A resource-based treatment method for high-salt and high-COD wastewater from aluminum mines

Abstract

A resource-recycling treatment method for high-salt, high-COD wastewater from aluminum mines, characterized by comprising the following steps: adding a pH regulator to adjust the pH of the raw water, adding a defluoridating agent to react; adding a coagulant and a flocculant to coagulate after the reaction; filtering after coagulation; adding an alkaline solution to adjust the pH of the wastewater; passing the wastewater through a nanofiltration system to separate the salt to obtain concentrated water and fresh water; passing the concentrated water obtained by nanofiltration through a flotation system to remove oil, and treating it with activated carbon to obtain produced water; evaporating and crystallizing the produced water to obtain solid sodium carbonate. The present invention utilizes a combined process of "coagulation + filtration + nanofiltration membrane + flotation system + activated carbon + evaporation and crystallization" to effectively remove fluoride ions, aluminum ions, heavy metal ions, COD, suspended solids, and color from aluminum mine production wastewater, thereby resolving emission issues, saving water resources, and achieving efficient resource utilization.

Description

Technical Field

[0001] The present invention relates to a method for resource-based treatment of wastewater, and in particular to a method for resource-based treatment of aluminum mine wastewater. Background Art

[0002] my country is rich in bauxite resources, and the wastewater produced from the traditional alkaline process for producing alumina is weakly alkaline. The wastewater generated by the alkaline production process contains high levels of fluoride, aluminum, chloride, arsenic, carbonate, sodium, suspended solids, COD, and oily organic matter, making it a typical high-salt, high-COD wastewater. This wastewater is high in pollutants, complex in composition, difficult to treat, and expensive. To better develop and utilize bauxite resources, there is an urgent need to improve the resource-recovery technology for high-salt wastewater in the bauxite industry and achieve low-cost recycling of this high-salt wastewater.

[0003] Currently, there are few technologies for resource-recycling high-salinity wastewater in the aluminum mining industry. CN108394978A discloses a method for preparing a composite flocculant for treating aluminum-containing wastewater. This flocculant can remove various pollutants from aluminum-containing wastewater, such as aluminum, suspended solids, nickel, copper, chromium, and manganese, with high removal rates and effectiveness. However, it struggles with high-salinity and high-COD wastewater.

[0004] CN108249697A discloses a method for treating aluminum-containing wastewater produced by Friedel-Crafts reaction. This method is suitable for aluminum-containing wastewater produced by Friedel-Crafts reaction. The amount of oxidant used is large, the cost is high, and the storage and use of the oxidant have certain safety hazards. Therefore, this method is difficult to apply to the aluminum mining industry with a large amount of high-salt wastewater. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a resource-based treatment method for high-salt and high-COD wastewater from aluminum mines with simple process, low investment cost and effectiveness.

[0006] The technical solutions adopted by the present invention to solve the technical problems are as follows:

[0007] A resource-based treatment method for high-salt and high-COD wastewater from aluminum mines, comprising the following steps:

[0008] (1) Add pH regulator to adjust the pH value of raw water, and add defluoridation agent to react; this process can remove fluoride ions, aluminum ions and heavy metal ions in wastewater;

[0009] (2) After the reaction is completed, coagulant and flocculant are added for coagulation;

[0010] (3) Filtration after coagulation treatment; this process can remove suspended matter and flocs in wastewater;

[0011] (4) Add alkali solution to adjust the pH value of wastewater;

[0012] (5) Salt is separated through the nanofiltration system to obtain concentrated water and fresh water;

[0013] (6) The concentrated water obtained by nanofiltration is deoiled through an air flotation system to reduce the COD content in the wastewater; activated carbon treatment is used to remove the remaining COD in the water and decolorize the wastewater to obtain product water;

[0014] (7) The produced water is evaporated and crystallized to obtain solid sodium carbonate.

[0015] Preferably, the raw water has a carbonate content of 10,000 to 50,000 mg / L, a sodium ion content of 10,000 to 50,000 mg / L, a fluoride ion content of 100 to 500 mg / L, an aluminum ion content of 10 to 500 mg / L, a COD content of 500 to 3,000 mg / L, and a pH value of 10 to 12.

[0016] Preferably, in step (1), the pH adjusting agent is hydrochloric acid; the pH value is adjusted to 6 to 9, more preferably 7 to 8.

[0017] Preferably, in step (1), the defluoridating agent is a soluble calcium salt or a soluble magnesium salt, which removes fluoride by combining with fluoride ions to form insoluble salts, and the amount used is sufficient to remove fluoride ions in the raw water; calcium fluoride is more preferred.

[0018] Preferably, in step (2), the coagulant is polyaluminum chloride or polyaluminum ferric chloride, and the flocculant is anionic polyacrylamide.

[0019] Preferably, in step (2), the amount of coagulant used is 100-200 mg / L, and the amount of flocculant used is 5-20 mg / L.

[0020] Preferably, in step (3), the filter is a sand filter.

[0021] Preferably, in step (4), the alkali solution is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is more preferably 1 to 10 wt %; the pH value is adjusted to 10 to 13, more preferably 11 to 12.

[0022] Preferably, in step (5), the fresh water obtained is reused as process water for aluminum ore production. The monovalent ions and divalent ions are separated by a nanofiltration system, with the monovalent ions entering the fresh water and the divalent ions entering the concentrated water.

[0023] Preferably, in step (6), the flotation system uses a pressurized dissolved air device.

[0024] This invention provides a resource-based process for treating saline wastewater using membrane separation technology. This process utilizes a "coagulation + filtration + nanofiltration membrane + flotation system + activated carbon + evaporation and crystallization" process to address the high salinity and COD discharge issues currently encountered in the aluminum mining industry's alkaline, high-salinity wastewater, while also recovering water resources. This process effectively reduces the discharge of high-salinity wastewater, allowing some of the produced water to be reused for production processes. The concentrated brine undergoes flotation and activated carbon treatment to remove COD and color, and then undergoes evaporation and crystallization to produce sodium carbonate, achieving efficient utilization of both water and salt resources.

[0025] The beneficial effects of the present invention are as follows: (1) The present invention adopts a combined process of "coagulation + filtration + nanofiltration membrane + flotation system + activated carbon + evaporation crystallization", which can effectively remove fluoride ions, aluminum ions, heavy metal ions, COD, suspended matter, chroma, etc. in aluminum ore production wastewater; (2) The nanofiltration system can effectively improve the purity of salt by salt separation; (3) The flotation system has low energy consumption and high efficiency in oil removal; (4) The intermediate water is reused to solve the emission problem and save water resources; (5) The sodium carbonate product obtained by evaporation crystallization realizes the effective utilization of salt resources. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the examples.

[0027] The raw materials used in the examples of the present invention were all obtained through conventional commercial channels.

[0028] Example 1

[0029] The wastewater used in this example is wastewater from a certain aluminum smelting enterprise. The chromaticity of 10 kg of wastewater is 100 times, COD=2700 mg / L, the appearance is brown-yellow, the suspended solids content is 251 mg / L, and the Al 3+ Content 272mg / L, F - Content 172mg / L, CO3 2- Content 28500mg / L, Na + Content 21900mg / L, As 3+ The content is 0.86 mg / L and the pH value is 10.5.

[0030] The resource processing method of this embodiment is:

[0031] (1) Add 10 wt% hydrochloric acid to adjust the pH of the wastewater to 7.1, then add 5.03 g of CaCl2 (defluoridant) and stir until the reaction is complete;

[0032] (2) After the reaction in step (1) is completed, the wastewater enters the coagulation tank, and 200 mg / L polyaluminium chloride (PAC, coagulant) and 10 mg / L anionic polyacrylamide (PAM, flocculant) are added for reaction;

[0033] (3) After the wastewater is coagulated, it passes through a sand filter to remove suspended solids and flocs in the wastewater;

[0034] (4) Add 5% sodium hydroxide solution to adjust the pH to 12.0 to remove bicarbonate ions from the wastewater;

[0035] (5) After entering the nanofiltration membrane system for salt separation, 1.61 kg of concentrated water and 8.10 kg of fresh water were obtained. The arsenic content in the fresh water was 0.1 mg / L, the suspended solids content was 12 mg / L, the fluoride ion content was 0.5 mg / L, the aluminum ion content was 18 mg / L, and the chromaticity was 10. The fresh water was reused as process water for aluminum ore production.

[0036] (6) The concentrated water from step (5) enters the flotation system using a pressurized dissolved air device to remove oil and reduce the COD content in the wastewater, and then enters the activated carbon treatment pool. This process can further remove COD in the wastewater and decolorize the wastewater to obtain produced water; the CO3 in the produced water 2- Content 162300mg / L, Na + Content 126600mg / L;

[0037] (7) The produced water obtained in step (6) enters the evaporation crystallization device to obtain sodium carbonate solid.

[0038] After analysis and testing, the quality of the sodium carbonate solid obtained meets the requirements of "GB201-2004 Industrial Sodium Carbonate and Its Test Methods" Class qualified product standards.

[0039] Example 2

[0040] The wastewater used in this example is mixed wastewater from an aluminum smelting enterprise. The chromaticity of 10 kg of wastewater is 80 times, COD = 2100 mg / L, the appearance is brown-yellow, the suspended solids content is 159 mg / L, and the Al 3+ Content 210mg / L, F - Content 90mg / L, CO3 2- Content 19900mg / L, Na + Content 13500mg / L, As 3+ The content is 0.61 mg / L and the pH value is 10.25.

[0041] The resource processing method of this embodiment is:

[0042] (1) Add 10 wt% hydrochloric acid to adjust the pH of the wastewater to 7.5, then add 2.64 g of CaCl2 (defluoridant) and stir until the reaction is complete;

[0043] (2) After the reaction in step (1) is completed, the wastewater enters the coagulation tank, and 150 mg / L polyaluminium chloride (PAC, coagulant) and 10 mg / L anionic polyacrylamide (PAM, flocculant) are added for reaction;

[0044] (3) After the wastewater is coagulated, it passes through a sand filter to remove suspended solids and flocs in the wastewater;

[0045] (4) Add 5% sodium hydroxide solution to adjust the pH to 11.8 to remove bicarbonate ions from the wastewater;

[0046] (5) The water enters the nanofiltration membrane system for salt separation, and 1.65 kg of concentrated water and 8.02 kg of fresh water are obtained. The arsenic content in the fresh water is 0.2 mg / L, the suspended solids content is 15 mg / L, the fluoride ion content is 0.4 mg / L, the aluminum ion content is 15 mg / L, and the chromaticity is 10. The fresh water is reused as process water for aluminum ore production;

[0047] (6) The concentrated water from step (5) enters the flotation system with a pressurized dissolved air device to remove oil and reduce the COD content in the wastewater, and then enters the activated carbon treatment pool. This process can further remove COD in the wastewater and decolorize the wastewater to obtain produced water. The CO3 in the produced water 2- Content 113100mg / L, Na + Content 88500mg / L;

[0048] (7) The produced water obtained in step (6) enters the evaporation crystallization device to obtain sodium carbonate solid.

[0049] After analysis and testing, the quality of the sodium carbonate solid obtained meets the requirements of "GB201-2004 Industrial Sodium Carbonate and Its Test Methods" Class qualified product standards.

[0050] Comparative Example

[0051] Mixed wastewater from an aluminum smelting enterprise, 10kg of wastewater has a chromaticity of 80 times, COD = 2100mg / L, a brownish-yellow appearance, and a suspended solids content of 159mg / L. 3+ Content 210mg / L, F - Content 90mg / L, CO3 2- Content 19900mg / L, Na + Content 13500mg / L, As 3+ The content is 0.61 mg / L and the pH value is 10.25.

[0052] The resource recovery method of this comparative example is:

[0053] (1) Add 10 wt% hydrochloric acid to adjust the pH of the wastewater to 7.5, then add 2.64 g of CaCl2 (defluoridant) and stir until the reaction is complete;

[0054] (2) After the reaction in step (1) is completed, the wastewater enters the flotation system using a pressurized dissolved air device to remove oil and reduce the COD content in the wastewater;

[0055] (3) After step (2), the wastewater enters the coagulation tank, and 150 mg / L polyaluminium chloride (PAC, coagulant) and 10 mg / L anionic polyacrylamide (PAM, flocculant) are added for reaction;

[0056] (4) After the wastewater is coagulated, it passes through a sand filter to remove suspended solids and flocs in the wastewater;

[0057] (5) Add 5% sodium hydroxide solution to adjust the pH to 11.8 to remove bicarbonate ions from the wastewater;

[0058] (6) After entering the nanofiltration membrane system for salt separation, 1.65 kg of concentrated water and 8.02 kg of fresh water were obtained. The arsenic content in the fresh water was 0.2 mg / L, the suspended solids content was 15 mg / L, the fluoride ion content was 0.4 mg / L, the aluminum ion content was 15 mg / L, and the chromaticity was 10. The fresh water was reused as process water for aluminum ore production.

[0059] (7) The concentrated water from step (6) enters the activated carbon treatment pool to remove part of the COD in the wastewater and decolorize the wastewater to obtain produced water. The CO3 2- Content 109100mg / L, Na + Content 88100mg / L;

[0060] (8) The produced water obtained in step (7) enters the evaporation crystallization device to obtain sodium carbonate solid.

[0061] The above comparative example adopts the process of "flotation + coagulation + filtration + nanofiltration membrane + activated carbon + evaporation crystallization". After analysis and testing, the obtained sodium carbonate solid is yellowish in color and does not meet the quality requirements of "GB201-2004 Industrial Sodium Carbonate and Its Test Methods" Class qualified product standards.

Claims

1. A resource treatment method for high-salt and high-COD wastewater from aluminum mines, characterized in that: The processing steps are as follows: (1) Adding a pH regulator to adjust the pH value of the raw water to 7.1-9, and adding a defluoridation agent to react; the raw water has a carbonate content of 10,000-50,000 mg / L, a sodium ion content of 10,000-50,000 mg / L, a fluoride ion content of 100-500 mg / L, an aluminum ion content of 10-500 mg / L, a COD content of 500-3,000 mg / L, and a pH value of 10-12; the defluoridation agent is calcium chloride; (2) After the reaction is completed, coagulant and flocculant are added for coagulation; (3) Filtration after coagulation treatment; (4) Add alkali solution to adjust the pH value of the wastewater to 10-13; (5) The salt is separated by the nanofiltration system to obtain concentrated water and fresh water; the obtained fresh water is reused as water in the aluminum ore production process; (6) The concentrated water obtained by nanofiltration is deoiled by a flotation system and treated with activated carbon to obtain produced water; the flotation system adopts a pressurized dissolved air device; (7) The produced water is evaporated and crystallized to obtain solid sodium carbonate.

2. The resource recovery treatment method for high-salt and high-COD wastewater from aluminum mines according to claim 1, characterized in that: In step (1), the pH adjusting agent is hydrochloric acid.

3. The resource recovery treatment method for aluminum mine high-salt and high-COD wastewater according to claim 1 or 2, characterized in that: In step (2), the coagulant is polyaluminum chloride or polyaluminum ferric chloride, and the flocculant is anionic polyacrylamide.

4. The resource recovery treatment method for aluminum mine high-salt and high-COD wastewater according to claim 1 or 2, characterized in that: In step (2), the dosage of the coagulant is 100-200 mg / L, and the dosage of the flocculant is 5-20 mg / L.

5. The resource recovery treatment method for aluminum mine high-salt and high-COD wastewater according to claim 3, characterized in that: In step (2), the dosage of the coagulant is 100-200 mg / L, and the dosage of the flocculant is 5-20 mg / L.

6. The resource recovery treatment method for high-salt and high-COD wastewater from aluminum mines according to claim 1 or 2, characterized in that: In step (3), the filter is a sand filter.

7. The resource recovery treatment method for high-salt and high-COD wastewater from aluminum mines according to claim 1 or 2, characterized in that: In step (4), the alkali solution is a sodium hydroxide solution, the concentration of the sodium hydroxide solution is 1 to 10 wt %; and the pH value is adjusted to 11 to 12.

8. The resource recovery treatment method for high-salt and high-COD wastewater from aluminum mines according to claim 3, characterized in that: In step (4), the alkali solution is a sodium hydroxide solution, the concentration of the sodium hydroxide solution is 1 to 10 wt %; and the pH value is adjusted to 11 to 12.

9. The resource recovery treatment method for high-salt and high-COD wastewater from aluminum mines according to claim 4, characterized in that: In step (4), the alkali solution is a sodium hydroxide solution, the concentration of the sodium hydroxide solution is 1 to 10 wt %; and the pH value is adjusted to 11 to 12.