Method for recovering ammonia nitrogen in rare earth smelting wastewater

Abstract

The invention provides a method for recovering ammonia nitrogen in rare earth smelting wastewater, and belongs to the technical field of industrial wastewater treatment. According to the method, metal ions such as iron and magnesium in the rare earth smelting wastewater are precipitated or form complexes through alkali treatment, meanwhile, the pH value of the wastewater is adjusted, and the absorption efficiency of a membrane absorption method is improved; then metal precipitates and complexes are removed through ultrafiltration, large-particle substances in the wastewater are removed at the same time, the turbidity of the wastewater is reduced, and the loss and burden of a membrane material are reduced; finally, ammonia nitrogen in the wastewater is absorbed through a membrane absorption method, energy consumption devices such as gas heating are not needed, and the problem that the energy consumption of ammonia nitrogen removal processes such as ammonia stripping is high is solved; the ammonia nitrogen absorption efficiency is improved by optimizing the process parameters of the membrane absorption method.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial wastewater treatment, and in particular relates to a method for recovering ammonia nitrogen in rare earth smelting wastewater. Background Art

[0002] my country is a major exporter of rare earth elements. Rare earth ores are mainly extracted using chemical precipitation processes. For example, the ammonia soap reaction can promote rare earth separation at a low cost without reducing product quality. However, it also causes a large amount of ammonia soap wastewater with high ammonia nitrogen concentration (ammonia nitrogen concentration is between 15,000 and 30,000 mg / L) to be produced during the extraction process.

[0003] At present, the most widely used method for removing ammonia nitrogen from wastewater is biological method, such as sequencing batch reactor. However, rare earth wastewater has complex composition, contains a large amount of inorganic salts (TDS≈12g / L) and ammonia nitrogen, and has high biological toxicity, making it difficult for conventional microorganisms to survive in rare earth wastewater and unable to effectively remove ammonia nitrogen. With the increasing attention paid to material recycling, several new ammonia nitrogen recovery technologies have emerged, including air stripping (ammonia stripping), ion exchange and absorption, electrochemical oxidation and photocatalysis, chemical precipitation, etc. Among these technologies, ammonia stripping is the most commonly used method in practical applications, which can effectively recover ammonia nitrogen from wastewater. Although the new technology can effectively recover ammonia nitrogen, there is a problem of high energy consumption. Summary of the invention

[0004] The purpose of the present invention is to provide a method for recovering ammonia nitrogen from rare earth smelting wastewater. The recovery method provided by the present invention can achieve high-efficiency recovery of ammonia nitrogen at low energy consumption.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for recovering ammonia nitrogen in rare earth smelting wastewater, comprising:

[0007] Pre-treating rare earth smelting wastewater to obtain pre-treated wastewater; the rare earth smelting wastewater has an ammonia nitrogen concentration of 500-5000 mg / L; the pre-treatment includes alkali treatment and ultrafiltration performed in sequence; the pH value of the pre-treated wastewater is ≥11;

[0008] The pretreated wastewater is recycled by using a membrane absorption method to obtain wastewater with ammonia nitrogen removed and an ammonium salt solution; the membrane material used in the membrane absorption method is a hollow fiber membrane;

[0009] During the recovery treatment, the pH value of the absorption liquid is ≤2, the flow rate of the feed liquid is not less than 12.5 mL / min, and the flow rate of the absorption liquid is not less than 12.5 mL / min.

[0010] Preferably, the rare earth smelting wastewater includes ammonia soap wastewater and low ammonia nitrogen rare earth smelting wastewater; the ammonia nitrogen concentration of the low ammonia nitrogen rare earth smelting wastewater is below 10 mg / L.

[0011] Preferably, the volume ratio of the ammonia soap wastewater to the low ammonia nitrogen rare earth smelting wastewater is 1: (3-8).

[0012] Preferably, the pH value of the pretreated wastewater is 11-12.

[0013] Preferably, the pH value of the absorption liquid during the recovery treatment is 0.5-1.5.

[0014] Preferably, the flow rate of the feed liquid during the recovery process is 12.5 to 25 mL / min.

[0015] Preferably, the flow rate of the absorption liquid during the recovery process is 12.5 to 25 mL / min.

[0016] Preferably, the temperature of the feed liquid during the recovery process is 20-45°C.

[0017] Preferably, the alkali used in the alkali treatment is quicklime.

[0018] Preferably, the absorption liquid used in the recovery process is hydrochloric acid.

[0019] The invention provides a method for recovering ammonia nitrogen in rare earth smelting wastewater, comprising: pre-treating the rare earth smelting wastewater to obtain pre-treated wastewater; the ammonia nitrogen concentration of the rare earth smelting wastewater is 500-5000 mg / L; the pre-treatment comprises alkali treatment and ultrafiltration performed in sequence; the pH value of the pre-treated wastewater is ≥11; the pre-treated wastewater is recovered by a membrane absorption method to obtain wastewater with ammonia nitrogen removed and an ammonium salt solution; the membrane material used in the membrane absorption method is a hollow fiber membrane; during the recovery treatment, the pH value of the absorption liquid is ≤2, the feed liquid flow rate is not less than 12.5 mL / min, and the absorption liquid flow rate is not less than 12.5 mL / min. The present invention first precipitates or forms complexes of metal ions such as iron and magnesium in rare earth smelting wastewater by alkali treatment, and adjusts the pH value of the wastewater to improve the absorption efficiency of the membrane absorption method; then removes metal precipitation and complexes by ultrafiltration, and simultaneously removes large particles in the wastewater, reduces the turbidity of the wastewater, and reduces the loss and burden of the membrane material; finally, absorbs ammonia nitrogen in the wastewater by the membrane absorption method, without the need to use energy-consuming devices such as gas heating, thereby avoiding the problem of high energy consumption of ammonia nitrogen removal processes such as ammonia stripping; and improves the ammonia nitrogen absorption efficiency by optimizing the process parameters of the membrane absorption method. The results of the embodiment show that by adopting the recovery method provided by the present invention, the ammonia nitrogen concentration in the treated wastewater is reduced to 0.02 mg / L, the removal efficiency reaches 99.99%, and the obtained ammonium salt solution can obtain an ammonium salt with a purity of 86.52% after crystallization treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the process of Example 1 of the present invention;

[0021] Figure 2 1 is a state diagram of wastewater at each stage of pretreatment in Example 1 of the present invention, wherein a is the raw wastewater, b is the state just after quicklime is added, c is the state after quicklime is added and allowed to stand for 10 minutes, and d is the state of pretreated wastewater;

[0022] Figure 3 This is a graph showing changes in ammonia nitrogen concentration and recovery efficiency over time during the recovery process of Example 1 of the present invention;

[0023] Figure 4 The graph of the change of ammonia nitrogen concentration during the recovery process of Examples 2 to 4 of the present invention and Comparative Example 1;

[0024] Figure 5 It is a curve diagram of ammonia nitrogen concentration change during the recovery process of Examples 5 to 8 of the present invention and Comparative Example 2;

[0025] Figure 6 This is a graph showing changes in ammonia nitrogen concentration during the recovery process of Examples 9 to 13 of the present invention;

[0026] Figure 7 This is a graph showing changes in ammonia nitrogen concentration during the recovery process of Examples 14 to 16 of the present invention;

[0027] Figure 8 This is a graph showing the ammonia nitrogen removal rate during the recovery process of Examples 17 to 20 of the present invention;

[0028] Fig. 9 This is a curve chart of the change in ammonia nitrogen concentration during the recovery process of Examples 21 to 23 of the present invention. DETAILED DESCRIPTION

[0029] All raw materials of the present invention have no particular limitation on their sources and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0030] There is no particular restriction on the purity of all raw materials in the present invention, and industrial pure raw materials are preferably used in the present invention.

[0031] The present invention provides a method for recovering ammonia nitrogen in rare earth smelting wastewater, comprising:

[0032] Pre-treating rare earth smelting wastewater to obtain pre-treated wastewater; the rare earth smelting wastewater has an ammonia nitrogen concentration of 500-5000 mg / L; the pre-treatment includes alkali treatment and ultrafiltration performed in sequence; the pH value of the pre-treated wastewater is ≥11;

[0033] The pretreated wastewater is recycled by using a membrane absorption method to obtain wastewater with ammonia nitrogen removed and an ammonium salt solution; the membrane material used in the membrane absorption method is a hollow fiber membrane;

[0034] During the recovery treatment, the pH value of the absorption liquid is ≤2, the flow rate of the feed liquid is not less than 12.5 mL / min, and the flow rate of the absorption liquid is not less than 12.5 mL / min.

[0035] The invention pretreats rare earth smelting wastewater to obtain pretreated wastewater.

[0036] In the present invention, the ammonia nitrogen concentration of the rare earth smelting wastewater is 500-5000 mg / L, preferably 2000-3000 mg / L; as an embodiment of the present invention, the ammonia nitrogen concentration of the rare earth smelting wastewater can be 1500 mg / L, 2000 mg / L, 2500 mg / L, 3000 mg / L, 3500 mg / L, 4000 mg / L or 4500 mg / L. When the ammonia nitrogen concentration of the rare earth smelting wastewater is within the above range, the membrane absorption method can be used to recover the ammonia nitrogen, so as to avoid the erosion of the membrane material caused by the excessive ammonia nitrogen concentration, reduce the service life of the membrane material, or reduce the absorption efficiency.

[0037] In the present invention, the rare earth smelting wastewater preferably includes ammonia soap wastewater and low ammonia nitrogen rare earth smelting wastewater; the ammonia nitrogen concentration of the low ammonia nitrogen rare earth smelting wastewater is preferably below 10 mg / L. The present invention mixes the ammonia soap wastewater with the low ammonia nitrogen rare earth smelting wastewater to preliminarily reduce the ammonia nitrogen concentration in the ammonia soap wastewater, which is conducive to further improving the recovery efficiency of ammonia nitrogen by the membrane absorption method.

[0038] In the present invention, the volume ratio of the ammonia soap wastewater to the low ammonia nitrogen rare earth smelting wastewater is preferably 1: (3-8), more preferably 1: (4-6); as an embodiment of the present invention, the volume ratio of the ammonia soap wastewater to the low ammonia nitrogen rare earth smelting wastewater can be 1: 3, 1: 4, 1: 5, 1: 6, 1: 7 or 1: 8. The volume ratio of the ammonia soap wastewater to the low ammonia nitrogen rare earth smelting wastewater is within the above range, which is conducive to controlling the ammonia nitrogen concentration of the wastewater within a preferred range, and is conducive to further improving the ammonia nitrogen recovery efficiency and the service life of the membrane material.

[0039] In the present invention, the pretreatment includes alkali treatment and ultrafiltration performed in sequence.

[0040] In the present invention, the alkali used in the alkali treatment is preferably quicklime. The present invention can dissolve some insoluble substances in the wastewater, such as the extractant P507, under alkaline conditions and form a complex by alkali treatment of rare earth smelting wastewater, and can also form precipitation or complexes of metal ions in the wastewater, thereby reducing the burden of membrane absorption recovery treatment and facilitating the improvement of the recovery efficiency of ammonia nitrogen.

[0041] The present invention has no special requirements for the specific operation of the alkali treatment, and the conventional alkali treatment method in the art can be used. As an embodiment of the present invention, during the alkali treatment, an excess of quicklime can be added, the wastewater is allowed to stand to separate into layers, and the supernatant is subsequently subjected to ultrafiltration.

[0042] The present invention has no special requirements on the membrane material used in the ultrafiltration, and membrane materials well known to those skilled in the art can be used. The UF membrane used in the embodiments of the present invention is homemade.

[0043] In the present invention, the pH value of the pretreated wastewater is ≥ 11, preferably 11 to 12. When the pH value of the pretreated wastewater is within the above range, the recovery efficiency of ammonia nitrogen is high when the membrane absorption method is used for subsequent recovery treatment.

[0044] After obtaining the pretreated wastewater, the present invention uses a membrane absorption method to recycle the pretreated wastewater to obtain wastewater with ammonia nitrogen removed and an ammonium salt solution.

[0045] In the present invention, the membrane material used in the membrane absorption method is a hollow fiber membrane; the present invention has no requirement on the specific type of the hollow fiber membrane, and a conventional hollow fiber membrane in the art can be used. In an embodiment of the present invention, the hollow fiber membrane is a PP hollow fiber membrane.

[0046] In the present invention, the absorption liquid is preferably hydrochloric acid during the recovery process, and the pH value of the absorption liquid is ≤2, preferably 0.5-1.5; as an embodiment of the present invention, the pH value of the absorption liquid can be 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3 or 1.4. When the pH value of the absorption liquid is within the above range, the mass transfer coefficient K can be maintained at a high level, the boundary layer mass transfer resistance can be reduced, and the absorption of ammonia nitrogen can be promoted. As an embodiment of the present invention, the pH of the absorption liquid can be maintained by supplementing acid during the recovery process.

[0047] In the present invention, the flow rate of the feed liquid during the recovery treatment is not less than 12.5 mL / min, preferably 12.5 to 25 mL / min, and more preferably 16 to 20 mL / min; as an embodiment of the present invention, the flow rate of the feed liquid can be 13 mL / min, 15 mL / min, 16 mL / min, 18 mL / min, 19 mL / min, 20 mL / min or 25 mL / min. When the flow rate of the feed liquid is within the above range, the hydraulic conditions can be improved, the mass transfer coefficient K can be maintained at a high level, and it is beneficial to the recovery of ammonia nitrogen.

[0048] In the present invention, the flow rate of the absorption liquid during the recovery treatment is not less than 12.5 mL / min, preferably 12.5 to 25 mL / min, and more preferably 12.5 to 16 mL / min; as an embodiment of the present invention, the flow rate of the absorption liquid can be 12.5 mL / min, 13 mL / min, 14 mL / min, 15 mL / min, 19 mL / min, 20 mL / min or 25 mL / min. When the flow rate of the absorption liquid is within the above range, the mass transfer coefficient K can be maintained at a high level, which is beneficial to the recovery of ammonia nitrogen.

[0049] In the present invention, the temperature of the feed liquid during the recovery treatment is preferably 20-45°C, more preferably 20-30°C; as an embodiment of the present invention, the temperature of the feed liquid during the recovery treatment may be 22°C, 25°C, 28°C, 32°C, 35°C, 42°C or 45°C. When the temperature of the feed liquid during the recovery treatment is within the above range, it is conducive to faster absorption of ammonia nitrogen and further improves the recovery efficiency of ammonia nitrogen.

[0050] The present invention has no special requirements for the time of recycling treatment, as long as the ammonia nitrogen concentration in the wastewater from which ammonia nitrogen is removed meets the discharge standard. As an embodiment of the present invention, the time of recycling treatment can be 5 to 30 minutes, or 10 to 25 minutes, specifically 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes.

[0051] The present invention has no special requirements on other parameters of the membrane absorption method, and the parameters of the conventional membrane absorption method in the art can be adopted.

[0052] After the recovery treatment, the present invention preferably performs evaporative crystallization on the obtained ammonium salt solution to obtain ammonium salt crystals. The present invention has no special requirements on the specific parameters of the evaporative crystallization, and the conventional evaporative crystallization parameters in the art can be used.

[0053] The invention firstly precipitates or forms complexes of metal ions such as iron and magnesium in rare earth smelting wastewater by alkali treatment, and adjusts the pH value of the wastewater at the same time, thereby improving the absorption efficiency of the membrane absorption method; then removes the metal precipitates and complexes by ultrafiltration, and simultaneously removes large particles in the wastewater, thereby reducing the turbidity of the wastewater and reducing the loss and burden of the membrane material; finally, absorbs ammonia nitrogen in the wastewater by the membrane absorption method, without using energy-consuming devices such as gas heating, thereby avoiding the problem of high energy consumption of ammonia nitrogen removal processes such as ammonia stripping; improves the ammonia nitrogen absorption efficiency by optimizing the process parameters of the membrane absorption method; and the ammonia nitrogen concentration in the wastewater treated by the method of the invention can reach 0.2 mg / L, which is lower than the national emission standard (GB 26451-2011) of 15 mg / L.

[0054] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] In the embodiments of the present invention, the ammonia nitrogen content is measured using the Nessler reagent spectrophotometry (Chinese Standard HJ535-2009); the COD content is tested using the potassium dichromate method (Chinese Standard HJ828-2017); the cations in the wastewater are quantitatively analyzed using ICP-OES (American PE Optima8000); the NH 4 + and Cl - The concentration was measured by ion chromatography (cation analysis using the American Thermo Scientific Aquion, anion analysis using the American Thermo Scientific ICS-90).

[0056] Example 1

[0057] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the flow chart is as follows Figure 1 As shown, the specific steps are as follows:

[0058] The rare earth smelting wastewater in this embodiment is obtained by mixing ammonia soap wastewater of a rare earth company and wastewater from low ammonia nitrogen rare earth smelting (referred to as comprehensive wastewater) at a volume ratio of 1:5, and is referred to as raw wastewater; the component analysis results of ammonia soap wastewater and comprehensive wastewater are shown in Table 1;

[0059] Table 1 Composition analysis of raw wastewater

[0060] mg / L COD <![CDATA[NH 3 -N]]> Ca Na Fe Mg Ammonia soap wastewater 3460 15600 502 21210 2.1 60 Comprehensive wastewater 1145 0.9 2638 2059 63 72

[0061] After adding quicklime, ultrafiltration was performed to obtain wastewater with a pH value of 12;

[0062] After adding quicklime to the raw wastewater and letting it stand for 10 minutes, ultrafiltration was performed to obtain pretreated wastewater. The status of the wastewater at each stage was recorded, such as Figure 2 As shown. Figure 2 It can be seen that after quicklime is added to the raw wastewater, a large amount of white flocculent precipitate is generated, which settles to the bottom of the beaker after standing. The wastewater shows obvious stratification, and the pretreated wastewater obtained after ultrafiltration is clear and transparent.

[0063] The membrane material used for ultrafiltration was homemade, and some parameters are recorded in Table 2.

[0064] Table 2 UF membrane parameter record table

[0065] Material <![CDATA[Pure water permeation flux (L·m -2 ·h -1 ·bar -1 )]]> BSA retention rate (%) Water contact angle (°) Molecular weight cut-off (Da) PSF 1371.2 93.41 58.0 12000

[0066] The pretreated wastewater was recycled by membrane absorption for 30 min. The feed liquid flow rate was 18.75 mL / min, the absorption liquid was hydrochloric acid with a pH value of 1.0, and the flow rate was 12.5 mL / min. The pH value of the absorption liquid was monitored during the recycling process, and the pH value was maintained between 1.0 and 1.3 by adding 37% concentrated hydrochloric acid. After recycling, wastewater with ammonia nitrogen removed and ammonium chloride solution were obtained. The membrane material was PP hollow fiber membrane (HFMs, Tianjin Jiehai Ruiquan Membrane Technology Co., Ltd.).

[0067] The ammonia nitrogen concentration of the wastewater was tested when the recovery treatment time was 5min, 10min, 20min and 30min respectively, and the ammonia nitrogen recovery efficiency was calculated, and a curve of ammonia nitrogen concentration-recovery efficiency versus recovery treatment time was drawn, such as Figure 3 shown.

[0068] The concentration of ammonium chloride in the ammonium chloride solution is 1850 mg / L, and the ammonium chloride content in the crystals after evaporation and crystallization is 86.52%.

[0069] The raw wastewater, pre-treated wastewater and wastewater from which ammonia nitrogen was removed in this example were subjected to component analysis, and the results are shown in Table 3.

[0070] Table 3 Analysis of wastewater components at each stage

[0071] Unit: mg / L Ammonia soap wastewater Comprehensive wastewater Raw material wastewater Pre-treatment of wastewater Removal of ammonia nitrogen from wastewater COD 3460 1145 260 150 140 <![CDATA[NH 3 -N]]> 15600 0.9 2835 2330 0.2 Ca 502 2638 2919 7503 7048 Na 21210 2059 5911 4431 3448 Fe 2.1 63 66 1.1 0.01 Mg 60 72 90 0 0

[0072] from Figure 3 It can be seen from Table 3 that the ammonia nitrogen concentration in the wastewater from which ammonia nitrogen is removed is 0.2 mg / L, and the ammonia nitrogen removal rate reaches 99.99%.

[0073] Example 2

[0074] Ammonia nitrogen recovery was performed using the prepared pre-treated wastewater simulation liquid, in which the ammonia nitrogen concentration was 1260 mg / L and the pH value was 12; the membrane recovery method was used to recover ammonia nitrogen for 60 min, the flow rate of the feed liquid was 18.75 mL / min, the absorption liquid was hydrochloric acid with a pH value of 2.0, and the flow rate was 12.5 mL / min; the other conditions were the same as in Example 1. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time was 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 45 min, and 60 min, respectively, was recorded in Table 4.

[0075] Comparative Example 1

[0076] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the method and parameters are the same as those in Example 2, except that the pH value of the pre-treated wastewater simulation liquid is 10. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5min, 10min, 15min, 20min, 25min, 30min, 45min, and 60min is recorded in Table 4.

[0077] Example 3

[0078] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the method and parameters are the same as those in Example 2, except that the pH value of the pre-treated wastewater simulation liquid is 11. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5min, 10min, 15min, 20min, 25min, 30min, 45min, and 60min is recorded in Table 4.

[0079] Example 4

[0080] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the method and parameters are the same as those in Example 2, except that the pH value of the pre-treated wastewater simulation liquid is 12.98. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5min, 10min, 15min, 20min, 25min, 30min, 45min, and 60min is recorded in Table 4.

[0081] Table 4 Record of changes in ammonia nitrogen concentration during the recovery process of Examples 2 to 4 and Comparative Example 1

[0082] mg / L Comparative Example 1 Example 2 Example 3 Example 4 0min 1260 1260 1260 1260 5min 1158 943 114 161.8 10min 868 551 1 0.79 15min 600 306 0.4 0 20min 557 33.7 0.3 0 25min 506 29 0 0 30min 460 3.7 0 0 45min 358 3.4 0 0 60min 341 2.8 0 0

[0083] According to the changes in ammonia nitrogen concentration during the recovery process of Examples 2 to 4 and Comparative Example 1, a curve diagram of ammonia nitrogen concentration change is drawn, as shown in FIG. Figure 4 As shown. Figure 4 It can be seen that increasing the pH value of the feed liquid is beneficial to the absorption of ammonia nitrogen. When the pH value of the feed liquid is 10, the ammonia nitrogen concentration cannot be reduced to below 300 mg / L; when the pH value of the feed liquid reaches 11, the ammonia nitrogen concentration can be reduced to below 15 mg / L within 30 minutes; when the pH value of the feed liquid reaches 12, the absorption of ammonia nitrogen reaches the optimal state, and the ammonia nitrogen absorption efficiency does not change much when the pH value of the feed liquid continues to increase.

[0084] Example 5

[0085] A method for recovering ammonia nitrogen from rare earth smelting wastewater, wherein the raw material is a prepared pre-treated wastewater simulation liquid, the ammonia nitrogen concentration is 950 mg / L, and the pH value is 12; a membrane recovery method is used to recover ammonia nitrogen for 25 minutes, the flow rate of the feed liquid is 18.75 mL / min, the absorption liquid is hydrochloric acid with a pH value of 1.96, and the flow rate is 12.5 mL / min; the other conditions are the same as those in Example 1. The ammonia nitrogen concentrations of the wastewater when the recovery treatment time is 5 minutes, 10 minutes, 15 minutes, 20 minutes, and 25 minutes are recorded in Table 5.

[0086] Example 6

[0087] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 5, except that the pH value of the absorption liquid is 1.45. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5min, 10min, 15min, 20min, and 25min is recorded in Table 5.

[0088] Example 7

[0089] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 5, except that the pH value of the absorption liquid is 0.98. The ammonia nitrogen concentration of the wastewater when the recovery treatment time is 5 minutes, 10 minutes, 15 minutes, 20 minutes, and 25 minutes is recorded in Table 5.

[0090] Example 8

[0091] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 5, except that the pH value of the absorption liquid is 0.56. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5min, 10min, 15min, 20min, and 25min is recorded in Table 5.

[0092] Comparative Example 2

[0093] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 5, except that the pH value of the absorption liquid is 2.45. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5min, 10min, 15min, 20min, and 25min is recorded in Table 5.

[0094] Table 5 Record of changes in ammonia nitrogen concentration during the recovery process of Examples 5 to 8 and Comparative Example 2

[0095] mg / L Comparative Example 2 Example 5 Example 6 Example 7 Example 8 0min 950 950 950 950 950 5min 549 380 168.44 108.57 80.34 10min 323 226 48.78 7.92 4.34 15min 256 158 4.58 1.04 0.51 20min 254 96.4 0.27 0 0 25min 250 34.5 0 0 0

[0096] A curve of ammonia nitrogen concentration change was drawn according to the ammonia nitrogen concentration change during the recovery process of Examples 5 to 8 and Comparative Example 2, as shown in FIG. Figure 5 As shown. Figure 5It can be seen that the lower the pH value of the absorption liquid, the faster the ammonia nitrogen is absorbed: when the pH value of the absorption liquid is 2.45, the ammonia nitrogen concentration almost stops decreasing after 15 minutes and cannot be reduced to below 200 mg / L; when the pH value of the absorption liquid reaches 1.96, the ammonia nitrogen concentration can be reduced to below 35 mg / L within 25 minutes; when the pH value of the absorption liquid is less than 1.45, the ammonia nitrogen absorption efficiency reaches a higher level, and the ammonia nitrogen concentration can be reduced to below 15 mg / L within 15 minutes; the ammonia nitrogen absorption efficiency increases slightly by continuing to reduce the pH value of the absorption liquid.

[0097] Example 9

[0098] A method for recovering ammonia nitrogen from rare earth smelting wastewater, wherein the raw material is a prepared pre-treated wastewater simulation liquid, the ammonia nitrogen concentration is 850 mg / L, and the pH value is 12; a membrane recovery method is used to recover ammonia nitrogen for 20 minutes, the flow rate of the feed liquid is 12.5 mL / min, and the absorption liquid is hydrochloric acid with a pH value of 2, and the flow rate is 12.5 mL / min; the other conditions are the same as those in Example 1. The ammonia nitrogen concentrations of the wastewater when the recovery treatment time is 5 minutes, 10 minutes, 15 minutes, and 20 minutes are recorded in Table 6.

[0099] Example 10

[0100] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 9, except that the flow rate of the feed liquid is 15.63 mL / min. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5 min, 10 min, 15 min, and 20 min is recorded in Table 6.

[0101] Embodiment 11

[0102] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 9, except that the flow rate of the feed liquid is 18.75 mL / min. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5 min, 10 min, 15 min, and 20 min is recorded in Table 6.

[0103] Example 12

[0104] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 9, except that the flow rate of the feed liquid is 21.88 mL / min. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5 min, 10 min, 15 min, and 20 min is recorded in Table 6.

[0105] Embodiment 13

[0106] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 9, except that the flow rate of the feed liquid is 25 mL / min. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5 min, 10 min, 15 min, and 20 min is recorded in Table 6.

[0107] Table 6 Record of changes in ammonia nitrogen concentration during the recovery process of Examples 9 to 13

[0108] mg / L Example 9 Example 10 Embodiment 11 Example 12 Embodiment 13 0min 850 850 850 850 850 5min 25.58 21.61 14.93 12.61 10.58 10min 3.91 3.54 1.5 1.31 0.2 15min 0.59 0.59 0.52 0.2 0 20min 0 0 0 0 0

[0109] According to the change of ammonia nitrogen concentration in the recovery process of Examples 9 to 13, a curve diagram of ammonia nitrogen concentration change is drawn, as shown in FIG. Figure 6 As shown. Figure 6 It can be seen that when the flow rate of the feed liquid is above 12.5 mL / min, the faster the flow rate, the faster the ammonia nitrogen absorption. The ammonia nitrogen concentration can be reduced to below 15 mg / L within 10 minutes and can be completely absorbed within 20 minutes.

[0110] Embodiment 14

[0111] A method for recovering ammonia nitrogen from rare earth smelting wastewater, wherein the raw material is a prepared pre-treated wastewater simulation liquid, the ammonia nitrogen concentration is 1225 mg / L, and the pH value is 12; a membrane recovery method is used for ammonia nitrogen recovery treatment, the flow rate of the feed liquid is 18.75 mL / min, the absorption liquid is hydrochloric acid with a pH value of 2, and the flow rate is 12.5 mL / min; the other conditions are the same as those in Example 1. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5 min, 10 min, and 20 min, respectively, is recorded in Table 7.

[0112] Embodiment 15

[0113] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 14, except that the flow rate of the absorption liquid is 18.75 mL / min. The ammonia nitrogen concentration of the wastewater when the recovery treatment time is 5 min, 10 min, and 20 min is recorded in Table 7.

[0114] Example 16

[0115] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the raw materials and method are the same as those in Example 14, except that the flow rate of the absorption liquid is 25 mL / min. The ammonia nitrogen concentration of the wastewater when the recovery treatment time is 5 min, 10 min, and 20 min is recorded in Table 7.

[0116] Table 7 Record of changes in ammonia nitrogen concentration during the recovery process of Examples 14 to 16

[0117] mg / L Embodiment 14 Embodiment 15 Example 16 0min 1225 1225 1225 5min 104 113 108 10min 13 15.6 14.5 20min 0.4 0.2 0.6

[0118] A curve of ammonia nitrogen concentration change was drawn according to the ammonia nitrogen concentration change during the recovery process of Examples 14 to 16, as shown in FIG. Figure 7 As shown. Figure 7 It can be seen that when the flow rate of the absorption liquid is above 12.5 mL / min, ammonia nitrogen can be absorbed quickly, and the ammonia nitrogen concentration can be reduced to below 15 mg / L within 20 minutes.

[0119] Embodiment 17

[0120] A method for recovering ammonia nitrogen from rare earth smelting wastewater, wherein the raw material is a prepared pre-treated wastewater simulation liquid, the ammonia nitrogen concentration is 2000 mg / L, and the pH value is 12; a membrane recovery method is used to recover ammonia nitrogen for 30 minutes, the flow rate of the feed liquid is 18.75 mL / min, the absorption liquid is hydrochloric acid with a pH value of 2, and the flow rate is 12.5 mL / min; the other conditions are the same as those in Example 1. The ammonia nitrogen concentration of the wastewater when the recovery treatment time is 5 minutes, 15 minutes, and 30 minutes, respectively, is tested, and the ammonia nitrogen removal rate is calculated and recorded in Table 8.

[0121] Embodiment 18

[0122] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the method and parameters are the same as those in Example 17, except that the ammonia nitrogen concentration of the pre-treated wastewater simulation liquid is 3000 mg / L. The ammonia nitrogen concentration of the wastewater when the recovery treatment time is 5 min, 15 min, and 30 min, respectively, is tested, and the ammonia nitrogen removal rate is calculated and recorded in Table 8.

[0123] Embodiment 19

[0124] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the method and parameters are the same as those in Example 17, except that the ammonia nitrogen concentration of the pre-treated wastewater simulation liquid is 4000 mg / L. The ammonia nitrogen concentration of the wastewater when the recovery treatment time is 5 min, 15 min, and 30 min, respectively, is tested, and the ammonia nitrogen removal rate is calculated and recorded in Table 8.

[0125] Embodiment 20

[0126] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the method and parameters are the same as those in Example 17, except that the ammonia nitrogen concentration of the pre-treated wastewater simulation liquid is 5000 mg / L. The ammonia nitrogen concentration of the wastewater when the recovery treatment time is 5 min, 15 min, and 30 min, respectively, is tested, and the ammonia nitrogen removal rate is calculated and recorded in Table 8.

[0127] Table 8 Record of changes in ammonia nitrogen removal rate during the recovery process of Examples 14 to 16

[0128] mg / L Embodiment 17 Embodiment 18 Embodiment 19 Embodiment 20 0min 0％ 0％ 0％ 0％ 5min 91.66％ 92.70％ 91.33％ 90.65％ 15min 99.95％ 99.98％ 99.97％ 98.83％ 30min 99.98％ 100％ 99.98％ 100％

[0129] According to the change of ammonia nitrogen concentration in the recovery process of Examples 17 to 20, the ammonia nitrogen removal rate was calculated, and an ammonia nitrogen removal rate curve was drawn, as shown in FIG. Figure 8 As shown. Figure 8 It can be seen that when the ammonia nitrogen concentration of the feed liquid is in the range of 2 to 5 g / L, the concentration change curves almost completely overlap. At 15 minutes, the ammonia nitrogen removal rate can reach 98.8%, and at 30 minutes, the ammonia nitrogen removal rate exceeds 99.9%.

[0130] Embodiment 21

[0131] A method for recovering ammonia nitrogen from rare earth smelting wastewater, wherein the raw material is a prepared pre-treated wastewater simulation liquid, the ammonia nitrogen concentration is 715 mg / L, and the pH value is 12; a membrane recovery method is used to recover ammonia nitrogen for 20 minutes, the flow rate of the feed liquid is 18.75 mL / min, the temperature of the feed liquid is controlled at 22-25° C., the absorption liquid is hydrochloric acid with a pH value of 2, and the flow rate is 12.5 mL / min; the other conditions are the same as those in Example 1. The ammonia nitrogen concentrations of the wastewater when the recovery treatment time is 5 minutes, 10 minutes, and 20 minutes are recorded in Table 9.

[0132] Embodiment 22

[0133] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the method and parameters are the same as those in Example 21, except that the temperature of the feed liquid is controlled at 33-35° C. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5 min, 10 min, and 20 min is recorded in Table 9.

[0134] Embodiment 23

[0135] A method for recovering ammonia nitrogen from rare earth smelting wastewater, the method and parameters are the same as those in Example 21, except that the temperature of the feed liquid is controlled at 42-45° C. The ammonia nitrogen concentration of the wastewater when the test recovery treatment time is 5 min, 10 min, and 20 min is recorded in Table 9.

[0136] Table 9 Record of changes in ammonia nitrogen concentration during the recovery process of Examples 21 to 23

[0137]

[0138]

[0139] A curve of ammonia nitrogen concentration change was drawn according to the ammonia nitrogen concentration change during the recovery process of Examples 21 to 23, as shown in FIG. Fig. 9 As shown. Fig. 9 It can be seen that the lower the temperature of the feed liquid, the faster the ammonia nitrogen is removed.

[0140] It can be seen from the above embodiments and comparative examples that the method for recovering ammonia nitrogen in rare earth smelting wastewater provided by the present invention can efficiently recover ammonia nitrogen in the wastewater.

[0141] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for recovering ammonia nitrogen from rare earth smelting wastewater, comprising: Pre-treating rare earth smelting wastewater to obtain pre-treated wastewater; The ammonia nitrogen concentration of the rare earth smelting wastewater is 500-5000 mg / L; the pretreatment includes alkali treatment and ultrafiltration performed in sequence; The pH value of the pretreated wastewater is ≥11; The pretreated wastewater is recycled by using a membrane absorption method to obtain wastewater with ammonia nitrogen removed and an ammonium salt solution; the membrane material used in the membrane absorption method is a hollow fiber membrane; During the recovery treatment, the pH value of the absorption liquid is ≤2, the flow rate of the feed liquid is not less than 12.5 mL / min, and the flow rate of the absorption liquid is not less than 12.5 mL / min.

2. The recycling method according to claim 1, characterized in that: The rare earth smelting wastewater includes ammonia soap wastewater and low ammonia nitrogen rare earth smelting wastewater; the ammonia nitrogen concentration of the low ammonia nitrogen rare earth smelting wastewater is below 10 mg / L.

3. The recycling method according to claim 2, characterized in that: The volume ratio of the ammonia soap wastewater to the low ammonia nitrogen rare earth smelting wastewater is 1: (3-8).

4. The recycling method according to claim 1, characterized in that: The pH value of the pretreated wastewater is 11-12.

5. The recycling method according to claim 1, characterized in that: The pH value of the absorption liquid during the recovery treatment is 0.5-1.

5.

6. The recycling method according to claim 1, characterized in that: The flow rate of the feed liquid during the recovery treatment is 12.5 to 25 mL / min.

7. The recycling method according to claim 1, characterized in that: The flow rate of the absorption liquid during the recovery treatment is 12.5 to 25 mL / min.

8. The recycling method according to claim 1, characterized in that: The temperature of the feed liquid during the recovery process is 20-45°C.

9. The recycling method according to claim 1, characterized in that: The alkali used in the alkali treatment is quicklime.

10. The recycling method according to claim 1, characterized in that: The absorption liquid used in the recovery process is hydrochloric acid.

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