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WO2025105299A1 - Procédé de traitement des eaux usées et procédé de récupération d'une substance de valeur à faible poids moléculaire - Google Patents

Procédé de traitement des eaux usées et procédé de récupération d'une substance de valeur à faible poids moléculaire Download PDF

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Publication number
WO2025105299A1
WO2025105299A1 PCT/JP2024/039803 JP2024039803W WO2025105299A1 WO 2025105299 A1 WO2025105299 A1 WO 2025105299A1 JP 2024039803 W JP2024039803 W JP 2024039803W WO 2025105299 A1 WO2025105299 A1 WO 2025105299A1
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Prior art keywords
membrane
wastewater
molecular weight
valuables
low molecular
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English (en)
Japanese (ja)
Inventor
顕太郎 小林
悟 石原
康博 富
靖尚 古葉
拓朗 安江
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Nitto Denko Corp
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Nitto Denko Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/04—Feed pretreatment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis

Definitions

  • wastewater from industries such as plating and metal processing may contain low molecular weight valuables such as boron, and depending on the state of the wastewater, boron may be present in the wastewater in the form of boric acid, etc.
  • various methods are being considered for recovering and reusing elements such as boron and compounds containing boron, among the low molecular weight valuables contained in wastewater.
  • Known methods for such recovery and reuse include, for example, coagulation sedimentation, resin adsorption, dry concentration, and a method that combines crystallization with the dry concentration method.
  • coagulation sedimentation resin adsorption
  • dry concentration dry concentration
  • a more efficient treatment method was desired.
  • Patent Document 1 discloses a method for treating wastewater that contains sulfate ions and boron, which includes a first step of removing sulfate ions from the wastewater and a second step of contacting the wastewater from which the sulfate ions have been removed with a layered double hydroxide to remove boron by adsorbing it to the layered double hydroxide, and which uses a reverse osmosis membrane or a nanofiltration membrane (NF membrane) when removing the sulfate ions in the first step.
  • NF membrane nanofiltration membrane
  • the object of the present invention is to provide a method for treating wastewater that can selectively separate and highly purify low molecular weight valuables, and a method for recovering low molecular weight valuables using the same.
  • the present invention includes the following aspects.
  • a method for treating wastewater comprising a step of separating wastewater containing low molecular weight valuables and cations having a molecular weight of less than 100 using an NF membrane,
  • the NF membrane has a rejection rate of SO 4 2- of 90% or more when treating an aqueous MgSO 4 solution having a concentration of 2000 mg/L at an operating pressure of 0.76 MPa and at 25°C;
  • the method for treating wastewater further comprises a step of adding a sulfate ion component to the wastewater.
  • the wastewater treatment method of the present invention since an NF membrane is used, low molecular weight valuables having a molecular weight of less than 100 can easily pass through, while the rejection rate of SO 4 2- of the NF membrane is 90% or more, so that most of the SO 4 2- can be separated to the feed liquid side. Ions tend to pass through the NF membrane in an electrically neutral state, that is, in the state of counter ions, and the addition of sulfate ion components increases the amount of SO 4 2- on the feed side, which then forms counter ions with cations such as alkali metals, and the number of cations passing through the NF membrane is relatively reduced, which is thought to increase the rejection rate of cations such as alkali metals. Intrinsically, cations such as alkali metals easily pass through the NF membrane, and as a result of the increased rejection rate, the wastewater treatment method of the present invention can selectively separate low molecular weight valuables to achieve high purification.
  • ions tend to pass through the NF membrane in the form of counter ions, and as the amount of monovalent anions that form counter ions with alkali metal cations and the like increases, the number of alkali metal cations and the like that pass through the NF membrane increases relatively, and the rejection rate of alkali metal cations and the like tends to decrease. Therefore, the greater the ratio of the equivalent of sulfate ions to the equivalent of monovalent anions in the supply wastewater, the higher the rejection rate of alkali metal cations and the like due to the balance between the two, and when the equivalent ratio exceeds 30, low molecular weight valuables can be more selectively separated and highly purified.
  • a wastewater treatment method according to any one of [1] to [3], in which an aqueous solution of sulfuric acid is added when adding sulfate ion components.
  • Aqueous solutions of sulfuric acid generate protons, which are hydrogen cations.
  • protons which are hydrogen cations.
  • the amount of monovalent anions that form counter ions with alkali metal cations also increases, further reducing the rejection rate of alkali metal cations by the NF membrane and improving the selective separation of low molecular weight valuables.
  • a method for recovering low molecular weight valuables comprising a step of separating wastewater containing low molecular weight valuables and cations having a molecular weight of less than 100 using an NF membrane and recovering the low molecular weight valuables from the permeate,
  • the NF membrane has a rejection rate of SO 4 2- of 90% or more when treating an aqueous MgSO 4 solution having a concentration of 2000 mg/L at an operating pressure of 0.76 MPa and at 25°C;
  • the method for recovering low molecular weight valuables comprises a step of adding a sulfate ion component to the wastewater.
  • the method for recovering low molecular weight valuables of the present invention makes it possible to selectively separate and highly purify low molecular weight valuables as described above through wastewater treatment, and therefore it is possible to recover highly purified low molecular weight valuables as the permeate. This makes it possible to save energy and simplify processes in subsequent processes.
  • the method for recovering low molecular weight valuables of the present invention is effective, particularly from the viewpoint of energy saving, as it can selectively separate and highly purify low molecular weight valuables.
  • the present invention provides a wastewater treatment method that can selectively separate and highly purify low molecular weight valuables, and a method for recovering low molecular weight valuables using the same.
  • FIG. 1 is a schematic diagram showing an example of a wastewater treatment method.
  • FIG. 1 is a schematic diagram showing an example of a method for recovering low molecular weight valuables.
  • FIG. 1 is a partially cutaway perspective view showing an example of a spiral membrane element used in a wastewater treatment method.
  • the wastewater treatment method of the present invention includes a step of separating wastewater with an NF membrane, and uses wastewater containing low-molecular-weight valuables and alkali metals having a molecular weight of less than 100 as the wastewater to be treated.
  • the wastewater to be treated may be one from which impurities, silt, clay, fungi, algae, and colloidal suspended solids have been removed by a pretreatment step using a UF membrane (ultrafiltration membrane) or an MF membrane (microfiltration membrane).
  • the low molecular weight valuables contained in the wastewater include any element or compound containing the element that is a compound having a molecular weight of less than 100 and can be recovered.
  • the element or compound may be dissolved in the wastewater as it is, or may be dissolved in the form of ions, etc.
  • Examples of such low molecular weight valuables include one or more selected from the group consisting of boron, boron-containing compounds, deuterium, deuterium-containing compounds, organic acids, and alcohols.
  • organic acids include aliphatic carboxylic acids such as acetic acid, formic acid, and propionic acid, and sulfonic acids such as methanesulfonic acid.
  • Examples of alcohols include ethanol, methanol, propanol, and butanol.
  • boron-containing compounds include boric acid such as orthoboric acid and metaboric acid, metal salts of boric acid, and boron halides.
  • deuterium-containing compounds include compounds in which one or more hydrogen atoms of these compounds are replaced with deuterium.
  • boron is particularly preferred as a target low-molecular-weight valuable material because it is contained in large amounts in wastewater generated in the plating and metal processing industries, and various recovery methods are being considered.
  • Cations contained in wastewater include monovalent or divalent or higher cations, but the present invention is particularly effective for wastewater containing monovalent cations because it can increase the blocking performance of monovalent cations in particular.
  • monovalent cations include alkali metal ions, ammonium ions, oxonium ions, etc.
  • alkali metals include one or more of sodium, potassium, lithium, etc.
  • Alkali metals exist in wastewater as cations, but may also include those present as fine particles.
  • the concentration of cations or alkali metals contained in the wastewater to be treated is, for example, 100 to 10,000 mg/L, and from the viewpoint of maintaining a certain level of blocking rate of alkali metal ions by the NF membrane and from the viewpoint of membrane treatment osmotic pressure, it is preferably 50,000 mg/L or less.
  • the wastewater may also contain monovalent anions, and examples of the monovalent anions contained in the wastewater include one or more anions of halogen atoms such as fluorine, chlorine, bromine, and iodine, and nitrate ions.
  • halogen atoms such as fluorine, chlorine, bromine, and iodine, and nitrate ions.
  • the concentration of monovalent anions contained in the wastewater to be treated is preferably 1,000 mg/L or less, and more preferably 100 mg/L or less, from the viewpoint of enhancing the effect of adding sulfate ion components.
  • the membrane separation device shown in FIG. 1 includes a membrane module M1 that includes a separation membrane 1, which is an NF membrane, a supply section for a feed liquid 7, a discharge section for a permeate liquid 8, and a discharge section for a concentrated liquid 9, and includes a chemical supply tank 16 in the line for the feed liquid 7 for supplying an aqueous sulfuric acid solution 17, which is a sulfate ion component.
  • a separation membrane 1 which is an NF membrane
  • a supply section for a feed liquid 7 a discharge section for a permeate liquid 8
  • a discharge section for a concentrated liquid 9 and includes a chemical supply tank 16 in the line for the feed liquid 7 for supplying an aqueous sulfuric acid solution 17, which is a sulfate ion component.
  • Such a membrane separation device is configured so that it can be operated under desired conditions by adding other equipment such as pumps, sensors, tanks, control valves, and control devices as necessary.
  • a line for circulating part or all of the concentrated liquid 9 to the supply liquid 7 may be provided.
  • the sulfate ion component may be any compound containing SO 4 2- , such as sulfuric acid, sulfate, hydrogen sulfate, etc.
  • sulfuric acid is preferred.
  • the concentration of the sulfate ion component to be added to the wastewater is preferably 1 to 90% by mass, and more preferably 15 to 75% by mass.
  • the feed wastewater to which sulfate ion components are added and supplied to the NF membrane has an equivalent ratio of sulfate ions to monovalent anions of more than 30, and it is even more preferable that this equivalent ratio is 40 or more. Furthermore, if this equivalent ratio becomes too large, the corresponding effect decreases, so if the equivalent ratio is around 100, sufficient separation performance can be obtained.
  • the sulfate ion concentration of the feed wastewater to which sulfate ion components have been added is preferably 1,000 to 50,000 mg/L, and more preferably 2,000 to 10,000 mg/L.
  • General NF membrane operating conditions can be adopted for the operating conditions of the membrane separation device, such as operating pressure, permeate recovery rate, operating temperature, etc. However, from the viewpoint of stable continuous use, it is preferable to adjust the operating pressure so that the membrane flux is 5 to 40 LMH (L ⁇ m ⁇ 2 ⁇ h ⁇ 1 ).
  • NF membrane As the NF membrane (nanofiltration membrane), one having a rejection rate of SO 4 2- of 90% or more when a 2000 mg/L MgSO 4 aqueous solution is treated at an operating pressure of 0.76 MPa and 25° C. is used, preferably the rejection rate is 95% or more, more preferably the rejection rate is 98% or more, and most preferably the rejection rate is 99% or more.
  • the rejection rate of SO 4 2- is specifically a value measured by the method described in the examples.
  • the molecular weight cutoff of the NF membrane is preferably 50 to 200 daltons, and more preferably 80 to 120 daltons.
  • the molecular weight cutoff of the NF membrane is measured as follows. First, a plurality of polyethylene glycols having different average molecular weights and monodisperse molecular weight distributions are prepared. An aqueous solution containing one of the plurality of polyethylene glycols at a concentration of 5000 ppm is supplied to the membrane surface of the NF membrane under conditions of a temperature of 25° C. and a pressure of 4 kg/cm 2. This allows the rejection rate of the polyethylene glycol to be measured. The rejection rates of the other polyethylene glycols are measured in the same manner. A fractionation curve showing the relationship between the obtained rejection rate and the average molecular weight of the polyethylene glycol is created. Based on the fractionation curve, the average molecular weight of the polyethylene glycol at which the rejection rate is 90% is specified. The specified average molecular weight can be regarded as the molecular weight cutoff of the NF membrane.
  • the NF membrane may be, for example, a composite semipermeable membrane that includes a porous support membrane and a separation functional layer, with the separation functional layer being supported by the porous support membrane.
  • the material and structure of the porous support membrane are not particularly limited.
  • As the porous support membrane for example, an ultrafiltration membrane in which a microporous layer having an average pore size of 0.01 to 0.4 ⁇ m is formed on a nonwoven fabric is used.
  • materials for forming the microporous layer include polysulfone, polyarylethersulfone such as polyethersulfone, polyimide, polyvinylidene fluoride, polytetrafluoroethylene, etc.
  • NF membranes are classified into charged and uncharged types depending on whether or not there is a charge on the surface, but either type can be used in the present invention. However, when the wastewater contains a small amount of organic compounds, a negatively charged NF membrane is preferred.
  • An example of a negatively charged NF membrane is one that has a separation functional layer that has an anionic group.
  • anionic groups include sulfonic acid groups and carboxylic acid groups, with sulfonic acid groups being preferred as strong acid groups.
  • the resin constituting the separation functional layer may be a polysulfone-based resin, polyamide, cellulose acetate, or polyvinyl alcohol, with polysulfone-based resin being particularly preferred from the viewpoint of chemical, mechanical, and thermal stability.
  • polysulfone-based resins include polysulfone, polyethersulfone, and polyphenylsulfone.
  • a preferred separation functional layer for an NF membrane is one that contains a polysulfone-based resin having sulfonic acid groups.
  • an NF membrane having such a separation functional layer has higher durability against alkaline cleaning solutions and chlorine-based cleaning solutions.
  • NF membranes in which the separation functional layer is made of sulfonated polyethersulfone with a negative fixed charge those described in JP-A-61-4505 and JP-A-61-4506 are particularly preferred.
  • polysulfone-based resins having sulfonic acid groups include those having the following repeating units (A) or (B).
  • the membrane module M1 using an NF membrane can be composed of one or more membrane elements.
  • the membrane element is typically a spiral-type membrane element using an NF membrane.
  • the membrane module M1 may be composed of a pressure vessel and one or more spiral-type membrane elements arranged inside the pressure vessel.
  • the structure of the membrane element including the NF membrane is not limited to the spiral type, and may be other types such as a hollow fiber type, a tubular type, or a frame and plate type.
  • the spiral membrane element includes a perforated central tube 5 and a wound body R including a separation membrane 1 wound around the central tube 5.
  • the element includes a plurality of membrane leaves L with a permeate-side flow path material 3 interposed between opposing separation membranes 1, a feed-side flow path material 2 interposed between the membrane leaves L, a perforated central tube 5 around which the membrane leaves L and the feed-side flow path material 2 are wound, and a sealing portion 12 for preventing mixing of the feed-side flow path and the permeate-side flow path.
  • the permeate-side flow path in the membrane leaf L can be formed by a permeate-side flow path material 3 (also called a permeate-side spacer).
  • Figure 3 shows an example in which the sealing portion includes both end sealing portions and an outer peripheral sealing portion 12.
  • the both end sealing portions are formed by sealing two side ends on both sides of the membrane leaf L in the axial direction A1 with an adhesive.
  • the outer peripheral sealing portion 12 is formed by sealing the end of the outer peripheral tip of the membrane leaf L with an adhesive.
  • the area surrounded by the opposing separation membrane 1, both end sealing portions, and the outer peripheral sealing portion 12 becomes the permeation side flow path, which is structured to communicate with the opening 5a of the central tube 5.
  • a first end member 10 having a function such as a seal carrier may be provided on the upstream side of the membrane element wound body R, and a second end member 20 having a function such as an anti-telescope material may be provided on the downstream side.
  • the membrane element When the membrane element is in use, it is housed in a pressure vessel and the feed liquid 7 is supplied from one end of the membrane element.
  • the supplied feed liquid 7 flows along the feed-side flow path material 2 in a direction parallel to the axial direction A1 of the central tube 5, and is discharged from the other end of the membrane element as a concentrated liquid 9.
  • the permeated liquid 8 that permeates the separation membrane 1 as the feed liquid 7 flows along the feed-side flow path material 2 flows along the permeation-side flow path material 3, then flows from the opening 5a into the interior of the central tube 5 and is discharged from the end of the central tube 5.
  • Pretreatment process prior to the separation process using the NF membrane, it is also possible to carry out pretreatment processes such as removal of solids, reduction of monovalent anions, softening of water, and removal of soluble organic impurities that are not to be recovered.
  • pretreatment processes such as removal of solids, reduction of monovalent anions, softening of water, and removal of soluble organic impurities that are not to be recovered.
  • a UF membrane ultrafiltration membrane
  • MF membrane microfiltration membrane
  • the UF membrane is a membrane with an average pore size of about 0.001 ⁇ m to 0.01 ⁇ m.
  • the MF membrane is a membrane with an average pore size of about 0.01 ⁇ m to 10 ⁇ m.
  • the material of the UF membrane or MF membrane is not particularly limited, and for example, polymeric materials such as cellulose ester polymers such as cellulose acetate, polyethylene, polypropylene, polysulfone, polyvinylidene fluoride, polyethersulfone, etc. can be used. From the viewpoint of durability and washability, polyvinylidene fluoride and polyethersulfone are preferred.
  • the shape of the UF membrane or MF membrane is not particularly limited, and can be selected from flat membrane, hollow fiber membrane, pleated membrane, tubular membrane, etc.
  • the concentration of monovalent anions in the wastewater to be treated is high, it may be effective to reduce the concentration of monovalent anions by passing the wastewater through an ion exchange device that has an ion exchange membrane, ion exchange resin, etc.
  • Anion exchange resins include strongly basic anion exchange resins that have a quaternary amine as a functional group, and weakly basic anion exchange resins that have primary, secondary, or tertiary amines, and anion exchange membranes also have a similar chemical structure.
  • strongly basic anion exchange resins can be used over a wide pH range and can adsorb a wide variety of anions, for example, having ion exchange properties in the following order: SO 4 2- >I - >NO 3 - >Br - >Cl - .
  • the sulfate ions are also adsorbed onto the anion exchange resin, but in the separation step, sulfate ion components can be added to the feed wastewater to compensate for the sulfate ions that have been adsorbed and reduced.
  • the method for recovering low molecular weight valuables of the present invention comprises a step of separating wastewater containing low molecular weight valuables having a molecular weight of less than 100 and alkali metals using an NF membrane and recovering the low molecular weight valuables from the permeate, characterized in that the NF membrane has a rejection rate of SO 4 2- of 90% or more when an aqueous MgSO 4 solution having a concentration of 2000 mg/L is treated at an operating pressure of 0.76 MPa and at 25° C., and further comprises a step of adding a sulfate ion component to the wastewater.
  • the method for recovering low molecular weight valuables of the present invention utilizes the wastewater treatment method of the present invention, and the separation step, pretreatment step, etc. are as described above.
  • the method of recovering low molecular weight valuables from the permeate can be a combination of processes such as further concentrating the low molecular weight valuables in the permeate, crystallizing (or reactive crystallizing) the low molecular weight valuables in the permeate, separating the solid low molecular weight valuables from the liquid, and drying the low molecular weight valuables.
  • concentration methods such as heating evaporation, vacuum evaporation, and membrane separation using RO membranes can be used; for crystallization, methods such as cooling crystallization, vacuum crystallization, and reactive crystallization can be used; for solid-liquid separation, methods such as centrifugation and filter separation can be used.
  • the distillation equipment can be combined with processes such as absorption, dehydration, and membrane separation (VP method) to recover the low molecular weight valuables in high purity.
  • VP method membrane separation
  • the method for recovering low molecular weight valuables of the present invention can be carried out, for example, using an apparatus as shown in Figure 2.
  • the permeate obtained by carrying out the wastewater treatment method of the present invention is heated to evaporate the water and further concentrate the low molecular weight valuables in the permeate, and then cooled to crystallize the low molecular weight valuables in the permeate.
  • the crystals of the low molecular weight valuables are separated from the liquid, and the obtained low molecular weight valuables are dried, allowing the low molecular weight valuables to be recovered.
  • the rejection rate of low molecular weight valuable substances by the NF membrane was determined using the compounds shown in Table 1 as low molecular weight valuable substances. The results are shown in Table 1 together with the molecular weight.
  • Example 1 The NF membrane used was PRO-XS3 manufactured by Nitto Denko. The SO 4 2- rejection rate of this NF membrane was measured by the method described above, and was found to be 99.7%. As the wastewater to be treated, wastewater containing SO 4 2- at a concentration of 1000 mg/L was used. This wastewater is a model of boric acid-containing wastewater that may be generated in various processes, and has the composition shown in Table 5 (Comparative Example 1).
  • the negative value for the rejection rate of iodine anions indicates that the concentration of iodine anions in the permeate is higher than in the feed liquid. Ions tend to pass through an NF membrane in an electrically neutral state, i.e., in the form of counter ions. The addition of sulfuric acid increases the hydrogen ions on the feed side, and the amount of iodine anions that pass through also increases, which is thought to result in a higher concentration of iodine anions in the permeate.
  • the molar amount of hydrogen ions increases relative to cations such as Na + that form counter ions with iodine anions, thereby decreasing the amount of permeation of cations such as Na + and increasing the rejection rate of the cations.
  • the greater the ratio of the equivalent of sulfate ions to the equivalent of monovalent anions the higher the rejection rate of cations such as Na + and the higher the purity of low-molecular-weight valuables.
  • Example 2 membrane separation was performed using a feed wastewater having the composition shown in Table 3 by adding 10 mL of a 75% aqueous sulfuric acid solution per 1 L of wastewater, and samples were taken from the permeate under the same conditions as in Example 1, to determine the rejection rate of each component. The results are shown in Table 3 together with the difference in rejection rate and the anion equivalent ratio.
  • Example 3 membrane separation was performed using a feed wastewater having the composition shown in Table 4 by adding 2 mL of a 75% aqueous sulfuric acid solution per 1 L of wastewater, and samples were taken from the permeate under the same conditions as in Example 1, to determine the rejection rate of each component. The results are shown in Table 4 together with the rejection rate difference and the anion equivalent ratio.
  • Example 1 Comparative Example 1
  • Example 2 In Example 1, except that membrane separation was performed using wastewater having the composition shown in Table 5 to which no aqueous sulfuric acid solution was added, samples were taken from the permeate and the rejection rate of each component was determined under the same conditions as in Example 1. The results are shown in Table 5 together with the difference in rejection rate and the anion equivalent ratio.
  • this feed wastewater was fed to an NF membrane at a temperature of 25°C, and the concentrated liquid and permeate were discharged. After 30 minutes, a sample was taken from the permeate, and the concentration of each component in the permeate was measured as described above to determine the rejection rate. The results are shown in Table 6 together with the difference in rejection rate and the anion equivalent ratio.
  • the NF membrane used was PRO-XS3 manufactured by Nitto Denko Corp. Wastewater to be treated contained SO 4 2- at a concentration of 10,400 mg/L and Cl - at a concentration of 750 mg/L and had the composition shown in Table 7.
  • this feed wastewater was fed to an NF membrane at a temperature of 25°C, and the concentrated liquid and permeate were discharged. After 30 minutes, a sample was taken from the permeate, and the concentration of each component in the permeate was measured as described above to determine the rejection rate. The results are shown in Table 7 together with the difference in rejection rate and the anion equivalent ratio.
  • the present invention provides a wastewater treatment method that can selectively separate and highly purify low molecular weight valuables such as boric acid. Highly purified low molecular weight valuables can be recovered as the permeate, which makes it possible to save energy and simplify processes in subsequent processes, making it particularly useful as a method for recovering low molecular weight valuables.

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Abstract

Le but de la présente invention est de fournir : un procédé de traitement des eaux usées permettant de séparer sélectivement une substance de valeur à faible poids moléculaire et de lui conférer une grande pureté ; et un procédé de récupération d'une substance de valeur à faible poids moléculaire à l'aide du procédé de traitement. Ce procédé de traitement des eaux usées comprend une étape au cours de laquelle des eaux usées contenant une substance de valeur à faible poids moléculaire, inférieur à 100, et des cations sont séparées à l'aide d'une membrane de nanofiltration. Le procédé de traitement des eaux usées est caractérisé en ce que la membrane de nanofiltration, lorsqu'elle est utilisée pour traiter une solution aqueuse de MgSO4 dont la concentration est de 2000 mg/l à 25 °C et la pression de fonctionnement de 0,76 MPa, présente un rejet de SO4 2- de 90 % ou plus, et par l'ajout d'un ion d'acide sulfurique à l'eau usée.
PCT/JP2024/039803 2023-11-14 2024-11-08 Procédé de traitement des eaux usées et procédé de récupération d'une substance de valeur à faible poids moléculaire Pending WO2025105299A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000202442A (ja) * 1999-01-19 2000-07-25 Sumitomo Chem Co Ltd 硼素含有水中の硼素の分離回収方法
JP2015144997A (ja) * 2014-02-03 2015-08-13 株式会社神鋼環境ソリューション 硫酸イオンおよびホウ素を含有する排水の処理方法、および処理設備
JP2023067737A (ja) * 2021-11-01 2023-05-16 日東電工株式会社 複合半透膜

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000202442A (ja) * 1999-01-19 2000-07-25 Sumitomo Chem Co Ltd 硼素含有水中の硼素の分離回収方法
JP2015144997A (ja) * 2014-02-03 2015-08-13 株式会社神鋼環境ソリューション 硫酸イオンおよびホウ素を含有する排水の処理方法、および処理設備
JP2023067737A (ja) * 2021-11-01 2023-05-16 日東電工株式会社 複合半透膜

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