A comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater

Abstract

The present invention belongs to the field of wastewater treatment, and particularly relates to a comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater. The specific steps are as follows: (1) A catalyst is added to the sulfur-containing wastewater, and hydrogen is introduced. After stirring, it is left to stand, and the supernatant of the sulfur-containing wastewater is obtained by filtration; (2) The supernatant of the sulfur-containing wastewater is slowly added to the aluminum-containing wastewater, and hydrogen sulfide gas is absorbed with sodium hydroxide solution. When the pH of the system reaches 5.0, the addition of the supernatant of the sulfur-containing wastewater is stopped, and the temperature is continued to be raised and stirred; (3) After driving out the hydrogen sulfide gas, sodium hydroxide solution is added to prepare a sodium aluminate solution. The sodium aluminate solution is slowly added to the aluminum-containing wastewater. After all the sodium aluminate solution is added, it is stirred and then transferred to a sedimentation tank. After sedimentation, a flocculant is obtained. This method treats waste with waste, saves costs and energy consumption, reduces the generation of solid hazardous waste, more than 80% of aluminum is recovered and prepared into a flocculant, and more than 99% of S is recycled.

Description

Technical Field

[0001] The present invention belongs to the field of wastewater treatment, and specifically relates to a comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater. Background Art

[0002] Sulfur-containing wastewater and aluminum-containing wastewater are two types of typical difficult-to-treat wastewaters. The treatment methods for sulfur-containing wastewater mainly include air oxidation method, electrochemical oxidation method, electrodialysis method, chemical precipitation method, chemical oxidation method, and biological method, etc., aiming to convert low-valent sulfur into sulfate, elemental sulfur or sulfide precipitate, and precipitate it from water in solid form; the more economical treatment method for aluminum-containing wastewater is to convert it into by-products with economic benefits such as aluminum sulfate, basic aluminum chloride, ammonium alum, and flocculant.

[0003] The difficulties in the above treatment of sulfur-containing wastewater lie in low efficiency, high treatment cost, and small unit treatment capacity. Since sulfate has a certain solubility in wastewater, it is difficult to remove it completely, and it is challenging to carry out subsequent biochemical treatment of sulfate-containing wastewater. Among the more economical treatment methods for aluminum-containing wastewater mentioned above, the aluminum-containing wastewater that can produce qualified by-products is relatively limited, and most of them are wastewaters containing a mixture of various inorganic salts. Therefore, most treatment methods for aluminum-containing wastewater mainly produce waste salts, and a large amount of solid hazardous waste is generated while treating the wastewater. Summary of the Invention

[0004] In view of the many problems existing in the treatment process of the above sulfur-containing wastewater and aluminum-containing wastewater, the present invention provides a comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater. This method uses waste to treat waste, saves costs and energy consumption, reduces the generation of solid hazardous waste containing aluminum and sodium salts, and more than 80% of aluminum is recovered and prepared into flocculant, and more than 99% of S is recovered and prepared into a mixture of sodium sulfide and sodium hydrosulfide as a reducing agent for use as a production raw material.

[0005] The inventor first catalytically reduces and converts different valent sulfur-containing compounds in the wastewater into sulfur in the -2 valence state. Considering the extremely low water solubility of hydrogen sulfide under acidic conditions and the acidity of aluminum-containing wastewater, the reduced sulfur-containing wastewater is slowly added to the aluminum-containing wastewater, and the pH of the system is controlled to be less than 5.0. The sulfide in the -2 valence state in the sulfur-containing wastewater is converted into hydrogen sulfide gas, and this gas is absorbed by liquid caustic soda and converted into a mixture of sodium sulfide and sodium hydrosulfide. When the pH of the system reaches 5.0, the addition of sulfur-containing wastewater is stopped, and a certain amount of liquid caustic soda is slowly added to prepare sodium aluminate. The sodium aluminate solution is slowly added to the aluminum-containing wastewater, and the pH of the system is 3 - 5. After stirring and sedimentation, a flocculant is obtained.

[0006] The technical solution of the present invention is specifically as follows:

[0007] A comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater, the specific steps are as follows:

[0008] (1) Add a catalyst to the sulfur-containing wastewater at 20 - 30 °C, introduce hydrogen gas and stir. When the pressure of the system reaches above 0.1 MPa, stop introducing hydrogen gas, continue stirring and then let it stand to precipitate the catalyst, and filter to obtain the supernatant of the sulfur-containing wastewater;

[0009] (2) Slowly add the supernatant of the sulfur-containing wastewater to the aluminum-containing wastewater to generate hydrogen sulfide. Use sodium hydroxide solution A to absorb the hydrogen sulfide gas to prepare a mixture of sodium sulfide and sodium hydrosulfide. When the pH of the system reaches 5.0, stop adding the supernatant of the sulfur-containing wastewater, continue heating to 90 - 100 °C and keep stirring at this temperature for 0.5 - 1 h to drive out the remaining hydrogen sulfide gas;

[0010] (3) After driving out the hydrogen sulfide gas, slowly add sodium hydroxide solution B to prepare a sodium aluminate solution. Keep adding the sodium aluminate solution to the aluminum-containing wastewater at 50 - 60 °C slowly. After all the sodium aluminate solution is added, continue stirring and then transfer it to a sedimentation tank. After sedimentation, a flocculant is obtained.

[0011] Preferably, the indexes for detecting the sulfur-containing wastewater are: COD 90000 - 10000 mg / L, ammonia nitrogen 3000 - 5000 mg / L, and sulfide content 25000 - 30000 mg / L.

[0012] Preferably, in the aluminum-containing wastewater, the aluminum content is 30000 - 40000 mg / L.

[0013] Preferably, in step (1), the mass ratio of the catalyst to the sulfur-containing wastewater is 0.001 - 0.002:1.

[0014] Preferably, in step (3), the mass ratio of the 30% sodium hydroxide solution B to the aluminum-containing wastewater is 0.1 - 0.2:1.

[0015] Preferably, in step (3), the mass ratio of the sodium aluminate solution to the aluminum-containing wastewater is 1 - 2:1.

[0016] Preferably, when the supernatant of the sulfur-containing wastewater is slowly added to the aluminum-containing wastewater in step (2), keep the pH below 5.0 and the pressure below 0.01 MPa.

[0017] Preferably, the sulfur-containing wastewater is a sulfur-containing wastewater containing sodium polysulfide, sodium sulfate, sodium sulfite, sodium thiosulfate and mainly composed of sodium polysulfide.

[0018] Preferably, the aluminum-containing wastewater is an acidic aluminum-containing wastewater generated from Friedel-Crafts acylation and Friedel-Crafts alkylation reactions.

[0019] Preferably, the reduction catalyst is one of Raney nickel, nickel-cobalt composite catalyst, and nickel-iron composite catalyst.

[0020] Preferably, in step (3), the feeding rate of sodium hydroxide solution B is maintained at 200 - 400 kg / h, and the flow rate of sodium aluminate solution is maintained at 200 - 220 kg / h to relieve the precipitation of aluminum salts.

[0021] In the present invention, hydrogen is used as a reducing agent, and a reduction catalyst is added. Under the condition of 20 - 30 °C, mixed sulfur-containing compounds such as sodium polysulfide, sodium sulfate, sodium sulfite, and sodium thiosulfate in sulfur-containing wastewater are reduced to sodium sulfide by catalytic reduction. When the system no longer absorbs hydrogen, the reduction reaction is stopped, and the mixture is allowed to stand for precipitation. The supernatant is slowly added to acidic aluminum-containing wastewater, and hydrogen sulfide gas overflows from the system. A 20% sodium hydroxide solution is used to absorb and prepare a mixture of sodium sulfide and sodium hydrosulfide. When the total mass content of sodium sulfide and sodium hydrosulfide is greater than 20%, it can be used as a reducing agent for production raw materials. As the sulfur-containing wastewater is added, the acidity of the system decreases. When the pH reaches 5.0, the addition of sulfur-containing wastewater is stopped, and the temperature is raised to 80 - 90 °C and stirred at this temperature to continue driving out the residual hydrogen sulfide gas. Then, a quantitative 30% sodium hydroxide solution is added to prepare a sodium aluminate solution, and then the sodium aluminate solution is slowly added to a quantitative amount of aluminum-containing wastewater to prepare a flocculant for decolorizing wastewater and removing organic matter in the petrochemical industry; among them, the reduction catalyst is separated from the wastewater by standing precipitation and can be reused.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) Realize the recycling of sulfur. Compared with the traditional method of converting sulfur into sulfate form for solid-liquid separation, which generates sulfur-containing solid waste while treating sulfur-containing wastewater, in the present invention, various valent sulfides are reduced to divalent sulfide after reduction, and then the wastewater and sulfur are separated by gas-liquid separation, and hydrogen sulfide is absorbed and reused.

[0024] (2) The desulfurization of wastewater is more thorough. Compared with solid-liquid separation, gas-liquid separation is more thorough. Solid-liquid separation has a lower requirement for the system temperature, and the energy consumption is high during the process of achieving low temperature conditions. While gas-liquid separation is mainly affected by pH, that is, affected by the ratio of sulfur-containing wastewater and aluminum-containing wastewater, and gas-liquid separation is also affected by temperature. The higher the temperature, the better the separation effect. Just use the heat released by the acid-base neutralization reaction to improve the gas-liquid separation efficiency.

[0025] (3) Zero discharge of wastewater, realizing the treatment of waste with waste, comprehensively treating sulfur-containing wastewater and aluminum-containing wastewater, saving costs and energy consumption, reducing the generation of solid hazardous waste containing aluminum and sodium salts, more than 80% of aluminum is recycled to prepare a flocculant, and more than 99% of S is recycled to prepare a mixture of sodium sulfide and sodium hydrosulfide as a reducing agent for production raw materials. Specific embodiments

[0026] The following is a detailed description of the above content of the present invention in the form of specific embodiments, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention. Unless otherwise specified, conventional existing technologies are used in the following embodiments.

[0027] Example 1

[0028] A comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater, and its specific steps are as follows:

[0029] The wastewater indexes before treatment are as follows: the sulfur-containing wastewater is detected with a COD of 91756 mg / L, ammonia nitrogen of 3930 mg / L, and a sulfide content of 30000 mg / L; the aluminum-containing wastewater is detected with an aluminum content of 36000 mg / L.

[0030] 6 cubic meters of sulfur-containing wastewater is placed in a reduction reactor, 12 kg of Raney nickel is added, hydrogen is passed while maintaining a temperature of 20 - 30 °C, and the hydrogen flow rate is 0.5 kg / h. When the system pressure significantly rises to 0.1 MPa, hydrogen passing is stopped, and stirring continues for 0.5 h and then standing for 0.5 h to precipitate the Raney nickel catalyst; 3 cubic meters of aluminum-containing wastewater is placed in a desulfurization reactor, and the supernatant of the sulfur-containing wastewater after catalytic reduction is slowly added at a flow rate of 2 cubic meters / h. The pH and pressure of the system are monitored, maintaining a pH below 5.0 and a pressure below 0.01 MPa. A 20% sodium hydroxide solution is used to absorb hydrogen sulfide gas to prepare a mixture of sodium sulfide and sodium hydrosulfide. The hydrogen sulfide absorption uses three-stage alkali absorption. The contents of sodium sulfide and sodium hydrosulfide in the absorption liquid (20% sodium hydroxide solution) are detected every 5 h. When the contents of sodium sulfide and sodium hydrosulfide in the absorption liquid reach more than 20%, a new absorption liquid needs to be replaced. When the system pH reaches 5.0, the addition of sulfur-containing wastewater is stopped. A total of 5 cubic meters of sulfur-containing wastewater is consumed. The desulfurization reactor is slowly heated to 90 °C and stirred. At this time, the remaining hydrogen sulfide gas is continuously expelled to improve the desulfurization effect. After stirring for 1 h at this temperature, 600 kg of 30% sodium hydroxide solution is slowly added to prepare a sodium aluminate solution, maintaining a feeding speed of 300 kg / h; 5 cubic meters of aluminum-containing wastewater is placed in an aluminum removal reactor, and the above sodium aluminate solution is slowly added while maintaining a temperature of 50 °C and a flow rate of 200 kg / h of the sodium aluminate solution to relieve aluminum salt precipitation. After all the sodium aluminate solution is added, stirring continues for 1 h and then it is transferred to a sedimentation tank. After sedimentation for 40 h, 13 cubic meters of flocculant is obtained, with an alumina content of 8.5%, a basicity of 85.5%, a COD of 18250 mg / L, a removal rate of 80.1%, ammonia nitrogen of 120 mg / L, a removal rate of 96.9%, a sulfur content of 2 mg / L, a removal rate of 100%, and an aluminum recovery rate of 85%.

[0031] Tertiary alkali absorption: Hydrogen sulfide first enters the first absorption tank. The hydrogen sulfide remaining after the first absorption enters the second absorption tank. If there is still remaining hydrogen sulfide after the second absorption, it enters the third absorption tank. The third absorption is the final protection to ensure that hydrogen sulfide will not escape. Generally, after the first absorption reaches the required concentration, the absorption liquid (i.e., sodium hydroxide solution) is transferred out, the second absorption liquid is poured into the first absorption tank, and the third absorption liquid is poured into the second absorption tank. A new absorption liquid is used in the third absorption tank.

[0032] Example 2

[0033] A comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater, the specific steps of which are as follows:

[0034] The wastewater indexes before treatment are as follows: The sulfur-containing wastewater is detected with a COD of 91756 mg / L, ammonia nitrogen of 3930 mg / L, and sulfide content of 30000 mg / L. The aluminum-containing wastewater is detected with an aluminum content of 36000 mg / L.

[0035] Preparation of nickel and cobalt composite catalyst: 10% nickel chloride, 5% cobalt chloride, and the balance is alumina powder. The above raw materials are added in accordance with the formula ratio to an appropriate amount of methanol solvent containing 10% water, stirred at 30 °C for 20 h, slowly heated to evaporate the solvent to dryness, and activated at 300 °C to obtain a solid catalyst;

[0036] 6 cubic meters of sulfur-containing wastewater is placed in a reduction reactor, and 12 kg of nickel-cobalt composite catalyst is added. While maintaining a temperature of 20 - 30 °C, hydrogen gas is introduced with a hydrogen gas flow rate of 0.5 kg / h. When the system pressure significantly rises to reach 0.1 MPa, hydrogen introduction is stopped. After continuing to stir for 0.5 h, it is left to stand for 0.5 h to precipitate the nickel-cobalt composite catalyst. 3 cubic meters of aluminum-containing wastewater is placed in a desulfurization reactor, and the supernatant of the sulfur-containing wastewater after catalytic reduction mentioned above is slowly added at a flow rate of 2 cubic meters per hour. The pH and pressure of the system are monitored, maintaining the pH below 5.0 and the pressure below 0.01 MPa. A 20% sodium hydroxide solution is used to absorb hydrogen sulfide gas to prepare a mixture of sodium sulfide and sodium hydrosulfide. The hydrogen sulfide absorption uses three-stage alkali absorption, and the contents of sodium sulfide and sodium hydrosulfide in the absorption liquid are detected every 5 h. When the system pH reaches 5.0, the addition of sulfur-containing wastewater is stopped, and a total of 5.2 cubic meters of sulfur-containing wastewater is consumed. The desulfurization reactor is slowly heated to 85 °C. At this time, the remaining hydrogen sulfide gas is continuously expelled to improve the desulfurization effect. After stirring for 0.5 h at this temperature, 600 kg of 30% sodium hydroxide solution is slowly added to prepare a sodium aluminate solution, maintaining a feeding speed of 300 kg / h. 5 cubic meters of aluminum-containing wastewater is placed in an aluminum removal reactor, and the above sodium aluminate solution is slowly added while maintaining a temperature of 60 °C. The sodium aluminate solution is added at a flow rate of 200 kg / h to relieve the precipitation of aluminum salts. After all the sodium aluminate solution is added, it is continuously stirred for 1 h and then transferred to a sedimentation tank. After sedimentation for 40 h, 13.2 cubic meters of flocculant is obtained, with an alumina content of 8.4%, a basicity of 89.0%, a COD of 17530 mg / L, a removal rate of 80.9%, an ammonia nitrogen of 155 mg / L, a removal rate of 96.1%, a sulfur content of 1200 mg / L, and a removal rate of 96.0%, and an aluminum recovery rate of 85%.

[0037] Comparative Example 1 (Example 1 in CN201711185392.3 is used as Comparative Example 1)

[0038] A sulfur-containing wastewater treatment process:

[0039] Before treatment, the pH of the sulfur-containing wastewater is 10.2, the sulfide concentration is 5000 mg / L, and the SS concentration is 500 mg / L. First, the pH of the sulfur-containing wastewater is adjusted to 3, and the wastewater is desulfurized using the negative pressure desulfurization method for 30 minutes. The hydrogen sulfide gas generated during desulfurization is absorbed using an alkali solution. After negative pressure desulfurization, a pH regulator is used to continue adjusting the above wastewater to make the wastewater pH 8. The wastewater is passed into a coagulation treatment unit, and a coagulant and a co-coagulant are added to the coagulation treatment unit. The molar concentration ratio of ferrous sulfate to calcium hydroxide added is 1:1. After the sulfur is removed by precipitation in the coagulation unit, the supernatant is transferred to an oxidation reactor, and ozone is introduced into the oxidation reactor with an ozone concentration of 60 mg / L and an ozone residence time of 40 minutes. After being treated by the above method, the pH of the sulfur-containing wastewater is 7.6, the sulfide concentration is 1.0 mg / L, and the SS concentration is 1.0 mg / L.

[0040] The above comparative example is a sulfur-containing wastewater treatment process. For the comparative example 1 of the sulfur-containing wastewater treatment process, negative pressure desulfurization treatment and caustic soda absorption are mentioned. When the valence state of sulfur in the system is -2, the treatment effect is relatively ideal, but the treatment effect for the sulfur-containing wastewater with mixed valence states is poor. Therefore, it needs to enter the coagulation unit for further treatment. After treatment, the concentration of sulfide in the wastewater is significantly reduced, and the sulfide is transferred to solid hazardous waste and separated from the wastewater. In the present invention, the sulfur with mixed valence states in the sulfur-containing wastewater is first reduced to -2-valent sulfur, and then hydrogen sulfide is recovered, which can not only achieve the purpose of sulfur removal but also realize the recovery of sulfur. In comparative example 1, the pH of the sulfur-containing wastewater is adjusted to 3, and hydrochloric acid is generally used to adjust the pH. In the present invention, aluminum-containing wastewater is used instead of hydrochloric acid to adjust the pH of the sulfur-containing wastewater, avoiding the increase in the amount of wastewater and achieving waste treatment with waste. The present invention provides a comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater. This method treats waste with waste, saves costs and energy consumption, reduces the generation of solid hazardous waste containing aluminum and sodium salts, and more than 80% of aluminum is recovered and prepared into a flocculant, and more than 99% of sulfur is recovered and prepared into a mixture of sodium sulfide and sodium hydrosulfide as a reducing agent for use as a production raw material.

Claims

1. A comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater, characterized in that, The specific steps are as follows: (1) Add a catalyst to the sulfur-containing wastewater at 20 - 30 °C, introduce hydrogen gas and stir. When the pressure of the system reaches above 0.1 MPa, stop introducing hydrogen gas, continue to stir and then let it stand to precipitate the catalyst, and filter to obtain the supernatant of the sulfur-containing wastewater; (2) Slowly add the supernatant of the sulfur-containing wastewater to the aluminum-containing wastewater in the desulfurization reactor to generate hydrogen sulfide. Use sodium hydroxide solution A to absorb the hydrogen sulfide gas to prepare a mixture of sodium sulfide and sodium bisulfide. When the pH of the system reaches 5.0, stop adding the supernatant of the sulfur-containing wastewater, continue to heat up to 90 - 100 °C and stir at this temperature for 0.5 - 1 h to drive out the remaining hydrogen sulfide gas; (3) After driving out the hydrogen sulfide gas, slowly add sodium hydroxide solution B to prepare a sodium aluminate solution. Keep the temperature at 50 - 60 °C and slowly add the sodium aluminate solution to the aluminum-containing wastewater in the de-aluminum reactor. After all the sodium aluminate solution is added, continue to stir and then transfer it to the sedimentation tank. After sedimentation, a flocculant is obtained; The aluminum-containing wastewater is the acidic aluminum-containing wastewater generated from Friedel-Crafts acylation and Friedel-Crafts alkylation reactions; In step (3), the mass ratio of the sodium aluminate solution to the aluminum-containing wastewater in the de-aluminum reactor is 1 - 2:

1.

2. The integrated treatment method for sulfur-containing wastewater and aluminum-containing wastewater according to claim 1, wherein The detection indexes of the sulfur-containing wastewater are: COD 90000 - 10000 mg / L, ammonia nitrogen 3000 - 5000 mg / L, sulfide 25000 - 30000 mg / L.

3. The integrated treatment method for sulfur-containing wastewater and aluminum-containing wastewater according to claim 1, wherein, In the aluminum-containing wastewater, the aluminum content is 30000 - 40000 mg / L.

4. A comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater according to claim 1, characterized in that, In step (1), the mass ratio of the catalyst to the sulfur-containing wastewater is 0.001 - 0.002:

1.

5. A comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater according to claim 1, characterized in that, When the supernatant of the sulfur-containing wastewater is slowly added to the aluminum-containing wastewater in step (2), keep the pH below 5.0 and the pressure below 0.01 MPa.

6. The comprehensive treatment method for sulfur-containing wastewater and aluminum-containing wastewater according to claim 1, characterized in that, In step (2), the mass percentage of sodium hydroxide solution A is 20%.

7. The integrated treatment method for sulfur-containing wastewater and aluminum-containing wastewater according to claim 3, characterized in that, In step (3), the mass ratio of sodium hydroxide solution B to the aluminum-containing wastewater in the desulfurization reactor is 0.1 - 0.2:1, and the mass percentage of sodium hydroxide solution B is 30%.

8. The integrated treatment method for sulfur-containing wastewater and aluminum-containing wastewater according to claim 1, characterized in that, In step (3), keep the feeding speed of sodium hydroxide solution B at 200 - 400 kg / h.

9. The integrated treatment method for sulfur-containing wastewater and aluminum-containing wastewater according to claim 1, wherein, In step (3), keep the flow rate of the sodium aluminate solution at 200 - 220 kg / h.