Treatment method of high-temperature wastewater

Abstract

The invention discloses a high-temperature wastewater treatment method which comprises the following steps: performing nanofiltration treatment according to the content of calcium ions, the content of magnesium ions and the content of total organic matters in filtered water, and when the sum of the content of the calcium ions and the content of the magnesium ions in the filtered water is greater than or equal to 50mg / L, performing first nanofiltration treatment by adopting a nanofiltration membrane with the molecular weight cutoff less than 300, then carrying out high-temperature reverse osmosis treatment; when the sum of the content of calcium ions and magnesium ions in the filtered water is less than 50mg / L and the content of total organic matters is more than or equal to 50mg / L, carrying out second nanofiltration treatment on the nanofiltration membrane with the molecular weight cutoff less than (the number-average molecular weight of the organic matters in the water / 2), and then carrying out high-temperature reverse osmosis treatment; when the sum of the content of calcium ions and magnesium ions in the filtered water is less than 50mg / L and the content of total organic matters is less than 50mg / L, high-temperature reverse osmosis treatment is directly carried out without nanofiltration treatment. The method prolongs the service life of the high-temperature reverse osmosis membrane and reduces the cleaning frequency.

Description

Technical Field

[0001] This invention relates to the field of high-temperature wastewater treatment technology, and more specifically, to a method for treating high-temperature wastewater. Background Technology

[0002] Membrane separation is widely used in various processes that require the separation of solutes from water, with material purification and wastewater treatment being the most common applications. Most membranes can only operate normally for extended periods below 40°C. Therefore, for high-temperature materials or wastewater, cooling is often necessary before treatment, wasting significant energy. Furthermore, for processes requiring material purification during production, cooling can negatively impact product quality or even be impractical. These situations necessitate the use of high-temperature resistant membranes.

[0003] Many high-temperature resistant membranes have been developed, but due to limitations in materials and processing technology, the variety of high-temperature resistant membranes is far less than that of room-temperature membranes, thus restricting their application range. For example, while high-temperature resistant reverse osmosis membranes have good desalination rates at high temperatures, high-temperature pretreatment methods cannot guarantee that the pretreated material meets the feed water quality requirements for high-temperature reverse osmosis. If used to separate materials with complex compositions, membrane fouling is likely to occur, limiting the applicable processes. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of low removal rate of some substances in the existing high-temperature reverse osmosis pretreatment method, and to provide a high-temperature wastewater treatment method. This method selects a high-temperature resistant nanofiltration membrane with an appropriate molecular weight cutoff to protect the high-temperature reverse osmosis according to the influent water quality, which can significantly improve the life of the high-temperature reverse osmosis membrane under complex influent water quality.

[0005] To achieve the above objectives, the present invention provides a method for treating high-temperature wastewater, the method comprising the following steps:

[0006] S1. Filter the high-temperature wastewater to obtain filtered water; test the calcium ion content, magnesium ion content and total organic matter content in the filtered water;

[0007] S2. When the sum of calcium and magnesium ion content in the filtered water is ≥50mg / L, a first nanofiltration treatment is performed first, followed by a high-temperature reverse osmosis treatment; wherein, the first nanofiltration treatment uses a first nanofiltration membrane, and the molecular weight cutoff of the first nanofiltration membrane is <300.

[0008] When the sum of calcium and magnesium ion content in the filtered water is <50 mg / L and the total organic matter content is ≥50 mg / L, a second nanofiltration treatment is performed first, followed by a high-temperature reverse osmosis treatment; wherein, the second nanofiltration treatment uses a second nanofiltration membrane, the molecular weight cutoff of the second nanofiltration membrane is <(number average molecular weight of organic matter in water / 2), and the molecular weight cutoff of the second nanofiltration membrane is not less than 300.

[0009] When the sum of calcium and magnesium ion content in the filtered water is <50 mg / L and the total organic matter content is <50 mg / L, nanofiltration is not required, and high-temperature reverse osmosis can be performed directly.

[0010] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0011] The high-temperature wastewater treatment method proposed in this invention can significantly improve the lifespan of high-temperature reverse osmosis membranes under complex influent water quality and reduce the cleaning frequency. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] This invention provides a method for treating high-temperature wastewater, which includes the following steps:

[0014] S1. Filter the high-temperature wastewater to obtain filtered water; test the calcium ion content, magnesium ion content and total organic matter content in the filtered water;

[0015] S2. When the sum of calcium and magnesium ion content in the filtered water is ≥50mg / L, a first nanofiltration treatment is performed first, followed by a high-temperature reverse osmosis treatment; wherein, the first nanofiltration treatment uses a first nanofiltration membrane, and the molecular weight cutoff of the first nanofiltration membrane is <300.

[0016] When the sum of calcium and magnesium ion content in the filtered water is <50 mg / L and the total organic matter content is ≥50 mg / L, a second nanofiltration treatment is performed first, followed by a high-temperature reverse osmosis treatment; wherein, the second nanofiltration treatment uses a second nanofiltration membrane, the molecular weight cutoff of the second nanofiltration membrane is <(number average molecular weight of organic matter in water / 2), and the molecular weight cutoff of the second nanofiltration membrane is not less than 300.

[0017] When the sum of calcium and magnesium ion content in the filtered water is <50 mg / L and the total organic matter content is <50 mg / L, nanofiltration is not required, and high-temperature reverse osmosis can be performed directly.

[0018] In this invention, the calcium ion content in the filtered water refers to the calcium ion concentration, and the magnesium ion content refers to the magnesium ion concentration. Both the calcium ion content and magnesium ion content in the filtered water are determined using ion chromatography.

[0019] In this invention, the total organic matter (TOC) content in the filtered water is tested according to the method specified in GB3838-2002 "Surface Water Environmental Quality Standard".

[0020] In this invention, gel permeation chromatography (GPC) is used to determine the number-average molecular weight of organic matter in water.

[0021] According to a preferred embodiment of the present invention, the temperature of the high-temperature wastewater is 60-90°C, for example, 60°C, 75°C, 80°C, 85°C, 90°C, or any value within a range of any two values.

[0022] According to a preferred embodiment of the present invention, in step S1, the filter used is a filter with a filtration accuracy of 0.5-2μm and a maximum operating temperature of ≥90℃.

[0023] In the method of the present invention, the filter used in step S1 with a filtration accuracy of 0.5-2μm and a maximum operating temperature of ≥90℃ is a high-temperature resistant precision filter.

[0024] According to the present invention, a high-temperature resistant nanofiltration membrane with a suitable molecular weight cutoff is selected for nanofiltration treatment based on the content of calcium and magnesium ions in the water and the average molecular weight of organic matter. The pretreated water obtained in step (1) that meets the conditions can be directly sent to the high-temperature reverse osmosis unit.

[0025] According to the present invention, depending on the condition of the high-temperature wastewater, a suitable high-temperature resistant composite nanofiltration membrane can be selected from high-temperature resistant composite nanofiltration membranes with a molecular weight cutoff ranging from 200 to 2000.

[0026] According to the present invention, both the first nanofiltration membrane and the second nanofiltration membrane are high-temperature resistant composite nanofiltration membranes. They have different molecular weight cutoffs.

[0027] According to this invention, unless otherwise specified, the unit of molecular weight cutoff is g / mol.

[0028] According to a preferred embodiment of the present invention, in step S2, the method for preparing the first nanofiltration membrane includes the following steps:

[0029] (1) Dissolve the heat-resistant polymer in a first solvent to obtain a casting solution; coat the casting solution into a film, and then immerse it in a second solvent to transform it into a solid film.

[0030] (2) The solid membrane is subjected to a first treatment in an aqueous solution, then to a second treatment in an oil solution, and then subjected to heat treatment to obtain a composite nanofiltration membrane; wherein, the aqueous monomer in the aqueous solution is selected from at least one of the following aromatic polyamines, wherein the aromatic polyamine has at least two primary or secondary amino groups, has at least one aliphatic side group with ≤3 carbon atoms, and at least one primary or secondary amino group is located on the aliphatic side group; the oil monomer in the oil solution is selected from at least one of phenyl acyl chlorides.

[0031] According to a preferred embodiment of the present invention, the aromatic polyamine is 2-amino-N-methylbenzylamine and / or 4-amino-N-(1-methylethyl)benzylamine.

[0032] According to a preferred embodiment of the present invention, the phenyl acyl chloride is pyromellitic tricarboxylate chloride and / or pyromellitic tetracarboxylate chloride.

[0033] According to a preferred embodiment of the present invention, in step S2, the method for preparing the second nanofiltration membrane includes the following steps:

[0034] (1) Dissolve the heat-resistant polymer in a first solvent to obtain a casting solution; coat the casting solution into a film, and then immerse it in a second solvent to transform it into a solid film.

[0035] (2) The solid membrane is subjected to a first treatment in an aqueous solution, a second treatment in an oil solution, and then heat treatment to obtain a composite nanofiltration membrane; wherein, the aqueous monomer in the aqueous solution includes component A and component B, component A is selected from at least one heterocyclic polyamine having at least two primary or secondary amino groups and a nitrogen atom in the ring; component B is selected from at least one aliphatic polyamine having at least two primary or secondary amino groups and a carbon chain length ≥ 4 carbon atoms; and the oil monomer in the oil solution is selected from at least one phenyl acyl chloride.

[0036] According to the present invention, the solid membranes used in the first nanofiltration membrane and the second nanofiltration membrane can be the same or different, preferably the same solid membrane. The preparation method of the solid membrane specifically includes the following steps: dissolving a heat-resistant polymer in a first solvent at room temperature, normal pressure and a stirring speed of 200-400 rpm to obtain a casting solution with a mass concentration of 10-30 wt%; coating the casting solution into a membrane with a thickness of 50-300 μm, and then immersing it in a second solvent to allow it to undergo phase transformation into a solid membrane.

[0037] According to a preferred embodiment of the present invention, component A is N-aminoethylpiperazine and / or 1,4-bis(aminopropyl)piperazine; component B is 1,6-hexanediamine and / or 1,10-decanediamine.

[0038] According to the present invention, component A and component B in the aqueous monomer are compounded in a certain proportion according to the required molecular weight cutoff.

[0039] According to a preferred embodiment of the present invention, the molar ratio of component A to component B is 0.1-8:1, for example, 0.1:1, 0.2:1, 0.5:1, 0.8:1, 1:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, and any value within the range of any two values, preferably 0.2-5:1.

[0040] According to a preferred embodiment of the present invention, the heat-resistant polymer is selected from one or more of polyimide, polyetherimide, polyethersulfone, and polyetheretherketone.

[0041] According to a preferred embodiment of the present invention, the first solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

[0042] According to a preferred embodiment of the present invention, the second solvent is selected from one or more of water and small molecule alcohols; preferably, the small molecule alcohols are selected from one or more of methanol, ethanol, ethylene glycol, diethylene glycol, propanol, isopropanol, 1,2-propanediol, 1,3-propanediol and glycerol.

[0043] According to a preferred embodiment of the present invention, the aqueous solution is an aqueous solution containing an aqueous monomer, a catalyst, and a hydrogen chloride absorbent.

[0044] According to a preferred embodiment of the present invention, the catalyst is selected from one or more organic weak acids; more preferably, the catalyst is oxalic acid and / or DL-camphorsulfonic acid.

[0045] According to a preferred embodiment of the present invention, the hydrogen chloride absorbent is selected from one or more of C4-C12 tertiary amines; more preferably, the hydrogen chloride absorbent is triethylamine and / or N,N-dimethylaniline.

[0046] According to a preferred embodiment of the present invention, the concentration of the aqueous monomer is [(0.05-0.1) ÷ the average number of hydrogen atoms on the amino group per molecule] mol / L.

[0047] According to a preferred embodiment of the present invention, the concentration of the catalyst is 0.05-0.2 mol / L.

[0048] According to a preferred embodiment of the present invention, the concentration of the hydrogen chloride absorbent is 0.05-0.2 mol / L.

[0049] According to a preferred embodiment of the present invention, the oil phase solution is an oily solvent containing oil phase monomers.

[0050] According to a preferred embodiment of the present invention, the oily solvent is selected from one or more of C6-C20 aliphatic alkanes.

[0051] According to the present invention, C6-C20 aliphatic alkanes include, but are not limited to: n-heptane, n-octane, isooctane, Isopar-G (ExxonMobil product), Isopar-H (ExxonMobil product), etc.

[0052] According to a preferred embodiment of the present invention, the concentration of the oil phase monomer is [(0.1-0.5) ÷ the average number of acyl chloride groups per molecule] mol / L.

[0053] The present invention will be described in detail below through preparation examples and embodiments, but the scope of protection of the present invention is not limited to the following description.

[0054] Unless otherwise specified in the following preparation examples, embodiments, and comparative examples, all conditions should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0055] In the following examples, the total organic matter (TOC) content in the water was tested according to the method specified in GB3838-2002 "Environmental Quality Standard for Surface Water".

[0056] In the following examples, ion chromatography was used to determine the concentrations of calcium and magnesium ions in water. The specific testing method was as follows: An ion chromatograph was equipped with a cation exchange column, and an aqueous solution containing 3.0 mmol / L phthalic acid was used as the eluent at a flow rate of 0.8 mL / min. Calcium chloride aqueous solutions with lithium ion concentrations of 0.1, 0.5, 1, 5, 10, 20, 40, 60, 80, and 100 mg / L, as well as magnesium chloride solutions of the same concentration, were prepared and injected into the ion chromatograph. The peak areas of calcium and magnesium ions were measured, and a standard curve was obtained by linear fitting with cation concentration as the x-axis and peak area as the y-axis. The water sample was filtered through a 0.45 μm microporous membrane and then injected into the ion chromatograph. The peak areas of calcium and magnesium ions were measured, and the concentrations of calcium and magnesium ions were obtained by substituting these values ​​into the corresponding standard curve equations. If the concentration is greater than 100 mg / L, the water sample is diluted by a certain factor so that the diluted cation concentration is less than 100 mg / L, and then measured again. The measured cation concentration is multiplied by the dilution factor to obtain the original cation concentration.

[0057] In the following examples and comparative examples, gel permeation chromatography (GPC) was used to determine the number-average molecular weight of organic matter in water. Water was used as the mobile phase in the GPC, and a column suitable for water as the mobile phase (e.g., a Waters Ultrahydrogel 120 column) with a lower molecular weight limit of 200 or less was selected. If the TOC in the water is <50 mg / L, it is not necessary to determine the number-average molecular weight of organic matter in the water. If the TOC in the water is >500 mg / L, the sample needs to be diluted with purified water to bring the TOC to the range of 50-500 mg / L. Before injection, the sample must be filtered through a 0.22 μm filter membrane.

[0058] Example 1

[0059] (1) The wastewater is coagulated wastewater from the brominated butyl rubber unit, with a temperature of 78℃. The precision filter element is high-temperature resistant PP filter cotton with a filtration accuracy of 0.5μm, resulting in pretreated water.

[0060] (2) The water quality of the pretreated water obtained in step (1) was measured. The results were: TOC 278 mg / L, calcium ion concentration 5 mg / L, magnesium ion concentration 2 mg / L, and the number average molecular weight of organic matter in the water was 1580.

[0061] (3) A high-temperature resistant nanofiltration membrane with a molecular weight cutoff of 713 was selected to perform high-temperature nanofiltration treatment on the pretreated water obtained in step (1). The specific preparation method of the nanofiltration membrane is as follows: (a) Polyetherimide (purchased from SABIC, brand name 1000) was dissolved in N,N-dimethylformamide to obtain a casting solution with a mass concentration of 24wt%; (b) The casting solution obtained in step (a) was coated on polyester nonwoven fabric to form a liquid film with a thickness of 200μm, and then immediately immersed in water to obtain a solid film; (c) The solid film obtained in step (b) was immersed in an aqueous phase solution, wherein the aqueous phase monomer in the aqueous phase solution was 0.004mol / L of 1,4-bis(aminopropyl)piperazine and 0.012mol / L of bis(aminopropyl)piperazine. The membrane was prepared by adding 0.1 mol / L of 1,6-hexanediamine, 0.1 mol / L of triethylamine as the hydrogen chloride absorbent, and 0.1 mol / L of DL-camphor sulfonic acid as the catalyst. After 3 minutes, the membrane was removed and the aqueous phase solution on the surface was cleaned with an air knife. Then, it was immersed in an oil phase solution. The oil phase monomer in the oil phase solution was 0.037 mol / L of pyromellitic acid, and the oily solvent was Isopar-G (purchased from ExxonMobil). After 1 minute, the membrane was removed and the oil phase solution on the surface was cleaned with an air knife. Then, it was baked at 90°C for 10 minutes using a forced-air dryer to obtain the nanofiltration membrane.

[0062] The permeate after high-temperature nanofiltration in step (3) was sent to a high-temperature reverse osmosis system for single-cycle life measurement, and the result was 714 hours.

[0063] Example 2

[0064] (1) The wastewater is production wastewater from a pharmaceutical factory, with a temperature of 85℃. The precision filter element is high-temperature resistant PP filter cotton, with a filtration accuracy of 0.5μm.

[0065] (2) The water quality of the pretreated water obtained in step (1) was measured. The results were: TOC 1085 mg / L, calcium ion concentration 12 mg / L, magnesium ion concentration 7 mg / L, and the number average molecular weight of organic matter in the water was 1160.

[0066] (3) A high-temperature resistant nanofiltration membrane with a molecular weight cutoff of 525 was selected to perform high-temperature nanofiltration treatment on the pretreated water obtained in step (1). The preparation method of the nanofiltration membrane is the same as that in Example 1, except that in step (c), the aqueous phase monomers are 0.01 mol / L N-aminoethylpiperazine and 0.006 mol / L 1,10-decanediamine.

[0067] The permeate after high-temperature nanofiltration in step (3) was sent to a high-temperature reverse osmosis system for single-cycle life measurement, and the result was 745 hours.

[0068] Example 3

[0069] (1) The wastewater is fly ash wastewater obtained from the fly ash washing process, and the temperature is 70℃. The precision filter element is high-temperature resistant PP filter cotton, and the filtration accuracy is 0.5μm.

[0070] (2) The water quality of the pretreated water obtained in step (1) was measured. The results were: TOC 35 mg / L, calcium ion concentration 2400 mg / L, and magnesium ion concentration 1400 mg / L.

[0071] (3) A high-temperature resistant nanofiltration membrane with a molecular weight cutoff of 239 was selected to perform high-temperature nanofiltration treatment on the pretreated water obtained in step (1). The preparation method of the nanofiltration membrane is the same as that in Example 1, except that in step (c), the aqueous phase monomer is 0.02 mol / L of 2-amino-N-methylbenzylamine.

[0072] The high-temperature nanofiltration process in step (3) was sent to a high-temperature reverse osmosis system for a single cycle life test, and the result was 698 hours.

[0073] Example 4

[0074] (1) The wastewater is steam condensate from a thermal power plant, with a temperature of 82℃. The precision filter element is high-temperature resistant PP filter cotton, with a filtration accuracy of 0.5μm.

[0075] (2) The water quality of the pretreated water obtained in step (1) was measured. The results were: TOC 35 mg / L, calcium ion concentration 25 mg / L, magnesium ion concentration 15 mg / L. No nanofiltration treatment was required.

[0076] The pretreated water obtained in step (1) was sent to a high-temperature reverse osmosis system for a single cycle life test, and the result was 685 hours.

[0077] Comparative Example 1

[0078] The same method as in Example 1 is used, except that step (3) is omitted.

[0079] The pretreated water obtained in step (1) was sent to a high-temperature reverse osmosis system for a single cycle life test, and the result was 163 hours.

[0080] Comparative Example 2

[0081] The same method as in Example 1 was used, except that in step (3), a high-temperature resistant nanofiltration membrane with a molecular weight cutoff of 1236 was selected to perform high-temperature nanofiltration treatment on the pretreated water obtained in step (1). The preparation method of this nanofiltration membrane was the same as in Example 1, except that in step (c), the aqueous phase monomer was 0.015 mol / L of 1,10-decanediamine.

[0082] The permeate after high-temperature nanofiltration in step (3) was sent to a high-temperature reverse osmosis system for single-cycle life measurement, and the result was 406 hours.

[0083] Comparative Example 3

[0084] The same method as in Example 2 is used, except that step (3) is omitted.

[0085] The pretreated water obtained in step (1) was sent to a high-temperature reverse osmosis system for a single cycle life test, and the result was 133 hours.

[0086] Comparative Example 4

[0087] The same method as in Example 2 was used, except that in step (3), a high-temperature resistant nanofiltration membrane with a molecular weight cutoff of 1005 was selected to perform high-temperature nanofiltration treatment on the pretreated water obtained in step (1). The preparation method of this nanofiltration membrane was the same as in Example 1, except that in step (c), the oil phase monomer was 0.055 mol / L isophthaloyl chloride.

[0088] The permeate after high-temperature nanofiltration in step (3) was sent to a high-temperature reverse osmosis system for single-cycle life measurement, and the result was 375 hours.

[0089] Comparative Example 5

[0090] The same method as in Example 3 is used, except that step (3) is omitted.

[0091] The pretreated water obtained in step (1) was sent to a high-temperature reverse osmosis system for a single cycle life test, and the result was 88 hours.

[0092] Comparative Example 6

[0093] The same method as in Example 3 was used, except that in step (3), a high-temperature resistant nanofiltration membrane with a molecular weight cutoff of 537 was selected to perform high-temperature nanofiltration treatment on the pretreated water obtained in step (1). The preparation method of this nanofiltration membrane was the same as in Example 1, except that in step (c), the aqueous phase monomer was 0.02 mol / L N-aminoethylpiperazine.

[0094] The permeate after high-temperature nanofiltration in step (3) was sent to a high-temperature reverse osmosis system for single-cycle life measurement, and the result was 501 hours.

[0095] In the above embodiments and comparative examples, the method for determining the single cycle life of the reverse osmosis membrane is as follows: The permeate after high-temperature nanofiltration treatment in step (3) or the pretreated water obtained in step (1) is sent as reverse osmosis feed water into the high-temperature reverse osmosis system. The high-temperature reverse osmosis system uses DuPont XUS120308 high-temperature reverse osmosis membrane. It is operated continuously at a temperature of 75°C and a pressure of 1.5MPa, and the water flux is recorded periodically. The continuous operating time when the water flux decreases to 80% of the initial value is the single cycle life of the reverse osmosis membrane.

[0096] The results from the above embodiments and comparative examples show that the embodiments using the method of the present invention can significantly improve the single-cycle life of high-temperature resistant reverse osmosis membranes, reduce the cleaning frequency of the membranes during use, thereby reducing costs, improving efficiency, and enabling the membranes to be used for wastewater treatment with complex compositions.

[0097] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for treating high-temperature wastewater, characterized in that, The processing method includes the following steps: S1. Filter the high-temperature wastewater to obtain filtered water; test the calcium ion content, magnesium ion content and total organic matter content in the filtered water; S2. When the sum of calcium and magnesium ion content in the filtered water is ≥50mg / L, a first nanofiltration treatment is performed first, followed by a high-temperature reverse osmosis treatment; wherein, the first nanofiltration treatment uses a first nanofiltration membrane, and the molecular weight cutoff of the first nanofiltration membrane is <300. When the sum of calcium and magnesium ion content in the filtered water is <50 mg / L and the total organic matter content is ≥50 mg / L, a second nanofiltration treatment is performed first, followed by a high-temperature reverse osmosis treatment; wherein, the second nanofiltration treatment uses a second nanofiltration membrane, the molecular weight cutoff of the second nanofiltration membrane is <(number average molecular weight of organic matter in water / 2), and the molecular weight cutoff of the second nanofiltration membrane is not less than 300. When the sum of calcium and magnesium ion content in the filtered water is <50 mg / L and the total organic matter content is <50 mg / L, nanofiltration is not required, and high-temperature reverse osmosis can be performed directly.

2. The processing method according to claim 1, wherein, The temperature of the high-temperature wastewater is 60-90℃.

3. The processing method according to claim 1 or 2, wherein, In step S1, the filter used has a filtration accuracy of 0.5-2μm and a maximum operating temperature of ≥90℃.

4. The processing method according to any one of claims 1-3, wherein, In step S2, the preparation method of the first nanofiltration membrane includes the following steps: (1) Dissolve the heat-resistant polymer in a first solvent to obtain a casting solution; coat the casting solution into a film, and then immerse it in a second solvent to transform it into a solid film. (2) The solid membrane is subjected to a first treatment in an aqueous solution, then to a second treatment in an oil solution, and then subjected to heat treatment to obtain a composite nanofiltration membrane; wherein, the aqueous monomer in the aqueous solution is selected from at least one of the following aromatic polyamines, wherein the aromatic polyamine has at least two primary or secondary amino groups, has at least one aliphatic side group with ≤3 carbon atoms, and at least one primary or secondary amino group is located on the aliphatic side group; the oil monomer in the oil solution is selected from at least one of phenyl acyl chlorides.

5. The processing method according to claim 4, wherein, The aromatic polyamine is selected from 2-amino-N-methylbenzylamine and / or 4-amino-N-(1-methylethyl)benzylamine; And / or, the phenyl acyl chloride is selected from pyromellitic acyl chloride and / or pyromellitic tetracarboxylic chloride.

6. The processing method according to any one of claims 1-3, wherein, In step S2, the method for preparing the second nanofiltration membrane includes the following steps: (1) Dissolve the heat-resistant polymer in a first solvent to obtain a casting solution; coat the casting solution into a film, and then immerse it in a second solvent to transform it into a solid film. (2) The solid membrane is subjected to a first treatment in an aqueous solution, a second treatment in an oil solution, and then heat treatment to obtain a composite nanofiltration membrane; wherein, the aqueous monomer in the aqueous solution includes component A and component B, component A is selected from at least one heterocyclic polyamine having at least two primary or secondary amino groups and a nitrogen atom in the ring; component B is selected from at least one aliphatic polyamine having at least two primary or secondary amino groups and a carbon chain length ≥ 4 carbon atoms; and the oil monomer in the oil solution is selected from at least one phenyl acyl chloride.

7. The processing method according to claim 6, wherein, Component A is N-aminoethylpiperazine and / or 1,4-bis(aminopropyl)piperazine; component B is 1,6-hexanediamine and / or 1,10-decanediamine; And / or, the molar ratio of component A to component B is 0.1-8:1; And / or, the phenyl acyl chloride is selected from one or more of terephthaloyl chloride, trimesoyl chloride and pyromellitic acyl chloride.

8. The processing method according to any one of claims 4-7, wherein, The heat-resistant polymer is selected from one or more of polyimide, polyetherimide, polyethersulfone, and polyetheretherketone; And / or, the first solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; And / or, the second solvent is selected from one or more of water and small molecule alcohols; preferably, the small molecule alcohols are selected from one or more of methanol, ethanol, ethylene glycol, diethylene glycol, propanol, isopropanol, 1,2-propanediol, 1,3-propanediol and glycerol.

9. The processing method according to any one of claims 4-8, wherein, The aqueous solution is an aqueous solution containing an aqueous monomer, a catalyst, and a hydrogen chloride absorbent; Preferably, the catalyst is selected from one or more organic weak acids; more preferably, the catalyst is oxalic acid and / or DL-camphorsulfonic acid. Preferably, the hydrogen chloride absorbent is selected from one or more C4-C12 tertiary amines; more preferably, the hydrogen chloride absorbent is triethylamine and / or N,N-dimethylaniline. Preferably, the concentration of the aqueous monomer is [(0.05-0.1) ÷ the average number of hydrogen atoms on the amino group per molecule] mol / L; Preferably, the concentration of the catalyst is 0.05-0.2 mol / L; Preferably, the concentration of the hydrogen chloride absorbent is 0.05-0.2 mol / L.

10. The processing method according to any one of claims 4-9, wherein, The oil phase solution is an oily solvent containing oil phase monomers; Preferably, the oily solvent is selected from one or more of C6-C20 aliphatic alkanes; Preferably, the concentration of the oil phase monomer is [(0.1-0.5) ÷ the average number of acyl chloride groups per molecule] mol / L.