TWI786081B - Method for modifying reverse osmosis membrane, reverse osmosis membrane, and method for processing water containing non-charged substance - Google Patents

Abstract

The invention provides a method for modifying a reverse osmosis membrane that is capable of adjusting the rejection ratio for non-charged substances by the reverse osmosis membrane to a predetermined value. Specifically provided is a method for modifying a reverse osmosis membrane that alters the rejection ratio for non-charged substances by bringing a halogen-based oxidizing agent into contact with a polyamide-based reverse osmosis membrane, wherein the modification processing is performed on the basis of the measured value for the pure water-equivalent flux of the reverse osmosis membrane. Also provided is a method for operating a reverse osmosis membrane which can suppress any reduction in rejection performance due to alkali cleaning in a modified polyamide-based reverse osmosis membrane. This method for operating a reverse osmosis membrane includes a reverse osmosis membrane treatment step in which water to be treated is passed through a modified reverse osmosis membrane which has been modified by bringing a bromine-based oxidizing agent into contact with the polyamide-based reverse osmosis membrane, thus obtaining a permeate and a concentrate, and an alkali cleaning step in which the modified reverse osmosis membrane is subjected to alkali cleaning at a pH of 8 or higher.

Description

Modification method of reverse osmosis membrane, reverse osmosis membrane, treatment method of water containing non-charged substances

The present invention relates to a modification method of a polyamide-based reverse osmosis membrane, a reverse osmosis membrane modified by the modification method, a method for treating water containing uncharged substances using the reverse osmosis membrane, and operation of the reverse osmosis membrane Method and reverse osmosis membrane device.

In order to effectively use water resources, we have introduced a process that collects discharged water, regenerates it, and reuses it. In order to obtain high-quality treated water, a reverse osmosis membrane (RO membrane) that can remove electrolytes and low-molecular substances must be used.

However, when the discharge water contains non-charged substances such as urea, isopropanol, and boron, it is difficult to remove these non-charged substances even with reverse osmosis membranes. For example, even if the blocking rate of sodium chloride, which is a charged substance, is more than 99%, the blocking rate of isopropanol, which is an uncharged substance, is about 90~97%, and the blocking rate of urea is about 99%. Situations where only about a few 10% of blocking rates can be obtained. Therefore, it is sought to improve the rejection rate of uncharged substances of the reverse osmosis membrane.

There are many methods for improving the permeate water quality of the reverse osmosis membrane. Among them, there is a method of improving performance by bringing a halogen-based modifier such as free chlorine containing bromine into contact with the reverse osmosis membrane for a predetermined time.

For example, Patent Document 1 describes a method for treating reverse osmosis membrane elements. In a membrane separation device equipped with a reverse osmosis membrane element having a polyamide skin layer, the reverse osmosis membrane element is filled with the pressure in the membrane separation device. After the container, the free chlorine aqueous solution containing bromine is brought into contact with the aforementioned reverse osmosis membrane element.

Patent Document 2 describes a method for reforming a reverse osmosis membrane by bringing a hypobromous acid stabilized composition as a modifying agent into contact with a polyamide-based reverse osmosis membrane.

However, the methods of Patent Documents 1 and 2 have the following problems: Since the modification is managed by time, the barrier rate of the reverse osmosis membrane cannot be adjusted to a predetermined value, and the barrier performance after modification depends on the type of the membrane. larger. Also, Patent Documents 1 and 2 do not discuss how much the barrier performance of uncharged substances will be improved by the contact conditions of the modifying agent.

Non-Patent Document 1 describes that when a polyamide-based reverse osmosis membrane is brought into contact with a halogen-based oxidizing agent in an acidic environment, the amount of permeated water decreases.

However, Non-Patent Document 1 does not describe the relationship between the amount of permeated water and the barrier performance of uncharged substances.

Non-Patent Document 2 discloses that the removal rate of boron is improved when the pore size of the reverse osmosis membrane is reduced.

However, Non-Patent Document 2 does not describe the relationship between the modification of the reverse osmosis membrane and the removal rate of boron which is an uncharged substance.

On the other hand, when the reverse osmosis membrane device is operated for a long period of time, biofouling and the like will occur, so the reverse osmosis membrane is cleaned with alkali by using an aqueous alkali solution or the like. For example, in the reverse osmosis membrane helical element, there is a problem that the grid spacer with a thickness of about 1 mm for forming a narrow raw water flow path or a concentrated water flow path generates sticky material, resulting in blockage of the flow path. Alkali washing is generally known as a method for removing the accumulated slime.

However, if the polyamide-based reverse osmosis membrane whose performance is improved by contacting it with a chlorine-based oxidizing agent as in the method of Patent Document 1 is washed with alkali, the reverse osmosis membrane deteriorates and the barrier performance decreases. Patent Document 2 does not examine the persistence of the effect of improving the barrier performance with respect to alkaline cleaning under the assumption of actual use.

[Prior Art Literature]

[Patent Document]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2003-088730

[Patent Document 2] Japanese Patent Laid-Open No. 2016-155067

[Non-patent literature]

[Non-Patent Document 1] Guo-Dong Kang etc., "Study on hypochlorine degradation of aromatic polyamide reverse osmosis membrane", Journal of Membrane Science, 300, 2007, pp.165-171.

[Non-Patent Document 2] Masahiro Hisami, Takashi Ogawa, "Reverse Osmosis Membrane Technology Promoting Seawater Desalination and Reuse of Sewer Wastewater", Journal of the Academic Society "EICA", Vol. 15, No. 4 (2011), pp. 44-47 .

The object of the present invention is to provide: a method for modifying a reverse osmosis membrane capable of adjusting the blocking rate of uncharged substances of a reverse osmosis membrane to a predetermined value, a reverse osmosis membrane modified by the modification method, and a reverse osmosis membrane utilizing the Reverse osmosis membrane treatment method for water containing non-charged substances.

In addition, the purpose of the present invention is to provide a reverse osmosis membrane operation method and a reverse osmosis membrane device, which can suppress the reduction of the barrier performance of the modified polyamide-based reverse osmosis membrane relative to alkali cleaning.

The present invention is a method for modifying reverse osmosis membranes, which is to change the blocking rate of non-charged substances by contacting halogen-based oxidants with polyamide-based reverse osmosis membranes; it is based on the pure water conversion of the aforementioned reverse osmosis membranes The measured value of the flux is modified.

In the modification method of the aforementioned reverse osmosis membrane, it is preferable to carry out the aforementioned modification treatment according to the relational expression between the pure water-converted flux of the aforementioned reverse osmosis membrane and the rejection rate of the aforementioned non-charged substances prepared in advance.

In the modification method of the aforementioned reverse osmosis membrane, the aforementioned non-charged substance is preferably a low molecular weight substance with a molecular weight of 200 or less.

In the modification method of the aforementioned reverse osmosis membrane, the aforementioned contacting is preferably carried out within the range of pH 4~6.5.

In the modification method of the aforementioned reverse osmosis membrane, the concentration of the aforementioned halogen-based oxidant during the aforementioned contacting is preferably in the range of 0.1-100 mg/L.

In the upgrading method of the aforementioned reverse osmosis membrane, the aforementioned contacting is preferably carried out under a pressure in the range of 0.1-20 MPa.

Also, the present invention is a reverse osmosis membrane, which is modified by the aforementioned method for modifying the reverse osmosis membrane.

In addition, the present invention is a method for treating water containing non-charged substances, which uses a reverse osmosis membrane modified by the above-mentioned method for modifying reverse osmosis membranes to perform reverse osmosis membrane treatment on water containing non-charged substances.

The present invention is a method for operating a reverse osmosis membrane, comprising the following steps: a reverse osmosis membrane treatment step, for the modified reverse osmosis membrane to be treated by making the bromine-based oxidant contact with the polyamide-based reverse osmosis membrane for modification water to obtain permeable water and concentrated water; and an alkali cleaning step, wherein the modified reverse osmosis membrane is alkali-cleaned above pH 8.

In the operation method of the aforementioned reverse osmosis membrane, it is preferable to include a re-modification step, which is to make the bromine-based oxidant contact with the aforementioned modified reverse osmosis membrane cleaned by alkali to perform re-modification.

In the operation method of the aforementioned reverse osmosis membrane, the contact of the aforementioned bromine-based oxidizing agent is preferably carried out at a pH lower than the pH of the aforementioned treated water.

In the operation method of the aforementioned reverse osmosis membrane, the aforementioned brominated oxidizing agent preferably includes a stabilized hypobromous acid composition containing a brominated oxidizing agent and an amine sulfonic acid compound.

In the operation method of the aforementioned reverse osmosis membrane, the aforementioned bromine-based oxidizing agent preferably includes a stabilized hypobromous acid composition containing bromine and sulfamic acid compounds.

In addition, the present invention is a reverse osmosis membrane device, comprising: a reverse osmosis membrane treatment device having a modified reverse osmosis membrane that is modified by contacting a bromine-based oxidant with a polyamide-based reverse osmosis membrane, and passing the treated water through To obtain permeable water and concentrated water, and alkali cleaning means, the above-mentioned modified reverse osmosis membrane is alkali-cleaned above pH8; in the aforementioned alkali cleaning means, the aforementioned treated water is passed into the aforementioned modified reverse After permeating the membrane for a predetermined time, the alkali solution is brought into contact with the modified reverse osmosis membrane at a pH above 8.

In the above-mentioned reverse osmosis membrane device, it is preferable to have a re-modification means, which is to make the bromine-based oxidant contact with the above-mentioned modified reverse osmosis membrane cleaned by alkali to perform re-modification.

In the reverse osmosis membrane device, the contact of the bromine-based oxidizing agent is preferably performed at a pH lower than the pH of the water to be treated.

In the aforementioned reverse osmosis membrane device, the aforementioned brominated oxidizing agent preferably includes a stabilized hypobromous acid composition containing a brominated oxidizing agent and an amine sulfonic acid compound.

In the aforementioned reverse osmosis membrane device, the aforementioned bromine-based oxidizing agent preferably includes a stabilized hypobromous acid composition containing bromine and an amine sulfonic acid compound.

According to the present invention, it is possible to provide a method for modifying a reverse osmosis membrane capable of adjusting the blocking rate of uncharged substances of a reverse osmosis membrane to a predetermined value, a reverse osmosis membrane modified by the method, and a reverse osmosis membrane utilizing the reverse osmosis membrane. Treatment of water containing non-charged substances with permeable membranes.

In addition, the operation method of the reverse osmosis membrane and the reverse osmosis membrane device of the present invention can suppress the reduction of the barrier performance of the modified polyamide-based reverse osmosis membrane relative to alkaline cleaning.

1: reverse osmosis membrane device

10: Reverse osmosis membrane treatment device

12: Treated water piping

14: Permeable water piping

16: Concentrated water piping

[ Fig. 1 ] is a schematic configuration diagram showing an example of a reverse osmosis membrane device according to an embodiment of the present invention.

[Fig. 2] is a graph showing the relationship between pure water converted flux [m/d/MPa] and TOC rejection rate [%] obtained in Examples.

Embodiments of the present invention will be described below. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

<Modification method of reverse osmosis membrane and reverse osmosis membrane>

The modification method of the reverse osmosis membrane according to the embodiment of the present invention is the following method: by contacting the halogen-based oxidant with the polyamide-based reverse osmosis membrane, the blocking rate of uncharged substances is changed, which is based on the reverse osmosis membrane The measured value of the flux converted to pure water is used for upgrading treatment. In the upgrading method, the upgrading treatment should be carried out according to the relational expression between the conversion flux of pure water and the blocking rate of non-charged substances of the prefabricated reverse osmosis membrane. Also, the reverse osmosis membrane according to the embodiment of the present invention is a reverse osmosis membrane modified by the method for modifying the reverse osmosis membrane. In addition, the "modification" of the reverse osmosis membrane in this specification refers to the improvement of the rejection rate of uncharged substances.

The inventors of the present invention have established an improvement by controlling the flux in terms of pure water (hereinafter sometimes referred to as "flux in terms of pure water") by contacting a halogen-based oxidizing agent with a polyamide-based reverse osmosis membrane. A technique to quantify the blocking performance (blocking rate) of any non-charged substance. According to the research of the inventors of this case, it can be known that regardless of the type of reverse osmosis membrane, the presence or absence of modification, etc., there is a correlation between the blocking rate of uncharged substances in the reverse osmosis membrane and the conversion flux of pure water. Therefore, by performing modification treatment according to the measured value of the pure water conversion flux of the reverse osmosis membrane, preferably according to the relational expression between the pure water conversion flux of the reverse osmosis membrane and the rejection rate of the uncharged substance prepared in advance, it is possible to Adjust the blocking rate of the non-charged substances of the reverse osmosis membrane to a predetermined value.

For upgrading, for example, set the concentration and pH of the predetermined halogen-based oxidant, and for example, pass water through the reverse osmosis membrane under pressure, and use a flow meter to monitor the flow rate, and calculate the conversion flux of pure water while converting the reverse osmosis membrane. The blocking rate of the non-charged substance of the permeable membrane can be adjusted to a predetermined value. Also, for example, set the concentration and pH of a predetermined halogen-based oxidant, pass water through the reverse osmosis membrane under pressure, monitor the flow rate with a flow meter, etc., and calculate the pure water conversion flux according to the above-mentioned relationship prepared in advance. The formula can be adjusted to the pure water conversion flux that achieves the rejection rate of the non-charged substance of the reverse osmosis membrane as the target. When multiple uncharged substances are used as the target, the pure water conversion flux can be adjusted to the target value based on the uncharged substance with the lowest blocking rate.

According to the modification method of the reverse osmosis membrane of this embodiment, the rejection rate of the uncharged substance of the reverse osmosis membrane can be adjusted to a predetermined value. According to the purpose of using the reverse osmosis membrane, the water quality required for the treated water, etc., determine the extent of the modification, that is, determine the blocking rate of the non-charged substances, and the modification can be obtained. The level of flux converted to pure water can be obtained as the rejection rate of the target. Using this method, even if multiple reverse osmosis membranes are used, and the rejection rate of each membrane is different due to the difference in batches of the membrane, etc., the rejection rate of each membrane can be made consistent by modification, and the reverse osmosis membrane can be eliminated. batch variance.

For example, it is also considered to monitor the concentration of uncharged substances towards the inlet and outlet of the reverse osmosis membrane device, and modify it so that it becomes the predetermined outlet concentration of uncharged substances, but generally speaking, the determination of the concentration of uncharged substances (such as , in the case of organic substances, the measurement of TOC concentration, in the case of boron and other inorganic substances, is time-consuming, so it is difficult to adjust the blocking rate of the non-charged substances of the reverse osmosis membrane to a predetermined value in real time during the modification process. value. However, according to the modification method of the reverse osmosis membrane of the present embodiment, by simply monitoring the flow rate by using a flow meter, etc., and performing modification while calculating the conversion flux of pure water, the barrier of the non-charged substance of the reverse osmosis membrane can be immediately eliminated. The rate is adjusted to a predetermined value.

Here, "non-charged substance" refers to a non-electrolyte organic substance, boron that does not dissociate in the neutral region (pH6~8). Low-molecular non-electrolyte organic substances include, for example, alcohol compounds such as methanol, ethanol, and isopropanol; amine compounds such as urea; and organic substances with a molecular weight of 200 or less such as tetraalkylammonium salts such as tetramethylammonium hydroxide.

"Pure water conversion flux (m/d/MPa)" is obtained by dividing the permeable water volume by the membrane area and operating pressure, and converting it into pure water according to the following formula.

Pure water conversion flux [m/d/MPa] = permeable water volume / membrane area / (effective pressure on membrane surface - osmotic pressure)

In the method for modifying a reverse osmosis membrane according to this embodiment, in order to obtain a membrane modified by a halogen-based oxidizing agent, the halogen-based oxidizing agent is present in feed water, washing water, etc. supplied to the reverse osmosis membrane, and mixed with The reverse osmosis membrane can be in contact.

The halogen-based oxidizing agent is not particularly limited as long as it contains halogens such as chlorine and bromine and has an oxidizing effect. Examples include: chlorine-based oxidizing agents, bromine-based oxidizing agents, stabilized hypochlorous acid compositions, stabilized Hypobromous acid composition, etc.

Chlorine-based oxidizing agents include, for example, chlorine gas, chlorine dioxide, hypochlorous acid or a salt thereof, chlorous acid or a salt thereof, chloric acid or a salt thereof, perchloric acid or a salt thereof, chlorinated isocyanuric acid, or its salt etc. Among them, salts include, for example: alkali metal hypochlorite salts such as sodium hypochlorite and potassium hypochlorite; alkaline earth metal salts of hypochlorite such as calcium hypochlorite and barium hypochlorite; sodium chlorite and potassium chlorite Alkali metal chlorite such as chlorite; alkaline earth metal chlorite such as barium chlorite; other metal chlorite such as nickel chlorite; alkali metal chlorate such as ammonium chlorate, sodium chlorate, and potassium chlorate; chlorine Calcium chlorate, barium chlorate and other alkaline earth metal salts of chlorate. These chlorine-based oxidizing agents may be used alone or in combination of two or more. As the chlorine-based oxidizing agent, sodium hypochlorite is preferably used in consideration of workability and the like.

Bromine-based oxidizing agents include bromine (liquid bromine), bromine chloride, bromic acid, bromate, hypobromous acid, and the like. Hypobromous acid may be produced by reacting a bromide such as sodium bromide with a chlorine-based oxidizing agent such as hypochlorous acid.

The stabilized hypochlorous acid composition contains chlorine-based oxidants and sulfamic acid compounds. The "stabilized hypochlorous acid composition containing chlorine-based oxidizing agent and sulfamic acid compound" may be a stabilized hypochlorous acid composition containing a mixture of "chlorine-based oxidizing agent" and "sulfamic acid compound", or may contain Stabilized hypochlorous acid composition of "reaction product of chlorine-based oxidizing agent and sulfamic acid compound".

The stabilized hypobromous acid composition contains bromine-based oxidants and sulfamic acid compounds. "Stabilized hypobromous acid composition containing brominated oxidizing agent and sulfamic acid compound" may contain "brominated oxidizing agent" and "amine The stabilized hypobromous acid composition of the mixture of "sulfonic acid compound" may also be the stabilized hypobromous acid composition containing "reaction product of bromine-based oxidizing agent and sulfamic acid compound".

As for the halogen-based oxidizing agent, among these, a stabilized hypochlorous acid composition or a stabilized hypobromous acid composition is preferable, and a stabilized hypobromous acid composition is more preferable. Although the stabilized hypochlorous acid composition or the stabilized hypobromous acid composition, especially the stabilized hypobromous acid composition exerts the modification effect equal to or more than that of chlorine-based oxidizing agents such as hypochlorous acid, but compared with chlorine-based oxidizing agents, It has low impact on the deterioration of the reverse osmosis membrane, and can suppress the deterioration of the membrane caused by repeated modification. Therefore, the stabilized hypochlorous acid composition or the stabilized hypobromous acid composition used in the method for upgrading the reverse osmosis membrane of this embodiment, especially the stabilized hypobromous acid composition is suitable as a modifier.

That is to say, the modification method of the reverse osmosis membrane of this embodiment is preferably by making a stabilized hypobromous acid composition containing a bromine-based oxidant and an amine sulfonic acid compound and a stabilized hypobromous acid composition containing a chlorine-based oxidant and an amine sulfonic acid compound. When at least one of the chloric acid compositions is in contact with the polyamide-based reverse osmosis membrane to change the rejection rate of uncharged substances, the modification treatment is performed based on the measured value of the pure water-converted flux of the reverse osmosis membrane.

In the modification method of the reverse osmosis membrane of this embodiment, especially when the "bromine-based oxidant" is bromine, since there is no chlorine-based oxidant, the effect on the deterioration of the reverse osmosis membrane is significantly lower, and it has the modification effect of the reverse osmosis membrane .

In the modification method of the reverse osmosis membrane of this embodiment, for example, a mixture of a "bromine-based oxidizing agent" and an "amine sulfonic acid compound" or a mixture of a "chlorine-based oxidizing agent" and an "amine sulfonic acid compound" is used as a modifying agent What is necessary is just to exist in feed water etc. which are supplied to a reverse osmosis membrane. This is considered to generate a stabilized hypobromous acid composition or a stabilized hypochlorous acid composition in the feed water supplied to the reverse osmosis membrane.

In addition, in the modification method of the reverse osmosis membrane of this embodiment, for example, the "reaction product of bromine-based oxidizing agent and sulfamic acid compound", which is a stabilized hypobromous acid composition, or the "chlorine-based oxidizing agent The reaction product with the sulfamic acid compound, that is, the stabilized hypochlorous acid composition may exist in the feed water or the like supplied to the reverse osmosis membrane.

Specifically, in the modification method of the reverse osmosis membrane of this embodiment, for example, the modification agent "bromine", "bromine chloride", "hypobromous acid" or "reaction of sodium bromide and hypochlorous acid Product" and the mixture of "sulfamic acid compound" may exist in feed water or the like supplied to the reverse osmosis membrane. Alternatively, a mixture of "hypochlorous acid" and "sulfamic acid compound" as a modifying agent may be present in feed water or the like supplied to the reverse osmosis membrane.

In addition, in the modification method of the reverse osmosis membrane of this embodiment, for example, "reaction product of bromine and sulfamic acid compound", "reaction product of bromine chloride and amine sulfonic acid compound", "The reaction product of hypobromous acid and sulfamic acid compound", or "the reaction product of sodium bromide and hypochlorous acid, and the reaction product of sulfamic acid compound", that is, the stabilized hypobromous acid composition exists in the supply to The reverse osmosis membrane can be supplied to water, etc. Alternatively, the "reaction product of hypochlorous acid and sulfamic acid compound", that is, the stabilized hypochlorous acid composition as a modifying agent may be present in feed water or the like supplied to the reverse osmosis membrane.

In the method for upgrading the reverse osmosis membrane of this embodiment, the contact of the halogen-based oxidant with the reverse osmosis membrane is preferably carried out within the range of more than pH 3 and less than pH 8, more preferably within the range of pH 4-6.5. If the contact between the halogen-based oxidant and the reverse osmosis membrane is carried out at a pH below 3, when the halogen-based oxidant is in contact with the reverse osmosis membrane for a long time, the reverse osmosis membrane will deteriorate and the rejection rate will decrease. If it is carried out at a pH above 8, there will be When the reforming effect is insufficient. Especially in the range of pH 4~6.5, it can inhibit reverse osmosis The deterioration of the membrane can be fully improved at the same time, the blocking rate of the uncharged substance of the reverse osmosis membrane. In order to carry out the contact of the modifying agent within the above pH range, for example, the pH of feed water supplied to the reverse osmosis membrane may be maintained within the above range.

In the modification method of the reverse osmosis membrane of this embodiment, for example, when the reverse osmosis membrane device equipped with the reverse osmosis membrane is in operation, the "chlorine-based oxidant", "bromine-based oxidant", or "bromine "Chlorine-based oxidizing agent" or "chlorine-based oxidizing agent" and "sulfamic acid compound" are injected into the feed water supplied to the reverse osmosis membrane, etc. The "bromine-based oxidizing agent" or "chlorine-based oxidizing agent" and the "sulfamic acid compound" may be added to feed water or the like separately, or the raw solutions may be mixed with each other and then added to the feed water or the like supplied to the reverse osmosis membrane.

Also, for example, the "reaction product of bromine-based oxidizing agent and sulfamic acid compound" or the "reaction product of chlorine-based oxidizing agent and sulfamic acid compound" can be injected into the supply to the reverse osmosis membrane by using a chemical injection pump or the like. water etc.

The modification by using a halogen-based oxidizing agent can be continuously or intermittently added to the feed water, washing water, etc. supplied to the reverse osmosis membrane during operation of a reverse osmosis membrane device equipped with a reverse osmosis membrane, When the rejection rate of the reverse osmosis membrane decreases, the halogen-based oxidizing agent may be continuously or intermittently added to the feed water, washing water, etc. supplied to the reverse osmosis membrane.

The contact of the halogen-based oxidant with the reverse osmosis membrane can be carried out under normal pressure conditions, under pressure conditions or under reduced pressure conditions. Considering that the reverse osmosis membrane device can still be modified without stopping the reverse osmosis membrane device, the reverse osmosis membrane can be reliably carried out. From the point of view of modification, etc., it is suitable to carry out under pressure. The contact of the halogen-based oxidizing agent with the reverse osmosis membrane is preferably carried out, for example, under a pressure condition in the range of 0.1 to 20 MPa, more preferably under a pressure condition in the range of 0.1 MPa to 8.0 MPa.

The contact of the halogen-based oxidizing agent with the reverse osmosis membrane may be performed, for example, under temperature conditions in the range of 5°C to 35°C.

In the modification method of the reverse osmosis membrane of the present embodiment, the ratio of the equivalent of the "ammonia sulfonic acid compound" to the equivalent of the "bromine-based oxidant" or "chlorine-based oxidant" is preferably 1 or more, and is in the range of 1 to 2 better. If the ratio of the equivalent of the "sulfamic acid compound" to the equivalent of the "bromine-based oxidizing agent" or "chlorine-based oxidizing agent" is less than 1, the reverse osmosis membrane may be deteriorated, and if it exceeds 2, the production cost may increase.

The concentration (total chlorine concentration) of the halogen-based oxidant in contact with the reverse osmosis membrane should be in the range of 0.1~100mg/L in terms of available chlorine concentration. If the concentration of the halogen-based oxidant (total chlorine concentration) in contact with the reverse osmosis membrane is less than 0.1 mg/L, sufficient modification effect may not be obtained, and if it exceeds 100 mg/L, the reverse osmosis membrane may be deteriorated , piping, etc. corrosion.

"Bromine and sulfamic acid compound (a mixture of bromine and sulfamic acid compound)" or "reaction product of bromine and sulfamic acid compound" using bromine, compared to "hypochlorous acid and bromine compound and sulfamic acid compound" Bromic acid" preparations and "bromine chloride and sulfamic acid" preparations, etc., bromic acid has less by-products and will not further deteriorate the reverse osmosis membrane, so it is better as a modifier.

That is, in the modification method of the reverse osmosis membrane of the present embodiment, it is preferable to contact the stabilized hypobromous acid composition containing bromine and sulfamic acid compound with the polyamide-based reverse osmosis membrane to change the For the blocking rate of the charged substance, the modification treatment is carried out according to the measured value of the pure water-converted flux of the reverse osmosis membrane.

At this time, the bromine and the amine sulfonic acid compound are preferably present (the mixture of the bromine and the amine sulfonic acid compound is present) in feed water or the like supplied to the reverse osmosis membrane. Moreover, it is preferable to make the reaction product of bromine and an aminesulfonic acid compound exist in feed water etc. which are supplied to a reverse osmosis membrane.

Examples of the bromine compound include sodium bromide, potassium bromide, lithium bromide, ammonium bromide, and hydrobromic acid. Among these, sodium bromide is preferable from the viewpoint of preparation cost and the like.

The sulfamic acid compound is a compound represented by the following general formula (1).

R ₂ NSO ₃ H (1)

(In the formula, R is independently a hydrogen atom or an alkyl group with 1 to 8 carbons.)

For sulfamic acid compounds, for example, sulfamic acid (sulfamic acid) in which both of the two R groups are hydrogen atoms can be mentioned, and other examples include: N-methylsulfamic acid, N-ethylamine One of the two R groups such as sulfonic acid, N-propylaminesulfonic acid, N-isopropylaminesulfonic acid, and N-butylaminesulfonic acid is a hydrogen atom, and the other is an alkyl group with 1 to 8 carbon atoms. Ammonium sulfonic acid compounds; N,N-dimethylamine sulfonic acid, N,N-diethylsulfamic acid, N,N-dipropylsulfamic acid, N,N-dibutylsulfamic acid, N-methyl-N-ethylaminesulfonic acid, N-methyl-N-propylaminesulfonic acid and other aminesulfonic acid compounds in which both of the two R groups are alkyl groups with 1 to 8 carbon atoms; N - Phenylaminesulfonic acid and other aminesulfonic acid compounds in which one of the two R groups is a hydrogen atom and the other is an aryl group with 6 to 10 carbon atoms, or their salts, etc. Examples of sulfamic acid salts include alkali metal salts such as sodium salts and potassium salts; alkaline earth metal salts such as calcium salts, strontium salts, and barium salts; manganese salts, copper salts, zinc salts, iron salts, cobalt salts, and nickel salts. and other metal salts; ammonium salts and guanidine salts, etc. Aminosulfonic acid compounds and salts thereof may be used alone or in combination of two or more. As the sulfamic acid compound, sulfamic acid (sulfamic acid) is preferably used in consideration of environmental load and the like.

In the reverse osmosis membrane upgrading method of this embodiment, at least one of the stabilized hypobromous acid composition and the stabilized hypochlorous acid composition is present in the feed water supplied to the reverse osmosis membrane in the form of a modifier When waiting, a base can also be further present. Examples of the base include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In consideration of product stability at low temperature, etc., sodium hydroxide and potassium hydroxide may be used in combination. Also, the base can be used in the form of an aqueous solution instead of a solid state.

The modification method of the reverse osmosis membrane in this embodiment is suitable for the current mainstream polyamide-based polymer membrane. Polyamide-based polymer membranes have relatively low resistance to oxidizing agents, and when free chlorine or the like is continuously brought into contact with the polyamide-based polymer membrane, a significant decrease in membrane performance may sometimes occur. However, in the method for upgrading the reverse osmosis membrane of this embodiment, by using at least one of the stabilized hypobromous acid composition and the stabilized hypochlorous acid composition, especially by using the stabilized hypobromous acid composition Even in polyamide polymer membranes, such a significant reduction in membrane performance hardly occurs.

In a reverse osmosis membrane device equipped with a polyamide-based reverse osmosis membrane, when feed water to the reverse osmosis membrane is fouled at a pH of 5.5 or higher, a dispersant and a halogen-based oxidizing agent may be used in combination to suppress fouling. As a dispersant, polyacrylic acid, polymaleic acid, phosphonic acid, etc. are mentioned, for example. The amount of the dispersant added to the supply water etc., for example, the concentration in RO concentrated water is in the range of 0.1 to 1,000 mg/L.

In addition, in order not to use a dispersant and to suppress the generation of fouling, for example, adjusting the operating conditions such as the recovery rate of the reverse osmosis membrane device, so that the concentration of silica in the RO concentrated water becomes below the solubility, and the index of calcium fouling is The Blue's index becomes 0 or less.

The application of the reverse osmosis membrane device equipped with the polyamide-based reverse osmosis membrane modified by the method of modifying the reverse osmosis membrane according to this embodiment includes, for example, desalination of seawater, recovery of discharged water, and the like. especially suitable for use The polyamide-based reverse osmosis membrane modified by the method for modifying the reverse osmosis membrane of this embodiment performs reverse osmosis membrane treatment on water containing boron-containing water and other water containing non-charged substances. By modifying the polyamide-based reverse osmosis membrane using the method for modifying the reverse osmosis membrane of this embodiment, the blocking rate of uncharged substances is significantly improved.

<Operation method of reverse osmosis membrane and reverse osmosis membrane device>

An example of a reverse osmosis membrane device according to an embodiment of the present invention is schematically shown in FIG. 1 , and its configuration will be described. The reverse osmosis membrane device 1 shown in FIG. 1 includes a reverse osmosis membrane treatment device 10 having a modified reverse osmosis membrane modified by contacting a bromine-based oxidant with a polyamide-based reverse osmosis membrane.

In the reverse osmosis membrane device 1 shown in FIG. 1 , the water to be treated pipe 12 is connected to the inlet of the reverse osmosis membrane treatment device 10 . The permeated water outlet of the reverse osmosis membrane treatment device 10 is connected to the permeated water pipe 14 , and the concentrated water outlet is connected to the concentrated water pipe 16 .

The operation method of the reverse osmosis membrane and the operation of the reverse osmosis membrane device 1 of this embodiment will be described.

The water to be treated is supplied to the reverse osmosis membrane treatment device 10 through the water to be treated pipe 12, and in the reverse osmosis membrane treatment device 10, the treated water is carried out using a modified reverse osmosis membrane modified by contacting it with a bromine-based oxidant. Reverse osmosis membrane treatment of water (reverse osmosis membrane treatment step). The permeated water obtained in the reverse osmosis membrane treatment is discharged through the permeated water pipe 14 , and the concentrated water is discharged through the concentrated water pipe 16 .

After passing the water to be treated into the modified reverse osmosis membrane and performing reverse osmosis membrane treatment for a predetermined time, the modified reverse osmosis membrane is subjected to alkali cleaning at a pH above 8 (alkali cleaning step). By combining polyamide-based reverse osmosis membrane with bromine-based Contacting and modifying the oxidizing agent can suppress the reduction of the barrier performance of the modified polyamide-based reverse osmosis membrane relative to alkali cleaning.

Alkaline cleaning can be performed, for example, by bringing an alkaline solution such as an aqueous alkaline solution into contact with the modified reverse osmosis membrane. For example, the modified reverse osmosis membrane can be passed through the modified reverse osmosis membrane for a predetermined time with an alkali solution such as an aqueous alkali solution, or immersed in an alkaline solution such as an aqueous alkali solution for a predetermined time. For example, the alkaline solution is passed into the modified reverse osmosis membrane through the alkaline solution water pipe, the immersion tank used to immerse the modified reverse osmosis membrane in the alkaline solution, etc., as alkaline cleaning of the modified reverse osmosis membrane at a pH above 8 The alkaline cleaning means to play a role.

As a base, sodium hydroxide, tetrasodium edetate, sodium lauryl sulfate, sodium tripolyphosphate, etc. are mentioned, for example. Alkali cleaning may use an alkali solution such as an aqueous alkali solution.

The pH in the alkaline cleaning step is 8 or more, preferably in the range of 8 to 13, more preferably in the range of 10 to 12. If the pH in the alkaline cleaning step is less than 8, the cleaning effect will be low, and if it exceeds 13, the reverse osmosis membrane may deteriorate.

The temperature in the alkali cleaning step is not particularly limited, for example, it is in the range of 5°C to 45°C, preferably in the range of 20°C to 35°C. If the temperature in the alkaline cleaning step is less than 5°C, the cleaning effect will be low, and if it exceeds 45°C, the reverse osmosis membrane may deteriorate.

In the operation method of the reverse osmosis membrane of this embodiment, the modified reverse osmosis membrane cleaned by alkali may also be brought into contact with a bromine-based oxidizing agent to perform re-modification (re-modification step). Since the deterioration of the polyamide-based reverse osmosis membrane is suppressed even after repeated alkali cleaning and modification, the reverse osmosis membrane device can still operate stably even in long-term operation.

The reverse osmosis membrane treatment device 10 is, for example, filled with a modified reverse osmosis membrane that is modified by contacting a bromine-based oxidant with a polyamide-based reverse osmosis membrane, and passes through treated water to obtain permeated water and concentrated water. Reverse osmosis membrane module.

The polyamide-based reverse osmosis membrane used in the reverse osmosis membrane treatment device 10 is a modified reverse osmosis membrane that is modified by contacting it with a bromine-based oxidant. Here, the "modification" of the reverse osmosis membrane in this specification refers to the improvement of the permeable water quality, that is, the improvement of the rejection rate. By using a reverse osmosis membrane modified by contacting a bromine-based oxidant with a polyamide-based reverse osmosis membrane, it is possible to perform reverse osmosis membrane treatment on water to be treated with a high rejection rate. By means of the modification method, the deterioration of the reverse osmosis membrane is suppressed, and at the same time, the blocking rate of the reverse osmosis membrane can be improved, and the quality of permeated water can be improved. Since the bromine-based oxidizing agent hardly degrades the polyamide-based reverse osmosis membrane, it is not a temporary water quality improvement. The deterioration of the reverse osmosis membrane can be suppressed, and the reduction of the rejection rate of the reverse osmosis membrane can be suppressed, that is, the reduction of water quality can be suppressed.

The bromine-based oxidizing agent used for reforming (and re-reforming, the same applies hereinafter) is not particularly limited. Bromine-based oxidizing agents include: "hypobromite", "reaction products of chlorine-based oxidizing agents and bromide ions", "stabilized hypobromous acid composition", etc., preferably "stabilized hypobromous acid composition ". The "stabilized hypobromous acid composition" has particularly little adverse effect on the rejection rate of the reverse osmosis membrane, and can operate stably for a long period of time even if it is continuously in contact with the reverse osmosis membrane.

The modified reverse osmosis membrane in the operation method of the reverse osmosis membrane of this embodiment is a membrane modified by the following method: using a bromine-based oxidant as a modifying agent, for example, using "bromine-based oxidant" and "ammoniasulfone A mixture of "acid compounds" exists in the feed water, wash water, etc. supplied to the polyamide-based reverse osmosis membrane, So that it is in contact with the polyamide-based reverse osmosis membrane. This is considered to generate a stabilized hypobromous acid composition in the feed water or the like.

In addition, the modified reverse osmosis membrane in the operation method of the reverse osmosis membrane of this embodiment is a membrane modified by the following method: for example, the reaction of "bromine-based oxidizing agent and amine sulfonic acid compound as a modifying agent produces "Substance" that is, a stabilized hypobromous acid composition exists in the feed water, washing water, etc. supplied to the polyamide-based reverse osmosis membrane so as to be in contact with the polyamide-based reverse osmosis membrane.

Specifically, the modified reverse osmosis membrane in the operation method of the reverse osmosis membrane of this embodiment is a membrane modified by the following method: for example, "bromine", "bromine chloride", "hypobromous acid" Or a mixture of "reaction product of sodium bromide and hypochlorous acid" and "sulfamic acid compound" exists in the feed water supplied to the polyamide-based reverse osmosis membrane, so that it can be combined with the polyamide-based reverse osmosis membrane membrane contact.

In addition, the modified reverse osmosis membrane in the operation method of the reverse osmosis membrane of this embodiment is a membrane modified by the following method: for example, "reaction product of bromine and sulfamic acid compound", "bromine chloride Reaction product with sulfamic acid compound", "reaction product of hypobromous acid and sulfamic acid compound", or "reaction product of sodium bromide and hypochlorous acid, and reaction product of sulfamic acid compound" The stabilized hypobromous acid composition is present in feed water or the like supplied to the polyamide-based reverse osmosis membrane so as to be in contact with the polyamide-based reverse osmosis membrane.

The modification of the reverse osmosis membrane in the operation method of the reverse osmosis membrane of this embodiment, for example, can be used as the modification agent when the reverse osmosis membrane device with the polyamide-based reverse osmosis membrane is operated, using a chemical injection pump, etc. Brominated oxidizing agent, for example, "brominated oxidizing agent" and "sulfamic acid compound" are injected into the feed water supplied to the reverse osmosis membrane, etc. "Brominated oxidizing agent" and "ammonia sulfonic acid compound" can be added separately to supply water, etc. Or you may add to supply water etc. after mixing undiluted|stock solutions together. Also, for example, the polyamide-based reverse osmosis membrane can be immersed for a predetermined time in water added with a bromine-based oxidant as a modifying agent, such as a "bromine-based oxidant" and a "sulfamic acid compound". touch.

Also, for example, "the reaction product of a bromine-based oxidizing agent and an amine sulfonic acid compound" or "the reaction product of a bromine compound and a chlorine-based oxidizing agent, and an amine sulfonic acid compound" may be injected using a chemical injection pump or the like. To the feed water etc. supplied to the polyamide-based reverse osmosis membrane. Also, for example, the polyamide-based reverse osmosis membrane can be added with "reaction product of bromine-based oxidizing agent and sulfamic acid compound", or "reaction product of bromine compound and chlorine-based oxidizing agent, and sulfamic acid compound". product" in water for a predetermined period of time to bring it into contact.

The modification by using a bromine-based oxidant, for example, when a reverse osmosis membrane device equipped with a polyamide-based reverse osmosis membrane is in operation, a bromine-based oxidant can be continuously or intermittently added to the feed water supplied to the reverse osmosis membrane, etc., When the rejection rate of the reverse osmosis membrane decreases, the bromine-based oxidizing agent may be continuously or intermittently added to feed water or the like supplied to the reverse osmosis membrane, or the reverse osmosis membrane may be immersed in water containing the bromine-based oxidizing agent. For example, adding pipes for adding bromine-based oxidizing agents to feed water supplied to reverse osmosis membranes, immersion tanks for immersing reverse osmosis membranes or modified reverse osmosis membranes in water containing bromine-based oxidizing agents, etc., are used as A reforming means of contacting a bromine-based oxidant with a reverse osmosis membrane for reforming, or a re-modification means of bringing a bromine-based oxidant into contact with a modified reverse osmosis membrane washed with alkali to perform re-modification functions.

The contact of the bromine-based oxidant with the reverse osmosis membrane can be carried out under normal pressure conditions, under pressure conditions or under reduced pressure conditions. Considering that the reverse osmosis membrane device can still be modified without stopping the reverse osmosis membrane device, the reverse osmosis membrane can be reliably carried out. From the point of view of modification, etc., it is suitable to carry out under pressure. The contact of the bromine-based oxidizing agent with the reverse osmosis membrane is preferably carried out under pressurized conditions in the range of 0.1 MPa to 8.0 MPa, for example.

The contact of the bromine-based oxidizing agent with the reverse osmosis membrane may be performed, for example, under temperature conditions in the range of 5°C to 35°C.

When the stabilized hypobromous acid composition is used, the ratio of the equivalent of the "ammonia sulfonic acid compound" to the equivalent of the "bromine-based oxidizing agent" is preferably 1 or more, more preferably 1 or more and 2 or less. If the ratio of the equivalent of the "sulfamic acid compound" to the equivalent of the "brominated oxidizing agent" is less than 1, the reverse osmosis membrane may be deteriorated, and if it exceeds 2, the production cost may increase.

The total chlorine concentration in contact with the reverse osmosis membrane should be 0.01~100mg/L in terms of available chlorine concentration. If it is less than 0.01 mg/L, a sufficient reforming effect may not be obtained, and if it exceeds 100 mg/L, deterioration of the reverse osmosis membrane and corrosion of piping, etc. may be caused.

Bromine-based oxidizing agents used in the stabilized hypobromous acid composition include bromine (liquid bromine), bromine chloride, bromic acid, bromate, hypobromous acid, and the like. Hypobromous acid may be produced by reacting a bromide such as sodium bromide with a chlorine-based oxidizing agent such as hypochlorous acid.

Among them, preparations of "bromine and sulfamic acid compound (mixture of bromine and sulfamic acid compound)" or "reaction product of bromine and sulfamic acid compound" using bromine, compared with "hypochlorous acid Preparations with bromine compounds and sulfamic acid” and preparations of “bromine chloride and sulfamic acid” have less chloride ions and will not further deteriorate the polyamide-based reverse osmosis membrane and cause corrosion of metal materials such as piping The probability is low, so it is better.

That is to say, the reverse osmosis membrane in the operation method of the reverse osmosis membrane of this embodiment is preferably a membrane modified by the following method: making bromine and amine sulfonic acid compound contact (making the mixture of bromine and amine sulfonic acid compound contact Contact) polyamide-based reverse osmosis membrane, or make the reaction product of bromine and sulfamic acid compound contact polyamide-based reverse osmosis membrane.

The bromine compound, chlorine-based oxidizing agent, and sulfamic acid compound are as described above.

In the modification of the reverse osmosis membrane in the operation method of the reverse osmosis membrane of this embodiment, an alkali may further exist. Examples of the base include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In consideration of product stability at low temperature, etc., sodium hydroxide and potassium hydroxide may be used in combination. Also, the base can be used in the form of an aqueous solution instead of a solid state.

The operation method of the reverse osmosis membrane of this embodiment is suitable for the polyamide-based polymer membrane that is currently the mainstream in terms of reverse osmosis membranes. Polyamide-based polymer membranes have relatively low resistance to oxidizing agents, and when free chlorine or the like is continuously brought into contact with the polyamide-based polymer membrane, a significant decrease in membrane performance may occur in some cases. However, the modification method of the reverse osmosis membrane using a bromine-based oxidant, especially a stabilized hypobromous acid composition, hardly causes such a significant decrease in membrane performance even in polyamide polymer membranes.

In the modification of the reverse osmosis membrane in the operation method of the reverse osmosis membrane of this embodiment, the contact of the bromine-based oxidant with the polyamide-based reverse osmosis membrane is preferably performed at a pH lower than that of the water to be treated. After the modification of the reverse osmosis membrane, when the water to be treated is continuously added with a bromine-based oxidant as a viscosity inhibitor, the pH of the water to be treated is higher than the pH at the time of modification (that is, the pH at the time of modification is lower If the pH of the water to be treated is maintained, the modification effect can be maintained, and the change of the permeation flow rate of the water to be treated can be suppressed. After the modification of the reverse osmosis membrane, when the water to be treated is continuously added with a bromine-based oxidant as a sticky inhibitor, the pH of the water to be treated is lower than the pH at the time of modification (that is, the pH at the time of modification is higher In the case of the pH of the treated water), there will be changes in the modification effect and the permeation flow of the treated water. The contact of bromine-based oxidants with polyamide-based reverse osmosis membranes, for example For example, it is carried out in the range of more than pH3 and less than pH8, or in the range of pH4~6.5. The lower the pH of the brominated oxidant contact, the higher the modification effect of the membrane, the better the barrier rate, and the better the permeable water quality.

In the reverse osmosis membrane device, when the feed water supplied to the reverse osmosis membrane has a pH of 5.5 or higher and fouling occurs, a dispersant and a bromine-based oxidizing agent may be used in combination to suppress fouling. As a dispersant, polyacrylic acid, polymaleic acid, phosphonic acid, etc. are mentioned, for example. The amount of the dispersant added to the supply water, for example, the concentration in RO concentrated water is in the range of 0.1 to 1,000 mg/L.

In addition, in order not to use a dispersant and to suppress the generation of fouling, for example, adjusting the operating conditions such as the recovery rate of the reverse osmosis membrane device, so that the concentration of silica in the RO concentrated water becomes below the solubility, and the index of calcium fouling is The Blue's index becomes 0 or less.

Applications of reverse osmosis membrane devices include, for example, pure water production, seawater desalination, and discharge water recovery.

In the operation method of the reverse osmosis membrane and the reverse osmosis membrane device 1 of the present embodiment, at least one of the degassing treatment device, the ion exchange treatment device, and the UV sterilization treatment device for treating the treated water of the reverse osmosis membrane treatment device 10 is provided. A device capable of performing at least one of degassing treatment, ion exchange treatment, and UV sterilization treatment on the water to be treated in the reverse osmosis membrane treatment device 10 (reverse osmosis membrane treatment step).

In addition, in the operation method of the reverse osmosis membrane of the present embodiment, an ion exchange treatment device for treating the permeated water of the reverse osmosis membrane treatment device 10, an electric desalination treatment device, a UV sterilization treatment device, a UV oxidation treatment device, a microparticle By removing at least one of the treatment device and the second reverse osmosis membrane treatment device, ion exchange treatment, At least one treatment selected from electrical desalination treatment, UV sterilization treatment, UV oxidation treatment, microparticle removal treatment, and second reverse osmosis membrane treatment.

<Modifier for reverse osmosis membrane>

The modifier for reverse osmosis membranes of this embodiment contains a halogen-based oxidizing agent. The modifying agent for reverse osmosis membrane in this embodiment is preferably a stabilized hypobromous acid composition containing a mixture of "bromine-based oxidizing agent" and "ammoniasulfonic acid compound", or a composition containing "chlorine-based oxidizing agent" and "amine sulfonic acid compound". The stabilized hypochlorous acid composition of the mixture of "sulfonic acid compounds" may further contain alkali.

In addition, the modifier for reverse osmosis membrane in this embodiment is preferably a stabilized hypobromous acid composition containing "the reaction product of a bromine-based oxidizing agent and an amine sulfonic acid compound", or a composition containing "a chlorine-based oxidizing agent and an amine sulfonic acid compound". The stabilized hypochlorous acid composition of "reaction product of sulfonic acid compound" may further contain a base.

The bromine-based oxidizing agent, bromine compound, chlorine-based oxidizing agent, and sulfamic acid compound are as described above.

As a commercially available product of the stabilized hypochlorous acid composition containing a chlorine-based oxidizing agent and an sulfamic acid compound, "KURIVERTER IK-110" manufactured by Kurita Kogyo Co., Ltd. is exemplified.

As far as the modifier for reverse osmosis membrane of this embodiment is concerned, in order not to further deteriorate the polyamide-based reverse osmosis membrane and to reduce the amount of effective halogen leakage to the RO permeated water, it is preferable to contain bromine and Ammonium sulfonic acid compounds (mixtures containing bromine and amine sulfonic acid compounds), such as mixtures of bromine, amine sulfonic acid compounds, alkali and water; or products containing bromine and amine sulfonic acid compounds, such as bromine The mixture of the reaction product with sulfamic acid compound, alkali and water.

The modifier for reverse osmosis membrane of this embodiment includes a stabilized hypobromous acid composition containing a bromine-based oxidant and an amine sulfonic acid compound, especially a stabilized hypobromous acid composition containing bromine and an amine sulfonic acid compound. As a modifier for acid compositions, compared with modifiers containing chlorine-based oxidants and sulfamic acid compounds (chloramine sulfonic acid, etc.), the former has higher oxidizing ability, and the modification effect, sticky inhibitory power, and sticky peeling power Significantly higher, however, hardly causes significant membrane degradation like hypochlorous acid, which also has high oxidizing power. In addition, compared with modifiers such as hypochlorous acid and free chlorine containing bromine, although it has the modifying effect of polyamide-based reverse osmosis membranes, it hardly causes significant damage like hypochlorous acid and free chlorine containing bromine. Membrane deterioration. At the usual concentration, the effect on membrane degradation can be substantially ignored. Therefore, it is the most ideal modifier for polyamide-based reverse osmosis membranes.

The reverse osmosis membrane modifier containing stabilized hypobromous acid composition or stabilized hypochlorous acid composition is different from hypochlorous acid, free chlorine containing bromine, etc., and hardly passes through the reverse osmosis membrane, so it hardly Affect the quality of treated water. In addition, since the concentration can be measured on site similarly to hypochlorous acid etc., more accurate concentration management can be performed.

The pH of the reverse osmosis membrane modifying agent containing the stabilized hypobromous acid composition is, for example, over 13.0, more preferably over 13.2. When the pH of the modifier for reverse osmosis membrane is 13.0 or less, the available halogen in the modifier may become unstable.

The bromic acid concentration in the reverse osmosis membrane modifier containing the stabilized hypobromous acid composition is preferably less than 5 mg/kg. If the concentration of bromic acid in the modifier is more than 5 mg/kg, the concentration of bromic acid ions in the RO permeated water may increase.

<Manufacturing method of modifier for reverse osmosis membrane>

The reverse osmosis membrane modifier containing stabilized hypobromous acid composition or stabilized hypochlorous acid composition can be obtained by mixing bromine-based oxidizing agent or chlorine-based oxidizing agent with sulfamic acid compound, or further mixing alkali .

The manufacturing method of the modifier for reverse osmosis membrane containing the stabilized hypobromous acid composition containing bromine and sulfamic acid compound, preferably including in the mixed solution containing water, alkali and sulfamic acid compound in an inert gas environment A step of adding bromine and allowing it to react; or a step of adding bromine to a mixture containing water, alkali and sulfamic acid compound under an inert gas atmosphere. By adding and reacting in an inert gas environment, or adding it in an inert gas environment, the concentration of bromate ions in the modifier for reverse osmosis membranes will decrease, and the concentration of bromate ions in RO permeate water will decrease. get lower.

The inert gas used is not limited, but it is preferably at least one of nitrogen and argon in consideration of production, and nitrogen is particularly preferred in consideration of production cost.

The oxygen concentration in the reactor when bromine is added is preferably 6% or less, more preferably 4% or less, more preferably 2% or less, and most preferably 1% or less. When the oxygen concentration in the reactor exceeds 6% during the bromine reaction, the amount of bromic acid produced in the reaction system may increase.

The addition rate of bromine is preferably not more than 25% by weight, more preferably not less than 1% by weight and not more than 20% by weight, based on the entire amount of the modifier. If the addition rate of bromine exceeds 25% by weight relative to the total amount of the reverse osmosis membrane modifier, the amount of bromic acid produced in the reaction system may increase. If it is less than 1% by weight, the reforming effect may be poor.

The reaction temperature when bromine is added should be controlled within the range of 0°C to 25°C, more preferably in the range of 0°C to 15°C in consideration of manufacturing costs. If the reaction temperature at the time of bromine addition exceeds 25°C, the amount of bromic acid produced in the reaction system may increase, and if it is lower than 0°C, freezing may occur.

[Example]

Hereinafter, the present invention will be described more specifically and in detail with examples and comparative examples, but the present invention is not limited to the following examples.

[Preparation of stabilized hypobromous acid composition]

Under a nitrogen atmosphere, liquid bromine: 16.9% by weight (wt%), sulfamic acid: 10.7% by weight, sodium hydroxide: 12.9% by weight, potassium hydroxide: 3.94% by weight, water: the rest are mixed to prepare a stable Composition of hypobromous acid. The pH of the stabilized hypobromous acid composition was 14, and the total chlorine concentration was 7.5% by weight. The total chlorine concentration is a value (mg/L asCl ₂ ) measured by the total chlorine measurement method (DPD (diethyl-p-phenylenediamine) method) using the multi-item water quality analyzer DR/4000 of HACH. The detailed preparation method of the stabilized hypobromous acid composition is as follows.

While controlling the flow rate with a mass flow controller, continuously inject and seal nitrogen gas so that the oxygen concentration in the reaction vessel is maintained at 1% in a 2L 4-neck flask, add 1436g of water, 361g of sodium hydroxide and mix, and then add 300g of sulfamic acid was mixed, and then the temperature of the reaction liquid was maintained to be cooled to 0~15°C, 473g of liquid bromine was added, and 230g of 48% potassium hydroxide solution was further added to obtain In terms of weight ratio, sulfamic acid is 10.7%, bromine is 16.9%, and the ratio of the equivalent of sulfamic acid to the equivalent of bromine is 1.04, which is the target stabilized hypobromous acid composition. The pH of the resulting solution was measured to be 14 by the glass electrode method. The bromine content of the resulting solution was measured by redox titration using sodium thiosulfate after converting bromine to iodine with potassium iodide. The result was 16.9%, which was the theoretical content. 100.0% of (16.9%). In addition, the oxygen concentration in the reaction container during the bromine reaction was measured using "Oxygen Monitor JKO-02 LJDII" manufactured by Jikco Co., Ltd. In addition, the concentration of bromic acid was less than 5 mg/kg.

In addition, pH measurement was performed under the following conditions.

Electrode type: glass electrode type

pH meter: manufactured by DKK Toa Co., Ltd., IOL-30 type

Electrode calibration: 2-point calibration with neutral phosphate pH (6.86) standard solution (type 2) manufactured by Kanto Chemical Co., Ltd. and borate pH (9.18) standard solution (type 2) manufactured by the same company

Measuring temperature: 25°C

Measured value: The electrode is immersed in the measuring solution, and the stabilized value is taken as the measured value, the average value of three measurements.

At pH 4, the test water obtained by using the stabilized hypobromous acid composition prepared above as a halogen-based oxidant and adjusting its concentration to 10 ppm was introduced into a polyamide-based polymer reverse osmosis membrane (Nitto Denko Co., Ltd. system, SWC5). While measuring the pressure and flow rate when passing water with the pressure gauge and flow meter, confirm the change of pure water converted flux. The relationship between pure water converted flux [m/d/MPa] and TOC (isopropanol (IPA)) rejection rate [%] is shown in Figure 2. From the results in Figure 2, we can see that the relationship is y=0.9x ² -10x+100. The relational expression is obtained by plotting the measured value of the blocking rate of the non-charged substance against the measured value of the pure water-converted flux and performing curve fitting. Regardless of the type of reverse osmosis membrane and the presence or absence of modification, there is a correlation between the blocking rate of uncharged substances in the reverse osmosis membrane and the conversion flux of pure water.

<Example 1, 2>

Sodium hypochlorite (Example 1) and the stabilized hypobromous acid composition (Example 2) prepared above were used as modifiers (halogen-based oxidizing agents) respectively to implement polyamide-based polymer reverse osmosis membranes (Nitto Denko Co., Ltd. ) Company system, modification of SWC5). The modification is based on the operating pressure of 2.0MPa, adding 10ppm of the above modifier to the water, It is passed into the reverse osmosis membrane device equipped with the reverse osmosis membrane under the conditions of pH 4 and 25±1°C. Set the target IPA rejection rate to 97%, and set the conversion flux of pure water to 0.28m/d/MPa according to the pre-made relational formula (Figure 2). While monitoring the flow rate with a flowmeter, water is supplied until the pure water conversion flux obtained by the following formula becomes 0.28m/d/MPa. Afterwards, at an operating pressure of 2.0 MPa, water to which 10 ppm of isopropanol was added as an uncharged substance in terms of TOC value was introduced at pH 7 and 25±1°C. The TOC concentrations of the raw water and the permeated water were measured with a TOC meter (manufactured by GEAI, Sievers M9e series), and the following IPA rejection rate was calculated. The results are shown in Table 1.

Pure water conversion flux [m/d/MPa] = permeable water volume / membrane area / (supply water pressure - osmotic pressure)

IPA rejection rate [%]=100-{TOC concentration of permeable water/[(TOC concentration of supply water+TOC concentration of concentrated water)/2]×100}

In this way, in the modification method of the reverse osmosis membrane that changes the blocking rate of uncharged substances by bringing the halogen-based oxidant into contact with the polyamide-based reverse osmosis membrane, the modification treatment is performed based on the measured value of the pure water conversion flux , the blocking rate of the non-charged substances of the reverse osmosis membrane can be adjusted to a predetermined value.

<Example 3, 4>

Using the stabilized hypobromous acid composition prepared above as a modifying agent, a polyamide-based polymer reverse osmosis membrane (manufactured by Nitto Denko Co., Ltd., "SWC4") (Example 3), polyamide It is a modification of a polymer reverse osmosis membrane (manufactured by Nitto Denko Co., Ltd., "SWC5") (Example 4). The modification system is to inject water with 10 ppm of the above-mentioned modifying agent at an operating pressure of 2.0 MPa into the Reverse osmosis membrane device of reverse osmosis membrane. While monitoring the flow rate with a flow meter, water was supplied until the pure water converted flux became 0.28 m/d/MPa. Thereafter, at an operating pressure of 2.0 MPa, water to which 10 ppm of IPA was added as an uncharged substance in terms of TOC value was passed through at pH 7 and 25±1°C. The TOC concentrations of the raw water and the permeated water were measured with a TOC meter, and the above-mentioned IPA rejection rate was calculated. The results are shown in Table 2.

In this way, even if the type of polyamide-based polymer reverse osmosis membrane is different, the blocking rate of uncharged substances of the reverse osmosis membrane can be adjusted to a predetermined value by performing modification treatment based on the measured value of pure water conversion flux. value.

<Comparative example 1, 2>

As described in paragraph [0044] of Patent Document 1, the reforming treatment is performed based on the reforming time, not the measured value of the pure water-converted flux. Using the stabilized hypobromous acid composition prepared above as a modifier, polyamide-based polymer reverse osmosis membrane (manufactured by FILMTEC, "SW30HRLE") (comparative example 1), polyamide-based polymer reverse osmosis Modification of a film (manufactured by Nitto Denko Co., Ltd., "SWC5") (Comparative Example 2). The modification is carried out by passing the water added with 10 ppm of the above-mentioned modifying agent at an operating pressure of 2.0 MPa into the reverse osmosis membrane device equipped with the reverse osmosis membrane under the conditions of pH 4 and 25±1°C for a predetermined time. Thereafter, at an operating pressure of 2.0 MPa, water to which 10 ppm of IPA was added as an uncharged substance in terms of TOC value was passed through at pH 7 and 25±1°C. The TOC concentrations of the raw water and the permeated water were measured with a TOC meter, and the above-mentioned IPA rejection rate was calculated. The results are shown in Table 3.

In this way, when the modification time is used to manage, the target TOC barrier performance cannot be achieved, and depending on the type of polyamide-based polymer reverse osmosis membrane, the modification effect is different, so depending on the type of membrane, The difference in the blocking rate of the modified non-charged substances becomes larger.

As described above, by carrying out the modification treatment based on the measured value of the pure water conversion flux as in the embodiment, the rejection rate of the uncharged substance of the reverse osmosis membrane can be adjusted to a predetermined value.

<Example 5, 6, Comparative Example 3, 4>

The stabilized hypobromous acid composition (Example 5), hypobromous acid (a mixture of sodium bromide and hypochlorous acid) (Example 6), and hypochlorous acid (Comparative Example 3) prepared above were used as modifiers respectively. The modification of the polyamide-based polymer reverse osmosis membrane ("SWC5" manufactured by Nitto Denko Co., Ltd.) was carried out. In addition, an unmodified polyamide-based polymer reverse osmosis membrane ("SWC5" manufactured by Nitto Denko Co., Ltd.) was also prepared (Comparative Example 4). The modification is implemented by passing the water added with 10 ppm of the above-mentioned modifying agent at an operating pressure of 2.0 MPa into the reverse osmosis membrane device equipped with the reverse osmosis membrane under the conditions of pH 4 and 25±1°C for 1 hour. For the modified reverse osmosis membranes of Examples 5 and 6, Comparative Example 3, and the unmodified reverse osmosis membrane of Comparative Example 4, at an operating pressure of 2.0 MPa, the TOC value of Water containing 10 ppm urea (molecular weight 60) was passed through for 1 hour at pH 7 and 25±1°C. After that, sodium hydroxide was added to pure water as an alkali, and each reverse osmosis membrane was soaked overnight (16 hours) at 20~25°C in an aqueous alkali solution adjusted to pH 12. 2.0MPa, will be added with Water containing 10 ppm of urea in terms of TOC value was passed through for 1 hour under conditions of pH 7 and 25±1°C. Use a TOC meter to measure the TOC concentration of the water to be treated and the permeated water, and calculate the following urea rejection rate. The results are shown in Table 4.

Urea rejection rate [%]=100-{permeable water TOC concentration÷[(supply water TOC concentration+concentrated water TOC concentration)÷2]×100}

Compared with the reverse osmosis membrane modified with bromine-based oxidant, the barrier performance of the reverse osmosis membrane modified with chlorine-based oxidant is greatly reduced due to alkali cleaning.

<Examples 7, 8, Comparative Example 5>

The membranes used in Example 5, Example 6, and Comparative Example 3 were modified again by the above-mentioned method to become Example 7, Example 8, and Comparative Example 5, respectively. In the same manner as in Examples 5, 6, and Comparative Example 3, the urea rejection rate of the remodified film was evaluated. The results are shown in Table 5.

In Examples 7 and 8, the barrier performance equal to that before alkaline cleaning was recovered by remodification.

In this way, by the operation method of the reverse osmosis membrane and the reverse osmosis membrane device of the embodiment, the reduction of the barrier performance of the modified polyamide-based reverse osmosis membrane relative to alkaline cleaning can be suppressed.

Claims (7)

A method for modifying a reverse osmosis membrane, which is to change the blocking rate of uncharged substances by contacting a halogen-based oxidant with a polyamide-based reverse osmosis membrane; The measured value of the amount, and the prefabricated relational expression of the pure water-converted flux of the reverse osmosis membrane and the rejection rate of the non-charged substance are modified. For example, the method for modifying reverse osmosis membranes in claim 1, wherein the non-charged substance is a low-molecular substance with a molecular weight of 200 or less. For example, the modification method of reverse osmosis membrane in claim 1 or 2 of the patent scope, wherein the contacting is carried out within the range of pH 4~6.5. Such as the modification method of reverse osmosis membrane in claim 1 or 2 of the patent scope, wherein the concentration of the halogen-based oxidizing agent during the contact is in the range of 0.1-100 mg/L. Such as the modification method of reverse osmosis membrane in claim 1 or 2 of the patent scope, wherein, the contact is carried out under the pressure in the range of 0.1~20MPa. A reverse osmosis membrane, which is modified by the modification method of reverse osmosis membrane according to any one of items 1 to 5 in the scope of the patent application. A treatment method for water containing non-charged substances, which uses a reverse osmosis membrane modified by the method of modifying reverse osmosis membranes according to any one of items 1 to 5 in the scope of the patent application to treat non-charged substances. The water is treated by reverse osmosis membrane.

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