A novel coal chemical wastewater treatment method

Abstract

The present application relates to the technical field of water treatment, and discloses a novel coal chemical industry wastewater treatment method. The method adopts physical and chemical pretreatment, oxidation deep treatment and ultrafiltration, etc., which can solve the pain points of high toxicity and difficult degradation of coal chemical industry wastewater, guarantee the final effluent to meet the standard stably, and balance the treatment efficiency and system impact resistance. The oxidation deep treatment adopts a novel rare earth MOFs loaded Janus catalyst, the catalyst can efficiently activate ozone to generate ·OH by virtue of the multiple active sites of the bimetal, the Janus structure realizes catalysis and salt resistance, the COD removal rate of the coal chemical industry wastewater can reach more than 80%, the colority is significantly reduced, and the catalyst is resistant to salting-out and corrosion, and has excellent cycle stability, which solves the problems of low activity, uneven loading and poor salt resistance of the traditional catalyst; the ultrafiltration removes the small impurities in the deep treatment water body, and further improves the water quality, so that the water meets the discharge standard or is reused.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a novel method for treating coal chemical wastewater. Background Technology

[0002] Coal chemical wastewater is a highly challenging industrial wastewater generated during the production process of coal chemical industries (such as coal-to-oil, coal-to-olefins, and coal-to-methanol). It is characterized by high pollutant concentrations, complex compositions, and strong toxicity, making it a key and difficult area in the field of industrial wastewater treatment.

[0003] With the upgrading of environmental standards, coal chemical wastewater treatment technology is also constantly being innovated. Early methods primarily focused on physicochemical pretreatment to reduce pollutant concentration and toxicity, employing extraction to remove phenols combined with chemical precipitation to soften the water. However, this only removed easily treatable pollutants, failing to achieve discharge or recycling standards. To further reduce the content of toxic pollutants in coal chemical wastewater, toxic-resistant microorganisms were used to degrade biodegradable organic matter, combined with physicochemical pretreatment. However, recalcitrant organic matter, such as polycyclic aromatic hydrocarbons (PAHs), could not be decomposed by microorganisms, and the wastewater still could not meet discharge and recycling standards. With the continuous development of the coal chemical industry, the treatment process for coal chemical wastewater has further iterated. Building upon the combination of pretreatment and biochemical treatment, advanced treatment units have been added, employing advanced oxidation, adsorption, and membrane separation technologies to further reduce the pollutant content in the wastewater and recover resources such as phenols and ammonia, ultimately achieving the dual goals of compliant discharge and resource recovery.

[0004] Chinese patent application CN101560045A discloses a coal chemical wastewater treatment process. This invention employs an air flotation device for pretreatment of the wastewater, uses Fenton's reagent for oxidation, and then the treated wastewater enters an activated sludge aeration tank for further treatment with activated carbon powder. Finally, it is separated by ultrafiltration to obtain reclaimed water, which is then subjected to reverse osmosis through a selective semi-permeable membrane and finally evaporated for crystallization. While Fenton's reagent effectively breaks down some recalcitrant organic matter, its reaction mechanism and the characteristics of coal chemical wastewater limit its effectiveness. The Fenton reaction requires strongly acidic conditions, but the pH of raw coal chemical wastewater is often between 6 and 9, necessitating the addition of large amounts of acid to adjust the pH. After the reaction, alkali is added for neutralization. Furthermore, after the Fenton reaction, Fe... 2+ Oxidized to Fe 3+ Fe during neutralization 3+ Will react with OH - Fe(OH)3 flocs are generated, which simultaneously adsorb suspended solids, colloids and some organic matter in the wastewater, forming a large amount of iron-containing chemical sludge. The sludge contains heavy metals, and if not treated properly, it may cause secondary pollution. Summary of the Invention

[0005] This invention aims to provide a novel method for treating coal chemical wastewater. This method combines physicochemical pretreatment such as filtration and softening with advanced ozone catalytic oxidation and ultrafiltration. The oxidation stage employs a novel rare-earth MOFs (Rare Earth Metal-Organic Frameworks) supported Janus catalyst (an asymmetric amphiphilic catalyst). The entire process addresses the challenges of highly toxic and difficult-to-degrade coal chemical wastewater while ensuring stable effluent compliance, simultaneously balancing treatment efficiency and system resilience. Filtration first removes interfering impurities such as suspended solids, coal dust, and colloidal particles from the wastewater, preventing them from clogging the catalyst channels or ultrafiltration membrane components of the ozone catalytic oxidation process and reducing the load on subsequent processes. Softening removes Ca... 2+ Mg 2+ These measures prevent high-hardness ions from forming scale on the inner wall of the ozone generator or forming inorganic pollutants on the surface of the ultrafiltration membrane, thus extending the service life of the catalyst and membrane. The rare earth MOFs-supported Janus nanoparticle catalyst is composed of multiple metal elements, has a stable and simple crystal phase structure, and possesses excellent corrosion resistance. It can better resist the erosion caused by complex components in high-salt wastewater and high-temperature and high-pressure process conditions, thereby delaying the catalyst deactivation process. Finally, the wastewater is filtered through the ultrafiltration membrane to obtain water that meets the discharge and reuse standards.

[0006] To achieve the above objectives, the present invention provides a novel method for treating coal chemical wastewater, comprising:

[0007] S1. Wastewater is filtered in a multi-media filter, and the filtered wastewater enters a softening tank for softening.

[0008] S2. The softened wastewater enters the flocculation tank, flocculant is added, the reaction occurs, and the filtered wastewater enters the deep oxidation tank.

[0009] S3. The wastewater in the deep oxidation tank is adjusted to pH 6-7.5, a catalyst is added, ozone is introduced, and the reaction is carried out to obtain deeply treated wastewater.

[0010] S4. Deeply treated wastewater is separated through an ultrafiltration membrane to obtain water that meets discharge standards.

[0011] Preferably, in step S1, the multi-media filter is filled with three filter layers, with particle sizes decreasing from top to bottom: the upper layer is anthracite with a particle size of 0.8~1.6mm, the middle layer is quartz sand with a particle size of 0.5~0.8mm, and the lower layer is refined garnet with a particle size of 0.3~0.5mm.

[0012] Preferably, in step S1, the filtration speed of the multi-media filter is 30-50 m / s. 3 / h, with a working pressure of 0.3~0.6MPa.

[0013] Preferably, in step S1, the softening is carried out using a lime-soda ash softening method, and the specific steps and parameters include: adjusting the pH of the wastewater to 10-11, the mass-volume ratio of calcium hydroxide, anhydrous sodium carbonate and wastewater being (600-800) mg: (350-420) mg: 1L, the softening time being 20-40 min, and the stirring speed being 50-100 rpm.

[0014] Preferably, in step S2, the flocculant is polyacrylamide; the mass-to-volume ratio of the flocculant to the wastewater is (0.5~2) mg: 1 L.

[0015] Preferably, in step S2, the specific parameters of the reaction include: a reaction time of 20-40 min, a stirring rate of 20-50 rpm, and the filtration using an inclined plate sedimentation tank with a hydraulic retention time of 20-30 min.

[0016] Preferably, in step S3, the catalyst is a rare earth MOF-supported Janus catalyst.

[0017] This invention also provides a method for preparing a rare earth MOF-supported Janus catalyst, comprising:

[0018] A1. Mix nickel salt, copper salt and ligand, disperse in deionized water, adjust pH to 6-7, microwave reaction, centrifuge, precipitate, wash and dry to obtain Ni-UIO-66(Cu) (nickel-copper bimetallic modified UIO-66 type metal-organic framework material).

[0019] A2. The porous titanium sheet is washed and dried. Ni-UIO-66 (Cu) and polyvinylpyrrolidone are dispersed in deionized water and ultrasonically treated to obtain an electrophoretic solution. The solution is placed in an electrolytic cell. The porous titanium sheet is vertically placed in the electrolytic cell, with one side immersed in the electrophoretic solution and the other side shielded by a polytetrafluoroethylene membrane. Electrophoresis is performed and the solution is dried. A catalytic layer is formed on the side immersed in the electrophoretic solution.

[0020] A3. Take out the dried porous titanium sheet, cover one side of the catalyst layer with a polytetrafluoroethylene film, and immerse the other side in the hydrophilic layer growth solution. After reaction and drying, a Janus intermediate (asymmetric amphiphilic intermediate) with a hydrophilic layer modified only on one side of the porous titanium sheet is obtained.

[0021] A4. Methyltriethoxysilane was dispersed in ethanol, and deionized water and hydrochloric acid solution were added. The mixture was stirred to form a silicon solution, which was then uniformly coated on the surface of the Janus intermediate. After drying, the solution was cured into a gel film to obtain a rare earth MOF-supported Janus catalyst.

[0022] Preferably, in A1, the copper salt is Cu(NO3)2·3H2O, the nickel salt is Ni(NO3)2·6H2O, and the ligand is terephthalic acid.

[0023] Preferably, in A1, the molar ratio of the copper salt to the nickel salt is (3~5):1, and the sum of the two is in a molar ratio of 1:1 with terephthalic acid.

[0024] Preferably, in A1, the power of the microwave reaction is 400~800W, the temperature of the microwave reaction is 120~180℃, and the time of the microwave reaction is 1~3h.

[0025] Preferably, in A1, the drying temperature is 60°C and the drying time is 4 hours.

[0026] Preferably, in step A2, the drying temperature is 100~105℃ and the drying time is 2~3h.

[0027] Preferably, in A2, the mass ratio of Ni-UIO-66 (Cu) to polyvinylpyrrolidone is 50:1.

[0028] Preferably, in A2, the electrophoresis voltage is 10~20V and the electrophoresis time is 10~25min.

[0029] Preferably, in step A2, the drying temperature is 40~50℃ and the drying time is 1~2 hours.

[0030] Preferably, in A3, the hydrophilic layer growth solution is lanthanum-ytterbium double rare earth modified hydrotalcite supported graphene oxide, wherein the main components of hydrotalcite are Mg(NO3)2·6H2O and Al(NO3)3·9H2O, the molar ratio of Mg(NO3)2·6H2O to Al(NO3)3·9H2O is (2~4):1, the lanthanum salt is La(NO3)3·6H2O, the ytterbium salt is Yb(NO3)3·6H2O, and the molar ratio of lanthanum to ytterbium is (1~2):1.

[0031] Preferably, in A3, the preparation method of the hydrophilic layer growth solution is as follows: (0.05~0.1) g of graphene oxide is dispersed in (50~100) mL of deionized water to obtain a graphene oxide dispersion. Mg(NO3)2·6H2O, Al(NO3)3·9H2O, La(NO3)3·6H2O and Yb(NO3)3·6H2O are added to 100 mL of deionized water, heated in a water bath at 25~30℃, and poured into the graphene oxide dispersion with stirring. The mixture is stirred, and the pH is adjusted to 10. The reaction temperature is 70~80℃, and the reaction time is 2~3 h.

[0032] Preferably, in step A3, the drying temperature is 50~60℃ and the drying time is 2~3h.

[0033] Preferably, in A4, the volume ratio of methyltriethoxysilane, ethanol, deionized water and hydrochloric acid is 1:(20~25):(0.5~0.75):0.5.

[0034] Preferably, in A4, the stirring time is 20-30 minutes.

[0035] Preferably, in A4, the drying temperature is 30~40℃ and the drying time is 1~2h.

[0036] Preferably, in A4, the concentration of the hydrochloric acid solution is 0.01~0.02 mol / L.

[0037] Preferably, in step S3, the mass-to-volume ratio of the catalyst to the wastewater is (10~15) g: 1 L.

[0038] Preferably, in step S3, the reaction temperature is 25~35℃.

[0039] Preferably, in step S4, the specific process and parameters of the ultrafiltration membrane filtration include: the deep-treated wastewater enters the pretreatment unit to remove grease, then enters the filtration unit, is pumped to the membrane module by a booster pump, the working pressure is 0.1~0.3MPa, the filtered water enters the water tank for temporary storage, and is monitored to see if it meets the discharge standards or is recycled.

[0040] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0041] (1) In the deep oxidation stage, this invention uses rare earth MOFs supported Janus catalyst to synergistically catalyze ozone oxidation. The rare earth MOFs supported Janus nanoparticle catalyst has a stable single crystal phase structure composed of multiple metal elements. This structure endows the catalyst with excellent corrosion resistance, enabling it to better resist the erosion caused by complex components in high-salt wastewater and high-temperature, high-pressure process conditions, thereby delaying the catalyst deactivation process. During the preparation process, Ni-UIO-66(Cu) is prepared by microwave-assisted hydrothermal method. The uniformity and rapid heating characteristics of microwave heating can promote the uniform doping of bimetallic components, forming a large number of metal ion active centers and oxygen vacancies, which can efficiently activate ozone decomposition to generate ·OH, improve the mineralization rate of recalcitrant organic matter by 20%~40%, and achieve a COD removal rate of over 80%, solving the problems of single active sites and low degradation efficiency of complex wastewater in traditional single-component MOF catalysts. Ni-UIO-66(Cu) is precisely loaded onto one side of a porous titanium sheet by directional electrophoretic deposition. The electric field orientation during the deposition process can avoid the agglomeration of active components, ensuring uniform exposure of active sites with a loading uniformity of over 90%, significantly improving the contact efficiency between ozone, wastewater and active sites, and avoiding the defects of uneven loading and active site burial in traditional impregnation methods.

[0042] (2) This invention employs multi-media filtration, softening, flocculation, deep oxidation, and ultrafiltration membrane separation to specifically address the complex pollution problems in industrial wastewater caused by the coexistence of suspended solids, high-hardness ions, colloids, and recalcitrant organic matter. Multi-media filtration can efficiently intercept large particulate impurities such as suspended solids, coal dust, and silt in the water, directly preventing particulate matter from clogging pipes, covering the active sites of flocculants, or scratching the surface of the ultrafiltration membrane, thus extending the life of subsequent equipment; the lime-soda ash softening method is used to remove Ca from the water. 2+ Mg 2+ The process involves converting substances into precipitates such as calcium carbonate and magnesium hydroxide, reducing the total hardness of the water and preventing high-hardness ions from forming scale in the deep oxidation tank. An inorganic scale layer is formed on the ultrafiltration membrane surface, ensuring stable ozone mass transfer efficiency and no decrease in membrane flux. Polyacrylamide is used as a flocculant to aggregate fine colloids into large flocs, which are then removed by filtration, reducing COD. Deep oxidation decomposes toxic substances in the wastewater, such as phenols, cyanides, and heavy metal complexes, reducing the acute toxicity of the wastewater by more than 80%. Finally, an ultrafiltration membrane is used to remove residual fine flocs, incompletely degraded macromolecular organic matter, and catalyst residues after deep oxidation, ensuring the effluent meets discharge standards. Attached Figure Description

[0043] Figure 1 The flowchart illustrates a novel coal chemical wastewater treatment method provided by this invention.

[0044] Figure 2 The present invention provides a flowchart for the preparation of a rare earth MOF-supported Janus catalyst.

[0045] Figure 3 The COD removal rate of coal chemical wastewater treated using the methods of Examples 4 to 6 and Comparative Examples 4 to 6 is given.

[0046] Figure 4 The color removal rate of coal chemical wastewater treated by the methods of Examples 4 to 6 and Comparative Examples 4 to 6 is given.

[0047] Figure 5 This is a photograph of the rare earth MOFs-supported Janus catalyst prepared in Example 3.

[0048] Figure 6 This is a transmission electron microscope (TEM) image of the rare earth MOFs-supported Janus catalyst prepared in Example 3. Detailed Implementation

[0049] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0050] The main compounds used in the examples and comparative examples were all commercially available products and were not subjected to any further purification treatment.

[0051] Example 1

[0052] like Figure 2 As shown, a rare earth MOF-supported Janus catalyst is prepared by the following method:

[0053] A1. Mix 0.073g of Ni(NO3)2·6H2O, 0.181g of Cu(NO3)2·3H2O and 0.166g of terephthalic acid, disperse in 30mL of deionized water, sonicate for 30min until completely dissolved, adjust pH to 6, microwave at 120℃ for 3h at 400W, centrifuge, wash the precipitate with deionized water and dry at 60℃ for 4h to obtain Ni-UIO-66(Cu).

[0054] A2. Using porous titanium sheets as a carrier, the porous titanium sheets were ultrasonically cleaned with deionized water and ethanol for 10 min in sequence, and dried at 100℃ for 3 h. 0.5 g of Ni-UIO-66 (Cu) and 0.01 g of polyvinylpyrrolidone were dispersed in 100 mL of deionized water and ultrasonically treated for 20 min to obtain an electrophoresis solution. The solution was placed in an electrolytic cell, and the porous titanium sheets were vertically placed in the electrolytic cell with one side immersed in the electrophoresis solution and the other side covered with a polytetrafluoroethylene membrane. Electrophoresis was performed at 10 V for 25 min and dried at 40℃ for 2 h. A catalytic layer was formed on the side immersed in the electrophoresis solution.

[0055] A3. Prepare the hydrophilic layer growth solution. Disperse 0.05 g of graphene oxide in 50 mL of deionized water to obtain a graphene oxide dispersion. Add 2.307 g of Mg(NO3)2·6H2O, 1.125 g of Al(NO3)3·9H2O, 0.2598 g of La(NO3)3·6H2O, and 0.1347 g of Yb(NO3)3·6H2O to 100 mL of deionized water. Heat in a 25°C water bath and pour into the graphene oxide dispersion with stirring. Adjust the pH to 10 to obtain the hydrophilic layer growth solution.

[0056] The dried porous titanium sheet was taken out, one side of the catalyst layer was covered with a polytetrafluoroethylene film, and the other side was immersed in the hydrophilic layer growth solution prepared above. After reacting at 70°C for 3 hours and drying at 50°C for 3 hours, Janus intermediate with a hydrophilic layer modified only on one side of the porous titanium sheet was obtained.

[0057] A4. Disperse 1 mL of methyltriethoxysilane in 20 mL of ethanol, add 0.5 mL of deionized water and 0.5 mL of 0.01 mol / L hydrochloric acid solution, stir for 20 min to form a silicon solution, uniformly coat it on the surface of Janus intermediate, dry at 30 °C for 2 h to solidify into a gel film, and obtain rare earth MOFs supported Janus catalyst.

[0058] Example 2

[0059] like Figure 2 As shown, a rare earth MOF-supported Janus catalyst is prepared by the following method:

[0060] A1. Mix 0.058g of Ni(NO3)2·6H2O, 0.193g of Cu(NO3)2·3H2O and 0.166g of terephthalic acid, disperse in 30mL of deionized water, sonicate for 30min until completely dissolved, adjust pH to 7, microwave at 150℃ for 2h at 600W, centrifuge, wash the precipitate with deionized water and ethanol, and dry at 60℃ for 4h to obtain Ni-UIO-66(Cu).

[0061] A2. Using porous titanium sheets as a carrier, the porous titanium sheets were ultrasonically cleaned with deionized water and ethanol for 10 min in sequence, and dried at 105℃ for 3 h. 0.5 g of Ni-UIO-66 (Cu) and 0.01 g of polyvinylpyrrolidone were dispersed in 100 mL of deionized water and ultrasonically treated for 20 min to obtain an electrophoresis solution. The solution was placed in an electrolytic cell, and the porous titanium sheets were vertically placed in the electrolytic cell with one side immersed in the electrophoresis solution and the other side covered with a polytetrafluoroethylene membrane. Electrophoresis was performed at 15 V for 15 min, and then dried at 45℃ for 1.5 h. A catalytic layer was formed on the side immersed in the electrophoresis solution.

[0062] A3. Prepare the hydrophilic layer growth solution. Disperse 0.05 g of graphene oxide in 75 mL of deionized water to obtain a graphene oxide dispersion. Add 2.307 g of Mg(NO3)2·6H2O, 1.125 g of Al(NO3)3·9H2O, 0.2338 g of La(NO3)3·6H2O, and 0.1617 g of Yb(NO3)3·6H2O to 100 mL of deionized water. Heat in a 30°C water bath and pour into the graphene oxide dispersion with stirring. Adjust the pH to 10 to obtain the hydrophilic layer growth solution.

[0063] The dried porous titanium sheet was taken out, one side of the catalyst layer was covered with a polytetrafluoroethylene film, and the other side was immersed in the hydrophilic layer growth solution prepared above. After reacting at 75°C for 2.5 h and drying at 55°C for 2.5 h, Janus intermediate was obtained.

[0064] A4. Disperse 1 mL of methyltriethoxysilane in 25 mL of ethanol, add 0.75 mL of deionized water and 0.5 mL of 0.015 mol / L hydrochloric acid solution, stir for 25 min to form a silicon solution, uniformly coat it on the surface of Janus intermediate, dry at 35 °C for 1.5 h to solidify into a gel film, and obtain rare earth MOFs supported Janus catalyst.

[0065] Example 3

[0066] like Figure 2 As shown, a rare earth MOF-supported Janus catalyst is prepared by the following method:

[0067] A1. Mix 0.048g of Ni(NO3)2·6H2O, 0.201g of Cu(NO3)2·3H2O and 0.166g of terephthalic acid, disperse in 30mL of deionized water, sonicate for 30min until completely dissolved, adjust pH to 7, microwave at 180℃ for 1h at 800W, centrifuge, wash the precipitate with deionized water and ethanol, and dry at 60℃ for 4h to obtain Ni-UIO-66(Cu).

[0068] A2. Using porous titanium sheets as a carrier, the porous titanium sheets were ultrasonically cleaned with deionized water and ethanol for 10 min in sequence, and dried at 105℃ for 2 h. 0.5 g of Ni-UIO-66 (Cu) and 0.01 g of polyvinylpyrrolidone were dispersed in 100 mL of deionized water and ultrasonically treated for 20 min to obtain an electrophoresis solution. The solution was placed in an electrolytic cell, and the porous titanium sheets were vertically placed in the electrolytic cell with one side immersed in the electrophoresis solution and the other side covered with a polytetrafluoroethylene membrane. Electrophoresis was performed at 20 V for 10 min and dried at 50℃ for 1 h. A catalytic layer was formed on the side immersed in the electrophoresis solution.

[0069] A3. Prepare the hydrophilic layer growth solution. Disperse 0.1g of graphene oxide in 100mL of deionized water to obtain a graphene oxide dispersion. Add 3.07g of Mg(NO3)2·6H2O, 1.125g of Al(NO3)3·9H2O, 0.3464g of La(NO3)3·6H2O, and 0.1796g of Yb(NO3)3·6H2O to 100mL of deionized water. Heat in a 30℃ water bath and pour into the graphene oxide dispersion with stirring. Adjust the pH to 10 to obtain the hydrophilic layer growth solution.

[0070] The dried porous titanium sheet was taken out, the catalyst layer was covered with a polytetrafluoroethylene film, and the other side was immersed in the hydrophilic layer growth solution prepared above. After reacting at 80°C for 2 hours and drying at 60°C for 2 hours, Janus intermediate was obtained.

[0071] A4. Disperse 1 mL of methyltriethoxysilane in 20 mL of ethanol, add 0.5 mL of deionized water and 0.5 mL of 0.02 mol / L hydrochloric acid solution, stir for 30 min to form a silicon solution, uniformly coat it on the surface of the Janus intermediate, dry at 40 °C for 1 h to solidify into a gel film, and obtain the rare earth MOFs supported Janus catalyst. The actual catalyst is shown in the figure. Figure 5 As shown, the transmission electron microscope image is as follows: Figure 6 As shown.

[0072] Comparative Example 1

[0073] A rare earth MOF-supported Janus catalyst is prepared in a manner that differs from that of Example 3 in that Ni(NO3)2·6H2O is not added to Al, while the other operating steps and process parameters are exactly the same as those of Example 3.

[0074] Comparative Example 2

[0075] A rare earth MOF-supported Janus catalyst is prepared in a manner that differs from that in Example 3. In A2, Ni-UIO-66 (Cu) is not coated onto one side of the porous titanium sheet by electrophoresis, but by a conventional coating method. Other operating steps and process parameters are exactly the same as in Example 3.

[0076] Comparative Example 3

[0077] A rare earth MOF-supported Janus catalyst is prepared in a manner different from that in Example 3. In A2, a porous titanium sheet with Ni-UIO-66 (Cu) is electrophoretically coated on one side, and the surface is not treated with a hydrophilic layer growth solution. Other operating steps and process parameters are exactly the same as in Example 3.

[0078] Example 4

[0079] like Figure 1 As shown, a novel method for treating coal chemical wastewater includes:

[0080] S1. The wastewater is pumped into a multi-media filter for filtration at a flow rate of 30m³. 3 At a rate of / h and a working pressure of 0.3MPa, the wastewater is filtered through an upper layer of anthracite with a particle size of 1.6mm, a middle layer of quartz sand with a particle size of 0.8mm, and a lower layer of refined garnet with a particle size of 0.5mm. The filtered wastewater then enters a softening tank, where the pH is adjusted to 10. Calcium hydroxide and anhydrous sodium carbonate are added, and the mixture is stirred at 50rpm for 40 minutes. The mass-to-volume ratio of calcium hydroxide, anhydrous sodium carbonate, and wastewater is 600mg:350mg:1L.

[0081] S2. The softened wastewater enters the flocculation tank, polyacrylamide is added, and the mixture is stirred at 20 rpm for 40 min. The mixture then enters the inclined plate sedimentation tank and remains for 30 min. The filtered wastewater enters the deep oxidation tank. The mass-volume ratio of polyacrylamide to wastewater is 0.5 mg: 1 L.

[0082] S3. Adjust the pH of the wastewater in the deep oxidation tank to 6, add the rare earth MOFs-supported Janus catalyst prepared in Example 1, start the ozone generator to introduce ozone, the ozone gas flow rate is 0.5 L / min, react at 25℃ for 4 h to obtain the deep-treated wastewater, the mass-volume ratio of rare earth MOFs-supported Janus catalyst to wastewater is 10 g: 1 L.

[0083] S4. The pretreatment unit of the deep-treatment wastewater enters the ultrafiltration system to remove grease from the surface of the water. Then it enters the filtration unit and is pumped to the membrane module by a booster pump. The membrane module operates at a pressure of 0.1 MPa. Under these conditions, the wastewater passes through the ultrafiltration membrane. Water and small molecules permeate through the membrane to form permeate water, while the filtrate is retained on the ultrafiltration membrane. The permeate water enters the water tank for temporary storage, and monitoring is conducted to determine whether it meets the discharge standards or can be recycled.

[0084] Example 5

[0085] like Figure 1 As shown, a novel method for treating coal chemical wastewater includes:

[0086] S1. The wastewater is pumped into a multi-media filter for filtration at a flow rate of 40m³. 3 At a rate of / h and a working pressure of 0.4MPa, the wastewater is filtered through an upper layer of anthracite with a particle size of 1.2mm, a middle layer of quartz sand with a particle size of 0.7mm, and a lower layer of refined garnet with a particle size of 0.4mm. The filtered wastewater then enters a softening tank, where the pH is adjusted to 11. Calcium hydroxide and anhydrous sodium carbonate are added, and the mixture is stirred at 75rpm for 30 minutes. The mass-to-volume ratio of calcium hydroxide, anhydrous sodium carbonate, and wastewater is 700mg:400mg:1L.

[0087] S2. The softened wastewater enters the flocculation tank, polyacrylamide is added, and the mixture is stirred at 35 rpm for 30 minutes. The mixture then enters the inclined plate sedimentation tank and remains for 25 minutes. The filtered wastewater enters the deep oxidation tank. The mass-volume ratio of polyacrylamide to wastewater is 1 mg: 1 L.

[0088] S3. Adjust the pH of the wastewater in the deep oxidation tank to 7, add the rare earth MOFs-supported Janus catalyst prepared in Example 2, start the ozone generator to introduce ozone, the ozone gas flow rate is 0.5 L / min, react at 30°C for 4 h to obtain the deep-treated wastewater, the mass-volume ratio of rare earth MOFs-supported Janus catalyst to wastewater is 12 g: 1 L.

[0089] S4. The pretreatment unit of the deep-treatment wastewater enters the ultrafiltration system to remove grease from the surface of the water. Then it enters the filtration unit and is pumped to the membrane module by a booster pump. The membrane module operates at a pressure of 0.2 MPa. Under these conditions, the wastewater passes through the ultrafiltration membrane. Water and small molecules permeate through the membrane to form permeate water, while the filtrate is retained on the ultrafiltration membrane. The permeate water enters the water tank for temporary storage, and monitoring is conducted to determine whether it meets the discharge standards or can be recycled.

[0090] Example 6

[0091] like Figure 1 As shown, a novel method for treating coal chemical wastewater includes:

[0092] S1. The wastewater is pumped into a multi-media filter for filtration, with the wastewater flowing at a rate of 50m³ / h. 3 At a rate of / h and a working pressure of 0.6MPa, the wastewater is filtered through an upper layer of anthracite with a particle size of 1.6mm, a middle layer of quartz sand with a particle size of 0.8mm, and a lower layer of refined garnet with a particle size of 0.5mm. The filtered wastewater then enters a softening tank, where the pH is adjusted to 10. Calcium hydroxide and anhydrous sodium carbonate are added, and the mixture is stirred at 100rpm for 20 minutes. The mass-to-volume ratio of calcium hydroxide, anhydrous sodium carbonate, and wastewater is 800mg:420mg:1L.

[0093] S2. The softened wastewater enters the flocculation tank, polyacrylamide is added, and the mixture is stirred at 50 rpm for 20 minutes. The mixture then enters the inclined plate sedimentation tank and remains for 20 minutes. The filtered wastewater enters the deep oxidation tank. The mass-volume ratio of polyacrylamide to wastewater is 2 mg: 1 L.

[0094] S3. Adjust the pH of the wastewater in the deep oxidation tank to 7.5, add the rare earth MOFs-supported Janus catalyst prepared in Example 3, start the ozone generator to introduce ozone, the ozone gas flow rate is 0.5 L / min, react at 35℃ for 4 h to obtain the deep-treated wastewater, the mass-volume ratio of rare earth MOFs-supported Janus catalyst to wastewater is 15 g: 1 L.

[0095] S4. The pretreatment unit of the deep-treatment wastewater enters the ultrafiltration system to remove grease from the surface of the water. Then it enters the filtration unit and is pumped to the membrane module by a booster pump. The membrane module operates at a pressure of 0.3 MPa. Under these conditions, the wastewater passes through the ultrafiltration membrane. Water and small molecules permeate through the membrane to form permeate water, while the filtrate is retained on the ultrafiltration membrane. The permeate water enters the water tank for temporary storage, and monitoring is conducted to determine whether it meets the discharge standards or can be recycled.

[0096] Comparative Example 4

[0097] A novel method for treating coal chemical wastewater differs from Example 4 in that S3 uses the catalyst prepared in Comparative Example 1.

[0098] Comparative Example 5

[0099] A novel method for treating coal chemical wastewater differs from Example 4 in that S3 uses the catalyst prepared in Comparative Example 2.

[0100] Comparative Example 6

[0101] A novel method for treating coal chemical wastewater differs from Example 4 in that S3 uses the catalyst prepared in Comparative Example 3.

[0102] The water samples that met the discharge standards obtained from Examples 4 to 6 and Comparative Examples 4 to 6 were used to analyze COD using a water quality analyzer and measure color using a spectrophotometer.

[0103] Figure 3 The COD removal rates are for samples from Examples 4-6 and Comparative Examples 4-6. The COD removal rates for samples from Examples 4-6 are all above 80%, while the COD removal rates for samples from Comparative Examples 4-6 are below 50%.

[0104] Figure 4 The color reduction efficiency of the samples from Examples 4-6 and Comparative Examples 4-6 is shown. The color reduction efficiency of the samples from Examples 4-6 is all above 80%, while the color removal efficiency of the samples from Comparative Examples 4-6 is below 60%.

[0105] This is because the catalyst used in Comparative Example 4 did not contain nickel doping, and the catalyst changed from a bimetallic site to a monometallic site, lacking the stability provided by the bimetallic site. Furthermore, the single active site resulted in a sharp drop in ozone activation efficiency, leading to a decrease in catalytic activity. In Comparative Example 5, the catalyst used did not employ electrophoretic directional sedimentation when coating Ni-UIO-66 (Cu) onto porous titanium sheets. Instead, a traditional coating method was used, resulting in an uneven thickness of the catalyst layer, which was prone to detachment and insufficient exposure of active sites, thus leading to a decrease in catalytic activity. In Comparative Example 6, the catalyst layer lacked an outer protective layer during the sol-gel sealing process, significantly reducing the catalyst layer's resistance to salt precipitation, decreasing the overall stability of Janus, and reducing its durability in the complex aquatic environment of coal chemical wastewater, thereby reducing the effectiveness of synergistic ozone catalytic oxidation.

[0106] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A novel method for treating coal chemical wastewater, characterized in that, include: S1. Wastewater is filtered in a multi-media filter, and the filtered wastewater enters a softening tank for softening. S2. The softened wastewater enters the flocculation tank, flocculant is added, the reaction occurs, and the filtered wastewater enters the deep oxidation tank. S3. The wastewater in the deep oxidation tank is adjusted to pH 6-7.5, a catalyst is added, ozone is introduced, and the reaction is carried out to obtain deeply treated wastewater. S4. Deeply treated wastewater is separated through an ultrafiltration membrane to obtain water that meets discharge standards or can be reused; The catalyst in S3 is a rare earth MOF-supported Janus catalyst, and the preparation method of the catalyst includes: A1. Mix nickel salt, copper salt and ligand, disperse in deionized water, adjust pH to 6-7, microwave reaction, centrifuge, wash and dry the precipitate to obtain Ni-UIO-66 (Cu). A2. The porous titanium sheet is washed and dried. Ni-UIO-66 (Cu) and polyvinylpyrrolidone are dispersed in deionized water and ultrasonically treated to obtain an electrophoretic solution. The solution is placed in an electrolytic cell. The porous titanium sheet is vertically placed in the electrolytic cell, with one side immersed in the electrophoretic solution and the other side shielded by a polytetrafluoroethylene membrane. Electrophoresis is performed and the solution is dried. A catalytic layer is formed on the side immersed in the electrophoretic solution. A3. Take out the dried porous titanium sheet, cover one side of the catalyst layer with a polytetrafluoroethylene film, and immerse the other side in the hydrophilic layer growth solution. React and dry to obtain Janus intermediate with a hydrophilic layer modified only on one side of the porous titanium sheet. A4. Methyltriethoxysilane was dispersed in ethanol, and deionized water and hydrochloric acid solution were added. The mixture was stirred to form a silicon solution, which was then uniformly coated on the surface of the Janus intermediate. The solution was dried and solidified into a gel film to obtain a rare earth MOF-supported Janus catalyst.

2. The novel coal chemical wastewater treatment method according to claim 1, characterized in that, In step S1, the multi-media filter is filled with three filter layers, with particle sizes decreasing from top to bottom: the upper layer is anthracite with a particle size of 0.8~1.6mm, the middle layer is quartz sand with a particle size of 0.5~0.8mm, and the lower layer is refined garnet with a particle size of 0.3~0.5mm; the filtration speed in the multi-media filter is 30~50m / s. 3 / h, working pressure is 0.3~0.6MPa; The softening process employs a lime-soda ash softening method, with specific steps and parameters including: adjusting the wastewater pH to 10-11, the mass-to-volume ratio of calcium hydroxide, anhydrous sodium carbonate, and wastewater being (600-800) mg: (350-420) mg: 1 L, the softening time being 20-40 min, and the stirring rate being 50-100 rpm.

3. The novel coal chemical wastewater treatment method according to claim 1, characterized in that, In step S2, the flocculant is polyacrylamide; the mass-volume ratio of the flocculant to the wastewater is (0.5~2) mg: 1L; the specific parameters of the reaction include: reaction time of 20~40 min, stirring speed of 20~50 rpm, and the filtration adopts an inclined plate sedimentation tank with a hydraulic retention time of 20~30 min.

4. The novel coal chemical wastewater treatment method according to claim 1, characterized in that, In A1, the copper salt is Cu(NO3)2·3H2O, the nickel salt is Ni(NO3)2·6H2O, and the ligand is terephthalic acid; the molar ratio of the copper salt to the nickel salt is (3~5):1, and the molar ratio of their sum to terephthalic acid is 1:1; the power of the microwave reaction is 400~800W, the temperature of the microwave reaction is 120~180℃, and the time of the microwave reaction is 1~3h; the drying temperature is 60℃, and the drying time is 4h.

5. A novel coal chemical wastewater treatment method according to claim 1, characterized in that, In A2, the drying temperature is 100~105℃ and the time is 2~3h; the mass ratio of Ni-UIO-66(Cu) to polyvinylpyrrolidone is 50:1; the electrophoresis voltage is 10~20V and the electrophoresis time is 10~25min; the drying temperature is 40~50℃ and the drying time is 1~2h.

6. The novel coal chemical wastewater treatment method according to claim 1, characterized in that, In A3, the hydrophilic layer growth solution is lanthanum-ytterbium salt dual rare earth modified hydrotalcite supported graphene oxide, wherein the main components of hydrotalcite are Mg(NO3)2·6H2O and Al(NO3)3·9H2O, the molar ratio of Mg(NO3)2·6H2O and Al(NO3)3·9H2O is (2~4):1, the lanthanum salt is La(NO3)3·6H2O, the ytterbium salt is Yb(NO3)3·6H2O, and the molar ratio of lanthanum and ytterbium is (1~2):

1.

7. A novel coal chemical wastewater treatment method according to claim 1, characterized in that, In A3, the preparation method of the hydrophilic layer growth solution is as follows: (0.05~0.1) g of graphene oxide is dispersed in (50~100) mL of deionized water to obtain a graphene oxide dispersion. Mg(NO3)2·6H2O, Al(NO3)3·9H2O, La(NO3)3·6H2O and Yb(NO3)3·6H2O are added to 100 mL of deionized water, heated in a water bath at 25~30℃, and poured into the graphene oxide dispersion with stirring. The pH is adjusted to 9~10. The reaction temperature is 70~80℃, and the reaction time is 2~3 h. The drying temperature is 50~60℃, and the drying time is 2~3 h.

8. A novel coal chemical wastewater treatment method according to claim 1, characterized in that, In A4, the volume ratio of methyltriethoxysilane, ethanol, deionized water and hydrochloric acid is 1:(20~25):(0.5~0.75):0.5; the stirring time is 20~30 min; the drying temperature is 30~40℃, the drying time is 1~2 h, and the concentration of the hydrochloric acid solution is 0.01~0.02 mol / L.

9. A novel coal chemical wastewater treatment method according to claim 1, characterized in that, In step S3, the mass-to-volume ratio of the catalyst to the wastewater is (10~15) g:1 L; the reaction temperature is 25~35℃; in step S4, the specific process and parameters of the ultrafiltration membrane filtration include: the deep-treated wastewater enters the pretreatment unit to remove grease, then enters the filtration unit, is pumped to the membrane module by a booster pump, the working pressure is 0.1~0.3 MPa, the filtered water enters the water tank for temporary storage, and is monitored to see if it meets the discharge standards or is recycled.

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