A method for treating tungsten wastewater containing ammonia and nitrogen

Abstract

The invention discloses a method for treating tungsten wastewater containing ammonia nitrogen. The method comprises the following steps: subjecting the tungsten wastewater containing ammonia nitrogen to pressure filtration, acid adjustment, and an RO desalination system for treatment, thereby significantly improving the enrichment effect and removal efficiency of ammonia nitrogen, reducing the amount of wastewater entering a stripping tower for treatment, saving treatment costs, and improving the efficiency of tungsten wastewater treatment. The method ensures that the effluent water quality indicators meet the standards and can be directly discharged or reused, thereby reducing the amount of discharged wastewater, and realizing efficient treatment of tungsten wastewater, green and clean production, and resource recycling.

Description

Technical Field

[0001] The present invention relates to a treatment technology for tungsten wastewater, in particular to a treatment method for tungsten wastewater containing ammonia nitrogen. Background Art

[0002] Tungsten smelting enterprises mostly use ion exchange process to produce ammonium paratungstate (APT). This process will produce a large amount of post-exchange liquid. Before the post-exchange liquid is recovered, it is discharged as alkaline wastewater. After recovery, the post-exchange liquid needs to be adsorbed again, and the secondary post-exchange liquid obtained is discharged as acidic wastewater. The discharged wastewater has high salt content, high ammonia nitrogen content and complex composition. The wastewater discharge volume is large and contains harmful substances such as NH3-N, As, P, Si, etc., which poses great hazards and is difficult to treat. If not properly treated, it will cause serious pollution and harm to water bodies and the ecological environment.

[0003] At present, wastewater is mainly treated through physical, chemical and biological methods to meet emission standards. For example, physical methods include precipitation, filtration, adsorption, etc., chemical methods include oxidation, reduction, neutralization, etc., and biological methods include aerobic treatment, anaerobic treatment, etc. In addition, some methods are combined to improve the treatment effect. However, when treating wastewater containing ammonia nitrogen, these methods are often unable to effectively remove ammonia nitrogen from the wastewater, resulting in the ammonia nitrogen content in the treated wastewater still exceeding the standard, and the ideal treatment effect cannot be achieved. In addition, the treatment cost is high, or the treatment process is complicated and cumbersome, resulting in secondary pollution, making it difficult to achieve resource utilization, increasing the production cost of the enterprise and the consumption of tungsten resources, and is not conducive to environmental protection and sustainable development of resources.

[0004] Patent application CN1785809A discloses a method for recovering tungsten and ammonium chloride from ammonium paratungstate crystallization mother liquor. The method utilizes a nanofiltration or ultrafiltration membrane separation process to separate tungsten and chloride ions from the ammonium paratungstate crystallization mother liquor and directly returns the tungsten-containing solution to the main ion exchange process for ammonium paratungstate production for reuse. However, this method has drawbacks: it requires the use of nanofiltration or ultrafiltration membrane equipment, which requires a large investment in the equipment, and the membrane equipment has high requirements for the properties of the solution, resulting in high maintenance costs and high processing costs.

[0005] Patent application CN101530737A discloses a method and apparatus for treating tungsten smelting wastewater and waste gas. The method utilizes an ion exchange method to directly treat wastewater and waste gas from alkaline wastewater produced by ammonium paratungstate and flue gas generated by boilers, including cyclone dust removal, spray dust removal, desulfurization, and deamination steps. However, this method has drawbacks: the process is complex and the treatment effect is unsatisfactory.

[0006] Therefore, how to improve the treatment method of tungsten wastewater containing ammonia nitrogen and realize green and clean production and resource recycling is of vital importance to tungsten smelting production enterprises. Summary of the Invention

[0007] The purpose of the present invention is to overcome the difficulties existing in the existing tungsten wastewater treatment and provide a treatment method for tungsten wastewater containing ammonia nitrogen. The method can significantly improve the enrichment effect and removal efficiency of ammonia nitrogen, reduce the amount of wastewater entering the stripping tower for treatment, save treatment costs, and improve the efficiency of tungsten wastewater treatment, ensure that the effluent water quality indicators are qualified, can be directly discharged or reused, reduce the amount of discharged wastewater, and realize efficient treatment of tungsten wastewater, green and clean production and resource recycling.

[0008] To achieve the above object, the technical solution of the present invention is:

[0009] A method for treating tungsten wastewater containing ammonia and nitrogen comprises the following steps: collecting tungsten wastewater containing ammonia and nitrogen from the forward pulling and backwashing steps of an ion exchange column, performing filter pressing, acid adjustment, and RO desalination system treatment, and controlling the flow ratio of concentrated water to fresh water at membrane outlet, obtaining effluent concentrated water and effluent fresh water after treatment, adjusting the pH of the effluent concentrated water and then entering a stripping tower for treatment, and directly discharging or reusing the effluent fresh water.

[0010] Furthermore, the ammonia nitrogen-containing tungsten wastewater comes from the ammonia nitrogen-containing tungsten wastewater generated in the ion exchange process during tungsten smelting.

[0011] Preferably, the tungsten element content of the ammonia nitrogen-containing tungsten wastewater is ≤0.1 g / L in terms of WO3 concentration.

[0012] Preferably, the NH3 concentration of the tungsten wastewater containing ammonia nitrogen is normally 45-250 mg / L; more preferably, the NH3 concentration of the tungsten wastewater containing ammonia nitrogen is 182-240 mg / L.

[0013] Furthermore, the filtration is performed using a filter press.

[0014] Furthermore, the acid adjustment is to add dilute acid to control the pH range of the membrane-influent wastewater to be 4-6.

[0015] Furthermore, the RO desalination system includes a 5um large flow filter, a high-pressure pump, an inter-stage booster pump, an RO membrane group, and a membrane shell, wherein the RO membrane group includes a desalination membrane reverse osmosis membrane.

[0016] Furthermore, the flow ratio of concentrated water to fresh water when the membrane is discharged is 1:(3-7), including but not limited to 1:3, 1:3.9, 1:4, 1:4.7, 1:5, 1:5.9, 1:6, 1:6.5, 1:7...etc.

[0017] Compared with the existing tungsten wastewater treatment method, the present invention has the following beneficial effects:

[0018] In view of the characteristics of high ammonia nitrogen and complex composition in tungsten wastewater, the present invention comprehensively treats the tungsten wastewater containing ammonia nitrogen through filter pressing, acid adjustment, and RO desalination system, which significantly improves the enrichment effect and removal efficiency of ammonia nitrogen. Among them, the present invention introduces RO desalination system treatment technology. On the one hand, a new filter press process is added in the early stage of RO desalination to filter and remove suspended matter, colloids, residual chlorine, etc. in tungsten wastewater, thereby reducing blockage and pollution of the RO desalination system, thereby improving membrane flux and desalination rate, and preventing residual chlorine from damaging membrane elements, providing favorable conditions for subsequent efficient desalination treatment. At the same time, dilute acid is added to control the pH range of the wastewater entering the membrane, so that various impurity ions in the wastewater form insoluble salts, thereby improving the desalination rate; on the other hand, an RO membrane group (seawater desalination membrane reverse osmosis membrane) is used for desalination to remove trace insoluble salts, microorganisms, organic and inorganic impurity particles in the wastewater, thereby centrally treating the part of the tungsten wastewater with a high ammonia nitrogen content, and by designing the flow ratio of concentrated water to fresh water at the membrane outlet, while improving the membrane flux, ensuring stable operation within the optimal performance range of the membrane system, reducing the amount of wastewater entering the stripping tower for treatment, and saving treatment costs.

[0019] After a large number of research and experiments, the present invention found that the design of the flow ratio of concentrated water to fresh water at the membrane outlet is particularly important for the treatment of tungsten wastewater. When the flow ratio is controlled within the range of 1: (3-7), the wastewater treatment efficiency is high, the desalination rate is high, and the effluent water quality is qualified; if it exceeds the range, it is easy for the ammonia nitrogen in the fresh water to remain high, the effluent conductivity to be high, or it cannot meet the requirements of discharge and reuse.

[0020] At the same time, the present invention can not only improve the efficiency of tungsten wastewater treatment, but also ensure that the effluent water quality indicators are qualified. It can be directly discharged or reused, reducing the amount of discharged wastewater, alleviating environmental pressure, and avoiding secondary pollution, unstable treatment effects, or inability to recycle when treating tungsten wastewater. It realizes efficient treatment of tungsten wastewater, green and clean production, and resource recycling; it is simple to operate, easy to industrialize, and has good application prospects. DETAILED DESCRIPTION

[0021] The preferred embodiments of the present invention are described in detail below, which are intended to explain the present invention and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the examples, the methods or conditions described in the literature in this area or the product specifications are used. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be obtained commercially. In the following examples, if not explicitly stated, "%" refers to percentage by weight.

[0022] Example 1

[0023] A method for treating tungsten wastewater containing ammonia and nitrogen, wherein a decomposing agent (NH4Cl+NH4OH) is added to the tungsten wastewater containing ammonia and nitrogen produced in the ion exchange process during tungsten smelting to convert sodium salt into ammonium salt, and then the wastewater is washed with salt-free water until the tungsten content of the column is ≤0.1g / L in terms of WO3 concentration, and then enters the forward pulling and backwashing steps, and the water from the forward pulling and backwashing steps is collected. The volume of the water discharged from the forward pulling is 14.5m 3 , backwash water volume is 18m 3 , the NH3 concentration of the forward and reverse flush water samples was measured to be 182mg / L. After that, the filtration, acid adjustment and RO desalination system treatment were carried out. The filtration was filtered by a filter press, and the acid adjustment was to add dilute acid to control the pH of the membrane-influent wastewater to 6. The RO desalination system includes a 5um large flow filter, a high-pressure pump, an inter-stage booster pump, an RO membrane group, and a membrane shell. The RO membrane group includes a seawater desalination membrane reverse osmosis membrane. The concentrated water flow rate during the RO desalination system treatment is 1.9m 3 / h, fresh water flow rate is 7.2m 3 / h. After treatment, the membrane effluent is concentrated water and fresh water, and the volume of concentrated water is 6.8m 3 , NH3 concentration is 812mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 26.1m 3 , NH3 concentration is 14mg / L, water conductivity is 180us / cm, and it can be directly discharged or returned to the process for use.

[0024] Example 2

[0025] A method for treating tungsten wastewater containing ammonia and nitrogen, wherein a decomposing agent (NH4Cl+NH4OH) is added to the tungsten wastewater containing ammonia and nitrogen produced in the ion exchange process during tungsten smelting to convert sodium salt into ammonium salt, and then the wastewater is washed with salt-free water until the tungsten content of the column is ≤0.1g / L in terms of WO3 concentration, and then enters the forward pulling and backwashing steps, and the water from the forward pulling and backwashing steps is collected. The volume of the water discharged from the forward pulling is 16.4m 3 , the backwash water volume is 21m 3 , the NH3 concentration of the forward and reverse flush water samples was measured to be 220mg / L. After that, the filtration, acid adjustment and RO desalination system treatment were carried out. The filtration was filtered by a filter press, and the acid adjustment was to add dilute acid to control the pH of the membrane-influent wastewater to 5. The RO desalination system includes a 5um large flow filter, a high-pressure pump, an inter-stage booster pump, an RO membrane group, and a membrane shell. The RO membrane group includes a seawater desalination membrane reverse osmosis membrane. The concentrated water flow rate during the RO desalination system treatment is 2.1m 3 / h, fresh water flow rate is 7.4m 3 / h. After treatment, the membrane effluent is concentrated water and fresh water, and the volume of concentrated water is 8.4m 3 , NH3 concentration is 768mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 28.5m 3, NH3 concentration is 9.83mg / L, water conductivity is 170us / cm, and it can be directly discharged or returned to the process for use.

[0026] Example 3

[0027] A method for treating tungsten wastewater containing ammonia and nitrogen, wherein a decomposing agent (NH4Cl+NH4OH) is added to the tungsten wastewater containing ammonia and nitrogen produced in the ion exchange process during tungsten smelting to convert sodium salt into ammonium salt, and then the wastewater is washed with salt-free water until the tungsten content of the column is ≤0.1g / L in terms of WO3 concentration, and then enters the forward pulling and backwashing steps, and the water from the forward pulling and backwashing steps is collected. The volume of the water discharged from the forward pulling is 15.3m 3 , the backwash water volume is 19.5m 3 , the NH3 concentration of the forward and reverse flush water samples was measured to be 201 mg / L. After that, the filtration, acid adjustment and RO desalination system treatment were carried out. The filtration was filtered by a filter press, and the acid adjustment was to add dilute acid to control the pH of the membrane-influent wastewater to 4. The RO desalination system includes a 5um large flow filter, a high-pressure pump, an inter-stage booster pump, an RO membrane group, and a membrane shell. The RO membrane group includes a seawater desalination membrane reverse osmosis membrane. The concentrated water flow rate during the RO desalination system treatment is 1.8m 3 / h, fresh water flow rate 7.1m 3 / h. After treatment, the membrane effluent is concentrated water and fresh water, and the volume of concentrated water is 7.04m 3 , NH3 concentration is 935mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 28.1m 3 , NH3 concentration is 8.6mg / L, water conductivity is 120us / cm, and it can be directly discharged or returned to the process for use.

[0028] Example 4

[0029] A method for treating tungsten wastewater containing ammonia and nitrogen, wherein a decomposing agent (NH4Cl+NH4OH) is added to the tungsten wastewater containing ammonia and nitrogen produced in the ion exchange process during tungsten smelting to convert sodium salt into ammonium salt, and then the wastewater is washed with salt-free water until the tungsten content of the column is ≤0.1g / L in terms of WO3 concentration, and then enters the forward pulling and backwashing steps, and the water from the forward pulling and backwashing steps is collected. The volume of the water discharged from the forward pulling is 17.1m 3 , the backwash water volume is 20.8m 3 , the NH3 concentration of the forward and reverse flush water samples was measured to be 198mg / L. After that, the filtration, acid adjustment and RO desalination system treatment were carried out. The filtration was filtered by a filter press, and the acid adjustment was to add dilute acid to control the pH of the membrane-influent wastewater to 6. The RO desalination system includes a 5um large flow filter, a high-pressure pump, an inter-stage booster pump, an RO membrane group, and a membrane shell. The RO membrane group includes a seawater desalination membrane reverse osmosis membrane. The concentrated water flow rate during the RO desalination system treatment is 1.5m 3 / h, fresh water flow rate is 9m 3 / h. After treatment, the membrane effluent is concentrated water and fresh water, and the volume of concentrated water is 8.65m 3 , NH3 concentration is 693.1mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 29.6m 3 , NH3 concentration is 12.3mg / L, water conductivity is 150us / cm, and it can be directly discharged or returned to the process for use.

[0030] Example 5

[0031] A method for treating tungsten wastewater containing ammonia and nitrogen, wherein a decomposing agent (NH4Cl+NH4OH) is added to the tungsten wastewater containing ammonia and nitrogen produced in the ion exchange process during tungsten smelting to convert sodium salt into ammonium salt, and then the wastewater is washed with salt-free water until the tungsten content of the column is ≤0.1g / L in terms of WO3 concentration, and then enters the forward pulling and backwashing steps, and the water from the forward pulling and backwashing steps is collected. The volume of the water discharged from the forward pulling is 16.5m 3 , the backwash water volume is 19.8m 3 , the NH3 concentration of the forward and reverse flush water samples was measured to be 240mg / L. After that, the filtration, acid adjustment and RO desalination system treatment were carried out. The filtration was filtered by a filter press, and the acid adjustment was to add dilute acid to control the pH of the membrane-influent wastewater to 6. The RO desalination system includes a 5um large flow filter, a high-pressure pump, an inter-stage booster pump, an RO membrane group, and a membrane shell. The RO membrane group includes a seawater desalination membrane reverse osmosis membrane. The concentrated water flow rate during the RO desalination system treatment is 1.5m 3 / h, fresh water flow rate is 10.5m 3 / h. After treatment, the membrane effluent is concentrated water and fresh water, and the volume of concentrated water is 6m 3 , NH3 concentration is 721mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 29.5m 3 , NH3 concentration is 9.6mg / L, water conductivity is 160us / cm, and it can be directly discharged or returned to the process for use.

[0032] Comparative Example 1

[0033] A method for treating tungsten wastewater containing ammonia and nitrogen, wherein a decomposing agent (NH4Cl+NH4OH) is added to the tungsten wastewater containing ammonia and nitrogen produced in the ion exchange process during tungsten smelting to convert sodium salt into ammonium salt, and then the wastewater is washed with non-salted water until the tungsten content of the column is ≤0.1g / L in terms of WO3 concentration, and then enters the forward pulling and backwashing steps, and the water from the forward pulling and backwashing steps is collected. The volume of the water discharged from the forward pulling is 17.3m 3 , the backwash water volume is 19.3m 3 The forward and reverse flush water samples were taken to determine the NH3 concentration to be 260 mg / L and the water conductivity to be 310 us / cm, and then the water entered the stripping tower for treatment.

[0034] It can be seen that the NH3 concentration of 260 mg / L in Comparative Example 1 is much higher than the NH3 concentration of 8.6-14 mg / L in the fresh water produced by Examples 1-5 of the present invention. The total volume of the forward and backwash effluents that need to enter the stripping tower for treatment in Comparative Example 1 is 36.6 m 3 , which is much larger than the concentrated water volume of 6-8.65m in Examples 1-5. 3 The water conductivity of 310 us / cm in comparative example 1 is also much higher than the water conductivity of 120-180 us / cm in Examples 1-5, indicating that when the tungsten wastewater in comparative example 1 is not comprehensively treated by filtration, acid adjustment, and RO desalination system, the NH3 concentration is high, the amount of discharged wastewater is large, and the water conductivity is high, and it cannot be directly discharged or returned to the process for use.

[0035] Comparative Example 2

[0036] The difference between this comparative example and Example 3 is that the forward and reverse flushing water is not subjected to filter press treatment, and other conditions remain unchanged. After treatment, the concentrated water and fresh water are obtained when the membrane is discharged. The volume of the concentrated water is 4.5m 3 , NH3 concentration is 821mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 25.2m 3 , NH3 concentration is 652mg / L, water conductivity is 250us / cm, and enters the stripping tower for treatment.

[0037] The results show that when comparative example 2 is not subjected to filter press treatment, the NH3 concentration of the fresh water produced is much higher than that of Example 3, and the volume of concentrated water and the water conductivity are also higher than those of Example 3, indicating that comparative example 2 is not effective in treating ammonia nitrogen in tungsten wastewater and cannot be discharged directly, and needs to enter the stripping tower for treatment.

[0038] Comparative Example 3

[0039] The difference between this comparative example and Example 3 is that the pH of the wastewater entering the membrane is controlled to 2 by adding dilute acid, and other conditions remain unchanged. After treatment, the concentrated water and fresh water are obtained when the membrane is discharged. The volume of the concentrated water is 9.5m 3 , NH3 concentration is 255mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 23m 3 , NH3 concentration is 86mg / L, water conductivity is 210us / cm, and it is returned to the process for reprocessing.

[0040] Comparative Example 4

[0041] The difference between this comparative example and Example 3 is that the pH of the wastewater entering the membrane is adjusted by adding dilute acid to control the pH of the wastewater to 7, and other conditions remain unchanged. After treatment, the concentrated water and fresh water are obtained when the membrane is discharged. The volume of the concentrated water is 12m 3 , NH3 concentration is 530mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 22.3m3 , NH3 concentration is 66mg / L, water conductivity is 220us / cm, and it is returned to the process for reprocessing.

[0042] It can be seen from Comparative Examples 3-4 that if the acid adjustment exceeds the pH range of 4-6, the ammonia nitrogen content of the produced fresh water is likely to be high, the water conductivity is also high, and the treatment effect is not obvious.

[0043] Comparative Example 5

[0044] The difference between this comparative example and Example 3 is that the concentrated water flow rate during the RO desalination system treatment is 1.2m 3 / h, fresh water flow rate is 10m 3 / h, other conditions remain unchanged. After treatment, the membrane effluent is concentrated water and fresh water, and the volume of concentrated water is 4.8m 3 , NH3 concentration is 563mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 35m 3 , NH3 concentration is 110mg / L, water conductivity is 235us / cm, and it is returned to the process for reprocessing.

[0045] Comparative Example 6

[0046] The difference between this comparative example and Example 3 is that the concentrated water flow rate during RO desalination system treatment is 3m 3 / h, fresh water flow rate is 6m 3 / h, other conditions remain unchanged. After treatment, the membrane effluent is concentrated water and fresh water, and the volume of concentrated water is 12.3m 3 , NH3 concentration is 265mg / L, after adjusting pH, it enters the stripping tower for treatment; the volume of fresh water produced is 24.2m 3 , NH3 concentration is 90mg / L, water conductivity is 229us / cm, and it is returned to the process for reprocessing.

[0047] It can be seen from Comparative Examples 5-6 and Example 3 that when the flow ratio of concentrated water to fresh water in the RO desalination system is controlled in the range of 1:(3-7), the treatment effect of tungsten wastewater containing ammonia nitrogen is best; if it exceeds the range, the ammonia nitrogen content of the fresh water is likely to be still high, the water conductivity is also high, the amount of wastewater entering the stripping tower for treatment is also large, and the treatment cost is higher.

[0048] In summary, the technical solution of the present invention is used to perform comprehensive treatment of tungsten wastewater containing ammonia and nitrogen by filtration pressing, acid adjustment, and RO desalination system, and when the pH of the acid adjustment and the flow ratio of concentrated water to fresh water treated by the RO desalination system are controlled within a certain range, it can not only improve the efficiency of tungsten wastewater treatment, but also ensure that the effluent water quality indicators are qualified and can be directly discharged or reused, while reducing the amount of discharged wastewater, alleviating environmental pressure, and avoiding secondary pollution, unstable treatment effect, or inability to recycle when treating tungsten wastewater. It realizes efficient treatment of tungsten wastewater, green and clean production, and resource recycling, and has good application prospects.

[0049] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A method for treating tungsten wastewater containing ammonia and nitrogen, characterized in that: The method comprises the following steps: collecting tungsten wastewater containing ammonia and nitrogen from the forward pulling and backwashing steps of the ion exchange column, then subjecting it to pressure filtration, acid adjustment, and RO desalination system treatment, and controlling the flow ratio of concentrated water to fresh water at the outlet of the membrane, obtaining effluent concentrated water and effluent fresh water after treatment, adjusting the pH of the effluent concentrated water and then entering a stripping tower for treatment, and directly discharging or reusing the effluent fresh water; The acid adjustment is to add dilute acid to control the pH range of the membrane-influent wastewater to 4-6; When the membrane discharges water, the flow ratio of concentrated water to fresh water is 1: (3-7).

2. The processing method according to claim 1, characterized in that The ammonia nitrogen-containing tungsten wastewater is derived from the ammonia nitrogen-containing tungsten wastewater produced in the ion exchange process during tungsten smelting.

3. The processing method according to claim 1, characterized in that The tungsten element content of the ammonia nitrogen-containing tungsten wastewater is ≤0.1 g / L in terms of WO3 concentration.

4. The processing method according to claim 1, characterized in that The NH3 concentration of the ammonia nitrogen-containing tungsten wastewater is 45-250 mg / L.

5. The processing method according to claim 1, characterized in that The NH3 concentration of the ammonia nitrogen-containing tungsten wastewater is 182-240 mg / L.

6. The processing method according to claim 1, characterized in that The filtration is performed using a filter press.

7. The processing method according to claim 1, characterized in that The RO desalination system includes a 5um large flow filter, a high-pressure pump, an inter-stage booster pump, an RO membrane group, and a membrane shell, wherein the RO membrane group includes a desalination membrane reverse osmosis membrane.