A method and apparatus for resource recovery from wastewater containing organic matter and miscellaneous salts.

Abstract

This invention relates to the field of industrial waste salt treatment technology in the chemical industry, specifically to a method and apparatus for recovering wastewater containing organic matter and miscellaneous salts. The invention provides a method for recovering wastewater containing organic matter and miscellaneous salts, comprising: subjecting the wastewater to air flotation, multi-stage sedimentation, multi-stage catalytic oxidation, and two-stage nanofiltration, followed by crystallization to obtain sodium chloride and crystalline sodium sulfate; wherein, the pH value of the wastewater containing organic matter and miscellaneous salts is controlled during the air flotation process; the catalyst for the first-stage catalytic oxidation is selected from a nano-foam metal-iron-based composite catalyst. By controlling the pH value during the air flotation process and using a specific catalyst in the first-stage catalytic oxidation process, the concentration of organic matter in the wastewater containing organic matter and miscellaneous salts can be effectively reduced, effectively improving the efficiency of subsequent treatment processes, thereby extending the service life of membrane equipment such as ultrafiltration, nanofiltration, and reverse osmosis, and resulting in a lower organic matter content in the target product.

Description

Technical Field

[0001] This invention relates to the field of industrial waste salt treatment technology in the chemical industry, specifically to a method and apparatus for resource recovery of wastewater containing organic matter and miscellaneous salts. Background Technology

[0002] Wastewater generated during industrial production processes in industries such as coal chemical, petrochemical, coking, pesticide, pharmaceutical, and papermaking contains a large amount of complex, recalcitrant organic matter and acid, alkali, and salt components. During treatment, a large amount of waste salt and concentrated waste liquid are generated. Currently, the main methods used to treat these waste salts or high-concentration concentrated waste liquids include membrane adsorption, separation, concentration evaporation crystallization, and electrodialysis. However, for mixed salts with high organic matter content, direct incineration or pyrolysis methods are usually used, which have drawbacks such as high energy consumption, high pollution, and high equipment investment, which seriously limit the promotion and application of these methods.

[0003] Chinese patent CN114057342A, entitled "A Method and System for Resource Recovery and Utilization of Mixed Salts," proposes a method combining pretreatment, catalytic oxidation degradation, ultrafiltration, ion exchange, nanofiltration, reverse osmosis, and evaporation crystallization. This method achieves the separation and resource recovery and utilization of solid mixed salts. The recovered sodium chloride product meets the physicochemical indicators of Grade I industrial dry salt in "Coal Chemical By-product Sodium Chloride," and the recovered sodium sulfate meets the physicochemical indicators of Class A Grade I product in "Coal Chemical By-product Sodium Sulfate." However, this system has limitations in processing mixed salts containing organic matter, and the target product obtained using this method has a high organic matter content. Furthermore, the organic matter content remains at a high level throughout the recovery process, which increases the energy consumption and reduces the lifespan of membrane equipment such as ultrafiltration, nanofiltration, and reverse osmosis membranes, and also affects the purity of the subsequent products. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problems of high organic matter levels in the resource recovery process of wastewater containing organic matter and salts in the prior art, which leads to high energy consumption, short lifespan and high organic matter content in the target product of membrane equipment. Thus, the present invention provides a method and apparatus for resource recovery of wastewater containing organic matter and salts.

[0005] This invention provides a method for resource recovery from wastewater containing organic matter and salts, comprising the following steps:

[0006] (1) Wastewater containing organic matter and salts is subjected to air flotation, first sedimentation treatment, first-stage catalytic oxidation, second sedimentation treatment, first filtration, second-stage catalytic oxidation, cation exchange, second filtration, and first-stage nanofiltration to obtain first-stage nanofiltration permeate and first-stage nanofiltration concentrate.

[0007] (2) The primary nanofiltration permeate is treated by secondary nanofiltration to obtain a monovalent salt solution and secondary nanofiltration concentrate. The monovalent salt solution is then treated by reverse osmosis to obtain a monovalent salt concentrate. The concentrate is then crystallized to obtain crystalline sodium chloride. The secondary nanofiltration concentrate is returned to the primary nanofiltration process for further treatment.

[0008] (3) The concentrated water from the first-stage nanofiltration is subjected to tertiary catalytic oxidation and then crystallized to obtain crystalline sodium sulfate;

[0009] Specifically, the pH value of the wastewater containing organic matter and salts is controlled during the air flotation process; when the wastewater containing organic matter and salts is acidic, the pH value of the wastewater containing organic matter and salts is reduced during the air flotation process; when the wastewater containing organic matter and salts is alkaline, the pH value of the wastewater containing organic matter and salts is increased during the air flotation process.

[0010] The catalyst for primary catalytic oxidation was selected from nanofoam metal-iron composite catalysts.

[0011] It is understandable that the iron in the nanofoam metal iron-based catalyst is zero-valent iron.

[0012] Optionally, the wastewater containing organic matter and miscellaneous salts described in this invention comes from wastewater generated by coking, pharmaceutical, printing and dyeing, fertilizer, and pesticide industries.

[0013] In one embodiment, the concentration of miscellaneous salts in the wastewater containing organic matter and miscellaneous salts is 20-150 g / L, and the TOC content is 30-2000 mg / L. The wastewater containing organic matter and miscellaneous salts includes chloride ions, sulfate ions, sodium ions, calcium ions, and fluoride ions.

[0014] In one embodiment, the wastewater containing organic salts also includes at least one of carbonate ions, bicarbonate ions, and magnesium ions.

[0015] Optionally, the TOC content in the wastewater containing organic matter and miscellaneous salts is 350 mg / L, 500 mg / L, 1000 mg / L, 1500 mg / L, or 1800 mg / L.

[0016] In one specific embodiment, the air flotation device is selected from any one or more combinations of horizontal flow pressurized dissolved air flotation device, high-efficiency shallow air flotation device, multiphase miscible air flotation device, vortex air flotation device, and multi-stage air flotation device; the working pressure of the air flotation device is 0.1-0.4 MPa.

[0017] In a more specific embodiment, the operating pressure of the air flotation device is 0.2-0.3 MPa.

[0018] In one embodiment, a coagulant, a coagulant aid, a water softener, and a defluorinator are added to the first precipitation treatment and the second precipitation treatment.

[0019] In another embodiment, a bactericide is added to the first precipitation treatment, wherein the amount of bactericide added is 5 to 20 ppm.

[0020] In one specific embodiment, the defluorinating agent is selected from polyaluminum chloride;

[0021] In one specific embodiment, the coagulant is selected from one or more of polyaluminum sulfate, polyferric chloride, and polyferric sulfate;

[0022] In one specific embodiment, the coagulant is selected from anionic polyacrylamide or cationic polyacrylamide;

[0023] In one specific embodiment, the bactericide is selected from sodium hypochlorite, chlorine dioxide, or hydrogen peroxide;

[0024] In one specific embodiment, the water softener is selected from at least one of sodium hydroxide and sodium carbonate.

[0025] In one embodiment, the nanofoam metal-iron-based composite catalyst has a particle size of 1-5 cm and a specific surface area of ​​5-20 m². 2 / g, pore size distribution range 10-100nm, average pore size 20-30nm; the material of the nanofoam metal iron-based composite catalyst contains 85-98wt% iron;

[0026] In one specific embodiment, the space velocity of the first-stage catalytic oxidation process is 0.2-2.0 h⁻¹. -1 The amount of H2O2 added is 50-2000ppm.

[0027] It is understandable that the amount of H2O2 added is relative to the volume of wastewater containing organic matter and miscellaneous salts.

[0028] The second precipitation treatment can reduce the concentration of fine particles and ions in wastewater containing organic matter and miscellaneous salts; the ions include: chloride ions, sulfate ions, sodium ions, calcium ions, and fluoride ions.

[0029] Optionally, the ions may also include carbonate ions, bicarbonate ions, and magnesium ions.

[0030] In one specific embodiment, the filter medium in the first filter is selected from modified polymer microporous suspended fiber filter cloth filter media particles.

[0031] The filter media particles have a pore size of 1-60μm and a thickness of 1-5mm.

[0032] The modified polymer microporous suspended fiber filter cloth particles were purchased from Huade Venture.

[0033] In a more specific embodiment, the filtration device in the first filter is selected from a high-speed high-efficiency filter; wherein the filter medium in the high-speed high-efficiency filter is selected from modified polymer microporous suspended fiber filter cloth filter media particles; the pore size of the filter media particles is 1-60μm, and the thickness of the filter medium is 1-5mm; the filtration form in the first filter adopts bottom inlet and top outlet, with the filter media above the tank body, naturally forming the filtration zone at the top of the tank body and the buffer settling zone in the lower part of the tank body, which has a certain deceleration and settling effect on some large and dense suspended particles. After being buffered by the dedicated distributor baffle at the inlet, they do not need to be decelerated and settled before reaching the filter media layer, and directly settle to the bottom or remain in the lower part of the tank body.

[0034] In a more specific embodiment, the filtration device in the first filter is the Huade Venture IAT high-speed precision filter.

[0035] In one embodiment, the turbidity range of the inlet wastewater from the first filter is 20-200 NTU, and the turbidity of the treated wastewater is less than 5 NTU. The Ca in the wastewater after the first filter is... 2+ Less than 30 ppm.

[0036] In one specific embodiment, the catalyst used for secondary catalytic oxidation is a nanocatalyst.

[0037] In a more specific embodiment, the active component of the nanocatalyst is an iron-nickel-copper ternary alloy, the particle size of the active component is 20-30 nm, and the nanocatalyst support is activated carbon.

[0038] In a more specific embodiment, the space velocity in the secondary and tertiary catalytic oxidation processes is 0.2-2.0 h⁻¹. -1 The amount of H2O2 added is 50-1000ppm.

[0039] In one embodiment, the cation exchange resin used in the cation exchange process is selected from styrene-type sulfonic acid cation exchange resin D001 or acrylic-type weak acid cation exchange resin D113.

[0040] Replacing the ion exchanger with a cation exchanger using only cation exchanger can reduce equipment costs, while also minimizing the impact on the composition of anions in the water and resulting in a higher resource recovery rate.

[0041] In one embodiment, the second filter is selected from an ultrafiltration device.

[0042] In a more specific embodiment, the ultrafiltration device is selected from the membrane equipment of Hangzhou Kemo Company.

[0043] In a more specific embodiment, the ultrafiltration device is selected from the Hangzhou Kemo Laboratory's ultrafiltration membrane pilot-scale equipment KM1812-UF.

[0044] In one specific embodiment, the catalyst used in the tertiary catalytic oxidation is a nanocatalyst.

[0045] In one embodiment, the primary nanofiltration unit and the secondary nanofiltration unit are connected in series, and the membrane flux of the nanofiltration membrane modules of the primary and secondary nanofiltration units is 10–30 L / m³. 2 h, the inlet water pressure is 1.5~4MPa, the first-stage nanofiltration permeate recovery rate is 60-90%, and the second-stage nanofiltration permeate recovery rate is 80-96%.

[0046] In one embodiment, the method for crystallizing a concentrated monovalent salt solution is selected from concentrated crystallization;

[0047] In one embodiment, the crystallization method in step (3) is selected from freeze crystallization; wherein the crystallization temperature is 0-5℃.

[0048] During freeze crystallization, the temperature is controlled at 0-5℃ to obtain crystalline sodium sulfate with a TOC of less than 10 mg / L and a sodium sulfate purity of at least 99%.

[0049] This invention also provides a system for resource recovery of wastewater containing organic salts, comprising:

[0050] The pretreatment device includes an air flotation device and a first sedimentation tank connected in sequence;

[0051] The inlet of the primary catalytic oxidation unit is connected to the outlet of the first sedimentation tank;

[0052] The second sedimentation tank has its inlet connected to the outlet of the first-stage catalytic oxidation unit.

[0053] A first filtration device, the inlet of which is connected to the outlet of a second sedimentation tank;

[0054] A secondary catalytic oxidation device is provided, with its inlet connected to the outlet of the first filtration device.

[0055] A cation exchange resin device, the inlet of which is connected to the outlet of the secondary catalytic oxidation device;

[0056] The second filtration device has its inlet connected to the outlet of the cation exchange resin device.

[0057] The first-stage nanofiltration unit has its inlet connected to the outlet of the second-stage filtration unit. The first-stage nanofiltration unit also includes a first-stage nanofiltration permeate outlet, a first-stage nanofiltration concentrate outlet, and a second-stage nanofiltration concentrate inlet.

[0058] The secondary nanofiltration unit has its inlet connected to the outlet of the primary nanofiltration permeate; the secondary nanofiltration unit also includes a monovalent salt solution outlet and a secondary nanofiltration concentrate outlet; the secondary nanofiltration concentrate outlet is connected to the secondary nanofiltration concentrate inlet.

[0059] The three-stage catalytic oxidation unit has its inlet connected to the outlet of the first-stage nanofiltration concentrate.

[0060] The reverse osmosis unit has its inlet connected to the outlet of the monovalent salt solution.

[0061] A sodium chloride evaporation and crystallization device, the inlet of which is connected to the outlet of the reverse osmosis device;

[0062] The sodium sulfate freeze crystallization device has its inlet connected to the outlet of the three-stage catalytic oxidation device.

[0063] Understandably, the outlet of the sodium chloride evaporation and crystallization device 800 connected to the reverse osmosis device 700 is the outlet for enriching sodium chloride solution; the purified water outlet of the reverse osmosis device 700 can be connected to other devices that require purified water.

[0064] In this invention, the sodium sulfate freeze crystallization apparatus also includes a portion of water that can be used in other process steps.

[0065] The technical solution of this invention has the following advantages:

[0066] This invention provides a method for resource recovery of wastewater containing organic matter and miscellaneous salts, comprising the following steps: (1) subjecting the wastewater containing organic matter and miscellaneous salts to air flotation, first sedimentation treatment, first-stage catalytic oxidation, second sedimentation treatment, first filtration, second-stage catalytic oxidation, cation exchange, second filtration, and first-stage nanofiltration to obtain first-stage nanofiltration permeate and first-stage nanofiltration concentrate; (2) subjecting the first-stage nanofiltration permeate to second-stage nanofiltration to obtain a monovalent salt solution and second-stage nanofiltration concentrate, subjecting the monovalent salt solution to reverse osmosis to obtain a monovalent salt concentrated solution, and then subjecting the latter monovalent salt concentrated solution to reverse osmosis... Crystallization was performed to obtain crystalline sodium chloride; the secondary nanofiltration concentrate was returned to the primary nanofiltration process for treatment; (3) the primary nanofiltration concentrate was subjected to tertiary catalytic oxidation and then crystallized to obtain crystalline sodium sulfate; wherein, the pH value of the wastewater containing organic matter and miscellaneous salts was controlled during the air flotation process; when the wastewater containing organic matter and miscellaneous salts was acidic, the pH value of the wastewater containing organic matter and miscellaneous salts was reduced during the air flotation process; when the wastewater containing organic matter and miscellaneous salts was alkaline, the pH value of the wastewater containing organic matter and miscellaneous salts was increased during the air flotation process; the catalyst for the primary catalytic oxidation was selected from nano foam metal iron-based composite catalysts.

[0067] This invention addresses the treatment of wastewater containing organic matter and salts. By controlling the pH value during the air flotation process and using a specific catalyst in the primary catalytic oxidation process, the concentration of organic matter in the wastewater containing organic matter and salts can be effectively reduced. This reduces the impact of organic matter on subsequent treatment processes, effectively improves the efficiency of subsequent treatment processes, and extends the service life of membrane equipment such as ultrafiltration, nanofiltration, and reverse osmosis. Furthermore, it results in a lower organic matter content in the target product. Attached Figure Description

[0068] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0069] Figure 1 This is a schematic diagram of a system for resource recovery of wastewater containing organic matter and miscellaneous salts according to an embodiment 1 of the present invention;

[0070] Reference numerals: 100, air flotation device; 201, first sedimentation tank; 202, second sedimentation tank; 301, primary catalytic oxidation device; 302, secondary catalytic oxidation device; 303, tertiary catalytic oxidation device; 401, first filtration device; 402, second filtration device; 500, cation exchange resin device; 601, primary nanofiltration device; 602, secondary nanofiltration device; 700, reverse osmosis device; 800, sodium chloride evaporation crystallization device; 900, sodium sulfate freeze crystallization device. Detailed Implementation

[0071] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0072] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0073] Example 1

[0074] This embodiment provides a system for resource recovery of wastewater containing organic matter and salts, such as... Figure 1 As shown, it includes:

[0075] The pretreatment device includes an air flotation device 100 and a first sedimentation tank 201 connected in sequence.

[0076] The inlet of the primary catalytic oxidation unit 301 is connected to the outlet of the first sedimentation tank 201.

[0077] The second sedimentation tank 202 is connected to the outlet of the first-stage catalytic oxidation device 301.

[0078] The first filter device 401 has its inlet connected to the outlet of the second sedimentation tank 202.

[0079] The secondary catalytic oxidation device 302 is connected to the outlet of the first filter device 401 at its inlet.

[0080] The cation exchange resin device 500 has its inlet connected to the outlet of the secondary catalytic oxidation device 302.

[0081] The second filter device 402 has its inlet connected to the outlet of the cation exchange resin device 500.

[0082] The first-stage nanofiltration device 601 has its inlet connected to the outlet of the second-stage filtration device 402. The first-stage nanofiltration device 601 also includes a first-stage nanofiltration permeate outlet, a first-stage nanofiltration concentrate outlet, and a second-stage nanofiltration concentrate inlet.

[0083] The secondary nanofiltration device 602 has an inlet connected to the outlet of the primary nanofiltration product water; the secondary nanofiltration device 602 also includes a monovalent salt solution outlet and a secondary nanofiltration concentrate outlet; the secondary nanofiltration concentrate outlet is connected to the secondary nanofiltration concentrate inlet.

[0084] The three-stage catalytic oxidation unit 303 has its inlet connected to the concentrate outlet of the first-stage nanofiltration unit 601.

[0085] The reverse osmosis unit 700 has its inlet connected to the outlet of the monovalent salt solution.

[0086] Sodium chloride evaporation and crystallization device 800, the inlet of sodium chloride evaporation and crystallization device 800 is connected to the outlet of reverse osmosis device 700;

[0087] The sodium sulfate freeze crystallization device 900 has its inlet connected to the outlet of the three-stage catalytic oxidation device 303.

[0088] The outlet of the sodium chloride evaporation and crystallization device 800 connected to the reverse osmosis device 700 is the outlet for enriching sodium chloride solution; the purified water outlet of the reverse osmosis device 700 can be connected to other devices that require purified water.

[0089] Wastewater containing organic matter and salts is first treated by air flotation in air flotation device 100, and then by first sedimentation in first sedimentation tank 201. The wastewater after first sedimentation is then treated by first-stage catalytic oxidation device 301. The wastewater after first-stage catalytic oxidation is then treated by second sedimentation in second sedimentation tank 202. The wastewater after second sedimentation is then treated by first filtration device 401, and then by second-stage catalytic oxidation device 302. Afterwards, cation exchange occurs in cation exchange resin device 500. Finally, after cation exchange, the wastewater undergoes second filtration in second filtration device 402. The wastewater after the second filtration is passed into a primary nanofiltration unit 601 for primary nanofiltration to obtain primary nanofiltration permeate and primary nanofiltration concentrate. The primary nanofiltration permeate is passed into a secondary nanofiltration unit 602 for secondary nanofiltration to obtain a monovalent salt solution and secondary nanofiltration concentrate. The secondary nanofiltration concentrate is returned to the primary nanofiltration unit 601 for primary nanofiltration. The monovalent salt solution is passed into a reverse osmosis unit 700 for treatment to obtain a monovalent salt concentrate. The monovalent salt concentrate is passed into a sodium chloride evaporation and crystallization unit 800 for crystallization to obtain crystalline sodium chloride. The primary nanofiltration concentrate is passed into a tertiary catalytic oxidation unit 303 for tertiary catalytic oxidation and then into a sodium sulfate freeze crystallization unit 900 for crystallization to obtain sodium sulfate.

[0090] In one embodiment, the air flotation device 100 is any one or a combination of a horizontal flow pressurized dissolved air flotation device, a high-efficiency shallow air flotation device, a multi-mixed dissolved air flotation device, a vortex air flotation device, and a multi-stage air flotation device. In a specific embodiment, the working pressure of the air flotation device 100 is 0.1-0.4 MPa.

[0091] In one embodiment, the first sedimentation tank 201 is selected from a high-efficiency sedimentation tank.

[0092] In one embodiment, the first filtration device 401 is selected from a high-speed high-efficiency filter, wherein the high-efficiency filter is a high-speed high-efficiency filter;

[0093] In a more specific embodiment, the high-speed high-efficiency filter is the Huade Venture IAT high-speed precision filter.

[0094] In one embodiment, the second filtration device 402 is selected from an ultrafiltration device.

[0095] In one embodiment, the reverse osmosis unit 700 is an ultra-high pressure reverse osmosis unit 700.

[0096] In a more specific implementation, the ultra-high pressure reverse osmosis unit 700 is from Xiamen Jiarong.

[0097] It is understandable that intermediate storage tanks can be set up between various devices for buffer connection.

[0098] In subsequent embodiments, the first filtration device 401 used in the first filtration is a Huade Venture IAT high-speed precision filter (wherein the pore size of the filter media particles is 1-60μm and the thickness of the filter medium is 3mm); the ultrafiltration device in the second filtration is selected from the membrane equipment of Hangzhou Kemo Company (Hangzhou Kemo Laboratory Ultrafiltration Membrane Pilot Equipment KM1812-UF); the reverse osmosis device 700 is Xiamen Jiarong RNF-1800-HP reverse osmosis laboratory equipment; and the cation exchange resin used in the cation exchange process is selected from styrene-type sulfonic acid-type cation exchange resin D001.

[0099] Example 2

[0100] This embodiment uses the apparatus provided in Embodiment 1 to recover resources from wastewater containing organic matter and impurities. The brine concentration of the wastewater containing organic matter and impurities is 41.99 g / L, and the water quality index is 6.24 g / L of Na. + 15.93 g / L Cl - SO4 13.92 g / L 2- 40.4 mg / L of F - 1.9 g / L of Ca 2+ 4 g / L Mg 2+ TOC was 487 mg / L; pH was 8.

[0101] Specifically, the steps include the following:

[0102] (1) The wastewater containing organic matter and salt was fed into the air flotation device 100 (a horizontal flow pressurized dissolved air flotation device) and air flotation was carried out at a pressure of 0.2 MPa. During the air flotation process, the pH value of the wastewater containing organic matter and salt was adjusted to 10 (the pH value was adjusted using sodium hydroxide). The TOC of the wastewater after air flotation was 380 mg / L.

[0103] (2) The wastewater treated after flotation is fed into the first sedimentation tank 201 for primary sedimentation treatment. During the primary sedimentation process, coagulant (polyaluminum sulfate), coagulant aid (anionic polyacrylamide), water softener (sodium hydroxide), defluorinator (polyaluminum chloride), and pesticide (sodium hypochlorite) are added. The total hardness of the wastewater after the primary sedimentation treatment is <40 mg / L; Ca 2+ and Mg 2+ Total <12mg / L;

[0104] (3) The wastewater after the first sedimentation treatment is fed into the primary catalytic oxidation unit 301 for primary catalytic oxidation treatment; wherein, the space velocity of the primary catalytic oxidation process is 0.5 h⁻¹. -1 The amount of H2O2 added was 974 ppm (relative to the volume of wastewater containing organic matter and miscellaneous salts); the catalyst used in the primary catalytic oxidation treatment was a nano-foam metal-iron-based composite catalyst with a particle size of 1-5 cm and a specific surface area of ​​13 m². 2 / g, average pore size 4nm; the material of the nanofoam metal iron-based composite catalyst contains 85wt% iron and 15wt% carbon; the TOC in the wastewater after primary catalytic oxidation is 121.75mg / L;

[0105] (4) The wastewater after the primary catalytic oxidation treatment is fed into the second sedimentation tank 202 for secondary sedimentation treatment. During the treatment process, coagulant (polyaluminum sulfate), coagulant aid (anionic polyacrylamide), water softener (sodium hydroxide), and defluorinating agent (polyaluminum chloride) are added.

[0106] (5) The wastewater after the second sedimentation treatment undergoes a first filtration in the first filtration device 401. The first filtration device 401 used in the first filtration is a Huade Venture IAT high-speed precision filter. The turbidity of the wastewater at the inlet of the first filtration is in the range of 27 NTU, and the turbidity of the treated wastewater is 0.3 NTU. The Ca in the wastewater after the first filtration is... 2+ Less than 30 ppm;

[0107] (6) The wastewater after the first filtration enters the secondary catalytic oxidation unit 302 for secondary catalytic oxidation. The catalyst for the secondary catalytic oxidation is a nano-catalyst, specifically a nano-nickel-iron alloy catalyst (the active component of the nano-catalyst is a ternary iron-nickel-copper alloy with a particle size of 20-30 nm, and the nano-catalyst support is activated carbon). The space velocity during the secondary catalytic oxidation process is 2 h⁻¹. -1 The amount of H2O2 added was 200 ppm (relative to the volume of wastewater containing organic matter and miscellaneous salts); the TOC after secondary catalytic oxidation was 28 mg / L.

[0108] (7) The wastewater after secondary catalytic oxidation is fed into the cation exchange resin device 500 for cation exchange; the cation exchange resin is styrene-sulfonic acid cation exchange resin D001; the wastewater after cation exchange is subjected to a second filtration in the second filtration device 402, the second filtration is an ultrafiltration membrane device from Hangzhou Kemo Membrane Co., Ltd.; the Ca+ concentration is reduced from 30ppm to less than 1ppm.

[0109] (8) The wastewater after the second filtration is passed into the first-stage nanofiltration unit 601 for first-stage nanofiltration to obtain first-stage nanofiltration permeate and first-stage nanofiltration concentrate; wherein, the membrane flux of the first-stage nanofiltration membrane is 14.35 L / m 2h; Inlet water pressure is 3.75 MPa; Product water recovery rate is 85%;

[0110] The primary nanofiltration permeate is passed into a secondary nanofiltration unit 602 for secondary nanofiltration treatment to obtain a monovalent salt solution and secondary nanofiltration concentrate; wherein, the secondary nanofiltration membrane flux is 14.68 L / m³. 2 h; inlet water pressure is 2.13 MPa; product water recovery rate is 85%; after treatment by primary nanofiltration unit 601 and secondary nanofiltration unit 602, the TOC rejection rate is 87.1%; the secondary nanofiltration concentrate contains NaCl: 21 g / L; Na2SO4: 128 g / L; the secondary nanofiltration concentrate is returned to primary nanofiltration unit 601 for primary nanofiltration;

[0111] (9) The monovalent salt solution is passed through a reverse osmosis unit 700 for treatment to obtain a concentrated monovalent salt solution; the concentrated monovalent salt solution is then passed through a sodium chloride evaporation and crystallization unit 800 for crystallization to obtain crystalline sodium chloride; wherein the reverse osmosis unit 700 adopts ultra-high pressure reverse osmosis, with a pressure of 8-12 MPa, an inlet salt concentration of 35 g / L, a product water salt concentration of 102 g / L NaCl, and a membrane flux of 41-50 L / m 2 h; The nucleation rate during the evaporation crystallization process was 0.3 mm / h, and the evaporation temperature was 60℃, yielding NaCl;

[0112] The concentrated water from the first-stage nanofiltration process is passed through a three-stage catalytic oxidation unit 303 for catalytic oxidation, and then passed through a sodium sulfate freeze crystallization unit 900 for crystallization to obtain sodium sulfate. The catalyst for the catalytic oxidation in the tertiary stage is a nanocatalyst, specifically a nano-nickel-iron alloy catalyst (the active component of the nanocatalyst is a ternary iron-nickel-copper alloy with a particle size of 20-30 nm, and the catalyst support is activated carbon). The space velocity (SPV) for the second-stage catalytic oxidation process is 2 h⁻¹. -1 The amount of H2O2 added was 200 ppm (relative to the volume of wastewater containing organic matter and miscellaneous salts); the freezing crystallization temperature was 5℃, and the freezing crystallization yield was 50%.

[0113] It is understood that the detection data in Example 2 and subsequent examples are the detection results after the system has been balanced.

[0114] Example 3

[0115] This embodiment uses the apparatus provided in Embodiment 1 to recover resources from wastewater containing organic matter and impurities. The brine concentration of the wastewater containing organic matter and impurities is 80 g / L, and the water quality index is 25.3 g / L of Na. + 35.5 g / L Cl - SO4 10.2 g / L 2- 4 mg / L of F - 4.5 g / L of Ca 2+2.4 ppm Mg 2+ 1.2 g / L CO3 2- 0.5 g / L HCO3 - TOC was 1092 mg / L; pH was 6.

[0116] Specifically, the steps include the following:

[0117] (1) The wastewater containing organic matter and salts was fed into the air flotation device 100 (a horizontal flow pressurized dissolved air flotation device) and air flotation was carried out at a pressure of 0.25 MPa. During the air flotation process, the pH value of the wastewater containing organic matter and salts was adjusted to 5 (the pH value was adjusted using hydrochloric acid). The TOC of the wastewater after air flotation was 747 mg / L.

[0118] (2) The wastewater treated after flotation is fed into the first sedimentation tank 201 for primary sedimentation treatment. During the primary sedimentation process, coagulant (polyaluminum sulfate), coagulant aid (anionic polyacrylamide), water softener (sodium hydroxide), defluorinator (polyaluminum chloride), and pesticide (sodium hypochlorite) are added. The total hardness of the wastewater after the primary sedimentation treatment is <50 mg / L; Ca 2+ and Mg 2+ Total <15mg / L;

[0119] (3) The wastewater after the first sedimentation treatment is fed into the primary catalytic oxidation unit 301 for primary catalytic oxidation treatment; wherein, the space velocity of the primary catalytic oxidation process is 0.5 h⁻¹. -1 The amount of H2O2 added was 974 ppm (relative to the volume of wastewater containing organic matter and miscellaneous salts); the catalyst used in the primary catalytic oxidation treatment was a nano-foam metal-iron-based composite catalyst with a particle size of 1-5 cm and a specific surface area of ​​13 m². 2 / g, average pore size 4nm; the nanofoam metal-iron based composite catalyst contains 85wt% iron and 15wt% carbon; the TOC in the wastewater after primary catalytic oxidation is 103mg / L.

[0120] (4) The wastewater after the primary catalytic oxidation treatment is fed into the second sedimentation tank 202 for secondary sedimentation treatment. During the treatment process, coagulant (polyaluminum sulfate), coagulant aid (anionic polyacrylamide), water softener (sodium hydroxide), and defluorinating agent (polyaluminum chloride) are added.

[0121] (5) The wastewater after the second sedimentation treatment undergoes a first filtration in the first filtration device 401. The first filtration device 401 used in the first filtration is a Huade Venture IAT high-speed precision filter. The turbidity of the wastewater at the inlet of the first filtration is in the range of 114 NTU, and the turbidity of the treated wastewater is 1 NTU. The Ca content in the wastewater after the first filtration is... 2+ Less than 30 ppm;

[0122] (6) The wastewater after the first filtration enters the secondary catalytic oxidation unit 302 for secondary catalytic oxidation. The catalyst for the secondary catalytic oxidation is a nano-catalyst, specifically a nano-nickel-iron alloy catalyst (the active component of the nano-catalyst is a ternary iron-nickel-copper alloy with a particle size of 20-30 nm, and the nano-catalyst support is activated carbon). The space velocity during the secondary catalytic oxidation process is 2 h⁻¹. -1 The amount of H2O2 added was 180 ppm (compared to the volume of wastewater containing organic matter and miscellaneous salts); the TOC after secondary catalytic oxidation was 30 mg / L.

[0123] (7) The wastewater after secondary catalytic oxidation is fed into the cation exchange resin device 500 for cation exchange; the cation exchange resin is styrene-sulfonic acid cation exchange resin D001; the wastewater after cation exchange is subjected to a second filtration in the second filtration device 402, the second filtration is an ultrafiltration membrane device from Hangzhou Kemo Membrane Co., Ltd.; the Ca+ concentration is reduced from 30ppm to less than 1ppm.

[0124] (8) The wastewater after the second filtration is passed into the first-stage nanofiltration unit 601 for first-stage nanofiltration to obtain first-stage nanofiltration permeate and first-stage nanofiltration concentrate; wherein, the membrane flux of the first-stage nanofiltration membrane is 15.5 L / m 2 h; Inlet water pressure is 3.75 MPa; Product water recovery rate is 80%;

[0125] The primary nanofiltration permeate is passed into a secondary nanofiltration unit 602 for secondary nanofiltration treatment to obtain a monovalent salt solution and secondary nanofiltration concentrate; wherein, the secondary nanofiltration membrane flux is 15.5 L / m³. 2 h; inlet water pressure is 5.12 MPa; product water recovery rate is 85%; after treatment by primary nanofiltration unit 601 and secondary nanofiltration unit 602, the TOC rejection rate is 84.5%; the secondary nanofiltration concentrate contains NaCl: 34 g / L; Na2SO4: 137 g / L; the secondary nanofiltration concentrate is returned to primary nanofiltration unit 601 for primary nanofiltration;

[0126] (9) The monovalent salt solution is passed through a reverse osmosis unit 700 for treatment to obtain a concentrated monovalent salt solution; the concentrated monovalent salt solution is then passed through a sodium chloride evaporation and crystallization unit 800 for crystallization to obtain crystalline sodium chloride; wherein the reverse osmosis unit 700 adopts ultra-high pressure reverse osmosis, with a pressure of 8-12 MPa, an inlet salt concentration of 45 g / L, a product water salt concentration of 136 g / L NaCl, and a membrane flux of 41-50 L / m 2 h; The nucleation rate during the evaporation crystallization process is 0.5 mm / h, the evaporation temperature is 80℃, and NaCl is obtained;

[0127] The concentrated water from the first-stage nanofiltration process is passed through a three-stage catalytic oxidation unit 303 for catalytic oxidation, and then passed through a sodium sulfate freeze crystallization unit 900 for crystallization to obtain sodium sulfate. The catalyst for the catalytic oxidation in this process is a nano-catalyst, specifically a nano-nickel-iron alloy catalyst (the active component of the nano-catalyst is a ternary iron-nickel-copper alloy with a particle size of 20-30 nm, and the catalyst support is activated carbon). The space velocity (SHV) for the catalytic oxidation process is 2 h⁻¹. -1 The amount of H2O2 added was 180 ppm (relative to the volume of wastewater containing organic matter and miscellaneous salts); the freeze crystallization temperature was 3℃, and the freeze crystallization yield was 65%.

[0128] Example 4

[0129] This embodiment uses the apparatus provided in Embodiment 1 to recover resources from wastewater containing organic matter and impurities. The brine concentration of the wastewater containing organic matter and impurities is 150 g / L, and the water quality index is 60.4 g / L of Na. + 49.8 g / L Cl - SO4 26.8 g / L 2- 4ppm F - 5.3 g / L of Ca 2+ 1.2 ppm Mg 2+ 0.5 g / L CO3 2- 6.4 g / L HCO3 - TOC was 1976 mg / L; pH was 8.

[0130] Specifically, the steps include the following:

[0131] (1) The wastewater containing organic matter and salts was fed into the air flotation device 100 (a horizontal flow pressurized dissolved air flotation device 100) and air flotation was carried out at a pressure of 0.3 MPa. During the air flotation process, the pH value of the wastewater containing organic matter and salts was adjusted to 9 (the pH value was adjusted using calcium hydroxide). The TOC of the wastewater after air flotation was 1430 mg / L.

[0132] (2) The wastewater treated after flotation is fed into the first sedimentation tank 201 for primary sedimentation treatment. During the primary sedimentation process, coagulant (polyaluminum sulfate), coagulant aid (anionic polyacrylamide), water softener (sodium hydroxide), defluorinator (polyaluminum chloride), and pesticide (sodium hypochlorite) are added. The total hardness of the wastewater after the primary sedimentation treatment is <55 mg / L; Ca 2+ and Mg 2+ Total <18mg / L;

[0133] (3) The wastewater after the first sedimentation treatment is fed into the primary catalytic oxidation unit 301 for primary catalytic oxidation treatment; wherein, the space velocity of the primary catalytic oxidation process is 0.5 h⁻¹. -1The amount of H2O2 added was 974 ppm (relative to the volume of wastewater containing organic matter and miscellaneous salts); the catalyst used in the primary catalytic oxidation treatment was a nano-foam metal-iron-based composite catalyst with a particle size of 1-5 cm and a specific surface area of ​​13 m². 2 / g, average pore size 4nm; the nanofoam metal-iron based composite catalyst contains 85wt% iron and 15wt% carbon; the TOC in the wastewater after primary catalytic oxidation is 135mg / L.

[0134] (4) The wastewater after the primary catalytic oxidation treatment is fed into the second sedimentation tank 202 for secondary sedimentation treatment. During the treatment process, coagulant (polyaluminum sulfate), coagulant aid (anionic polyacrylamide), water softener (sodium hydroxide), and defluorinating agent (polyaluminum chloride) are added.

[0135] (5) The wastewater after the second sedimentation treatment undergoes a first filtration in the first filtration device 401. The first filtration device 401 used in the first filtration is a Huade Venture IAT high-speed precision filter. The turbidity of the wastewater at the inlet of the first filtration is in the range of 198 NTU, and the turbidity of the treated wastewater is 5 NTU. The Ca in the wastewater after the first filtration is... 2+ Less than 30 ppm;

[0136] (6) The wastewater after the first filtration enters the secondary catalytic oxidation unit 302 for secondary catalytic oxidation. The catalyst for the secondary catalytic oxidation is a nano-catalyst, specifically a nano-nickel-iron alloy catalyst (the active component of the nano-catalyst is a ternary iron-nickel-copper alloy with a particle size of 20-30 nm, and the nano-catalyst support is activated carbon). The space velocity during the secondary catalytic oxidation process is 2 h⁻¹. -1 The amount of H2O2 added was 200 ppm (relative to the volume of wastewater containing organic matter and miscellaneous salts); the TOC after secondary catalytic oxidation was 28 mg / L.

[0137] (7) The wastewater after secondary catalytic oxidation is fed into the cation exchange resin device 500 for cation exchange; the cation exchange resin is styrene-sulfonic acid cation exchange resin D001; the wastewater after cation exchange is subjected to a second filtration in the second filtration device 402, the second filtration is an ultrafiltration membrane device from Hangzhou Kemo Membrane Co., Ltd.; the Ca+ concentration is reduced from 30ppm to less than 1ppm.

[0138] (8) The wastewater after the second filtration is passed into the first-stage nanofiltration unit 601 for first-stage nanofiltration to obtain first-stage nanofiltration permeate and first-stage nanofiltration concentrate; wherein, the membrane flux of the first-stage nanofiltration membrane is 15.8 L / m 2 h; Inlet water pressure is 3.75 MPa; Product water recovery rate is 80%;

[0139] The primary nanofiltration permeate is passed into the secondary nanofiltration unit 602 for secondary nanofiltration treatment to obtain a monovalent salt solution and secondary nanofiltration concentrate. The secondary nanofiltration membrane flux is 15.5 L / m²h; the inlet pressure is 5.12 MPa; the permeate recovery rate is 85%; the TOC rejection rate after treatment by the primary nanofiltration unit 601 and the secondary nanofiltration unit 602 is 82.8%; the secondary nanofiltration concentrate contains 39 g / L NaCl and 148 g / L Na₂SO₄; the secondary nanofiltration concentrate is returned to the primary nanofiltration unit 601 for primary nanofiltration.

[0140] (9) The monovalent salt solution is passed through a reverse osmosis unit 700 for treatment to obtain a concentrated monovalent salt solution; the concentrated monovalent salt solution is then passed through a sodium chloride evaporation and crystallization unit 800 for crystallization to obtain crystalline sodium chloride; wherein the reverse osmosis unit 700 adopts ultra-high pressure reverse osmosis, with a pressure of 8-12 MPa, an inlet salt concentration of 68 g / L, a product water salt concentration of 130 g / L NaCl, and a membrane flux of 41-50 L / m 2 h; The nucleation rate during the evaporation crystallization process is 1 mm / h, the evaporation temperature is 100℃, and NaCl is obtained;

[0141] The concentrated water from the first-stage nanofiltration process is passed through a three-stage catalytic oxidation unit 303 for catalytic oxidation, and then passed through a sodium sulfate freeze crystallization unit 900 for crystallization to obtain sodium sulfate. The catalyst for the catalytic oxidation in this process is a nano-catalyst, specifically a nano-nickel-iron alloy catalyst (the active component of the nano-catalyst is a ternary iron-nickel-copper alloy with a particle size of 20-30 nm, and the catalyst support is activated carbon). The space velocity (SHV) for the catalytic oxidation process is 2 h⁻¹. -1 The amount of H2O2 added was 200 ppm (relative to the volume of wastewater containing organic matter and impurities); the freeze crystallization temperature was 0℃, and the freeze crystallization yield was 75%.

[0142] Comparative Example 1

[0143] This comparative example uses the same wastewater containing organic matter and miscellaneous salts as Example 4, and the treatment process is similar. The difference is that pH is not controlled during the air flotation process; the TOC in the wastewater after air flotation is 1877 mg / L, which puts significant pressure on subsequent processes. The TOC after the first-stage catalytic oxidation is 330 mg / L, and the space velocity during the second-stage catalytic oxidation process is 2 h⁻¹. -1 The H2O2 addition amount was 200 ppm (relative to the volume of wastewater containing organic matter and miscellaneous salts); the TOC after the secondary catalytic oxidation was 125 mg / L; the space velocity of the tertiary catalytic oxidation process was 2 h⁻¹. -1 The amount of H2O2 added was 200 ppm (compared to the volume of wastewater containing organic matter and miscellaneous salts); the TOC after three-stage catalytic oxidation was 96 mg / L; the high organic matter content affected the membrane life and separation efficiency, the freeze crystallization yield decreased to 40%, and the purity of evaporated sodium chloride and crystallized sodium sulfate decreased.

[0144] Comparative Example 2

[0145] This comparative example is the same as the wastewater containing organic matter and miscellaneous salts in Example 4, and the treatment process is similar. The difference is that an iron alloy catalyst is used in the first-stage catalytic oxidation process, the TOC after the first-stage catalytic oxidation is 938 mg / L, and the space velocity in the second-stage catalytic oxidation process is 2 h⁻¹. -1 The H2O2 addition amount was 200 ppm (relative to the volume of wastewater containing organic matter and miscellaneous salts); the TOC after the secondary catalytic oxidation was 550 mg / L; the space velocity of the tertiary catalytic oxidation process was 2 h⁻¹. -1 The amount of H2O2 added was 200 ppm (compared to the volume of wastewater containing organic matter and miscellaneous salts); the TOC after three-stage catalytic oxidation was 235 mg / L; the high organic matter content affected the membrane life and separation efficiency, the freeze crystallization yield was significantly reduced to 20%, and the purity of evaporated sodium chloride and crystallized sodium sulfate was significantly reduced.

[0146] Test case

[0147] The components of NaCl and Glauber's salt obtained in the examples and comparative examples were determined by ion chromatography, and the results are shown in Table 1 and Table 2.

[0148] Table 1

[0149]

[0150] The evaluation was based on the Grade I standard for refined industrial dry salt in GB 5462-2015, "Industrial Salt".

[0151] Table 2

[0152]

[0153] The evaluation is based on the specifications and grades of Chinese medicinal materials as defined in T / CACM 1021.220-2018.

[0154] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for resource recovery from wastewater containing organic matter and miscellaneous salts, characterized in that, Includes the following steps: (1) Wastewater containing organic matter and salts is subjected to air flotation, first sedimentation treatment, first-stage catalytic oxidation, second sedimentation treatment, first filtration, second-stage catalytic oxidation, cation exchange, second filtration, and first-stage nanofiltration in sequence to obtain first-stage nanofiltration permeate and first-stage nanofiltration concentrate. (2) The primary nanofiltration permeate is subjected to secondary nanofiltration to obtain a monovalent salt solution and secondary nanofiltration concentrate. The monovalent salt solution is subjected to reverse osmosis to obtain a monovalent salt concentrate solution. The monovalent salt concentrate solution is crystallized to obtain crystalline sodium chloride. The concentrate from the secondary nanofiltration process is returned to the primary nanofiltration process for further treatment. (3) The concentrated water from the first-stage nanofiltration is subjected to tertiary catalytic oxidation and then crystallized to obtain crystalline sodium sulfate; Specifically, the pH value of the wastewater containing organic matter and salts is controlled during the air flotation process; when the wastewater containing organic matter and salts is acidic, the pH value of the wastewater containing organic matter and salts is reduced during the air flotation process; when the wastewater containing organic matter and salts is alkaline, the pH value of the wastewater containing organic matter and salts is increased during the air flotation process. The catalyst for primary catalytic oxidation was selected from nanofoam metal-iron-based composite catalysts; The TOC content in the wastewater containing organic matter and miscellaneous salts is 1000-2000 mg / L; The concentration of mixed salts in the wastewater containing organic matter and mixed salts is 20-150 g / L; The nanofoam metal-iron based composite catalyst has a particle size of 1-5 cm and a specific surface area of ​​5-20 m². 2 / g, pore size distribution range 10-100 nm, average pore size 20-30 nm; the material of the nanofoam metal iron-based composite catalyst contains 85-98wt% iron; The wastewater containing organic matter and salts comes from wastewater generated by coking, pharmaceutical, printing and dyeing, fertilizer, and pesticide industries. The space velocity for the first-stage catalytic oxidation process is 0.2-2.0 h⁻¹. -1 The amount of H2O2 added is 50-2000ppm.

2. The method according to claim 1, characterized in that, The organic wastewater contains chloride ions, sulfate ions, sodium ions, calcium ions, and fluoride ions.

3. The method according to claim 1, characterized in that, The wastewater containing organic salts also includes at least one of carbonate ions, bicarbonate ions, and magnesium ions.

4. The method according to claim 1, characterized in that, Coagulants, flocculants, water softeners, and defluorinators are added during the first and second sedimentation treatments.

5. The method according to claim 1, characterized in that, The nanofoam metal-iron-based composite catalyst also includes carbon.

6. The method according to claim 1, characterized in that, The catalysts used in the secondary and tertiary catalytic oxidation are nano-catalysts.

7. The method according to claim 6, characterized in that, The active component of the nanocatalyst is an iron-nickel-copper ternary alloy with a particle size of 20-30 nm, and the nanocatalyst support is activated carbon.

8. The method according to claim 1, characterized in that, The space velocity in two-stage and three-stage catalytic oxidation is 0.2-2.0 h⁻¹. -1 The amount of H2O2 added is 50-1000ppm.

9. The method according to claim 1, characterized in that, The filter medium in the first filtration is selected from modified polymer microporous suspended fiber filter cloth particles.

10. The method according to claim 1, characterized in that, The turbidity range of the inlet wastewater after the first filtration is 20-200 NTU, and the turbidity of the treated wastewater is less than 5 NTU. The Ca content in the wastewater after the first filtration is... 2+ Less than 30 ppm.

11. The method according to claim 1, characterized in that, The cation exchange resin used in the cation exchange process is selected from styrene-type sulfonic acid cation exchange resin D001 or acrylic-type weak acid cation exchange resin D113.

12. The method according to claim 1, characterized in that, The second filtration is performed using an ultrafiltration device.

13. The method according to claim 1, characterized in that, The primary nanofiltration unit and the secondary nanofiltration unit are connected in series. The membrane flux of the nanofiltration membrane modules in both units is 10–30 L / (m²). 2 *h), the inlet water pressure is 1.5~4MPa, the first-stage nanofiltration permeate recovery rate is 60-90%, and the second-stage nanofiltration permeate recovery rate is 80-96%.

14. The method according to claim 1, characterized in that, The method for crystallizing a concentrated monovalent salt solution is selected from concentrated crystallization.

15. The method according to claim 1, characterized in that, In step (3), the crystallization method is selected from freeze crystallization; the crystallization temperature is 0-5℃.

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