Method for removing nitrate radicals from salt separation mother liquor of chemical high-salt wastewater

Abstract

A method for removing nitrate from chemical high-salinity wastewater salt-separating mother liquor comprises the following steps: introducing the chemical high-salinity wastewater salt-separating mother liquor containing nitrate into an adjusting tank of a structural system of a primary reaction unit, reducing the nitrate into nitrite, pumping the nitrite into a settling tank of the structural system of the primary reaction unit, and settling the nitrite in a settling tank of the structural system of the primary reaction unit; supernate obtained after precipitation is treated wastewater; pumping the treated wastewater into a second-stage regulating tank serving as a structural system of a second-stage reaction unit, and obtaining denitrified water after the reaction is finished; introducing the obtained denitrified wastewater into a third regulating tank serving as a structural system of a post-treatment unit, regulating, introducing into a clarification tank of the post-treatment unit, pumping supernate in the clarification tank into a multi-medium filter of the post-treatment unit, and filtering; produced water filtered by the multi-medium filter is pumped into a storage pool of a structural system of the post-treatment unit, and a finished product is obtained. The method has the advantages that the process flow is simple, the treatment cost is low, and the high-salinity wastewater hybridization-free treatment requirement is met.

Description

Technical Field

[0001] The invention belongs to the field of chemical high-salt wastewater salt mother liquor treatment technology and water resource comprehensive utilization technology, and specifically relates to a method for removing nitrate from chemical high-salt wastewater salt mother liquor, especially for the treatment of coal chemical high-salt wastewater to reflect resource and high-value utilization. Background Art

[0002] Chemical high-salt wastewater refers to: ① Chemical production, incomplete chemical reactions or chemical reaction by-products, especially a large amount of high-COD, high-salt toxic wastewater generated in the production process of chemical products such as coal chemical industry, petrochemical industry, metallurgy, fine chemicals, dyes, pesticides, etc.; ② Wastewater treatment, during the wastewater treatment process, the mineralization brought about by the addition of water treatment agents and acids and alkalis, as well as the concentrated liquid produced by the recovery of most of the "fresh water".

[0003] After the chemical high-salt wastewater passes through the "zero discharge system", concentrated water with a mass fraction of total dissolved solids (TDS) greater than 5% is obtained, which is difficult to biochemically treat. The concentrated water is further treated by a salt separation crystallization process to obtain recyclable by-product salts, namely sodium sulfate Na2SO4 and sodium chloride NaCl. Since the mother liquor produced by the aforementioned salt separation crystallization process has a salt content greater than 20wt% (that is, the salt content accounts for 20% of the weight percentage of the mother liquor), it is mixed with monovalent salts such as sodium nitrate, potassium nitrate, sodium chloride and inert organic impurities. At present, the common practice in the chemical industry is to evaporate and crystallize the aforementioned mother liquor to produce miscellaneous salts (that is, hazardous waste, accounting for 15-20% of the total salt content). The cost of miscellaneous salt disposal is 2,000 to 5,000 yuan / ton, which brings a large economic burden to chemical companies.

[0004] Nitrate (NO3-) is the anion of nitrate and is the most stable form of nitrogen-containing compound in an aerobic environment. When nitrate in industrial wastewater continues to accumulate, it will pollute water sources if not handled properly. Moreover, this type of pollution is hidden and difficult to control. Its control and remediation are extremely difficult, such as complex processes and high costs.

[0005] In the prior art, there is no technical information on the method for removing nitrate from the salt mother liquor of the above-mentioned chemical high-salt wastewater. The technology for removing nitrate from chemical wastewater with low salt content (1.0-3.5wt%) is mainly electrocatalytic reduction: the research on electrocatalytic treatment of nitrates focuses on groundwater pollution treatment, electroplating wastewater treatment, cutting fluid, etc. There are two main ways to electrocatalytic cathode reduction of nitrates. One is that the cathode directly reduces the nitrates to nitrogen; the other is that the nitrates are first reduced to ammonia nitrogen at the cathode, and the ammonia nitrogen then reacts with the oxides produced at the anode to generate nitrogen.

[0006] CN118084239A discloses "a method for electrochemically treating nitrate nitrogen in electroplating wastewater and a copper-iron staggered layer combined electrode plate". In this method, acidic wastewater is introduced into a high-voltage pulse electrochemical reactor for electrochemical reduction reaction. Electrodes are arranged in the high-voltage pulse electrochemical reactor. The electrodes are copper-iron staggered layer combined electrode plates. A single electrode plate is welded by half copper plate and half iron plate. The copper and iron parts of adjacent plates are staggered and fixed by positioning members. The voltage of the high-voltage pulse electrochemical reactor is 60V-90V, the current is 30A-60A, and the frequency is 1500Hz-2000Hz. If this method is used for mother liquor treatment, the input current is too high and lacks safety, because the mother liquor contains more sodium chloride. After power is turned on, hydrogen (H2) and chlorine (Cl2) are generated at the cathode and anode respectively. If they are not separated and collected in time, chlorine poisoning will occur, and even explosion of the mixed gas will occur. In addition, the electrodes are iron plates and copper plates, which are prone to produce a large amount of chemical sludge.

[0007] CN113121058 A discloses a "process for removing nitrate nitrogen from high-salinity wastewater". The method is aimed at treating NO3-N in reverse osmosis concentrated water with a concentration of 80-300 mg / L, which has great limitations. In addition, the input current density is 10-30 mA / cm 2 Only suitable for wastewater with salt content ≤3.5wt%.

[0008] CN118307095 A discloses "a method for efficiently removing nitrate from water by selective electrocatalysis-chemical reduction coupling". This method first utilizes an electrocatalytic reaction to selectively reduce nitrate to nitrite, and then utilizes a chemical reaction to selectively reduce nitrite to nitrogen. This method limits the treatment of nitrate pollution concentration to a range from 50ppm to 500ppm, which has great limitations.

[0009] CN118005224 A discloses a method for removing nitrate from liquid phase reduced silver powder wastewater. The anode of the method is an iron electrode or a stainless steel electrode; the cathode is a copper-based electrode, and the current density is 200-500A / m 2 The electrochemical treatment time is 2 to 5 hours, the current is too high, resulting in high energy consumption, and it is only suitable for wastewater with a salt content of ≤3.5wt%. In addition, the electrodes are iron plates and copper plates, which easily produce a large amount of chemical sludge.

[0010] It can be seen that how to explore the method of removing nitrate from the salt mother liquor of chemical high-salt wastewater from the perspective of simple process flow, low treatment cost, non-mixing treatment of high-salt wastewater and ensuring resource reuse of mother liquor not only has good positive significance, but is also a technical problem that is closely concerned and expected to be solved in this field. The technical solution to be introduced below was produced in this context. Summary of the invention

[0011] The task of the present invention is to provide a method for removing nitrate from the salt mother liquor of chemical high-salt wastewater. The method can solve the problem that nitrate from the mother liquor is difficult to remove, and has the advantages of simple process flow, low treatment cost, and can reflect the non-mixing of high-salt wastewater and pave the way for resource reuse of the purified mother liquor.

[0012] The task of the present invention is accomplished by a method for removing nitrate from a brine mother liquor of chemical high-salt wastewater, comprising the following steps:

[0013] (1) reducing nitrate in the mother liquor to nitrite, introducing the salted mother liquor of chemical high-salt wastewater containing nitrate into a regulating tank of the structural system as a primary reaction unit and adjusting the water temperature and pH value, introducing the first reaction tank of the structural system of the primary reaction unit after the adjustment, performing a micro-electric field catalytic reaction under the action of the micro-electric field and catalyst in the first reaction tank to reduce nitrate to nitrite, pumping the mother liquor into the sedimentation tank of the structural system of the first reaction unit for precipitation after the micro-electric field catalytic reaction, and obtaining the supernatant after the precipitation as the wastewater treated in this step (1);

[0014] (2) pumping the treated wastewater obtained in step (1) into a secondary regulating tank of the structural system serving as a secondary reaction unit and adjusting the water temperature and pH value, and then introducing the treated wastewater into the secondary reaction tank of the structural system of the secondary reaction unit after the adjustment, reacting under the action of the micro-electric field, buffer and reducing agent in the secondary reaction tank, and obtaining denitrified wastewater after the reaction is completed;

[0015] (3) Post-treatment, firstly introducing the denitrification wastewater obtained in step (2) into the third regulating tank of the structural system of the post-treatment unit and then adjusting the water temperature and pH value, and then introducing the adjusted wastewater into the clarification tank of the post-treatment unit for clarification, and then pumping the supernatant in the clarification tank into the multi-media filter of the post-treatment unit for filtration, and then pumping the produced water filtered by the multi-media filter into the storage tank of the structural system of the post-treatment unit to obtain the chemical high-salt wastewater brine mother liquor with nitrate removed.

[0016] In a specific embodiment of the present invention, the water temperature and pH value are adjusted in step (1) by adjusting the water temperature of the salt mother liquor of the chemical high-salt wastewater containing nitrate to 20-50°C and adjusting the pH to Ph=3-6; the mass ratio of the amount of catalyst added to the nitrate content in the primary reaction tank is 0.1-0.2:1; the micro-electric field catalytic reaction is carried out under aeration, the aeration reaction time is 60-240min, and the aeration air-water volume ratio is 2-5:1, wherein, when the nitrate content in the wastewater is 500-2000mg / L, the reaction time is 60-120min, and when the nitrate content in the wastewater is 2000-5000mg / L, the reaction time is 120-240min; the precipitation method in the precipitation tank is natural precipitation and the time is greater than 120min.

[0017] In another specific embodiment of the present invention, the catalyst described in step (1) is an ionic liquid catalyst, and the ionic liquid catalyst is one or a combination of trimethylamine hydrochloride, tetramethylammonium chloride, tetramethylammonium hydrogen sulfate, tributylmethylammonium chloride, tetramethylammonium p-toluenesulfonate, 1-hydroxyethyl-3-methylimidazolium chloride, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hydroxyethyl-3-methylimidazolium acetate, 1-hydroxyethyl-3-methylimidazolium p-toluenesulfonate, hydroxyethyltrimethylammonium chloride, hydroxyethyltrimethylammonium acetate, 1-aminopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-aminoethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0018] In another specific embodiment of the present invention, the adjustment of water temperature and pH value in step (2) is to adjust the water temperature to 20-50°C and the pH value to pH=3-6; the reaction under the action of the micro-electric field, buffer and reducing agent in the secondary reaction tank 22 is carried out under aeration, the aeration reaction time is 60-240min, and the aeration air-water volume ratio is 2-5:1, wherein, when the nitrite content in the wastewater is 200-1000mg / L, the reaction time is 60-120min, and when the nitrate content in the wastewater is 1000-2000mg / L, the reaction time is 120-240min.

[0019] In another specific embodiment of the present invention, the buffer capacity of the buffer in step (2) is calculated as β=(CxV) / (pKa+pH), wherein β represents the buffer capacity, C represents the concentration of the buffer in the buffer solution, V represents the volume of the buffer solution, pKa represents the pKa value of the buffer, and pH represents the pH value of the solution; the amount of the reducing agent added is equivalent to that of nitrite.

[0020] In another specific embodiment of the present invention, the buffer is a mixture of a weak acid and a salt thereof, and the mixture of a weak acid and a salt thereof is one of ethanol-ammonium acetate buffer, sodium formate buffer, phthalate buffer, citric acid-disodium hydrogen phosphate buffer, acetic acid-sodium acetate buffer, acetate-lithium salt buffer, and acetic acid-ammonium acetate buffer; the reducing agent is an ammonium salt, and the ammonium salt is one of ammonium acetate, ammonium phosphate, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium bicarbonate, ammonium fluoride, ammonium bromide, and potassium ammonium sulfate, or a combination of several thereof.

[0021] In a more specific embodiment of the present invention, the subsequent adjustment of water temperature and pH value in step (3) is to adjust the water temperature to 20-30°C and adjust the pH value to pH=8.5-9; the clarification method in the clarification tank is natural clarification and the clarification time is greater than 120 minutes; the multi-media filter is filled with filter material, which is refined quartz sand, and the filling of the refined quartz sand is divided into three layers, the particle size of the three layers of quartz sand decreases from bottom to top.

[0022] In a further specific embodiment of the present invention, the electrode material used in the micro-electric field described in steps (1) and (2) includes one or more of an iron electrode, a titanium-ruthenium-iridium alloy electrode, a titanium-iridium-tantalum alloy electrode, and a titanium-nickel-cobalt alloy electrode; in the primary reaction tank, the iron electrode area accounts for 10%-20% of the total electrode area, and the remaining electrode plates used are one or more of a titanium-ruthenium-iridium alloy electrode, a titanium-iridium-tantalum alloy electrode, and a titanium-nickel-cobalt alloy electrode; in the secondary reaction tank, the iron electrode area accounts for 5%-10% of the total electrode area, and the remaining electrode plates used are one or more of a titanium-ruthenium-iridium alloy electrode, a titanium-iridium-tantalum alloy electrode, and a titanium-nickel-cobalt alloy electrode.

[0023] In yet another specific embodiment of the present invention, the input voltage of the micro-electric field is 1-2.5V; the input current is 1-3A; the plate current density is 0.01-0.1mA / cm 2 , the distance between the plates is 5-25cm.

[0024] The technical effect of the technical solution provided by the present invention is that the purpose of removing nitrate from the salt mother liquor of chemical high-salt wastewater can be achieved by only reducing nitrate to nitrite, reducing nitrite to nitrogen and post-treatment, thereby reflecting the simplicity of the process flow, the cheapness of the treatment cost, meeting the requirements of non-mixed treatment of high-salt wastewater and laying a good foundation for the resource utilization of the treated mother liquor. In addition, due to the use of a micro-electric field reaction cell, the input voltage and current are 1-2.5V and 1-3A respectively, so that both low energy consumption and safety are ensured; adding a catalyst, a buffer and a reducing agent can significantly improve the treatment efficiency; it can be applied to the treatment of wastewater with a salt content greater than 20wt% and a nitrate content of 2000-5000mg / L; under the condition of a micro-electric field, chlorine evolution can be avoided as much as possible to cause electrochemical corrosion; the process flow is short, the reaction is carried out at normal pressure and temperature, and the required reagents are from a wide range of sources and are all conventional raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of an embodiment of a method for removing nitrate from brine mother liquor of high-salt wastewater from coal chemical industry. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail by specific embodiments below. However, it should be understood that the description herein is only used to explain the present invention and is not intended to limit the scope of the present invention.

[0027] Unless otherwise defined, all technical terms and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art of the present invention, and the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. Since the characterization means involved in the embodiments can refer to the relevant descriptions in the prior art, they will not be described in detail.

[0028] In order to further understand the present invention, a coal chemical high-salt wastewater salt mother liquor is taken as the treatment object and described in detail in combination with the best embodiment.

[0029] The water quality of the salt mother liquor (i.e. "crystallization mother liquor") of a coal chemical industry's high-salt wastewater is as follows: CODCr is 11200 mg / L, TDS is 205600 mg / L, total hardness (calculated as CaCO3) is 1330 mg / L, nitrate is 2860 mg / L, chloride ion is 70840 mg / L, sulfate ion is 49600 mg / L, pH is 12.7, and total silicon (calculated as SiO2) is 477 mg / L.

[0030] Embodiment 1:

[0031] See also Figure 1,like Figure 1 The process shown in the figure, the method for removing nitrate from the brine mother liquor of the coal chemical high-salt wastewater of the above water quality comprises the following steps:

[0032] (1) reducing the nitrate in the mother liquor to nitrite, the mother liquor referred to here is the salted mother liquor of the coal chemical high-salt wastewater, and introducing the salted mother liquor of the chemical high-salt wastewater containing nitrate into Figure 1 In the regulating tank 11 of the structural system of the primary reaction unit 1 (also referred to as "primary reaction mechanism", the same below) framed by the dotted line or the dotted line, the water temperature and the pH value (that is, the water temperature and the pH value of the salt mother liquor of the coal chemical high-salt wastewater) are adjusted to 50°C and Ph=4.5 respectively. After the adjustment, the primary reaction tank 12 of the structural system of the primary reaction unit 1 is introduced. Under the action of the micro-electric field and the catalyst in the primary reaction tank 12, a micro-electric field catalytic reaction is carried out to reduce most of the nitrate ions to nitrite ions. The micro-electric field catalytic reaction is carried out under aeration. The aeration reaction time is 240 minutes, and the aeration gas-water volume ratio is 2:1. Preferably, after sampling and testing, when the nitrate content in the wastewater is 500-2000 mg / L, the aeration reaction time is in the range of 60-120 minutes, and when the nitrate content in the wastewater is 2000-5000 mg / L, then The aeration reaction time is in the range of 120-240 minutes. It can be seen that the aeration reaction time is generally in step with the content of nitrate in the wastewater (i.e., proportional). After the micro-electric field catalytic reaction is completed, the natural precipitation time of the natural precipitation in the sedimentation tank 13 of the structural system of the primary reaction unit 1 is greater than 120 minutes. The supernatant obtained after precipitation is the wastewater treated in this step (1). The reason why it is called the wastewater treated in this step (1) is that the wastewater still contains a small part or a trace amount of unreduced nitrate, that is, most of the nitrate originally contained in the mother liquor has been reduced to nitrite. In this step, the mass ratio of the amount of the catalyst added to the nitrate content is 0.1:1, and the catalyst is an ionic liquid catalyst, specifically a mixture of trimethylamine hydrochloride, tetramethylammonium chloride and tetramethylammonium hydrogen sulfate in any mass ratio.

[0033] (2) The treated wastewater obtained in step (1) is pumped into Figure 1In the secondary regulating tank 21 of the structural system of the secondary reaction unit 2 (also referred to as "secondary reaction mechanism", the same below) framed by the dotted line or the dotted line, the water temperature and pH value are adjusted (i.e., "regulated"), that is, the water temperature and pH value of the wastewater treated in the step (1) are adjusted to: water temperature 35°C, pH=3, and after adjustment, the wastewater is introduced (i.e., pumped) into the secondary reaction tank 22 of the structural system of the secondary reaction unit 2, and reacts under the action of the micro-electric field, buffer and reductant in the secondary reaction tank 22. The reaction is carried out under aeration, the aeration reaction time is 240 minutes, and the aeration gas-water volume ratio is 5:1. As a preferred solution, after sampling and testing, when the nitrite content in the wastewater is 200-1000 mg / L, the aeration reaction time is in the range of 60-120 minutes, and when the nitrite content in the wastewater is When the nitrate content is 1000-2000 mg / L, the aeration reaction time is in the range of 120-240 min. It can be seen that the aeration reaction time is generally in step with the nitrite content in the wastewater (i.e., proportional). After the reaction is completed, denitrified wastewater is obtained. The buffer capacity calculation formula of the buffer in this step is β=(CxV) / (pKa+pH), wherein β represents the buffer capacity, C represents the concentration of the buffer in the buffer solution, V represents the volume of the buffer solution, pKa represents the pKa value of the buffer, and pH represents the pH value of the solution. The amount of the reducing agent added is equivalent to the nitrite. The buffer in this step is a mixture of a weak acid and its salt, and the mixture of the weak acid and its salt is an ethanol-ammonium acetate buffer. The reducing agent in this step is an ammonium salt, and the ammonium salt is ammonium sulfate.

[0034] (3) Post-treatment: first, the denitrified wastewater obtained in step (2) is introduced (pumped in) into the third regulating tank 31 of the structural system of the post-treatment unit 3 (also referred to as "post-treatment mechanism", the same below) framed by the dotted line or the dashed line in the figure, and the water temperature and pH value are subsequently adjusted, that is, the water temperature and pH value of the denitrified water are respectively adjusted to: water temperature = 25°C, pH value = 8.5, and then introduced into the clarification tank 32 of the structural system of the post-treatment unit 3 for clarification, and the clarification method is natural clarification. And the clarification time is greater than 120 minutes. After clarification, the supernatant in the clarification tank 32 is pumped into the multi-media filter 33 of the post-processing unit 3 for filtration. The multi-media filter 33 is filled with filter material, which is refined quartz sand, and the filling of the refined quartz sand is divided into three layers of upper, middle and lower layers. The particle size of the upper, middle and lower layers of quartz sand decreases from bottom to top. The produced water filtered by the multi-media filter 33 is pumped into the storage tank 34 of the structural system of the post-processing unit 3 for standby use, so as to obtain the chemical high-salt wastewater brine mother liquor with nitrate removed.

[0035] The electrode plate material used in the micro-electric field described in steps (1) and (2) of this embodiment 1 includes one or more of an iron electrode plate, a titanium-ruthenium-iridium alloy electrode plate, a titanium-iridium-tantalum alloy electrode plate, and a titanium-nickel-cobalt alloy electrode plate. In the primary reaction tank 12 of the primary reaction unit 1, the iron electrode area accounts for 10%-20% of the total electrode area, and the remaining electrode plates used are one or more of a titanium-ruthenium-iridium alloy electrode plate, a titanium-iridium-tantalum alloy electrode plate, and a titanium-nickel-cobalt alloy electrode plate. In the secondary reaction tank 22 of the secondary reaction unit 2, the iron electrode area accounts for 5%-10% of the total electrode area, and the remaining electrode plates used are one or more of a titanium-ruthenium-iridium alloy electrode plate, a titanium-iridium-tantalum alloy electrode plate, and a titanium-nickel-cobalt alloy electrode plate. In the micro-electric field, the input voltage is arbitrarily selected from a specific value in the range of 1-2.5V; the input current is arbitrarily selected from a specific value in the range of 1-3A; and the electrode plate current density is 0.01-0.1mA / cm 2 The specific value can be selected at random, and the plate spacing can be selected at random within the range of 5-25cm.

[0036] Embodiment 2:

[0037] See also Figure 1 ,like Figure 1 The process shown in the figure, the method for removing nitrate from the brine mother liquor of the coal chemical high-salt wastewater of the above water quality comprises the following steps:

[0038] (1) reducing the nitrate in the mother liquor to nitrite, the mother liquor referred to here is the salted mother liquor of the coal chemical high-salt wastewater, and introducing the salted mother liquor of the chemical high-salt wastewater containing nitrate into Figure 1In the regulating tank 11 of the structural system of the primary reaction unit 1 (also referred to as "primary reaction mechanism", the same below) framed by the dotted line or the dotted line, the water temperature and the pH value (that is, the water temperature and the pH value of the salt mother liquor of the coal chemical high-salt wastewater) are adjusted to 35°C and Ph=6 respectively, and after the adjustment, the primary reaction tank 12 of the structural system of the primary reaction unit 1 is introduced, and the micro-electric field catalytic reaction is carried out under the action of the micro-electric field and the catalyst in the primary reaction tank 12 to reduce most of the nitrate to nitrite. The micro-electric field catalytic reaction is carried out under the aeration state, the aeration reaction time is 60min, and the aeration gas-water volume ratio is 5:1. Preferably, after sampling and testing, when the nitrate content in the wastewater is 500-2000mg / L, the aeration reaction time is in the range of 60-120min, and when the nitrate content in the wastewater is 2000- When the concentration of nitrate in the wastewater is 5000 mg / L, the aeration reaction time is in the range of 120-240 min. It can be seen that the aeration reaction time is generally in step with the content of nitrate in the wastewater (i.e., proportional). After the micro-electric field catalytic reaction is completed, the wastewater is pumped into the sedimentation tank 13 of the structural system of the primary reaction unit 1 for natural precipitation. The natural precipitation time is greater than 120 min. The supernatant obtained after precipitation is the wastewater treated in step (1). The reason why it is called the wastewater treated in step (1) is that the wastewater still contains a small part or a trace amount of unreduced nitrate, that is, most of the nitrate originally contained in the mother liquor has been reduced to nitrite. In this step, the mass ratio of the amount of the catalyst added to the nitrate content is 0.2:1, and the catalyst is an ionic liquid catalyst, specifically hydroxyethyltrimethylammonium acetate;

[0039] (2) The treated wastewater obtained in step (1) is pumped into Figure 1In the secondary regulating tank 21 of the structural system of the secondary reaction unit 2 (also referred to as "secondary reaction mechanism", the same below) framed by the dotted line or the dotted line, the water temperature and pH value are adjusted (i.e., "regulated"), that is, the water temperature and pH value of the wastewater treated in the step (1) are adjusted to: water temperature 50°C, pH=6, respectively, and introduced (i.e., pumped) into the secondary reaction tank 22 of the structural system of the secondary reaction unit 2 after adjustment, and reacted under the action of the micro-electric field, buffer and reductant in the secondary reaction tank 22. The reaction is carried out under aeration, the aeration reaction time is 60 minutes, and the aeration gas-water volume ratio is 3:1. As a preferred solution, after sampling and testing, when the nitrite content in the wastewater is 200-1000 mg / L, the aeration reaction time is in the range of 60-120 minutes, and when the nitrite content in the wastewater is 200-1000 mg / L, the aeration reaction time is in the range of 60-120 minutes, and when the nitrite content in the wastewater is 200-1000 mg / L, the aeration reaction time is in the range of 60-120 minutes. When the nitrate content is 1000-2000 mg / L, the aeration reaction time is in the range of 120-240 min. It can be seen that the aeration reaction time is generally in step with the nitrite content in the wastewater (i.e., proportional). After the reaction is completed, denitrified wastewater is obtained. The buffer capacity calculation formula of the buffer in this step is β=(CxV) / (pKa+pH), wherein β represents the buffer capacity, C represents the concentration of the buffer in the buffer solution, V represents the volume of the buffer solution, pKa represents the pKa value of the buffer, and pH represents the pH value of the solution. The amount of the reducing agent added is equivalent to the nitrite. The buffer in this step is a mixture of a weak acid and its salt, and the mixture of the weak acid and its salt is a phthalate buffer. The reducing agent in this step is an ammonium salt, and the ammonium salt is ammonium chloride.

[0040] (3) Post-treatment: first, the denitrified wastewater obtained in step (2) is introduced (pumped in) into the third regulating tank 31 of the structural system of the post-treatment unit 3 (also referred to as "post-treatment mechanism", the same below) framed by the dotted line or the dashed line in the figure, and the water temperature and pH value are subsequently adjusted, that is, the water temperature and pH value of the denitrified water are respectively adjusted to: water temperature = 30°C, pH value = 9, and then introduced into the clarification tank 32 of the structural system of the post-treatment unit 3 for clarification, and the clarification method is natural clarification and The clarification time is greater than 120 minutes. After clarification, the supernatant in the clarification tank 32 is pumped into the multi-media filter 33 of the post-processing unit 3 for filtration. The multi-media filter 33 is filled with filter material, which is refined quartz sand. The filling of the refined quartz sand is divided into three layers, namely, upper, middle and lower layers. The particle size of the three layers of quartz sand decreases from bottom to top. The produced water filtered by the multi-media filter 33 is pumped into the storage tank 34 of the structural system of the post-processing unit 3 for standby use, so as to obtain the brine mother liquor of chemical high-salt wastewater with nitrate removed.

[0041] The electrode material used in the micro-electric field described in steps (1) and (2) of this embodiment 2 includes one or more of iron electrode plates, titanium-ruthenium-iridium alloy electrode plates, titanium-iridium-tantalum alloy electrode plates, and titanium-nickel-cobalt alloy electrode plates. In the primary reaction tank 12 of the primary reaction unit 1, the iron electrode area accounts for 10%-20% of the total electrode area, and the remaining electrode plates are one or more of titanium-ruthenium-iridium alloy electrode plates, titanium-iridium-tantalum alloy electrode plates, and titanium-nickel-cobalt alloy electrode plates; in the secondary reaction tank 22 of the secondary reaction unit 2, the iron electrode area accounts for 5%-10% of the total electrode area, and the remaining electrode plates are one or more of titanium-ruthenium-iridium alloy electrode plates, titanium-iridium-tantalum alloy electrode plates, and titanium-nickel-cobalt alloy electrode plates; for the micro-electric field, the input voltage is arbitrarily selected from 1-2.5V; the input current is arbitrarily selected from 1-3A; the electrode plate current density is 0.01-0.1mA / cm 2 The specific value can be selected at random, and the plate spacing can be selected at random within the range of 5-25cm.

[0042] Embodiment 3:

[0043] See also Figure 1 ,like Figure 1 The process shown in the figure, the method for removing nitrate from the brine mother liquor of the coal chemical high-salt wastewater of the above water quality comprises the following steps:

[0044] (1) reducing the nitrate in the mother liquor to nitrite, the mother liquor referred to here is the salted mother liquor of the coal chemical high-salt wastewater, and introducing the salted mother liquor of the chemical high-salt wastewater containing nitrate into Figure 1In the regulating tank 11 of the structural system of the primary reaction unit 1 (also referred to as "primary reaction mechanism", the same below) framed by the dotted line or the dotted line, the water temperature and the pH value (that is, the water temperature and the pH value of the salt mother liquor of the coal chemical high-salt wastewater) are adjusted to 20°C and Ph=3 respectively. After the adjustment, the primary reaction tank 12 of the structural system of the primary reaction unit 1 is introduced. Under the action of the micro-electric field and the catalyst in the primary reaction tank 12, a micro-electric field catalytic reaction is carried out to reduce most of the nitrate ions to nitrite ions. The micro-electric field catalytic reaction is carried out under aeration. The aeration reaction time is 150 minutes, and the aeration gas-water volume ratio is 3.5:1. Preferably, after sampling and testing, when the nitrate content in the wastewater is 500-2000 mg / L, the aeration reaction time is in the range of 60-120 minutes, and when the nitrate content in the wastewater is 2000-5000 mg / L, the aeration reaction time is in the range of 60-120 minutes. / L, then the aeration reaction time is in the range of 120-240min. It can be seen that the length of the aeration reaction time is generally in step with the degree of the nitrate content in the wastewater (i.e., proportional). After the micro-electric field catalytic reaction is completed, it is pumped into the sedimentation tank 13 of the structural system of the primary reaction unit 1 for natural precipitation. The natural precipitation time is greater than 120min. The supernatant obtained after precipitation is the wastewater treated in this step (1). The reason why it is called the wastewater treated in this step (1) is that the wastewater still contains a small part or a trace amount of unreduced nitrate, that is, most of the nitrate originally contained in the mother liquor has been reduced to nitrite. In this step, the mass ratio of the amount of the catalyst added to the nitrate content is 0.15:1, and the catalyst is an ionic liquid catalyst, specifically 1-aminoethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt;

[0045] (2) The treated wastewater obtained in step (1) is pumped into Figure 1In the secondary regulating tank 21 of the structural system of the secondary reaction unit 2 (also referred to as "secondary reaction mechanism", the same below) framed by the dotted line or the dot-dash line, the water temperature and pH value are adjusted (i.e., "regulated"), that is, the water temperature and pH value of the wastewater treated in the step (1) are adjusted to: water temperature 20°C, pH=4.5, respectively, and introduced (i.e., pumped) into the secondary reaction tank 22 of the structural system of the secondary reaction unit 2 after adjustment, and reacted under the action of the micro-electric field, buffer and reductant in the secondary reaction tank 22. The reaction is carried out under aeration, the aeration reaction time is 150 minutes, and the aeration air-water volume ratio is 2:1. As a preferred solution, after sampling and testing, when the nitrite content in the wastewater is 200-1000 mg / L, the aeration reaction time is in the range of 60-120 minutes, and when the nitrite content in the wastewater is 1 000-2000mg / L, then the aeration reaction time is in the range of 120-240min. It can be seen that the length of the aeration reaction time is generally in step with the degree of nitrite content in the wastewater (i.e., proportional). After the reaction is completed, denitrified wastewater is obtained. The buffer capacity calculation formula of the buffer in this step is β=(CxV) / (pKa+pH), wherein β represents the buffer capacity, C represents the concentration of the buffer in the buffer solution, V represents the volume of the buffer solution, pKa represents the pKa value of the buffer, and pH represents the pH value of the solution. The amount of the reducing agent added is equivalent to the nitrite. The buffer in this step is a mixture of a weak acid and its salt, which is an acetate-lithium salt buffer. The reducing agent in this step is an ammonium salt, which is a mixture of ammonium bicarbonate and ammonium sulfate mixed in any weight ratio.

[0046] (3) Post-treatment: first, the denitrified wastewater obtained in step (2) is introduced (pumped in) into the third regulating tank 31 of the structural system of the post-treatment unit 3 (also referred to as "post-treatment mechanism", the same below) framed by the dotted line or the dashed line in the figure, and the water temperature and pH value are subsequently adjusted, that is, the water temperature and pH value of the denitrified water are respectively adjusted to: water temperature = 20°C, pH value = 8.5, and then introduced into the clarification tank 32 of the structural system of the post-treatment unit 3 for clarification, and the clarification method is natural clarification. And the clarification time is greater than 120 minutes. After clarification, the supernatant in the clarification tank 32 is pumped into the multi-media filter 33 of the post-processing unit 3 for filtration. The multi-media filter 33 is filled with filter material, which is refined quartz sand, and the filling of the refined quartz sand is divided into three layers of upper, middle and lower layers. The particle size of the upper, middle and lower layers of quartz sand decreases from bottom to top. The produced water filtered by the multi-media filter 33 is pumped into the storage tank 34 of the structural system of the post-processing unit 3 for standby use, so as to obtain the chemical high-salt wastewater brine mother liquor with nitrate removed.

[0047] The electrode plate material used in the micro-electric field described in steps (1) and (2) of this embodiment 3 includes one or more of iron electrode plates, titanium-ruthenium-iridium alloy electrode plates, titanium-iridium-tantalum alloy electrode plates, and titanium-nickel-cobalt alloy electrode plates. In the primary reaction tank 12 of the primary reaction unit 1, the iron electrode area accounts for 10%-20% of the total electrode area, and the remaining electrode plates used are one or more of titanium-ruthenium-iridium alloy electrode plates, titanium-iridium-tantalum alloy electrode plates, and titanium-nickel-cobalt alloy electrode plates; in the secondary reaction tank 22 of the secondary reaction unit 2, the iron electrode area accounts for 5%-10% of the total electrode area, and the remaining electrode plates used are one or more of titanium-ruthenium-iridium alloy electrode plates, titanium-iridium-tantalum alloy electrode plates, and titanium-nickel-cobalt alloy electrode plates; for the micro-electric field, the input voltage is arbitrarily selected from 1-2.5V; the input current is arbitrarily selected from 1-3A; the electrode plate current density is 0.01-0.1mA / cm 2 The specific value can be selected at random, and the plate spacing can be selected at random within the range of 5-25cm.

[0048] The sludge in the sedimentation tank 13 and the clarification tank 32 described in Examples 1 to 3 of the present invention is regularly discharged into the sludge regulating tank and disposed of in a harmless and non-polluting standardized manner (including chemical adjustment, concentration, dehydration and outsourcing (entrustment to another organization)).

[0049] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, 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 within the scope of protection of the present invention.

Claims

1. A method for removing nitrate from brine mother liquor of chemical high-salt wastewater, characterized in that: The following steps are involved: (1) reducing nitrate in the mother liquor to nitrite, introducing the salted mother liquor of chemical high-salt wastewater containing nitrate into a regulating tank (11) of the structural system of the primary reaction unit (1) and adjusting the water temperature and pH value, and introducing the mother liquor into the primary reaction tank (12) of the structural system of the primary reaction unit (1) after adjustment, and performing a micro-electric field catalytic reaction under the action of the micro-electric field and catalyst in the primary reaction tank (12) to reduce nitrate to nitrite, and pumping the mother liquor into the sedimentation tank (13) of the structural system of the primary reaction unit (1) for precipitation after the micro-electric field catalytic reaction is completed, and obtaining the supernatant after precipitation as the wastewater treated in this step (1); (2) pumping the treated wastewater obtained in step (1) into a secondary regulating tank (21) of the structural system of the secondary reaction unit (2) and adjusting the water temperature and pH value, and then introducing the treated wastewater into a secondary reaction tank (22) of the structural system of the secondary reaction unit (2) to react under the action of the micro-electric field, buffer and reducing agent in the secondary reaction tank (22), and obtaining denitrified wastewater after the reaction is completed; (3) Post-treatment, firstly introducing the denitrification wastewater obtained in step (2) into the third regulating tank (31) of the structural system of the post-treatment unit (3) and then adjusting the water temperature and pH value, and then introducing the adjusted wastewater into the clarification tank (32) of the post-treatment unit (3) for clarification, and then pumping the supernatant in the clarification tank (32) into the multi-media filter (33) of the post-treatment unit (3) for filtration, and pumping the produced water filtered by the multi-media filter (33) into the storage tank (34) of the structural system of the post-treatment unit (3) to obtain the chemical high-salt wastewater salt mother liquor with nitrate removed.

2. The method for removing nitrate from the brine mother liquor of chemical high-salt wastewater according to claim 1, characterized in that: The water temperature and pH value are adjusted in step (1) by adjusting the water temperature of the salt mother liquor of the chemical high-salt wastewater containing nitrate to 20-50°C and adjusting the pH to Ph=3-6; the mass ratio of the amount of catalyst added to the nitrate content in the primary reaction tank (12) is 0.1-0.2:1; the micro-electric field catalytic reaction is carried out under aeration, the aeration reaction time is 60-240min, and the aeration air-water volume ratio is 2-5:1, wherein, when the nitrate content in the wastewater is 500-2000mg / L, the reaction time is 60-120min, and when the nitrate content in the wastewater is 2000-5000mg / L, the reaction time is 120-240min; the precipitation method in the precipitation tank (13) is natural precipitation and the time is greater than 120min.

3. The method for removing nitrate from the brine mother liquor of chemical high-salt wastewater according to claim 1 or 2, characterized in that: The catalyst described in step (1) is an ionic liquid catalyst, and the ionic liquid catalyst is one or a combination of trimethylamine hydrochloride, tetramethylammonium chloride, tetramethylammonium hydrogen sulfate, tributylmethylammonium chloride, tetramethylammonium p-toluenesulfonate, 1-hydroxyethyl-3-methylimidazolium chloride, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hydroxyethyl-3-methylimidazolium acetate, 1-hydroxyethyl-3-methylimidazolium p-toluenesulfonate, hydroxyethyltrimethylammonium chloride, hydroxyethyltrimethylammonium acetate, 1-aminopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-aminoethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

4. The method for removing nitrate from the brine mother liquor of chemical high-salt wastewater according to claim 1, characterized in that: The water temperature and pH value are adjusted in step (2) by adjusting the water temperature to 20-50°C and the pH value to 3-6; the reaction under the action of the micro-electric field, buffer and reducing agent in the secondary reaction tank (22) is carried out under aeration, the aeration reaction time is 60-240 minutes, and the aeration air-water volume ratio is 2-5:1, wherein, when the nitrite content in the wastewater is 200-1000 mg / L, the reaction time is 60-120 minutes, and when the nitrate content in the wastewater is 1000-2000 mg / L, the reaction time is 120-240 minutes.

5. The method for removing nitrate from the brine mother liquor of chemical high-salt wastewater according to claim 1, characterized in that: The calculation formula for the buffer capacity of the buffer described in step (2) is β=(CxV) / (pKa+pH), wherein β represents the buffer capacity, C represents the concentration of the buffer in the buffer solution, V represents the volume of the buffer solution, pKa represents the pKa value of the buffer, and pH represents the pH value of the solution; the dosage of the reducing agent is equivalent to that of nitrite.

6. The method for removing nitrate from the brine mother liquor of chemical high-salt wastewater according to claim 1 or 2, characterized in that: The buffer is a mixture of a weak acid and a salt thereof, and the mixture of a weak acid and a salt thereof is one of ethanol-ammonium acetate buffer, sodium formate buffer, phthalate buffer, citric acid-disodium hydrogen phosphate buffer, acetic acid-sodium acetate buffer, acetic acid-lithium salt buffer, and acetic acid-ammonium acetate buffer; the reducing agent is an ammonium salt, and the ammonium salt is one of ammonium acetate, ammonium phosphate, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium bicarbonate, ammonium fluoride, ammonium bromide, and potassium ammonium sulfate, or a combination of several thereof.

7. The method for removing nitrate from the brine mother liquor of chemical high-salt wastewater according to claim 1, characterized in that: The subsequent adjustment of water temperature and pH value described in step (3) is to adjust the water temperature to 20-30°C and adjust the pH value to pH=8.5-9; the clarification method in the clarification tank (32) is natural clarification and the clarification time is greater than 120 minutes; the multi-media filter is filled with filter material, which is refined quartz sand, and the filling of the refined quartz sand is divided into three layers of upper, middle and lower, and the particle size of the three layers of quartz sand decreases from bottom to top.

8. The method for removing nitrate from the brine mother liquor of chemical high-salt wastewater according to claim 1, characterized in that: The electrode material used in the micro-electric field described in steps (1) and (2) includes one or more of an iron electrode, a titanium-ruthenium-iridium alloy electrode, a titanium-iridium-tantalum alloy electrode, and a titanium-nickel-cobalt alloy electrode. In the primary reaction tank (12), the iron electrode area accounts for 10%-20% of the total electrode area, and the remaining electrode plates used are one or more of a titanium-ruthenium-iridium alloy electrode, a titanium-iridium-tantalum alloy electrode, and a titanium-nickel-cobalt alloy electrode. In the secondary reaction tank (22), the iron electrode area accounts for 5%-10% of the total electrode area, and the remaining electrode plates used are one or more of a titanium-ruthenium-iridium alloy electrode, a titanium-iridium-tantalum alloy electrode, and a titanium-nickel-cobalt alloy electrode.

9. The method for removing nitrate from the brine mother liquor of chemical high-salt wastewater according to claim 8, characterized in that: The input voltage of the micro-electric field is 1-2.5V; the input current is 1-3A; the plate current density is 0.01-0.1mA / cm 2 , the distance between the plates is 5-25cm.

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