A steam purification method for nonferrous metal wastewater

Abstract

The present invention belongs to the field of wastewater treatment technology, and specifically relates to a steam purification method for non-ferrous metal wastewater. The purification method comprises pouring the wastewater into an evaporator for reduced-pressure evaporation, evaporating for a certain period of time, then adding a flocculant while maintaining pressure and temperature, and continuing reduced-pressure evaporation until the water is completely evaporated; passing the obtained steam into an acid solution, passing the acid-treated steam into an alkaline solution, and exchanging heat with cooling water in a heat exchanger to obtain steam condensate after the alkaline-treated steam has been treated. A flocculant is added to the obtained steam cooling water, stirred, allowed to stand, and then filtered to obtain treated wastewater. The treatment method of the present application can effectively solve the problem of excessively high TDS content in steam, reduce ammonia nitrogen and COD content, and meet wastewater discharge standards.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and more specifically, relates to a steam purification method for non-ferrous metal wastewater. Background Art

[0002] Non-ferrous metal smelting wastewater is primarily generated by the use of liquid ammonia and ammonia water as precipitants for metals (such as tantalum and niobium) and extractants (such as in tungsten smelting). These wastewater is discharged directly into rivers and other water bodies in the form of metal precipitation mother liquor and wash water, or extraction residual liquid wastewater. Direct discharge into rivers and other water bodies pollutes the water, resulting in a serious waste of water resources. Furthermore, the wastewater contains a high salt content. During the treatment process, the salt precipitated after the reaction is reduced through solid-liquid separation, while the soluble salt remains dissolved in the feed liquid. As production wastewater continues to be generated, its concentration continues to accumulate and increase, making filter presses alone ineffective in addressing the wastewater treatment problem. Direct reuse in production would have a significant impact. Storage in pools, due to limited capacity, would prevent external discharge and present various severe environmental challenges.

[0003] With the deteriorating environment and the scarcity of mineral resources, existing methods are unable to meet the needs of water reuse and valuable resource recovery. Evaporation and stripping are important methods for resource recovery, which not only reduce treatment costs but also achieve certain economic benefits. Evaporation and concentration methods involve heating to vaporize a portion of the solvent in a solution, thereby increasing the solution concentration, or concentrating the solution to saturation to precipitate the solute. Due to its mature technology and simple process, evaporation and concentration methods are widely used in wastewater treatment across various industries.

[0004] Non-ferrous metal wastewater is treated by evaporation. The water contains salt, ammonia nitrogen and COD. The water in the solution is vaporized by heating to increase the concentration of non-volatile components in the solution. Continuous evaporation and concentration reaches saturation, causing salt to precipitate and crystallize from the solution. The vaporized water vapor is condensed and collected for reuse. However, during the evaporation process, ammonia nitrogen and part of the COD are volatile and will condense along with the water vapor. When the evaporated solution reaches saturation, the metals dissolved in the wastewater will enter the steam along with the steam and then redissolve in the steam condensate, causing the water quality to deteriorate. How to effectively reduce the content of metals, ammonia nitrogen and COD in the steam is still a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing technical problems and provide a steam purification method for non-ferrous metal wastewater.

[0006] The purpose of the present invention is to provide a steam purification method for non-ferrous metal wastewater. The purification method comprises pouring the wastewater into an evaporator for reduced-pressure evaporation, evaporating for a certain period of time, and then adding a flocculant while maintaining pressure and temperature, continuing reduced-pressure evaporation until the water is completely evaporated; passing the obtained steam into an acid solution, passing the acid-treated steam into an alkaline solution, and exchanging heat with cooling water in a heat exchanger to obtain steam condensate after the alkaline-treated steam has been treated. Preferably, a flocculant is added to the obtained steam cooling water, stirred, allowed to stand, and then filtered to obtain the treated wastewater. The treatment method of the present application can effectively solve the problem of excessively high TDS content in steam, reduce ammonia nitrogen and COD content, and meet wastewater discharge standards.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0009] Step (1): Pour the wastewater into an evaporator for reduced pressure evaporation for a certain period of time, then add a flocculant while maintaining the pressure and temperature, and continue to evaporate under reduced pressure until the water is completely evaporated;

[0010] Step (2): passing the steam obtained in step (1) into an acid solution, passing the acid-treated steam into an alkaline solution, and exchanging heat with cooling water in a heat exchanger to obtain steam condensate.

[0011] Preferably, the preparation method further comprises step (3), wherein the step (3) comprises adding a flocculant to the steam condensate obtained in step (2), stirring, allowing the mixture to stand, and then filtering.

[0012] Preferably, in step (1), the conditions for the reduced pressure evaporation are: absolute pressure of 47.373 kPa to 70.117 kPa, temperature of 80-90° C.; and evaporation time of 20-40 min.

[0013] Preferably, in step (1), the ratio of wastewater to flocculant is 200-300 mL: 0.05-0.15 g.

[0014] Preferably, in step (2), the acid is one or more of nitric acid, sulfuric acid, and acetic acid, and the concentration of the acid is 2 to 6 mol / L.

[0015] Preferably, in step (2), the base is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate, and the concentration of the base is 3 to 5 mol / L.

[0016] Preferably, in step (2), the acid is sulfuric acid and acetic acid, and the molar ratio of the sulfuric acid to the acetic acid is 1:0.5-1; the base is sodium hydroxide and sodium carbonate, and the molar ratio of the sodium hydroxide to the sodium carbonate is 1:0.4-0.8.

[0017] Preferably, in step (2), the flocculant is at least one of polyaluminium ferrosilicate and PAM.

[0018] Preferably, the flocculant is polyaluminium ferric silicate and PAM, and the mass ratio of the polyaluminium ferric silicate to PAM is 1:3-5.

[0019] Preferably, in step (3), the ratio of the steam condensate to the flocculant is 100 mL:0.01 g; the stirring time is 0.5 to 1 h, and the standing time is 2 to 4 h.

[0020] The present invention has the following beneficial effects:

[0021] (1) The present invention can effectively reduce the TDS content in the steam and reduce the amount of flocculant used by adding flocculants during the wastewater evaporation process. At the same time, the ammonia nitrogen in the steam is absorbed by combining acid solution treatment and the COD of the steam is absorbed by alkaline solution treatment, so as to achieve the purpose of effectively treating ammonia nitrogen and COD in the wastewater.

[0022] (2) When polyaluminium ferrous silicate and PAM are used together, the TDS content can be reduced to a minimum, and the final flocculation treatment can almost completely treat the TDS in the wastewater vapor.

[0023] (3) When sulfuric acid and acetic acid, as well as sodium hydroxide and sodium carbonate are used in combination, the TDS and COD in the wastewater vapor can be effectively reduced, making the treatment of COD and TDS in the wastewater vapor more complete.

[0024] (3) The treatment method of the present invention is simple and can effectively reduce costs, and is an ideal method for steam purification of colored wastewater. DETAILED DESCRIPTION

[0025] The present invention is further described below with reference to specific examples, which, however, are not intended to limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0026] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0027] Example 1

[0028] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0029] Step (1): 250 mL of non-ferrous metal wastewater was poured into an evaporator and evaporated under reduced pressure at an absolute pressure of 57.817 kPa and a temperature of 85° C. for 30 min. Then, while maintaining the pressure and temperature, 0.1 g of PAM was added and the reduced pressure evaporation was continued until the water was completely evaporated.

[0030] Step (2): The steam obtained in step (1) is passed into 200 mL of a 4 mol / L sulfuric acid solution, the steam treated with the sulfuric acid solution is passed into 200 mL of a 4 mol / L sodium hydroxide solution, and the steam treated with the sodium hydroxide solution is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0031] Example 2

[0032] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0033] Step (1): 300 mL of non-ferrous metal wastewater was poured into an evaporator and evaporated under reduced pressure at an absolute pressure of 70.117 kPa and a temperature of 90° C. for 20 minutes. Then, while maintaining the pressure and temperature, 0.15 g of polyaluminum ferrosilicate was added and the reduced pressure evaporation was continued until the water was completely evaporated.

[0034] Step (2): The steam obtained in step (1) is passed into 200 mL of 6 mol / L acetic acid solution, the steam treated with the acetic acid solution is passed into 200 mL of 5 mol / L potassium hydroxide solution, and the steam treated with the potassium hydroxide solution is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0035] Example 3

[0036] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0037] Step (1): 200 mL of non-ferrous metal wastewater was poured into an evaporator and evaporated under reduced pressure at an absolute pressure of 47.373 kPa and a temperature of 80° C. for 40 min. Then, while maintaining the pressure and temperature, 0.05 g of PAM was added and the reduced pressure evaporation was continued until the water was completely evaporated;

[0038] Step (2): The steam obtained in step (1) is passed into 200 mL of a 2 mol / L nitric acid solution, the steam treated with the nitric acid solution is passed into 200 mL of a 3 mol / L sodium carbonate solution, and the steam treated with the sodium carbonate solution is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0039] Example 4

[0040] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0041] Step (1): 250 mL of non-ferrous metal wastewater was poured into an evaporator and evaporated under reduced pressure at an absolute pressure of 57.817 kPa and a temperature of 85° C. for 30 min. Then, while maintaining the pressure and temperature, 0.1 g of PAM was added and the reduced pressure evaporation was continued until the water was completely evaporated.

[0042] Step (2): The steam obtained in step (1) is passed into 200 mL of a 4 mol / L sulfuric acid solution, the steam treated with the sulfuric acid solution is passed into 200 mL of a 4 mol / L sodium hydroxide solution, and the steam treated with the sodium hydroxide solution is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0043] Step (3): Add 0.01 g of PAM to 100 mL of the steam cooling water obtained in step (2), stir for 50 min, let stand for 3 h, and then filter.

[0044] Example 5

[0045] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0046] Step (1): 250 mL of non-ferrous metal wastewater was poured into an evaporator and evaporated under reduced pressure at an absolute pressure of 57.817 kPa and a temperature of 85° C. for 30 min. Then, while maintaining the pressure and temperature, 0.02 g of polyaluminium ferrosilicate and 0.08 g of PAM were added, and the reduced pressure evaporation was continued until the water was completely evaporated.

[0047] Step (2): The steam obtained in step (1) is passed into 200 mL of a 4 mol / L sulfuric acid solution, the steam treated with the sulfuric acid solution is passed into 200 mL of a 4 mol / L sodium hydroxide solution, and the steam treated with the sodium hydroxide solution is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0048] Step (3): Take 100 mL of the steam cooling water obtained in step (2), add 0.002 g of polyaluminium ferrosilicate and 0.008 g of PAM, stir for 50 min, let stand for 3 h, and then filter.

[0049] Example 6

[0050] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0051] Step (1): 250 mL of non-ferrous metal wastewater was poured into an evaporator and evaporated under reduced pressure at an absolute pressure of 57.817 kPa and a temperature of 85° C. for 30 min. Then, while maintaining the pressure and temperature, 0.1 g of PAM was added and the reduced pressure evaporation was continued until the water was completely evaporated.

[0052] Step (2): The steam obtained in step (1) is passed into 200 mL of a mixed solution containing 2.5 mol / L sulfuric acid and 1.5 mol / L acetic acid. The steam treated with the mixed solution of sulfuric acid and acetic acid is passed into 200 mL of a 4 mol / L sodium hydroxide solution. The steam treated with the sodium hydroxide solution is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0053] Step (3): Add 0.01 g of PAM to 100 mL of the steam cooling water obtained in step (2), stir for 50 min, let stand for 3 h, and then filter.

[0054] Example 7

[0055] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0056] Step (1): 250 mL of non-ferrous metal wastewater was poured into an evaporator and evaporated under reduced pressure at an absolute pressure of 57.817 kPa and a temperature of 85° C. for 30 min. Then, while maintaining the pressure and temperature, 0.1 g of PAM was added and the reduced pressure evaporation was continued until the water was completely evaporated.

[0057] Step (2): The steam obtained in step (1) is passed into 200 mL of 4 mol / L sulfuric acid solution, and the steam treated with the sulfuric acid solution is passed into 200 mL of a mixed solution containing 2.5 mol / L sodium hydroxide and 1.5 mol / L sodium carbonate. The steam treated with the mixed solution of sodium hydroxide and sodium carbonate is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0058] Step (3): Add 0.01 g of PAM to 100 mL of the steam cooling water obtained in step (2), stir for 50 min, let stand for 3 h, and then filter.

[0059] Example 8

[0060] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0061] Step (1): 250 mL of non-ferrous metal wastewater was poured into an evaporator and evaporated under reduced pressure at an absolute pressure of 57.817 kPa and a temperature of 85° C. for 30 min. Then, while maintaining the pressure and temperature, 0.02 g of polyaluminium ferrosilicate and 0.08 g of PAM were added, and the reduced pressure evaporation was continued until the water was completely evaporated.

[0062] Step (2): The steam obtained in step (1) is passed into 200 mL of a mixed solution containing 2.5 mol / L sulfuric acid and 1.5 mol / L acetic acid. The steam treated with the mixed solution of sulfuric acid and acetic acid is passed into 200 mL of a 4 mol / L sodium hydroxide solution. The steam treated with the sodium hydroxide solution is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0063] Step (3): Take 100 mL of the steam cooling water obtained in step (2), add 0.002 g of polyaluminium ferrosilicate and 0.008 g of PAM, stir for 50 min, let stand for 3 h, and then filter.

[0064] Example 9

[0065] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0066] Step (1): 250 mL of non-ferrous metal wastewater was poured into an evaporator and evaporated under reduced pressure at an absolute pressure of 57.817 kPa and a temperature of 85° C. for 30 min. Then, while maintaining the pressure and temperature, 0.02 g of polyaluminium ferrosilicate and 0.08 g of PAM were added, and the reduced pressure evaporation was continued until the water was completely evaporated.

[0067] Step (2): The steam obtained in step (1) is passed into 200 mL of a mixed solution containing 2.5 mol / L sulfuric acid and 1.5 mol / L acetic acid. The steam treated with the mixed solution of sulfuric acid and acetic acid is passed into a mixed solution containing 2.5 mol / L sodium hydroxide and 1.5 mol / L sodium carbonate. The steam treated with the mixed solution of sodium hydroxide and sodium carbonate is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0068] Step (3): Take 100 mL of the steam cooling water obtained in step (2), add 0.002 g of polyaluminium ferrosilicate and 0.008 g of PAM, stir for 50 min, let stand for 3 h, and then filter.

[0069] Comparative Example 1

[0070] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0071] Step (1): Pour 250 mL of nonferrous metal wastewater into an evaporator and evaporate under reduced pressure at an absolute pressure of 57.817 kPa and a temperature of 85° C. until the water is completely evaporated;

[0072] Step (2): The steam obtained in step (1) is passed into 200 mL of a 4 mol / L sulfuric acid solution, the steam treated with the sulfuric acid solution is passed into 200 mL of a 4 mol / L sodium hydroxide solution, and the steam treated with the sodium hydroxide solution is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0073] Comparative Example 2

[0074] A steam purification method for nonferrous metal wastewater, the specific steps of the purification method comprising:

[0075] Step (1): Pour 250 mL of nonferrous metal wastewater into an evaporator and evaporate under reduced pressure at an absolute pressure of 57.817 kPa and a temperature of 85° C. until the water is completely evaporated;

[0076] Step (2): The steam obtained in step (1) is passed into 200 mL of a 4 mol / L sulfuric acid solution, the steam treated with the sulfuric acid solution is passed into 200 mL of a 4 mol / L sodium hydroxide solution, and the steam treated with the sodium hydroxide solution is heat exchanged with cooling water in a heat exchanger to obtain steam condensate.

[0077] Step (3), add 0.1 g of PAM to the steam condensate obtained in step (2), stir for 50 min, let stand for 3 h, and then filter.

[0078] The TDS, ammonia nitrogen content (ammonia nitrogen content was determined using HJ535-2009), and COD content (determined using GB11914-89) of the treated water of Examples 1-9 and Comparative Examples 1-2 were measured, wherein TDS was measured using a TDS test pen (Xiaomi, product model XMTDS01YM). The TDS in the non-ferrous metal wastewater was 14950 mg / L, the ammonia nitrogen content was 98 mg / L, and the COD content was 4960 mg / L. The specific test results are shown in Table 1.

[0079] Table 1 Test results of Examples 1-9 and Comparative Examples 1-2

[0080] TDS (mg / L) Ammonia nitrogen (mg / L) COD (mg / L) Example 1 9.6 11.5 689 Example 2 10.2 11.8 692 Example 3 9.8 11.7 690 Example 4 7.6 11.4 687 Example 5 5.6 11.2 684 Example 6 9.4 10.9 679 Example 7 9.2 10.4 332 Example 8 5.1 9.8 663 Example 9 4.9 9.6 316 Comparative Example 1 153 12.5 736 Comparative Example 2 23 12.2 695

[0081] By comparing Examples 1-9 with Comparative Examples 1-2, it can be found that the present invention can effectively reduce the TDS in the wastewater vapor by adding a flocculant during the evaporation process, and can effectively reduce the ammonia nitrogen and COD contents in the wastewater by using the coordinated cooperation of the preferred acid and base.

[0082] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A steam purification method for non-ferrous metal wastewater, characterized in that: The specific steps of the purification method include: Step (1): pouring the non-ferrous metal wastewater into an evaporator for reduced pressure evaporation for a certain period of time, then adding a flocculant while maintaining the pressure and temperature, and continuing the reduced pressure evaporation until the water is completely evaporated; the conditions for the reduced pressure evaporation are: absolute pressure of 47.373 kPa to 70.117 kPa, and temperature of 80-90°C; Step (2): passing the steam obtained in step (1) into an acid solution, passing the acid-treated steam into an alkaline solution, and exchanging heat with cooling water in a heat exchanger to obtain steam condensate; the acid is one or more of nitric acid, sulfuric acid, and acetic acid; and the alkali is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate; Step (3): adding a flocculant to the steam condensate obtained in step (2), stirring, allowing to stand, and then filtering; The flocculant is polyaluminium ferric silicate and PAM, and the mass ratio of the polyaluminium ferric silicate to PAM is 1:3-5; Non-ferrous metal wastewater contains salt, ammonia nitrogen and COD; By adding flocculants during the wastewater evaporation process, the TDS content in the steam can be effectively reduced and the amount of flocculants used can be reduced. At the same time, the ammonia nitrogen in the steam can be absorbed by combining acid solution treatment, and the COD in the steam can be absorbed by alkaline solution treatment.

2. The steam purification method for non-ferrous metal wastewater according to claim 1, characterized in that: In step (1), the evaporation time is 20 to 40 minutes.

3. The steam purification method for non-ferrous metal wastewater according to claim 1 or 2, characterized in that: In step (1), the ratio of wastewater to flocculant is 200-300 mL: 0.05-0.15 g.

4. The steam purification method for non-ferrous metal wastewater according to claim 1, characterized in that: In step (2), the concentration of the acid is 2 to 6 mol / L.

5. The steam purification method for non-ferrous metal wastewater according to claim 1, characterized in that: In step (2), the concentration of the base is 3 to 5 mol / L.

6. The steam purification method for non-ferrous metal wastewater according to claim 4 or 5, characterized in that: In step (2), the acid is sulfuric acid and acetic acid, and the molar ratio of the sulfuric acid to the acetic acid is 1:0.5-1; the base is sodium hydroxide and sodium carbonate, and the molar ratio of the sodium hydroxide to the sodium carbonate is 1:0.4-0.

8.

7. The steam purification method for non-ferrous metal wastewater according to claim 1, characterized in that: In step (3), the ratio of the steam condensate to the flocculant is 100 mL:0.01 g; the stirring time is 0.5 to 1 h, and the standing time is 2 to 4 h.