Method and system for removing inert organic matter from coal chemical high-salinity wastewater

Abstract

The present application relates to a kind of coal chemical industry high-salinity wastewater end water treatment technology of difficult removal inert organic matter.A kind of coal chemical industry high-salinity wastewater inert organic matter removal method and system, the method includes the following steps: (1) high-salinity wastewater is reacted under the action of micro electric field and catalyst A;(2) the wastewater after step (1) is handled, is reacted under the action of catalyst B;(3) the wastewater after step (2) is handled, add flocculating agent and carry out reaction, carry out precipitation;(4) the wastewater after step (3) is handled, is filtered, is pumped into mesoporous molecular sieve system, and effluent is discharged into storage tank.A kind of coal chemical industry high-salinity wastewater inert organic matter removal system includes: first reaction unit;Second reaction unit;Mesoporous molecular sieve unit.The method and system of the present application can effectively remove inert organic matter in coal chemical industry high-salinity wastewater end water, realize high-salinity wastewater treatment no hybrid, and high-purity high-salinity wastewater after separation can be recycled.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal chemical industry high-salinity wastewater inert organic matter treatment, belongs to the field of water resource comprehensive utilization, and particularly relates to a liquid-phase pretreatment technology for high-salinity wastewater treatment without impurities and high-value utilization of byproduct salt. BACKGROUND

[0002] The inert organic matter in coal chemical industry high-salinity wastewater is organic phase impurities that still remain after removal by various wastewater treatment processes. The coal chemical industry wastewater treatment process generally includes an anaerobic and aerobic treatment system, an ultrafiltration (UF) and nanofiltration (NF) treatment system, a high-level oxidation treatment system, and an activated carbon adsorption system. At present, the high-salinity wastewater treatment process of the coal chemical industry is as follows: a biochemical treatment system (anaerobic + aerobic) → a hardening and impurity removal system (for removing calcium, magnesium, silicon, fluorine and other impurities) → a membrane treatment system (ultrafiltration / nanofiltration / reverse osmosis) → an evaporation and concentration system (MED / MVR / ED electrically driven membrane) → end water (if there is no evaporation and concentration system, the reverse osmosis concentrated liquid is the end water). The inert COD remaining in the end water leads to 10-15% of hazardous waste in the subsequent byproduct salt resource utilization section, and the disposal cost of the hazardous waste is 3000-5000 yuan / ton, which brings a large economic burden to the coal chemical industry enterprises.

[0003] The inert organic matter remaining in the end water of the coal chemical industry high-salinity wastewater includes nearly 40 kinds of humin, fulvic acid, dimethylpyridine, acetophenone, acetone, glutaraldehyde, citric anhydride, chloromethyl thiocyanate, ethyl acetamide, etc. The above-mentioned organic matters have the characteristics of complex components, small relative molecular weight (generally less than 150 Da), high biological toxicity and great difficulty in degradation, and it is very difficult to remove them using conventional technologies.

[0004] There are many existing methods for removing the inert COD in the end water of the coal chemical industry high-salinity wastewater, mainly including an ozone oxidation method, an activated carbon adsorption method, and a macroporous adsorption resin separation method. The ozone oxidation method has the disadvantages of large investment, high operation cost, and unsatisfactory removal effect of the inert COD. The activated carbon adsorption method has the relative simple process and easy-to-control equipment operation, but has the disadvantages of low adsorption efficiency of the inert organic matter, which is far lower than the theoretical value, high cost of raw materials due to the difficulty in regeneration after saturation, and the fact that the waste activated carbon after replacement is hazardous waste, which is not conducive to environmental protection. The macroporous adsorption resin separation method depends on the van der Waals force or the result of hydrogen bonding, also known as molecular force, which is much weaker than chemical bonds, so the adsorption and separation effect is very limited for the inert COD that is affected by chemical bonds. Moreover, the characteristics of the resin are not suitable for some special environments such as high temperature, high pressure, acid and alkali.

[0005] At present, the by-product salt produced by the treatment of high-salinity wastewater in the coal chemical industry in China is mainly sodium sulfate and sodium chloride, with a total of 2-3 million tons per year, which has a wide resource utilization prospect. However, due to the difficulty in removing the inert organic matter in the end water, the purity of the by-product salt cannot meet the purity requirements of industrial salt, hindering the resource utilization of high-salinity wastewater. The inert organic matter that is difficult to remove will cause such by-product salt to be defined as hazardous waste, and according to the hazardous waste disposal fee of 3000 yuan / ton, it will bring a heavy economic burden to the enterprise. Therefore, effectively removing the inert organic matter can save the cost of hazardous waste treatment and realize the resource utilization of high-salinity wastewater in the coal chemical industry, which is of great economic and social benefits.

[0006] Therefore, how to provide a method for removing the inert organic matter remaining in the end water of high-salinity wastewater in the coal chemical industry, simplify the process flow, reduce the cost, realize the non-heterogeneous treatment of wastewater, and further ensure the high-value utilization of by-product salt, has become an urgent problem to be solved in the field at present. SUMMARY

[0007] The present application aims to solve the problem of difficult removal of inert organic matter in high-salinity wastewater in the coal chemical industry in the related art, and provides a method and system for removing inert organic matter in high-salinity wastewater in the coal chemical industry, which is stable and reliable in industry, and the purified wastewater can be used for resource utilization.

[0008] In view of the above limitations, the present application provides a method and system for removing inert organic matter in high-salinity wastewater in the coal chemical industry.

[0009] A method for removing inert organic matter in high-salinity wastewater in the coal chemical industry, the method comprising the following steps:

[0010] (1) reacting the high-salinity wastewater under the action of a micro-electric field and a catalyst, the catalyst for the reaction being A, and the micro-electric field catalytic reaction can adjust the motion state of the extranuclear electrons of the inert organic matter;

[0011] (2) reacting the wastewater treated in step (1) under the action of a catalyst B, and the above-mentioned catalytic reaction further applies ionization energy to the electron cloud of the inert organic matter;

[0012] (3) adding a flocculating agent to the wastewater treated in step (2) to react and precipitate;

[0013] (4) filtering the wastewater treated in step (3) and pumping it into a mesoporous molecular sieve system, and discharging the effluent into a storage tank; since the motion state of the extranuclear electrons of the inert organic matter is adjusted in steps (1) and (2), and the ionization energy applied to the electron cloud of the inert organic matter is significantly improved, the adsorption effect of the mesoporous molecular sieve system on the inert organic matter is improved.

[0014] Further, in step (1), the high-salinity wastewater is pumped into a first-stage reaction conditioning tank for conditioning, then into a micro-electric field reaction tank for aeration reaction, and then catalyst A is added, and the reaction continues for 30-90 minutes under the action of the micro-electric field and catalyst A, and then the wastewater is pumped into a first clean water tank for natural sedimentation, and the supernatant in the first clean water tank is used as the wastewater after step (1) treatment.

[0015] In step (2), the wastewater after step (1) treatment is pumped into a second-stage reaction conditioning tank, and after conditioning in the second-stage reaction conditioning tank, the wastewater is pumped into a second-stage reaction tank, an appropriate amount of hydrogen peroxide is added, and aeration reaction is carried out, and then catalyst B is added; under the action of catalyst B, the reaction continues for 30-90 minutes, and then the wastewater is pumped into a coagulation and sedimentation conditioning tank.

[0016] In step (3), the wastewater after step (2) treatment is conditioned in the coagulation and sedimentation conditioning tank, a flocculating agent is added until the reaction is complete, and then the wastewater is pumped into a sedimentation tank, and after sedimentation, the wastewater is overflowed into a second clean water tank, and the supernatant in the second clean water tank is used as the wastewater after step (3) treatment.

[0017] In step (4), the wastewater after step (3) treatment is input into a multi-medium filter for filtration, and after conditioning in a storage tank, the wastewater is pumped into a mesoporous molecular sieve system, and after adsorption separation by the mesoporous molecular sieve system, the effluent is discharged into a storage tank.

[0018] Further, in step (1):

[0019] The wastewater is conditioned in the first-stage reaction conditioning tank by adjusting the water temperature to 15-60℃ and the pH to 3-6.

[0020] In the micro-electric field reaction tank, the aeration reaction time is 15-50 minutes.

[0021] In the first clean water tank, after natural sedimentation, the sludge is backflowed to the micro-electric field reaction tank.

[0022] Further, in step (2):

[0023] The wastewater is conditioned in the second-stage reaction conditioning tank by adjusting the water temperature to 15-60℃ and the pH to 3-6; in the second-stage reaction tank, the aeration reaction time is 5-30 minutes.

[0024] Further, in step (3):

[0025] The wastewater is conditioned in the coagulation and sedimentation conditioning tank by adjusting the water temperature to 15-60℃ and the pH to 8-8.5; after the flocculating agent is added to the wastewater, the reaction time required for complete reaction is 20-40 minutes, and then the wastewater is pumped into the sedimentation tank for sedimentation for 2 hours.

[0026] Further: in step (4):

[0027] The adjustment in the storage pool is as follows: the water temperature is adjusted to 15-60℃, and the pH is neutral; the mesoporous molecular sieve system is composed of one or more groups; each group is composed of 3-5 mesoporous molecular sieve adsorption tanks connected in series, and the inert organic matter is separated and adsorbed at a flow rate of 0.5-2.5 BV.

[0028] The mesoporous adsorbent is regenerated once every 12-24 hours, using 3-5% dilute alkali solution for desorption and regeneration, and then washing with pure water at a flow rate of 1-2 BV until the pH is neutral, and the pure water temperature is 20-60℃.

[0029] Further: the mass ratio of the amount of catalyst A added in step (1) to the content of inert organic matter is (0.1-0.2):1; and the mass ratio of the amount of catalyst B added in step (2) to the content of inert organic matter is (0.1-0.2):1.

[0030] Further: the gas-water volume ratio of aeration in step (1) is (2-10):1; and the gas-water volume ratio of aeration in step (2) is (3-15):1.

[0031] Further: the mass ratio of the amount of hydrogen peroxide added in step (2) to the content of inert organic matter is (0.1-0.8):1.

[0032] Further: the flocculant is a PAM flocculant, and the dissolution ratio of the PAM flocculant is 0.1%-0.2%.

[0033] Further: the micro-electric field uses one or more of the following materials for the electrode plate: iron electrode plate, aluminum electrode plate, graphite electrode plate, diamond electrode plate, and titanium-ruthenium-iridium alloy electrode plate.

[0034] Further: the micro-electric field uses a combination of the following materials for the electrode plate:

[0035] ① containing aluminum and / or iron;

[0036] and ② containing at least one of graphite, diamond, and titanium-ruthenium-iridium alloy;

[0037] Among them, the aluminum electrode area accounts for 10%-20% of the total electrode area, and the iron electrode area accounts for 10%-20% of the total electrode area.

[0038] Further: the micro-electric field uses direct current or alternating current, with an input voltage of 0.1-2.5 V, an input current of 0.01-1 A, and an electrode plate current density of 0.01-0.1 mA / cm 2 , and an electrode plate spacing of 5-25 cm.

[0039] Further, the catalyst A and B are ionic liquids; the catalyst A and catalyst B are selected from the combination of one or more of pyrrolidine ionic liquid, piperidine ionic liquid, and functionalized ionic liquid;

[0040] The alkyl group contained in the pyrrolidine ionic liquid includes one or more of ethyl, propyl, butyl, hexyl, and octyl;

[0041] The alkyl group contained in the piperidine ionic liquid includes one or more of ethyl, propyl, butyl, hexyl, and octyl;

[0042] The functional group contained in the functionalized ionic liquid includes one or more of hydroxyl, carboxyl, sulfonic acid group, alkenyl, ether group, ester group, amino, benzyl, and nitrile group.

[0043] A coal chemical high-salinity wastewater inert organic matter removal system, the system comprising:

[0044] The primary reaction unit comprises a primary reaction adjustment tank, a micro-electric field reaction tank, and a first clean water tank.

[0045] The secondary reaction unit comprises a secondary reaction adjustment tank, a secondary reaction tank, a coagulation and sedimentation adjustment tank, a sedimentation tank, and a second clean water tank.

[0046] The mesoporous molecular sieve unit comprises a multi-medium filter, a storage tank, a mesoporous molecular sieve system, and a storage tank.

[0047] Further, in the primary reaction unit, after the high-salinity wastewater is pumped into the primary reaction adjustment tank for adjustment, it is then pumped into the micro-electric field reaction tank for aeration reaction, and then catalyst A is added. Under the action of the micro-electric field and catalyst A, the reaction continues for 30-90 minutes, and then the wastewater is pumped into the first clean water tank for natural sedimentation, and the supernatant is used as the wastewater treated by the primary reaction unit.

[0048] In the secondary reaction unit, after the wastewater treated by the primary reaction unit is adjusted in the secondary reaction adjustment tank, it is then pumped into the secondary reaction tank, and an appropriate amount of hydrogen peroxide is added for aeration reaction, and then catalyst B is added. Under the action of catalyst B, the reaction continues for 30-90 minutes, and then the wastewater is pumped into the coagulation and sedimentation adjustment tank for adjustment, and a flocculating agent is added until the reaction is complete, and then the wastewater is pumped into the sedimentation tank, and after sedimentation, it is overflowed into the second clean water tank, and the supernatant in the second clean water tank is used as the wastewater treated by the secondary reaction unit.

[0049] In the mesoporous molecular sieve unit, the wastewater treated by the secondary reaction unit is input into the multi-medium filter for filtration, and then the filtered wastewater is pumped into the storage tank for adjustment, and then it is pumped into the mesoporous molecular sieve system. After being adsorbed and separated by the mesoporous molecular sieve system, the effluent is discharged into the storage tank.

[0050] Compared with the related art, the present application has the following advantages:

[0051] The present application is directed to a method for removing inert organic matter in coal chemical industry high-salinity wastewater end water, which comprises the following steps: passing the coal chemical industry high-salinity wastewater through a micro-electric field plus nano-catalysis technology to excite the activity of small-molecule inert organic matter, applying a micro-electric field to the organic phase nanoparticles to adjust the motion state of the extranuclear electrons; then using a catalyst to further apply ionization energy to the electron cloud of the inert organic matter, so that the bond energy of the inert organic matter in the independent microsystem changes and is in a metastable state, thereby having separation conditions; after the above two-stage catalytic reaction, the inertness of the organic matter is activated, i.e. the organic phase particles in the high-salinity wastewater are adjusted from the ground state to the excited state; finally, the high-salinity wastewater is pumped into a mesoporous molecular sieve system, and a mesoporous adsorption separation technology is used to separate the small-molecule (molecular diameter < 1 nm) inert organic matter in the water, so that the inert organic matter can be effectively adsorbed and separated by the mesoporous molecular sieve system due to the above two-stage catalytic reaction, thereby ensuring the effect of removing the inert organic matter, and the content of the organic matter in the obtained high-salinity wastewater is low enough to meet the requirements and standards of the subsequent resource chemical section, so that the high-salinity wastewater can be further utilized in a high-value manner.

[0052] The present application is directed to a system for removing inert organic matter in coal chemical industry high-salinity wastewater end water, which comprises the following steps: setting a first reaction unit, a second unit and a mesoporous molecular sieve unit; in the first reaction unit, a micro-electric field plus nano-catalysis technology is used to excite the activity of small-molecule inert COD, and a micro-electric field is applied to the organic phase nanoparticles to adjust the motion state of the extranuclear electrons; then, the high-salinity wastewater treated by the first reaction unit is input into the second reaction unit, and a catalyst is used in the second reaction tank to further apply ionization energy to the electron cloud of the inert organic matter, so that the bond energy of the inert organic matter in the independent microsystem changes and is in a metastable state, thereby having separation conditions; after the above two-stage catalytic reaction, the inertness of the organic matter is activated, i.e. the organic phase particles in the high-salinity wastewater are adjusted from the ground state to the excited state; finally, the high-salinity wastewater is pumped into a mesoporous molecular sieve system, and a mesoporous adsorption separation technology is used to separate the small-molecule (molecular diameter < 1 nm) inert organic matter in the water, thereby ensuring the effect of removing the inert organic matter, and the content of the organic matter in the obtained high-salinity wastewater is low enough to meet the requirements and standards of the subsequent resource chemical section, so that the high-salinity wastewater can be further utilized in a high-value manner. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 Flow chart of the coal chemical industry high-salinity wastewater inert organic matter removal method according to an embodiment of the present application;

[0054] Figure 2 Flow chart of the coal chemical industry high-salinity wastewater inert organic matter removal method according to another embodiment of the present application;

[0055] Figure 3 The structural diagram of the coal chemical industry high-salinity wastewater inert organic matter removal system is shown in another embodiment of the present application. DETAILED DESCRIPTION

[0056] In order to make the objects, technical solutions and advantages of the present application clearer and more comprehensible, the present application will be further described in detail below. However, it should be understood that the description herein is only used to explain the present application and is not intended to limit the scope of the present application.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs, and the terms used herein in the specification are only for the purpose of describing the specific embodiments and are not intended to limit the present application. The characterization means involved herein can be referred to the related description in the prior art, which will not be described herein.

[0058] In order to further understand the present application, the present application will be further described in detail below in combination with the best embodiments.

[0059] Embodiment 1

[0060] As shown in the figure, a method for removing inert organic matter from coal chemical industry high-salinity wastewater, the method comprises the following steps: Figures 1-3

[0061] (1) reacting the high-salinity wastewater under the action of a micro-electric field and a catalyst, the catalyst for the reaction is A, using micro-electric field and nano-catalysis technology to stimulate the activity of small-molecule inert organic matter, applying a micro-electric field to the organic phase nanoparticles to adjust the motion state of the extranuclear electrons;

[0062] (2) reacting the wastewater treated in step (1) under the action of a catalyst B; the above-mentioned catalytic reaction further applies ionization energy to the electron cloud of the inert organic matter, so that the bond energy of the inert organic matter changes in the independent microsystem and is in a metastable state, thereby having separation conditions;

[0063] (3) adding a flocculating agent to the wastewater treated in step (2) to react and precipitate;

[0064] (4) filtering the wastewater treated in step (3) and pumping into a mesoporous molecular sieve system, and discharging the effluent into a storage tank; since the motion state of the extranuclear electrons of the inert organic matter is adjusted in steps (1) and (2), and the ionization energy applied to the electron cloud of the inert organic matter is significantly improved, the adsorption effect of the mesoporous molecular sieve system on the inert organic matter is improved, so that the adsorption and separation of the inert organic matter by the mesoporous molecular sieve system can meet the relevant standards for removing the inert organic matter, and the separated high-salinity wastewater has high purity, so that qualified by-product salt can be prepared. ​

[0065] After two-stage catalytic reaction of step (1) plus step (2), the inertness of organic matter is activated, i.e. the organic phase particles in the high-salt wastewater are adjusted from ground state to excited state, thereby ensuring that the inert organic matter can be effectively adsorbed and separated in the subsequent mesoporous molecular sieve system; finally, the high-salt wastewater is pumped into the mesoporous molecular sieve system, and the mesoporous adsorption separation technology is used to separate the inert organic matter with small molecules (molecular diameter < 1 nm) in water. The separated high-salt wastewater has high purity, and the content of organic matter can reach the relevant standards, so that it can be further used as a resource, and the by-product salt produced can reach the relevant purity standards.

[0066] Example 2

[0067] As shown in the following table, on the basis of Example 1, the method further comprises the following steps: Figures 1-3

[0068] (1) The high-salt wastewater is pumped into the adjustment tank, and after adjusting the water temperature to 15-60℃ and the pH to 3-6, the wastewater enters the micro-electric field reaction tank, and aerated for 15-50 minutes, and catalyst A is added; under the action of the micro-electric field and catalyst A, the reaction continues for 30-90 minutes, and then it is pumped into the clean water tank, and naturally precipitates, and the sludge is returned to the micro-electric field reaction tank, and the supernatant is pumped into the secondary reactor adjustment tank.

[0069] (2) In the secondary reactor adjustment tank, after adjusting the water temperature to 15-60℃ and the pH to 3-6, the wastewater enters the reaction tank, and an appropriate amount of hydrogen peroxide is added, and aerated for 5-30 minutes, and catalyst B is added; under the action of catalyst B, the reaction continues for 30-90 minutes, and then it is pumped into the coagulation and sedimentation adjustment tank.

[0070] (3) In the coagulation and sedimentation adjustment tank, the water temperature is adjusted to 15-60℃ and the pH is adjusted to 8-8.5, and an appropriate amount of PAM flocculant is added as needed, and after fully reacting for 20-40 minutes, it is pumped into the sedimentation tank, and the sedimentation time is 2 hours, and it is overflowed into the clean water tank; the clean water is filtered by the multi-media filter and then enters the storage tank of the mesoporous molecular sieve unit, and the multi-media filter is backwashed once every 12-24 hours.

[0071] (4) In the storage tank, the water temperature is adjusted to 15-60℃ and the pH is adjusted to neutral, and the high-salt wastewater is pumped into the mesoporous molecular sieve system, each group of mesoporous molecular sieve system is 3-5 adsorption tanks in series, and the mesoporous material is packed in the adsorption tank in a fixed bed manner, and the adsorption separation COD is carried out at a flow rate of 0.5-2.5 BV, and the effluent is discharged into the storage tank; the mesoporous adsorption material is desorbed (regenerated) once every 12-24 hours, and 3%-5% dilute lye is used for desorption / regeneration, and then it is washed with pure water at a flow rate of 1-2 BV until it is neutral, and the water temperature of the pure water is 20-60℃.

[0072] Example 3 ​

[0073] As Figures 1-3 shown, on the basis of Embodiment 1, further: in step (1), after the high-salinity wastewater is pumped into a first-stage reaction conditioning tank for conditioning, it is pumped into a micro-electric field reaction tank for aeration reaction, and then catalyst A is added, and under the action of the micro-electric field and catalyst A, the reaction continues for 30-90 minutes, and then the wastewater is pumped into a first clear water tank for natural sedimentation, and the supernatant in the first clear water tank is used as the wastewater after step (1) treatment;

[0074] In step (2), the wastewater after step (1) treatment is pumped into a second-stage reaction conditioning tank, and after conditioning in the second-stage reaction conditioning tank, it is pumped into a second-stage reaction tank, an appropriate amount of hydrogen peroxide is added, and aeration reaction is carried out, and then catalyst B is added; under the action of catalyst B, the reaction continues for 30-90 minutes, and then the wastewater is pumped into a coagulation and sedimentation conditioning tank;

[0075] In step (3), the wastewater after step (2) treatment is conditioned in the coagulation and sedimentation conditioning tank, a flocculating agent is added until the reaction is complete, and then the wastewater is pumped into a sedimentation tank, and after sedimentation, it overflows into a second clear water tank, and the supernatant in the second clear water tank is used as the wastewater after step (3) treatment;

[0076] In step (4), the wastewater after step (3) treatment is input into a multi-medium filter for filtration, and after conditioning in a storage tank, the filtered wastewater is pumped into a mesoporous molecular sieve system, and after adsorption separation by the mesoporous molecular sieve system, the effluent is discharged into a storage tank.

[0077] Further: in step (1),

[0078] The conditioning mode of the wastewater in the first-stage reaction conditioning tank is to adjust the water temperature to 15-60℃ and the pH to 3-6;

[0079] In the micro-electric field reaction tank, the aeration reaction time is 15-50 minutes;

[0080] In the first clear water tank, after natural sedimentation, the sludge is backflowed to the micro-electric field reaction tank.

[0081] Further: in step (2),

[0082] The conditioning mode of the wastewater in the second-stage reaction conditioning tank is to adjust the water temperature to 15-60℃ and the pH to 3-6; in the second-stage reaction tank, the aeration reaction time is 5-30 minutes.

[0083] Further: in step (3),

[0084] The conditioning mode of the wastewater in the coagulation and sedimentation conditioning tank is to adjust the water temperature to 15-60℃ and the pH to 8-8.5;

[0085] The wastewater is added with flocculants, and the time required for the full reaction is 20-40 minutes, and then pumped into a sedimentation tank for 2 hours of sedimentation; the flocculants are PAM flocculants, and the dissolution ratio of the PAM flocculants is 0.1%-0.2%.

[0086] The PAM flocculants are also known as polyacrylamide flocculants, have good flocculation, and can reduce the frictional resistance between liquids. The polyacrylamide flocculants have long-chain (linear) molecular structures, long and thin molecules, and long molecular chains that extend to the outside and have many chemical active groups, can form larger flocculants by connecting with the precipitated particles, and can remove the original particle network in the solution.

[0087] Further, in step (4):

[0088] The adjustment in the storage tank is performed by adjusting the water temperature to 15-60℃ and the pH to neutral.

[0089] The mesoporous molecular sieve system is composed of one or more groups; each group is composed of 3-5 mesoporous molecular sieve adsorption tanks connected in series, and the inert organic matter is separated and adsorbed at a flow rate of 0.5-2.5 BV.

[0090] Further, the mesoporous adsorption material is regenerated once every 12-24 hours, desorbed and regenerated by using 3-5% dilute alkali liquor, and then cleaned with pure water at a flow rate of 1-2 BV until the pH is neutral, and the pure water has a temperature of 20-60℃.

[0091] Further, the micro-electric field in step (1) uses one or more of the following materials for the electrode plate: iron electrode plate, aluminum electrode plate, graphite electrode plate, diamond electrode plate, and titanium-ruthenium-iridium alloy electrode plate.

[0092] Experiments show that, under the action of the micro-electric field, compared with copper, nickel, steel, zinc, tungsten, and cobalt, the electrode plate material for activating the inert organic matter in coal chemical wastewater is iron, aluminum, graphite, diamond, and titanium-ruthenium-iridium alloy, which has the best effect.

[0093] Preferably, the electrode plate material for the micro-electric field is a combination of the following materials: aluminum and / or iron; and at least one of graphite, diamond, and titanium-ruthenium-iridium alloy, wherein the aluminum electrode area accounts for 10%-20% of the total electrode area, and the iron electrode area accounts for 10%-20% of the total electrode area.

[0094] Preferably, the electrode plate of the micro-electric field uses titanium-ruthenium-iridium alloy material and iron and aluminum materials, and the effective electrode area ratio is titanium-ruthenium-iridium: iron: aluminum = 8:1:1; or the electrode plate of the micro-electric field uses diamond material and iron and aluminum materials, and the effective electrode area ratio is diamond: iron: aluminum = 7:2:1; or the electrode plate of the micro-electric field uses graphite material and iron and aluminum materials, and the effective electrode area ratio is graphite: iron: aluminum = 6:2:2.

[0095] Preferably, the micro electric field in step (1) uses direct current or alternating current, with an input voltage of 0.1-2.5 V; for example, 0.1 V, 0.2 V, 0.3 V, 0.4 V, 0.5 V, 0.6 V, 0.7 V, 0.8 V, 0.9 V, 1.0 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V, 1.5 V, 1.6 V, 1.7 V, 1.8 V, 1.9 V, 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V, 2.5 V, but not limited to the listed values, and other values not listed within this range are also applicable;

[0096] Preferably, the micro electric field in step (1) uses direct current or alternating current, with an input current of 0.01-1 A; for example, 0.01 A, 0.02 A, 0.03 A, 0.04 A, 0.05 A, 0.06 A, 0.07 A, 0.08 A, 0.09 A, 0.1 A, 0.2 A, 0.3 A, 0.4 A, 0.5 A, 0.6 A, 0.7 A, 0.8 A, 0.9 A, 1 A, but not limited to the listed values, and other values not listed within this range are also applicable;

[0097] The direct current is converted using a rectifier, and the alternating current is adjusted directly in terms of voltage and current;

[0098] Preferably, the micro electric field in step (1) uses direct current or alternating current, with a plate current density of 0.01-0.1 mA / cm 2 .

[0099] Preferably, the micro electric field in step (1) has a plate spacing of 5-25 cm; for example, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm, 16 cm, 17 cm, 18 cm, 19 cm, 20 cm, 21 cm, 22 cm, 23 cm, 24 cm, 25 cm, but not limited to the listed values, and other values not listed within this range are also applicable;

[0100] Preferably, the micro electric field in step (1) has a plate current density of 0.01-0.1 mA / cm 2 ; for example, 0.01 mA / cm 2 , 0.02 mA / cm 2 , 0.03 mA / cm 2 , 0.04 mA / cm 2 , 0.05 mA / cm 2 , 0.06 mA / cm 2 , 0.07 mA / cm 2 , 0.08 mA / cm 20.09 mA / cm 2 0.1 mA / cm 2 but not limited to the values listed, other values within the range are also applicable;

[0101] Experiments show that, in order to make the particle nature of the micro electric field and the particle nature of the inert organic matter fuse in the quantum field, the difference between the high potential and the low potential is kept at 0.1V-2.5V, which is the most optimal. If the voltage is higher than 2.5V, the electrode plate is easy to heat and affect the particle agglomeration. If the current is too large, it is easy to cause the decomposition of the ionic liquid and other losses. If the current is too small, it cannot produce effective reaction effect. The above-mentioned electrode plate spacing is the most suitable distance to realize the application of micro electric field to the organic phase nanoparticles of inert organic matter and adjust the motion state of the extranuclear electrons.

[0102] Further, the catalyst A and B are ionic liquids;

[0103] The catalyst A and B are selected from one or more combinations of pyrrolidine ionic liquid, piperidine ionic liquid, and functionalized ionic liquid. The composition of the catalyst A and B can be the same or different.

[0104] The alkyl group contained in the pyrrolidine ionic liquid includes one or more of ethyl, propyl, butyl, hexyl, and octyl;

[0105] The alkyl group contained in the piperidine ionic liquid includes one or more of ethyl, propyl, butyl, hexyl, and octyl;

[0106] The functional group contained in the functionalized ionic liquid includes one or more of hydroxyl, carboxyl, sulfonic acid group, alkenyl, ether group, ester group, amino group, benzyl group, and nitrile group.

[0107] Further preferably, catalyst A is pyrrolidine ionic liquid + functionalized ionic liquid, wherein the mass ratio of pyrrolidine ionic liquid: functionalized ionic liquid is (0.3-1.5):(0.1-1); catalyst B is piperidine ionic liquid + functionalized ionic liquid; wherein the mass ratio of piperidine ionic liquid: functionalized ionic liquid is (0.5-1.5):1, preferably (0.5-0.8):1.

[0108] Alternatively, catalyst A is pyrrolidine ionic liquid + piperidine ionic liquid, wherein the mass ratio of pyrrolidine ionic liquid: piperidine ionic liquid is (1-2):1; catalyst B is pyrrolidine ionic liquid + piperidine ionic liquid + functionalized ionic liquid; wherein the mass ratio of pyrrolidine ionic liquid: piperidine ionic liquid: functionalized ionic liquid is (0.1-1):(0.1-2):1, preferably (0.3-0.6):(0.6-0.9):1.

[0109] Or, catalyst A = pyrrolidine ionic liquid + piperidine ionic liquid + functional ionic liquid, wherein the mass ratio of pyrrolidine ionic liquid: piperidine ionic liquid: functional ionic liquid is (0.4-0.6):(0.6-0.8):1; catalyst B = pyrrolidine ionic liquid + piperidine ionic liquid + functional ionic liquid; wherein the mass ratio of pyrrolidine ionic liquid: piperidine ionic liquid: functional ionic liquid is (0.1-1):(0.1-2):1, preferably (0.3-0.6):(0.6-0.9):1.

[0110] Or, catalyst A is only one of pyrrolidine ionic liquid, piperidine ionic liquid and functional ionic liquid;

[0111] Catalyst B is only one of pyrrolidine ionic liquid, piperidine ionic liquid and functional ionic liquid.

[0112] The present application is not limited to the above-mentioned combination, and other combinations not listed in the three categories of ionic liquids are also applicable.

[0113] Experiments show that for coal chemical high-salinity wastewater, pyrrolidine ionic liquid and piperidine ionic liquid as catalysts have good thermal stability, chemical stability and electrochemical performance, especially special induction effect, conjugation effect and steric hindrance effect on some organic matter; in addition to excellent electrical conductivity and chemical stability, functional ionic liquid also has "designability" due to its special structure, and the inert organic matter activated by steps (1) and (2) realizes nanoparticle agglomeration, greatly improving the adsorption and separation efficiency of inert organic matter.

[0114] Catalysts A and B are ionic liquids, and the mass ratio of the three types of ionic liquids can be adjusted according to the different components of the inert organic matter in the wastewater. The inert organic matter in the coal chemical high-salinity wastewater described in the present application has a molecular weight of less than 150 Da, and part of the organic matter and molecular weight are as follows.

[0115] Table of part of organic matter and molecular weight

[0116]

[0117] Ionic liquid (Ionic Liquid) is also called room temperature ionic liquid, room temperature molten salt or organic ionic liquid, which is composed of organic cation and inorganic anion.

[0118] Pyrrolidinium ionic liquids have good chemical stability. The cation is N-alkyl-N- methylpyrrolidinium, where the alkyl group includes ethyl, propyl, butyl, hexyl, octyl, etc. The anion includes bromide, hexafluorophosphate, tetrafluoroborate, bis(trifluoromethanesulfonyl)imide, etc. Pyrrolidinium ionic liquids include but are not limited to N- ethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-ethyl-N-methylpyrrolidinium acetate, N-ethyl-N-methylpyrrolidinium dicyanamide, N-propyl-N-methylpyrrolidinium chloride, N-propyl-N-methylpyrrolidinium bromide, N-propyl-N-methylpyrrolidinium iodide, N-propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-propyl-N-methylpyrrolidinium trifluoromethanesulfonate, N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide, N-propyl-N-methylpyrrolidinium acetate, N-butyl-N-methylpyrrolidinium chloride, etc.

[0119] Piperidinium ionic liquids have good chemical stability. The cation is N-alkyl-N- methylpiperidinium, where the alkyl group includes ethyl, propyl, butyl, hexyl, octyl, etc. The anion includes bromide, hexafluorophosphate, tetrafluoroborate, bis(trifluoromethanesulfonyl)imide, etc. Piperidinium ionic liquids include but are not limited to N-ethylpyridinium chloride, N-ethylpyridinium bromide, N-ethylpyridinium trifluoromethanesulfonate, N-butylpyridinium tetrafluoroborate, N-butylpyridinium trifluoromethanesulfonate, N-butylpyridinium acetate, N-ethylpyridinium nitrate, etc.

[0120] Functionalized ionic liquids contain functional groups including hydroxyl, carboxyl, ether, ester, amino, sulfonic acid, alkenyl, benzyl, nitrile, etc. Functionalized ionic liquids include but are not limited to 1-vinyl-3-butylimidazolium tetrafluoroborate, 1-vinyl-3-octylimidazolium bis(trifluoromethanesulfonyl)imide, hydroxyethyltrimethylammonium nitrate, 1-methoxyethyl-3-methylimidazolium hexafluorophosphate, N-methoxyethyl-N-methyl-diethylammonium bis(fluorosulfonyl)imide, 1-propylsulfonic acid-3-butylimidazolium inner salt, 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate, N-propylsulfonic acid pyridine trifluoromethanesulfonate, 1-butyl-3-methylimidazolium chloroferrate (1:1), 1-allyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium tetrafluoroborate, bis(triethylammonium)butane dibromide, 1-allyl-3-methylimidazolium trifluoromethanesulfonate, 1-allyl-3-methylimidazolium dicyanamide, 1-allyl-3-methylimidazolium p-toluenesulfonate, etc.

[0121] Preferably, the mass ratio of the amount of catalyst A to the inert organic matter content in step (1) is (0.1-0.2): 1, for example, it can be 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1 or 0.2:1, and further preferably (0.1-0.15):1, for example, it can be 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1 or 0.15:1; but the present application is not limited to the listed values, and other values not listed in the range are also applicable.

[0122] Preferably, the gas-water volume ratio of the aeration in step (1) is (2-10):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, and further preferably (5-8):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1; but the present application is not limited to the listed values, and other values not listed in the range are also applicable.

[0123] Preferably, the aeration reaction time in step (1) is 15-50 minutes, for example, it can be 15 minutes, 20 minutes, 25 minutes, 30 minutes, 40 minutes, 45 minutes or 50 minutes, and further preferably 20-30 minutes, for example, it can be 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes or 30 minutes; but the present application is not limited to the listed values, and other values not listed in the range are also applicable.

[0124] Preferably, the reaction under the action of the microelectric field and catalyst A in step (1) is continued for 30-90 minutes, for example, it can be 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes or 90 minutes, and further preferably 40-70 minutes, but the present application is not limited to the listed values, and other values not listed in the range are also applicable.

[0125] Preferably, the gas-water volume ratio of the aeration in step (2) is (3-15):1, for example, it can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1, and further preferably (5-10):1, but the present application is not limited to the listed values, and other values not listed in the range are also applicable.

[0126] Preferably, the aeration reaction time of step (2) is 5-30 minutes, for example, it can be 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes, further preferably 10-20 minutes, but the present application is not limited to the listed values, other values not listed within the range are also applicable;

[0127] Preferably, the mass ratio of the catalyst B dosage to the inert organic matter content in step (2) is (0.1-0.2):1, for example, it can be 0.1:1, 0.12:1, 0.14:1, 0.16:1, 0.18:1, 0.19:1 or 0.2:1, further preferably (0.1-0.15):1, but the present application is not limited to the listed values, other values not listed within the range are also applicable;

[0128] Preferably, the reaction under the action of catalyst B in step (2) continues for 30-90 minutes, for example, it can be 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes or 90 minutes, further preferably 30-60 minutes, but the present application is not limited to the listed values, other values not listed within the range are also applicable;

[0129] Preferably, the mass ratio of the hydrogen peroxide dosage to the inert organic matter content in step (2) is (0.1-0.8):1, for example, it can be 0.1:1, 0.2:1, 0.4:1, 0.5:1, 0.6:1 or 0.8:1, further preferably (0.1-0.5):1, but the present application is not limited to the listed values, other values not listed within the range are also applicable; the mass ratio is determined according to the components and content of the inert organic matter, and is in a proportional relationship. The role of hydrogen peroxide in this step is to decompose the hydroxyl radical ·OH and apply ionization energy to the inert organic matter together with the ionic liquid catalyst B, so as to promote the rearrangement reaction of the inert organic matter molecules, so as to achieve the effect of activating the inertness thereof.

[0130] Preferably, the water temperature in steps (1), (2), (3) and (4) is 15-60℃, for example, it can be 15℃, 20℃, 25℃, 30℃, 35℃, 45℃, 55℃ or 60℃, further preferably 25-40℃, but the present application is not limited to the listed values, other values not listed within the range are also applicable;

[0131] Preferably, the dissolution ratio of the PAM flocculant is 0.1%-0.2%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%; but the present application is not limited to the listed values, other values not listed within the range are also applicable;

[0132] Preferably, the mesoporous material filled in the adsorption tank in step (4) is carbon nanomaterial with a pore size of 1-20 nm, a specific surface area of 850-1500 m 2 / g, and a porosity of 75-85%. The reasons for selecting carbon-based mesoporous material are as follows: first, small-scale and pilot tests show that, for coal chemical industry high-salinity wastewater, the modified functional groups of carbon-based mesoporous adsorption material can achieve charge transfer and adsorption with inert organic particles activated in steps (1) and (2), thereby promoting the adsorption and separation of organic matter; second, compared with silicon-based mesoporous material, carbon-based mesoporous material has acid and alkali resistance, weather resistance, high thermal stability and hydrothermal stability, and has a service life of more than 3 years, while silicon-based material is easy to corrode and usually fails in one month. The preparation method of the carbon-based mesoporous material adopted in the present application is based on the published invention patent application “Preparation method and application of ordered mesoporous-microporous carbon composite material”, patent application number: 202310395265.5.

[0133] Preferably, the adsorption separation of COD in step (4) is performed at a flow rate of 0.5-2.5 BV, for example, 0.5 BV, 0.6 BV, 0.7 BV, 0.8 BV, 0.9 BV, 1.0 BV, 1.1 BV, 1.2 BV, 1.3 BV, 1.4 BV, 1.5 BV, 1.6 BV, 1.7 BV, 1.8 BV, 1.9 BV, 2.0 BV, 2.1 BV, 2.2 BV, 2.3 BV, 2.4 BV or 2.5 BV, and further preferably 1-1.5 BV, but the present application is not limited to the listed values, and other values not listed in the range are also applicable.

[0134] Preferably, the pure water used for regenerating and cleaning the mesoporous material in step (4) has a temperature of 20-60℃, for example, 20℃, 25℃, 30℃, 35℃, 45℃, 55℃ or 60℃, and further preferably 25-45℃, but is not limited to the listed values, and other values not listed in the range are also applicable; small-scale and pilot tests show that, if the water temperature is lower than 20℃, the regeneration and cleaning is not complete, because low temperature causes the pores to shrink, and if the water temperature is higher than 60℃, the pores expand too much, and frequent shrinkage and expansion of the pores every day can easily reduce the mechanical strength and chemical stability of the adsorption material.

[0135] Compared with the prior art, the present application has the following advantages:

[0136] (1) The process flow of the present application is short, the reaction temperature is low, and the required reagents are widely available, especially the catalysts A and B are room temperature ionic liquids, which have good thermal stability and chemical stability, are easy to separate from other substances, and can be recycled; the mesoporous material used for adsorption and separation is carbon nanomaterial, which is resistant to acid and alkali, has a small pore size and a high specific surface area, has a high adsorption efficiency for inert organic matter, and can be quickly desorbed and reused.

[0137] (2) The method provided by the application can remove 90% of inert organic matter in coal chemical high-salinity wastewater, and the treated high-salinity water has high purity, and can be further used to prepare sodium bicarbonate, and the purity of the soda ash product meets the requirements of industrial sodium bicarbonate III in GB / T 16062008; the purity of the byproduct ammonium chloride meets the requirements of agricultural ammonium chloride in GB / T 2946 2018; the purity of the byproduct ammonium sulfate meets the requirements of product standard I in GB535-2020, and the high-value comprehensive utilization of byproduct salt in high-salinity wastewater is realized.

[0138] (3) Compared with the traditional ozone oxidation method, activated carbon adsorption method and macroporous adsorption resin separation method, the method provided by the application adopts a mild treatment method, operates at normal temperature and pressure and has low power consumption, for example, does not need a high-temperature / high-energy consumption carbonization activated carbon regeneration process, greatly shortens the process flow, saves a large number of special equipment and is easy to operate.

[0139] (4) The addition of quicklime in the coagulation and sedimentation link of the secondary reactor can remove fluorine ions in the coal chemical high-salinity wastewater; the addition of magnesium chloride can remove silicon in the coal chemical high-salinity wastewater; one machine can be used for multiple purposes, and investment is saved.

[0140] Example 3

[0141] As shown in Figure 3 , a coal chemical high-salinity wastewater inert organic matter removal system, the system is used to realize the method as described in example 1 or 2, the system comprises:

[0142] The primary reaction unit: the micro-electric field reaction unit comprises a primary reaction adjustment tank, a micro-electric field reaction tank and a first clear water tank.

[0143] The secondary reaction unit: the secondary reaction unit comprises a secondary reaction adjustment tank, a secondary reaction tank, a coagulation and sedimentation adjustment tank, a sedimentation tank and a second clear water tank.

[0144] The mesoporous molecular sieve unit: the mesoporous molecular sieve unit comprises a multi-medium filter, a storage tank, a mesoporous molecular sieve system and a storage tank.

[0145] The present invention relates to a coal chemical high-salt wastewater inert organic matter removal system, comprising a primary reaction unit, a secondary unit, and a mesoporous molecular sieve unit. In the primary reaction unit, a micro-electric field combined with nanocatalysis is used to activate the activity of small-molecule inert COD, applying a micro-electric field to the organic phase nanoparticles to adjust the movement state of their outer electrons. Next, the high-salt wastewater treated in the primary reaction unit is input into the secondary reaction unit, where a catalyst further applies ionization energy to the electron cloud of the inert organic matter, causing a change in bond energy within the independent microscopic system, resulting in a metastable state and thus enabling separation. After these two stages of catalytic reaction, the inertness of the organic matter is activated, meaning the organic phase particles in the high-salt wastewater are adjusted from the ground state to an excited state. Finally, the high-salt wastewater is pumped into the mesoporous molecular sieve system, where mesoporous adsorption separation technology is used to separate small-molecule (molecular diameter <1 nm) inert organic matter in the water. This ensures effective removal of inert organic matter and guarantees that the organic matter content in the obtained high-salt wastewater meets standards, allowing for further resource utilization.

[0146] Example 4

[0147] like Figure 3 As shown, based on Example 3, further: in the first-stage reaction unit, high-salt wastewater is pumped into the first-stage reaction conditioning tank for conditioning, and then enters the micro-electric field reaction tank for aeration reaction. Catalyst A is then added, and under the action of the micro-electric field and catalyst A, the reaction continues for 30 to 90 minutes. Then, it is pumped into the first clear water tank for natural sedimentation, and the supernatant is used as the wastewater after treatment in the first-stage reaction unit.

[0148] In the secondary reaction unit, the wastewater treated by the primary reaction unit is regulated in the secondary reaction regulating tank and then enters the secondary reaction tank. An appropriate amount of hydrogen peroxide is added for aeration, and then catalyst B is added. Under the action of catalyst B, the reaction continues for 30 to 90 minutes. Then, it is pumped into the coagulation sedimentation regulating tank for regulation. Flocculant is added until the reaction is complete, and then it is pumped into the sedimentation tank. After sedimentation, it overflows into the second clear water tank. The supernatant in the second clear water tank is used as the wastewater treated by the secondary reaction unit.

[0149] In the mesoporous molecular sieve unit, the wastewater treated by the secondary reaction unit is fed into a multi-media filter for filtration. The filtered wastewater is then fed into the storage tank of the mesoporous molecular sieve unit for adjustment, and then pumped into the mesoporous molecular sieve system. After adsorption and separation by the mesoporous molecular sieve system, the effluent is discharged into the storage tank.

[0150] The catalysts A and B are the same as those in Example 1 or 2; the micro-electric field is the same as that in Example 1 or 2; the mesoporous molecular sieve system is the same as that in Example 1 or 2; the reaction conditions and time are the same as those in Example 1 or 2.

[0151] In the first clear water tank, a water pump is arranged to return the sludge to the micro electric field reaction tank, so as to realize the reuse of the catalyst A, thereby saving the cost; a slag remover is arranged to remove the foam generated in the reaction tank. In the first reactor and the second reactor, a medicine barrel is arranged to store and pump the catalyst A, B and flocculating agent into the reaction tank.

[0152] The multi-medium filter is a process for effectively removing suspended impurities to clarify water by passing water with high turbidity through a certain thickness of granular or non-granular material under a certain pressure by using two or more filtering media; the multi-medium filter material in the filter is uniformly granular gravel, quartz sand, magnetite, anthracite and the like; these filter materials are scientifically and orderly arranged in the filter tank according to their specific gravity and particle size.

[0153] Example 5

[0154] Experimental Example 1

[0155] (1) The high-salt wastewater is pumped into the adjusting tank, the water temperature is adjusted to 25 DEG C, and after the pH is 3, the wastewater enters the micro electric field reaction tank; the electrode plate of the micro electric field is made of titanium ruthenium iridium alloy material and iron and aluminum material, the ratio of effective electrode area is titanium ruthenium iridium: iron: aluminum = 8: 1: 1, direct current is used, the input voltage is 0.3V, and the current density is 0.03mA / cm 2, aeration reaction for 50 minutes, aeration amount is 3:1, adding catalyst A, mass ratio of catalyst A dosage and inert organic matter content is 0.1:1; under the action of micro electric field and catalyst A, continue to react for 70 minutes, then pump into clean water pool, natural sedimentation, bottom mud backflow to micro electric field reaction pool, supernatant pump into secondary reactor adjusting pool. Coal chemical high-salinity wastewater is input to the primary reactor, micro electric field + nano catalysis technology is adopted, the activity of small molecule inert COD is excited, a micro electric field is applied to the organic phase nanoparticles, under the influence of catalyst A and aeration disturbance, certain groups in the inert molecules are transferred, or the carbon atom skeleton is deviated, so that the motion state of the extranuclear electron is adjusted. Catalyst A is pyrrolidine ionic liquid, catalyst A is 2-ethyl-2-methyl pyrrolidine acetate; (2) after adjusting water temperature to 25 DEG C and PH to 3 in the secondary reactor adjusting pool, wastewater enters the reaction pool, adding appropriate amount of hydrogen peroxide, mass ratio of hydrogen peroxide dosage and inert organic matter content is 0.3:1, aeration reaction for 30 minutes, aeration amount is 3:1; adding catalyst B, mass ratio of catalyst B dosage and inert organic matter content is 0.11:1; under the action of catalyst B, continue to react for 60 minutes, then pump into coagulation sedimentation adjusting pool. High-salinity wastewater is input to the secondary reactor, catalyst B is further used to apply ionization energy to the electron cloud of inert organic matter, under the influence of acid condition and aeration, hydroxyl radical ·OH decomposed from hydrogen peroxide and ionic liquid catalyst B simultaneously apply external electric field to inert organic matter to cause dynamic induction effect and super conjugation effect, so that the bond energy of COD changes in independent microcosmic system and is in metastable state, so as to have separation conditions. Catalyst B is piperidine ionic liquid, catalyst B is 1-butyl-3-methyl piperidine chlorate.

[0156] (3) in the coagulation sedimentation adjusting pool, adjusting water temperature to 25 DEG C and pH to 8.0, adding appropriate PAM flocculant according to the situation, PAM is anionic, molecular weight is 10-20 million, dissolving ratio is 0.1%, after dropping PAM and fully reacting for 40 minutes, pump into the sedimentation pool, sedimentation time is 2 hours, overflow to the clean water pool; after clean water input into the multi-medium filter and filtering, enter the storage pool of mesoporous molecular sieve unit, the multi-medium filter is backwashed once every 12 hours. PAM polyacrylamide plays the role of flocculant in the sewage treatment process, is a conventional reagent, and is very common. PAM makes colloidal particles, suspended particles, heavy metal ions and the like in water coagulate on its surface and precipitate, so as to clean the water body.

[0157] (4) In the storage pool of mesoporous molecular sieve unit, adjust the water temperature to 25℃, the pH to neutral (pH = 7.0), and pump the high-salinity wastewater into the mesoporous molecular sieve system. Each group of the mesoporous molecular sieve system is composed of 3 adsorption tanks connected in series, in which the adsorption tanks are distributed in four levels in series, and the mesoporous material is filled in the adsorption tanks in a fixed bed mode. The adsorption separation of COD is carried out at a flow rate of 0.7 BV, and the effluent is discharged into the storage tank. The mesoporous adsorption material is regenerated once every 12 hours, and then desorbed and regenerated by using 3% dilute lye, and then cleaned to neutral by using pure water at a flow rate of 1 BV. The water temperature of the pure water is 35℃.

[0158] Experimental Example 2:

[0159] (1) Pump the high-salinity wastewater into the adjusting pool, and then into the micro-electric field reaction pool after adjusting the water temperature to 32℃ and the pH to 4. The micro-electric field is composed of diamond, iron and aluminum materials, and the ratio of the effective electrode area is diamond: iron: aluminum = 7:2:1. A direct current is used, the input voltage is 0.8V, and the current density is 0.05 mA / cm 2 . The aeration reaction is carried out for 18 minutes, the aeration amount is 8:1, the catalyst A is added, and the mass ratio of the catalyst A dosage to the inert organic matter content is 0.2:1. Under the action of the micro-electric field and the catalyst A, the reaction is continued for 30 minutes, and then the wastewater is pumped into the clean water pool for natural sedimentation. The sludge is backflowed to the micro-electric field reaction pool, and the supernatant is pumped into the secondary reactor adjusting pool. The catalyst A is pyrrolidine ionic liquid + functional ionic liquid, which is 1-propyl-2-methyl pyrrolidine acetate + hydroxyethyl trimethyl ammonium chloride, and the mass ratio of the two is 0.35:1.

[0160] (2) In the secondary reactor adjusting pool, adjust the water temperature to 40℃ and the pH to 4, and then pump the wastewater into the reaction pool. An appropriate amount of hydrogen peroxide is added, the mass ratio of the hydrogen peroxide dosage to the inert organic matter content is 0.7:1, the aeration reaction is carried out for 10 minutes, the aeration amount is 10:1, the catalyst B is added, and the mass ratio of the catalyst B dosage to the inert organic matter content is 0.2:1. Under the action of the catalyst B, the reaction is continued for 30 minutes, and then the wastewater is pumped into the coagulation and sedimentation adjusting pool. The catalyst B is pyrrolidine ionic liquid + piperidine ionic liquid + functional ionic liquid, which is 1-butyl-2-methyl pyrrolidine acetate + 3-ethyl-1-methyl piperidine chloride + 1-vinyl-3-butyl imidazole trifluoromethane sulfonate, and the mass ratio of the three is 0.45:0.8:1.

[0161] (3) In the coagulation sedimentation adjustment tank, the water temperature is adjusted to 40°C and the pH is adjusted to 8.5, and an appropriate amount of PAM flocculant is added as needed. The PAM is anionic, with a molecular weight of 10-20 million, and a dissolution ratio of 0.2%. After the PAM is added dropwise and fully reacted for 20 minutes, it is pumped into the sedimentation tank, with a sedimentation time of 2 hours, and then overflowed into the clear water tank. The clear water is filtered by a multi-medium filter and then enters the storage tank of the mesoporous molecular sieve unit. The multi-medium filter is backwashed once every 24 hours.

[0162] (4) In the storage tank of the mesoporous molecular sieve unit, the water temperature is adjusted to 40°C and the pH is adjusted to neutral. The high-salinity wastewater is pumped into the mesoporous molecular sieve system. Each group of mesoporous molecular sieve system consists of 5 adsorption tanks connected in series. The adsorption tanks are divided into three levels in series, and the mesoporous material is loaded in a fixed bed manner in the adsorption tanks. The adsorption separation of COD is carried out at a flow rate of 2BV, and the effluent is discharged into the storage tank. The mesoporous adsorption material is regenerated once every 24 hours, using 5% dilute alkali solution for desorption regeneration, and then washed with pure water at a flow rate of 2BV until neutral. The water temperature of the pure water is 40°C.

[0163] Experimental Example 3:

[0164] (1) The high-salinity wastewater is pumped into the adjustment tank, and after the water temperature is adjusted to 55°C and the pH is adjusted to 5, the wastewater enters the micro-electric field reaction tank. The micro-electric field electrode plate is made of graphite material and iron, aluminum material, and the effective electrode area ratio is diamond: iron: aluminum = 6:2:2. An alternating current is used, with an input voltage of 2V and a current density of 0.1 mA / cm 2 , aeration reaction for 15 minutes, aeration amount is 10:1, adding catalyst A, the mass ratio of catalyst A dosage to inert organic matter content is 0.15:1; under the action of micro-electric field and catalyst A, continue to react for 50 minutes, then pump into the clear water tank, natural sedimentation, bottom mud backflow to the micro-electric field reaction tank, supernatant pump into the secondary reactor adjustment tank. Catalyst A is pyrrolidine ionic liquid + functional ionic liquid, 2-butyl 3-methyl pyrrolidine nitrate + 1-propyl sulfonic acid pyridine trifluoromethanesulfonate, wherein the mass ratio of the two is 1.2:1;

[0165] (2) In the secondary reactor adjustment tank, after adjusting the water temperature to 55°C and the pH to 6, the wastewater enters the reaction tank, and an appropriate amount of hydrogen peroxide is added. The mass ratio of hydrogen peroxide dosage to inert organic matter content is 0.8:1. Aeration reaction for 6 minutes, aeration amount is 15:1, adding catalyst B, the mass ratio of catalyst B dosage to inert organic matter content is 0.15:1; under the action of catalyst B, continue to react for 40 minutes, then pump into the coagulation sedimentation adjustment tank. Catalyst B is piperidine ionic liquid plus functional ionic liquid; catalyst B is 1-butyl-2-methyl piperidine trifluoromethanesulfonate + 2-butyl sulfonic acid pyridine trifluoromethanesulfonate, wherein the mass ratio of the two is 0.6:1;

[0166] (3) In the coagulation sedimentation conditioning tank, the water temperature is adjusted to 55℃, the pH is 8.3, and an appropriate amount of PAM flocculant is added as needed. The PAM is anionic, with a molecular weight of 10-20 million, and a dissolution ratio of 0.15%. After adding PAM and fully reacting for 30 minutes, the water is pumped into the sedimentation tank, with a sedimentation time of 2 hours, and then overflowed into the clean water tank. The clean water is filtered by a multi-medium filter and then enters the storage tank of the mesoporous molecular sieve unit. The multi-medium filter is backwashed once every 20 hours.

[0167] (4) In the storage tank of the mesoporous molecular sieve unit, the water temperature is adjusted to 55℃, and the pH is neutral. The high-salt wastewater is pumped into the mesoporous molecular sieve system. Each group of mesoporous molecular sieve system consists of 4 adsorption tanks connected in series. The adsorption tanks are divided into two levels in series, and the mesoporous material is loaded in a fixed bed in the adsorption tank. The adsorption separation of COD is carried out at a flow rate of 1 BV. The effluent is discharged into the storage tank. The mesoporous adsorption material is regenerated once every 20 hours, using 4% dilute alkali solution for desorption regeneration, and then washed with pure water at a flow rate of 1.5 BV until neutral. The water temperature of the pure water is 55℃.

[0168] Experimental Example 4:

[0169] On the basis of Example 2, other conditions remain unchanged, and the catalyst A is a pyrrolidine ionic liquid + piperidine ionic liquid + functional ionic liquid, specifically: 1-pentyl-2-methyl pyrrolidine bis(trifluoromethanesulfonyl) imide salt + 1-propyl-3-methyl piperidine hexafluorophosphate + 1-butyl sulfonic acid-3-ethyl imidazole trifluoromethanesulfonate, wherein the mass ratio of the three is 0.5:0.75:1.

[0170] The catalyst B is a pyrrolidine ionic liquid + piperidine ionic liquid + functional ionic liquid, specifically: 1-propyl-2-methyl pyrrolidine acetate + 3-ethyl pyridine chloride + 1-propyl sulfonic acid-3-butyl imidazole inner salt, wherein the mass ratio of the three is 0.7:0.8:1.

[0171] Experimental Example 5:

[0172] On the basis of Example 3, other conditions remain unchanged, and the catalyst A is a pyrrolidine ionic liquid + functional ionic liquid, specifically: 2-ethyl-3-methyl pyrrolidine acetate + hydroxyethyl trimethyl ammonium nitrate, wherein the mass ratio of the two is 1:0.35.

[0173] The catalyst B is a piperidine ionic liquid + functional ionic liquid; specifically: 3-butyl pyridine tetrafluoroborate + 1-methoxyethyl-3-methyl imidazole hexafluorophosphate, wherein the mass ratio of the two is 0.55:1.

[0174] Comparative Example 1:

[0175] The process flow of ozone oxidation method for removing inert COD mainly includes dosing and mixing, reaction, precipitation, and discharge steps. The process is also called ozone oxidation treatment process or ozone catalytic oxidation method. It is a commonly used radial flow process, which is a method for removing organic matter in wastewater COD by ozone catalytic oxidation. The specific process flow is as follows:

[0176] (1) Dosing and mixing wastewater

[0177] After the ozone gas is mixed with the wastewater, it enters the mixing tank. In the mixing tank, the ozone gas reacts with the organic matter in the wastewater. The reaction produces oxides, particulates, etc., which exist in the wastewater in the form of dissolution or suspension and flow into the reactor with the mixture.

[0178] (2) Reaction

[0179] After the mixture in the mixing tank is left and mixed for a period of time, it enters the reaction tank. The reaction tank is equipped with UV lamps, which function to induce the conversion of oxygen molecules to ozone molecules. Under UV light irradiation, ozone molecules are further decomposed into free radicals of high oxidation state. In the reactor, free radicals react with organic pollutants to form corresponding oxidation products. At the same time, oxygen may need to be added to the reactor to meet the amount of oxidation required for the reaction.

[0180] (3) Precipitation

[0181] As a result of the reaction, particulates, suspended solids, etc. are produced, so after the reaction is completed, the mixture must be allowed to settle and precipitate.

[0182] (4) Discharge of clean water

[0183] After treatment and precipitation, the COD concentration in the wastewater is reduced. Therefore, the clean water can be discharged into the wastewater plant, river, or reused.

[0184] Because the inert organic molecules in coal chemical high-salinity wastewater have very small molecular weights, mainly carbon-hydrogen bonds (C-H bonds), the difference in electronegativity of this covalent single bond is very small (the difference in electronegativity is 0.35), so it is particularly stable, and the free radicals produced by ozone have very limited effect on it. Using this process flow, the inert COD in the wastewater can be reduced in a small range, but it cannot achieve the desired purpose. Most of the domestic coal chemical high-salinity wastewater treatment projects use ozone oxidation method to remove inert COD, and the removal rate is often less than 30%, which can be seen from the miscellaneous salt (hazardous waste) produced by coal chemical enterprises every year.

[0185] Comparative Example 2:

[0186] Activated carbon treatment of wastewater is a common water treatment method, and in the field of removal of inert organic matter in coal chemical high-salinity wastewater, the process flow mainly includes pretreatment, adsorption, depth filtration, and regeneration steps.

[0187] (1) Pretreatment, mainly to remove impurities and particles in wastewater, which is usually achieved by physical or chemical methods, such as sedimentation, clarification and filtration, etc.

[0188] (2) Adsorption, inert organic matter in wastewater is adsorbed onto the surface of activated carbon, which has small pore size and large surface area, and the operation is simple. The operation parameters such as solution pH, reaction time and activated carbon dosage need to be adjusted to achieve the best effect.

[0189] (3) Depth filtration, suspended solids and solid particles formed during the adsorption process need to be further removed, which can be achieved by multi-layer filter or filter.

[0190] (4) Regeneration, there are many methods for activated carbon regeneration, including heating regeneration, biological regeneration, wet oxidation, electrochemical regeneration, CWAO method, etc. Heating regeneration is the most widely used and mature method in industry. However, the carbonization temperature is as high as 800-900℃, and the investment and operating cost is high.

[0191] The activated carbon method is basically used to remove inert COD in high-salinity wastewater treatment projects in domestic coal chemical industry. Activated carbon adsorption mainly relies on hydrophobic force and intermolecular force, but both of these two forces are extremely limited on inert COD particles in coal chemical wastewater, resulting in low adsorption rate (often less than 30%). This can be seen from the miscellaneous salt (hazardous waste) produced by coal chemical enterprises every year.

[0192] Comparative Example 3:

[0193] Adsorption resin is widely used in industrial wastewater treatment industry, which is mainly aimed at the deep purification of wastewater, and has the advantages of high adsorption efficiency of conventional COD and rapid desorption. The adsorption principle of adsorption resin is similar to that of activated carbon, which is usually related to van der Waals force or hydrogen bond, and the operation steps are as follows.

[0194] (1) Pretreatment, the pretreatment process is ethanol soaking → washing with ethanol until the effluent is not turbid → washing with water until there is no alcohol smell → passing 5% hydrochloric acid through the resin column and soaking → washing with water until neutral → passing 2% alkali through the resin column and soaking → washing with water until neutral, ready for use.

[0195] (2) Column loading, 1 / 3 volume of water is injected into the column, and the pretreated adsorption resin is loaded into the column from the top of the adsorption column.

[0196] (3) Adsorption, open the relevant valves, for example, three columns in series, usually the first column and the second column are used in series, and the flow rate is controlled at 1-2 BV.

[0197] (4) Desorption, when the first column is saturated, open or close the relevant valve, desorb the first column, and then continue to use the second column and the third column in series, and so on.

[0198] Some domestic coal chemical industry high-salinity wastewater treatment projects use macroporous adsorption resin separation method to remove inert COD. Macroporous adsorption resin separation method is dependent on van der Waals force or the result of hydrogen bond, also known as molecular force, which is much weaker than chemical bond, so the effect of adsorption separation on inert COD acting by chemical bond is very limited (removal rate < 40%), which can be seen from the coal chemical industry enterprises producing miscellaneous salt (hazardous waste) every year.

[0199] Table 1 Comparison of inert organic matter removal effect

[0200] Number COD removal rate Experimental Example 1 91.6％ Experimental Example 2 90％ Experimental Example 3 94.2％ Experimental Example 4 93％ Experimental Example 5 91.3％ Comparative Example 1 ＜30％ Comparative Example 2 ＜30％ Comparative Example 3 None

[0201] As shown in Table 2, compared with the traditional method for removing inert organic matter, the method provided by the present application uses innovative process to treat coal chemical industry high-salinity wastewater, greatly shortens the process flow, saves a large number of special equipment, is simple to operate, is a skid-mounted device, and has low energy consumption. In addition, the removal efficiency of inert organic matter by the method provided by the present application can reach 90%, compared with the method used in the related art, the method and system of the present application greatly improve the removal efficiency of inert organic matter, have very significant progress, and also promote the separation and adsorption effect of mesoporous material on inert organic matter, the high-salinity water after treatment has high purity, is further used for preparing sodium bicarbonate, the purity of the obtained soda product meets the requirements of industrial sodium bicarbonate type III in GB / T 1606-2008, the purity of the byproduct ammonium chloride meets the requirements of agricultural ammonium chloride in GB / T 2946-2018, and the purity of the byproduct ammonium sulfate meets the requirements of fertilizer grade GB535-2020 type I product standard, realizing high-value utilization of high-salinity wastewater byproduct salt comprehensive utilization.

[0202] At present, the by-product salt produced by the treatment of high-salinity wastewater in the coal chemical industry in China is mainly sodium sulfate and sodium chloride, totaling 2-3 million tons / year, which should be resourceized according to the environmental protection policy. However, the organic pollution causes the by-product salt to be defined as hazardous waste, and the disposal fee of 3000 yuan / ton will bring a heavy economic burden to the enterprise. Therefore, it is necessary to keep pace with the times, innovate in science and technology, and turn waste into treasure by using the process combination of "mesoporous separation technology + chemical method for soda production technology". After the efficient removal of organic matter by mesoporous separation, the pure high-salinity water is added with ammonium bicarbonate for a double decomposition reaction, sodium bicarbonate is prepared by one-step method, sodium carbonate is obtained by calcining sodium bicarbonate, and by-product ammonium sulfate / ammonium chloride is obtained, so that the high-value utilization of by-product salt is realized. The existing demonstration project shows that the innovative process combination realizes the mode change of the environmental protection project from traditional "paying money" to "earning money", and creates excellent economic and social benefits from the perspectives of environmental protection, economy and business.

[0203] Soda (sodium bicarbonate, sodium carbonate), also known as the mother of industry, is an important inorganic chemical raw material, which is mainly used for the production of flat glass, glass products and ceramic glaze, and is also widely used for life washing, acid neutralization and food processing, etc. In the past three years, the average market price of soda in China is 1800-2300 yuan / ton, and the annual output is about 30 million tons. The high-salinity wastewater treated by the present application has high purity and can be used for preparing sodium bicarbonate and sodium carbonate to obtain products meeting the industrial purity standard.

[0204] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

[0205] In the embodiments of the present application, the method and system of the present application can be used for the removal of inert organic matter in coal chemical high-salinity wastewater, and it can be understood that the method and system are not limited to the above-mentioned applications, and can be used in all application scenarios suitable for the treatment of inert organic matter according to the inventive concept of the present application.

[0206] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A method for removing inert organic matter from coal chemical high-salinity wastewater, characterized in that, The method comprises the following steps: (1) high-salinity wastewater is pumped into a first-stage reaction conditioning tank, the water temperature is adjusted to 15-60 DEG C, the pH is adjusted to 3-6, and the wastewater is then introduced into a micro-electric field reaction tank, aerated for 15-50 minutes, the gas-water volume ratio of the aeration being (2-10):1, catalyst A is then added, the mass ratio of the amount of catalyst A added to the content of inert organic matter being (0.1-0.2):1, the reaction is continued for 30-90 minutes under the action of the micro-electric field and catalyst A, the micro-electric field uses direct current or alternating current, the input voltage being 0.1-2.5 V, the input current being 0.01-1 A, the electrode current density being 0.01-0.1 mA / cm2, the electrode spacing being 5-25 cm, the supernatant in the first-stage reaction conditioning tank is then pumped into a first-stage clean water tank for natural sedimentation, and the supernatant in the first-stage clean water tank is used as treated wastewater 2 ; (2) Pump the wastewater treated in step (1) into a secondary reaction conditioning tank, adjust the water temperature to 15-60℃ and the pH to 3-6, and then into a secondary reaction tank, add hydrogen peroxide, the mass ratio of the hydrogen peroxide dosage to the inert organic matter content is (0.1-0.8):1, carry out aeration reaction for 5-30 minutes, the gas-water volume ratio of aeration is (3-15):1, then add catalyst B, the mass ratio of the catalyst B dosage to the inert organic matter content is (0.1-0.2):1, continue to react for 30-90 minutes under the action of catalyst B, and then pump into a coagulation and sedimentation conditioning tank; (3) Adjust the water temperature to 15-60℃ and the pH to 8-8.5 in the coagulation and sedimentation conditioning tank for the wastewater treated in step (2), add PAM flocculant, the dissolution ratio of the PAM flocculant is 0.1%-0.2%, pump into a sedimentation tank after sufficient reaction for 20-40 minutes, and sediment for 2 hours, then overflow to a second clean water tank, and take the supernatant in the second clean water tank as treated wastewater; (4) Input the wastewater treated in step (3) into a multi-medium filter for filtration, adjust the water temperature to 15-60℃ and the pH to neutral in a storage tank for the filtered wastewater, pump into a mesoporous molecular sieve system, each group of the mesoporous molecular sieve system is composed of 3-5 mesoporous molecular sieve adsorption tanks connected in series, and inert organic matter is separated and adsorbed at a flow rate of 0.5-2.5 BV, and the effluent from the mesoporous molecular sieve system is discharged into a storage tank; The catalyst A and the catalyst B are ionic liquids; the catalyst A and the catalyst B are selected from one or more combinations of pyrrolidine ionic liquids, piperidine ionic liquids and functionalized ionic liquids.

2. The method of claim 1, wherein: in step (1), the bottom mud is backflowed to the micro-electric field reaction tank after natural sedimentation in the first clean water tank.

3. The method of claim 1, wherein: the micro-electric field uses one or more of iron electrode plates, aluminum electrode plates, graphite electrode plates, diamond electrode plates and titanium-ruthenium-iridium alloy electrode plates; and / or, the micro-electric field uses a combination of the following electrode plate materials: containing aluminum and / or iron; and containing at least one of graphite, diamond and titanium-ruthenium-iridium alloy; wherein the aluminum electrode area accounts for 10%-20% of the total electrode area, and the iron electrode area accounts for 10%-20% of the total electrode area.

4. The method of claim 1, wherein: the pyrrolidine ionic liquid contains one or more of ethyl, propyl, butyl, hexyl and octyl; the piperidine ionic liquid contains one or more of ethyl, propyl, butyl, hexyl and octyl; the functionalized ionic liquid contains one or more of hydroxyl, carboxyl, sulfonic acid group, alkenyl, ether group, ester group, amino group, benzyl group and nitrile group.

5. A coal chemical high-salinity wastewater inert organic matter removal system, applying the coal chemical high-salinity wastewater inert organic matter removal method of any one of claims 1-4, characterized in that: The system comprises: a primary reaction unit, which comprises a primary reaction conditioning tank, a micro-electric field reaction tank and a first clean water tank; Secondary reaction unit: the secondary reaction unit comprises a secondary reaction adjusting tank, a secondary reaction tank, a coagulation sedimentation adjusting tank, a sedimentation tank and a second clear water tank; Mesoporous molecular sieve unit: the mesoporous molecular sieve unit comprises a multi-medium filter, a storage tank, a mesoporous molecular sieve system and a storage tank.

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