Method for preparing sulfuric acid and sodium hydroxide from sodium sulfate and electrolytic bath

Abstract

The three-chamber ionic membrane electrolytic bath is composed of an anode, an ionic membrane, a cathode, a partition plate, an end plate and a pressing device, the partition plate is clamped between the anode and an anionic membrane to form an anode chamber, the partition plate is clamped between the anionic membrane and a cationic membrane to form a middle chamber, and the partition plate is clamped between the cationic membrane and the cathode to form a cathode chamber. By electrolyzing the sodium sulfate solution, the concentration of the produced sulfuric acid solution and sodium hydroxide solution can reach more than 30%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrochemistry, and relates to preparation of sulfuric acid and sodium hydroxide from sodium sulfate electrolysis. BACKGROUND

[0002] Sodium sulfate-containing wastewater produced in chemical production processes is extracted by crystallization to obtain ten-water sodium sulfate at a low price. At present, sodium sulfate solution can be prepared into sulfuric acid solution and sodium hydroxide solution by a method of bipolar membrane electrodialysis, but the concentration of the produced sulfuric acid solution can only reach 1 mol / L, and the concentration of the produced sodium hydroxide solution can only reach 2 mol / L, which is difficult to be applied on a large scale. SUMMARY

[0003] The present application provides a method for preparing sulfuric acid and sodium hydroxide from sodium sulfate and a three-chamber ion exchange membrane electrolytic cell. High-concentration sulfuric acid solution and sodium hydroxide solution are produced by electrolysis of sodium sulfate solution. The three-chamber ion exchange membrane electrolytic cell is composed of an anode, an ion exchange membrane, a cathode, a partition plate, an end plate and a pressing device.

[0004] In the three-chamber electrolytic cell, the anode and the anion exchange membrane are sandwiched by the partition plate to form an anode chamber, the anion exchange membrane and the cation exchange membrane are sandwiched by the partition plate to form an intermediate chamber, and the cation exchange membrane and the cathode are sandwiched by the partition plate to form a cathode chamber.

[0005] In the three-chamber electrolytic cell, a lower liquid inlet and an upper liquid outlet are provided on each chamber partition plate, as well as channels required for solution inlet and outlet of other chambers. The solutions in the three chambers are not mixed, and the ion exchange membrane cannot block the channels required for solution inlet and outlet of each chamber.

[0006] In the three-chamber electrolytic cell, the end plate on one side has solution inlets and outlets of the anode chamber, the intermediate chamber and the cathode chamber, and the solution circulation is provided by external equipment.

[0007] Technical method of the present application:

[0008] (1) The anode chamber and the intermediate chamber are separated by an anion exchange membrane, and the cathode chamber and the intermediate chamber are separated by a cation exchange membrane;

[0009] (2) The solution in the anode chamber is sulfuric acid solution, the solution in the intermediate chamber is sodium sulfate solution, and the solution in the cathode chamber is sodium hydroxide solution;

[0010] (3) Dilute sulfuric acid solution, dilute sodium hydroxide solution and concentrated sodium sulfate solution are prepared, and the liquid supply circulation system is connected to supply liquid to the three-chamber ion exchange membrane electrolytic cell;

[0011] (4) A direct current power supply is connected to supply power for electrolysis of the three-chamber ion exchange membrane electrolytic cell;

[0012] (5) Hydrogen ions are generated by anode reaction, and hydroxide ions are generated by cathode reaction;

[0013] (6) Under the action of an electric field, sulfate ions in the intermediate chamber solution move toward the anode and enter the anode chamber through the anion membrane, while sodium ions move toward the cathode and enter the cathode chamber through the cation membrane.

[0014] (7) Hydrogen ions in the anode chamber solution are blocked by the anion exchange membrane and remain in the anode chamber. The anolyte accepts hydrogen ions produced by the anode reaction and sulfate ions from the intermediate chamber, and the sulfuric acid concentration increases.

[0015] (8) Hydroxide ions in the cathode chamber solution are blocked by the cation membrane and remain in the cathode chamber. The cathode solution accepts hydroxide ions generated by the cathode reaction and sodium ions from the intermediate chamber, and the sodium hydroxide concentration increases.

[0016] (9) Sulfate ions in the intermediate chamber solution enter the anode chamber, sodium ions enter the cathode chamber, and the concentration of sodium sulfate solution decreases.

[0017] The advantage of this invention is that by using a three-chamber ion-exchange membrane electrolyzer to electrolyze sodium sulfate solution, the concentrations of the sulfuric acid solution and sodium hydroxide solution produced are much higher than those produced by bipolar membrane electrodialysis. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a three-chamber ion-exchange membrane electrolyzer. Figure 2 This is a schematic diagram illustrating the principle of the present invention.

[0019] The diagram is labeled as follows: 1-end plate, 2-anode, 3-anion exchange membrane, 4-cation exchange membrane, 5-cathode, 6-partition, 11-anode chamber solution inlet, 12-anode chamber solution outlet, 13-intermediate chamber solution inlet, 14-intermediate chamber solution outlet, 15-cathode chamber solution inlet, 16-cathode chamber solution outlet. Detailed Implementation

[0020] Referring to the attached diagram, the specific implementation method is as follows:

[0021] An anode chamber is formed by a partition between the anode and the anion exchange membrane. The partition has inlet and outlet for the anode chamber solution, with the solution entering from the bottom and exiting from the top.

[0022] An anion exchange membrane and a cation exchange membrane are sandwiched together to form an intermediate chamber. The partition has an inlet and outlet for the intermediate chamber solution, with the solution entering from the bottom and exiting from the top.

[0023] A partition is sandwiched between the cation membrane and the cathode to form a cathode chamber. The partition has inlet and outlet for the cathode chamber solution, with the solution entering from the bottom and exiting from the top.

[0024] The solutions in the three chambers do not mix with each other. Each chamber has a partition with channels for the solutions from other chambers to enter and exit. The ion membrane cannot block the channels for the solutions from each chamber to enter and exit.

[0025] A three-chamber ion-exchange membrane electrolyzer is constructed by assembling the anode, separator, anion exchange membrane, separator, cation exchange membrane, separator, and cathode in that order, with end plates on both sides.

[0026] The end plate on one side is equipped with the solution inlet and outlet of the anode chamber, the solution inlet and outlet of the intermediate chamber, and the solution inlet and outlet of the cathode chamber.

[0027] Terminals are provided for the cathode and anode.

[0028] The three-chamber ion membrane electrolyzer is compressed using a clamping device, and each inlet and outlet is connected accordingly.

[0029] The anode chamber and the intermediate chamber are separated by an anion exchange membrane, and the cathode chamber and the intermediate chamber are separated by a cation exchange membrane.

[0030] The solution in the anode chamber is sulfuric acid solution, the solution in the intermediate chamber is sodium sulfate solution, and the solution in the cathode chamber is sodium hydroxide solution.

[0031] Prepare 1 mol / L sulfuric acid solution, 2 mol / L sodium hydroxide solution, and saturated sodium sulfate solution, and connect the liquid supply circulation system to supply the solution to the three-chamber ion-exchange membrane electrolyzer.

[0032] Connect the DC power supply to power the three-chamber ion-exchange membrane electrolyzer.

[0033] The anodic reaction produces hydrogen ions, and the cathodic reaction produces hydroxide ions.

[0034] Under the influence of an electric field, sulfate ions in the intermediate chamber solution move towards the anode and enter the anode chamber through the anion exchange membrane, while sodium ions move towards the cathode and enter the cathode chamber through the cation exchange membrane.

[0035] Hydrogen ions in the anolyte solution are blocked by the anion exchange membrane and remain in the anolyte. The anolyte solution accepts hydrogen ions produced by the anolyte reaction and sulfate ions from the intermediate chamber, thus increasing the sulfuric acid concentration in the anolyte.

[0036] Hydroxide ions in the cathode chamber solution are blocked by the cation membrane and remain in the cathode chamber. The cathode chamber solution accepts hydroxide ions produced by the cathode reaction and sodium ions from the intermediate chamber, thus increasing the sodium hydroxide concentration in the cathode solution.

[0037] Sulfate ions in the intermediate chamber solution enter the anode chamber, and sodium ions enter the cathode chamber, thus reducing the sodium sulfate concentration in the intermediate chamber solution.

[0038] Electrolysis of sodium sulfate solution using a three-chamber ion-exchange membrane electrolyzer can produce sulfuric acid and sodium hydroxide solutions with concentrations exceeding 30%.

Claims

1. A method for preparing sulfuric acid and sodium hydroxide from sodium sulfate and an electrolytic cell, characterized in that: The electrolytic cell is a three-chamber ion-exchange membrane electrolytic cell, consisting of an anode, ion-exchange membrane, cathode, partition, end plate, and clamping device. It electrolyzes sodium sulfate solution to produce sulfuric acid solution and sodium hydroxide solution.

2. The method and electrolytic cell for preparing sulfuric acid and sodium hydroxide from sodium sulfate according to claim 1, characterized in that: In the three-chamber electrolytic cell, a partition is sandwiched between the anode and the anion membrane to form the anode chamber, a partition is sandwiched between the anion membrane and the cation membrane to form the intermediate chamber, and a partition is sandwiched between the cation membrane and the cathode to form the cathode chamber.

3. The method and electrolytic cell for preparing sulfuric acid and sodium hydroxide from sodium sulfate according to claim 1, characterized in that: In the three-chamber electrolytic cell, each chamber partition is provided with a lower liquid inlet and an upper liquid outlet, as well as channels for the entry and exit of solutions from other chambers. The solutions in the three chambers do not mix with each other, and the ion membrane cannot block the channels for the entry and exit of solutions from each chamber.

4. The method and electrolytic cell for preparing sulfuric acid and sodium hydroxide from sodium sulfate according to claim 1, characterized in that: The three-chamber electrolytic cell has solution inlet and outlet for the anode chamber, solution inlet and outlet for the middle chamber, and solution inlet and outlet for the cathode chamber on one end plate, with solution circulation provided by external equipment.

5. The method and electrolytic cell for preparing sulfuric acid and sodium hydroxide from sodium sulfate according to claim 1, characterized in that: (1) The anode chamber and the intermediate chamber are separated by anion exchange membrane, and the cathode chamber and the intermediate chamber are separated by cation exchange membrane; (2) The solution in the anode chamber is sulfuric acid solution, the solution in the intermediate chamber is sodium sulfate solution, and the solution in the cathode chamber is sodium hydroxide solution; (3) Prepare dilute sulfuric acid solution, dilute sodium hydroxide solution and concentrated sodium sulfate solution, and connect the liquid supply circulation system to supply liquid to the three-chamber ion membrane electrolyzer. (4) Connect the DC power supply to power the three-chamber ion-exchange membrane electrolyzer. (5) Hydrogen ions are produced by the anode reaction and hydroxide ions are produced by the cathode reaction. (6) Under the action of an electric field, sulfate ions in the intermediate chamber solution move toward the anode and enter the anode chamber through the anion membrane, while sodium ions move toward the cathode and enter the cathode chamber through the cation membrane. (7) Hydrogen ions in the anode chamber solution are blocked by the anion exchange membrane and remain in the anode chamber. The anode chamber solution receives hydrogen ions produced by the anode reaction and sulfate ions from the intermediate chamber, and the sulfuric acid concentration in the anode chamber solution increases. (8) Hydroxide ions in the cathode chamber solution are blocked by the cation membrane and remain in the cathode chamber. The cathode chamber solution receives hydroxide ions generated by the cathode reaction and sodium ions from the intermediate chamber, and the sodium hydroxide concentration in the cathode chamber solution increases. (9) Sulfate ions in the intermediate chamber solution enter the anode chamber, sodium ions enter the cathode chamber, and the sodium sulfate concentration in the intermediate chamber solution decreases.

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