene, and polyvinyl chloride. The active groups on the first and second anion exchange membranes are any one of quaternary phosphorus, amino, and aromatic amino groups; The active groups on the first cation exchange membrane, the second cation exchange membrane, and the third cation exchange membrane are any one of sulfonic acid groups, phosphate groups, and carboxylic acid groups.

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