TW201834739A - Method for modifying reverse osmosis membrane, reverse osmosis membrane, and method for processing water containing non-charged substance, method for operating reverse osmosis membrane and reverse osmosis membrane device - 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 substance, operation method of reverse osmosis membrane, and reverse osmosis membrane device

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

In order to effectively use water resources, a process for recovering, recycling, and reusing discharged water has been introduced. In order to obtain high-quality treated water, it is necessary to use a reverse osmosis membrane (RO membrane) capable of removing electrolytes and medium and low molecular substances.

However, when the discharged water contains non-charged substances such as urea, isopropanol, and boron, it is difficult to remove these non-charged substances even with a reverse osmosis membrane. For example, even a film with a blocking rate of more than 99% of sodium chloride as a charged substance will have a blocking rate of about 90 to 97% for isopropanol as a non-charged substance, and only about a few can be obtained in the case of urea. 10% blocking rate. Therefore, the improvement of the blocking rate of the non-charged substances of the reverse osmosis membrane is sought.

There are many modification methods for improving the permeability of reverse osmosis membranes and the like. Among them, there is a method of contacting a halogen-based modifier such as bromine-containing free chlorine with a reverse osmosis membrane for a predetermined time to improve performance.

For example, Patent Document 1 describes a method for processing a reverse osmosis membrane element, which is a pressure for filling a reverse osmosis membrane element in a membrane separation apparatus in a membrane separation apparatus equipped with a reverse osmosis membrane element having a polyurethane skin layer. After the container, the free chlorine aqueous solution containing bromine was brought into contact with the aforementioned reverse osmosis membrane element.

Patent Document 2 describes a method for modifying a reverse osmosis membrane in which a hypobromic acid-stabilizing composition as a modifier is brought into contact with a polyamine-based reverse osmosis membrane.

However, the methods of Patent Documents 1 and 2 have the following problems: Since the modification is performed based on time management, the barrier ratio of the reverse osmosis membrane cannot be adjusted to a predetermined value. Depending on the type of the membrane, the barrier performance after the modification is different. Larger. Moreover, Patent Documents 1 and 2 do not discuss how much the barrier performance of non-charged substances can be improved due to the contact conditions of the modifier.

Non-patent document 1 describes that when a halogen-based oxidant is brought into contact with a polyamide-based reverse osmosis membrane in an acidic environment, the amount of water permeation decreases.

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

Non-patent document 2 describes that when the pore diameter of the reverse osmosis membrane becomes smaller, the removal rate of boron is improved.

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 a non-charged substance.

On the other hand, when the reverse osmosis membrane device is operated for a long period of time, biological fouling and the like may occur. Therefore, the reverse osmosis membrane is subjected to alkaline cleaning with an alkaline aqueous solution or the like. For example, there is a problem in the reverse osmosis membrane spiral type element: the grid-shaped spacer used to form a narrow raw water flow path or a concentrated water flow path having a thickness of about 1 mm may cause stickiness and cause the flow path to be closed. As a method of removing this accumulated slime, alkaline washing is generally known.

However, if a polyamine-based reverse osmosis membrane that is brought into contact with a chlorine-based oxidant to improve performance as in the method of Patent Document 1 is subjected to alkaline cleaning, the reverse osmosis membrane is deteriorated and the barrier performance is reduced. Patent Literature 2 does not discuss the durability of the barrier performance improvement effect with respect to the alkaline cleaning when the actual use is assumed. [Prior Art Literature] [Patent Literature]

[Patent Document 1] JP 2003-088730 [Patent Document 2] JP 2016-155067 [Non-Patent Document]

[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] Bian Jian Changhong, Ogawa Takahashi, "Reverse osmosis membrane technology to promote desalination and reuse of sewer wastewater", Academic Journal "EICA", Vol. 15, No. 4 (2011), pp. 44-47.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a method for modifying a reverse osmosis membrane capable of adjusting the barrier ratio of a non-charged substance of a reverse osmosis membrane to a predetermined value, a reverse osmosis membrane modified by the modification method, and using the same Treatment method of reverse osmosis membrane for water containing non-charged substances.

In addition, an object of the present invention is to provide a method for operating a reverse osmosis membrane and a reverse osmosis membrane device, which can suppress a reduction in barrier performance of a modified polyamide-based reverse osmosis membrane with respect to alkali cleaning. [Means for solving problems]

The present invention is a method for modifying a reverse osmosis membrane, which is to change the barrier ratio of non-charged substances by contacting a halogen-based oxidant with a polyamide-type reverse osmosis membrane; The measured value of the flux is modified.

In the aforementioned method for modifying a reverse osmosis membrane, it is preferable to perform the aforementioned modification treatment according to a relational expression between a pure water conversion flux of the reverse osmosis membrane and a barrier ratio of the non-charged substance.

In the method for modifying a reverse osmosis membrane, the non-charged substance is preferably a low-molecular substance having a molecular weight of 200 or less.

In the method for modifying a reverse osmosis membrane, the contacting is preferably performed in a range of pH 4 to 6.5.

In the method for modifying a reverse osmosis membrane, the concentration of the halogen-based oxidant at the time of the contact is preferably in a range of 0.1 to 100 mg / L.

In the aforementioned method for modifying a reverse osmosis membrane, the aforementioned contacting is preferably performed under a pressure in a range of 0.1 to 20 MPa.

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

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

The present invention is a method for operating a reverse osmosis membrane, which includes the following steps: a reverse osmosis membrane treatment step for introducing a modified reverse osmosis membrane through contacting a bromine-based oxidant with a polyamide-based reverse osmosis membrane for modification Water to obtain permeate water and concentrated water; and an alkaline washing step, the aforementioned modified reverse osmosis membrane is subjected to alkaline washing at a pH of 8 or more.

The operation method of the aforementioned reverse osmosis membrane should preferably include a re-modification step, in which a bromine-based oxidant is brought into contact with the aforementioned alkali-washed modified reverse osmosis membrane for re-modification.

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

In the operation method of the reverse osmosis membrane, the bromine-based oxidant preferably includes a stabilized hypobromous acid composition containing a bromine-based oxidant and a sulfamic acid compound.

In the operation method of the reverse osmosis membrane, the bromine-based oxidant preferably includes a stabilized hypobromous acid composition containing bromine and a sulfamic acid compound.

In addition, the present invention is a reverse osmosis membrane device including a reverse osmosis membrane treatment device having a modified reverse osmosis membrane that is modified by bringing a bromine-based oxidant into contact with a polyamine-based reverse osmosis membrane, and passing the treated water through. To obtain permeate and concentrated water, and alkaline cleaning means, the above-mentioned modified reverse osmosis membrane is subjected to alkaline washing at pH 8 or higher; in the above-mentioned alkaline washing means, the treated water is passed into the above-mentioned modified reverse osmosis membrane After a predetermined time of the osmosis membrane, the alkaline solution is brought into contact with the aforementioned modified reverse osmosis membrane at a pH of 8 or more.

In the aforementioned reverse osmosis membrane device, it is preferable to further include a reforming means, which is to bring the bromine-based oxidant into contact with the reformed reverse osmosis membrane washed with the alkali to perform the reforming.

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

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

In the reverse osmosis membrane device, the bromine-based oxidant preferably contains a stabilized hypobromous acid composition containing bromine and a sulfamic acid compound. [Effect of the invention]

According to the present invention, it is possible to provide a method for modifying a reverse osmosis membrane capable of adjusting the barrier ratio of a non-charged substance of a reverse osmosis membrane to a predetermined value, a reverse osmosis membrane modified by the modification method, and using the reverse osmosis membrane. Treatment method for water containing non-charged substance in permeable membrane.

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

Hereinafter, embodiments of the present invention will be described. 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 reverse osmosis membrane of the embodiment of the present invention is the following method: by contacting a halogen-based oxidant with a polyamide-based reverse osmosis membrane, The barrier ratio of the charged substance is modified based on the measured value of the pure water conversion flux of the reverse osmosis membrane. In this modification method, the modification process should be performed according to the relational expression between the pure water conversion flux of the reverse osmosis membrane and the barrier ratio of the non-charged substance. 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 blocking rate of a non-charged substance.

The inventors of the present case established a reform by contacting a halogen-based oxidant with a reverse osmosis membrane made of a polyamide-based membrane and controlling the flux in terms of pure water (hereinafter sometimes referred to as "pure water equivalent flux"). A technique to characterize the blocking performance (blocking rate) of an arbitrary non-charged substance. According to the research by the inventors of the present case, it is found that there is a correlation between the blocking rate of non-charged substances of the reverse osmosis membrane and the pure water conversion flux, regardless of the type of the reverse osmosis membrane, the presence or absence of modification, and the like. Therefore, based on the measured value of the pure water conversion flux of the reverse osmosis membrane, it is preferable to perform the modification treatment based on the relationship between the pure water conversion flux of the reverse osmosis membrane and the barrier ratio of the non-charged substance. The barrier ratio of the non-charged substance of the reverse osmosis membrane is adjusted to a predetermined value.

In terms of modification, for example, a predetermined concentration and pH of a halogen-based oxidant are set, and water is passed through the reverse osmosis membrane under pressure, and the flow rate is monitored by a flow meter. The barrier ratio of the non-charged substance of the permeable membrane may be adjusted to a predetermined value. In addition, for example, the concentration and pH of a predetermined halogen-based oxidant are set, and water is passed through the reverse osmosis membrane under pressure, and the flow rate is monitored by a flow meter. The formula can be adjusted to a pure water conversion flux that is the target to achieve the barrier ratio of the non-charged material of the reverse osmosis membrane. When a variety of non-charged materials are targeted, the pure water conversion flux may be adjusted to the target value based on the non-charged material with the lowest blocking rate.

According to the method for modifying the reverse osmosis membrane of this embodiment, the barrier ratio of the non-charged substance of the reverse osmosis membrane can be adjusted to a predetermined value. Depending on the purpose of the reverse osmosis membrane, the water quality required for the treated water, etc., the extent to which the modification is determined, that is, how much the blocking rate of the non-charged substance will be determined, and the modification will be able to obtain the blocking rate that becomes the target. The degree of pure water equivalent flux is sufficient. With this method, even when multiple reverse osmosis membranes are used, and the barrier ratio of each membrane is different due to different batches of the membrane, etc., the barrier ratio of each membrane can be made uniform by modification to eliminate the membrane. Batch difference.

For example, it is also considered to monitor the concentration of the non-charged substance toward the inlet and outlet of the reverse osmosis membrane device and modify it so that it becomes the predetermined outlet concentration of the non-charged substance, but generally, the measurement of the concentration of the non-charged substance (for example, In the case of organic substances, the TOC concentration is measured, and in the case of inorganic substances such as boron, ICP luminescence analysis, etc.) It takes time, so it is difficult to adjust the barrier ratio of non-charged substances of the reverse osmosis membrane to a predetermined value in a timely manner during the modification process. value. However, according to the modification method of the reverse osmosis membrane of this embodiment, by simply monitoring the flow rate using a flow meter, etc., and performing the modification while calculating the pure water conversion flux, the non-charged substances of the reverse osmosis membrane can be blocked in real time. The rate is adjusted to a predetermined value.

Here, the "non-charged substance" means a non-electrolyte organic substance and boron that does not dissociate in a neutral region (pH 6 to 8). Examples of the low-molecular non-electrolyte organic substance include alcohol compounds such as methanol, ethanol, and isopropanol; amine compounds such as urea; and organic substances having a molecular weight of 200 or less such as tetraalkylammonium salts such as tetramethylammonium hydroxide.

"Flux in terms of pure water (m / d / MPa)" is obtained by dividing the amount of permeated water by the membrane area and operating pressure, and obtained by performing pure water conversion in accordance with the following formula. Pure water equivalent flux [m / d / MPa] = Permeable water volume / membrane area / (membrane surface effective pressure-osmotic pressure)

In the method for reforming a reverse osmosis membrane according to this embodiment, in order to obtain a membrane modified by a halogen-based oxidant, the halogen-based oxidant is present in the supply water, washing water, and the like supplied to the reverse osmosis membrane, and is combined with Just contact the reverse osmosis membrane.

The halogen-based oxidant is not particularly limited as long as it contains halogens such as chlorine and bromine and has an oxidizing effect. Examples include a chlorine-based oxidant, a bromine-based oxidant, a stabilized hypochlorous acid composition, and a stabilizer. Chemical composition and the like.

Examples of the chlorine-based oxidant include 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, chloroisocyanuric acid, or Its salt and so on. Among these, examples of the salt include alkali metal salts of hypochlorite 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 salts such as chlorite; Alkaline earth metal salts such as barium chlorite; Other metal chlorites such as nickel chlorite; Alkali metal salts such as ammonium chlorate, sodium chlorate, potassium chlorate; chlorine Alkaline earth metal chlorates such as calcium acid and barium chlorate. These chlorine-based oxidants may be used singly or in combination of two or more kinds. From the viewpoint of workability, etc., from the viewpoint of chlorine-based oxidant, sodium hypochlorite is preferably used.

Examples of the bromine-based oxidant include bromine (liquid bromine), bromine chloride, bromic acid, bromate, hypobromic acid, and the like. Hypobromic acid may be produced by reacting a bromide such as sodium bromide with a chlorine-based oxidant such as hypochlorous acid.

A stabilized hypochlorous acid composition containing a chlorine-based oxidant and a sulfamic acid compound. The "stabilized hypochlorous acid composition containing a chlorine-based oxidant and an amine sulfonic acid compound" may be a stabilized hypochlorous acid composition containing a mixture of a "chlorine-based oxidant" and an "amine sulfonic acid compound", or A stabilized hypochlorous acid composition that is a "reaction product of a chlorine-based oxidant and a sulfamic acid compound".

The stabilized hypobromous acid composition contains a bromine-based oxidant and a sulfamic acid compound. The "stabilized hypobromous acid composition containing a bromine-based oxidant and an amine sulfonic acid compound" may be a stabilized hypobromous acid composition containing a mixture of a "bromine-based oxidant" and an "amine sulfonic acid compound" A stabilized hypobromous acid composition of "the reaction product of a bromine-based oxidant and a sulfamic acid compound".

Among the halogen-based oxidants, 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, exhibits a modification effect equal to or higher than that of chlorine-based oxidants such as hypochlorous acid, but compared with chlorine-based oxidants, It has a low influence 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 modification method of the reverse osmosis membrane of this embodiment, especially the stabilized hypobromous acid composition is suitable as a modifier.

That is, the method for modifying the reverse osmosis membrane of the present embodiment is preferably a stabilized hypobromous acid composition containing a bromine-based oxidant and an amine sulfonic acid compound and a stabilization process containing a chlorine-based oxidant and an amine sulfonic acid compound. When at least one of the chloric acid composition is in contact with a polyamine-based reverse osmosis membrane to modify the barrier ratio of a non-charged substance, a modification treatment is performed based on the measured value of the pure water conversion flux of the reverse osmosis membrane.

In the method for modifying the reverse osmosis membrane of this embodiment, in particular, when the "bromine-based oxidant" is bromine, there is no chlorine-based oxidant, which has a significantly lower influence on the deterioration of the reverse osmosis membrane, and has a modification effect of the reverse osmosis membrane. .

In the method for modifying a reverse osmosis membrane of this embodiment, for example, a mixture of a "bromine-based oxidant" and an "amine sulfonic acid compound" as a modifier or a mixture of a "chlorine-based oxidant" and an "amine sulfonic acid compound" is used. It may exist in the supply water etc. which are supplied to a reverse osmosis membrane. Accordingly, it is thought that a stabilized hypobromous acid composition or a stabilized hypochlorous acid composition is generated in the feed water supplied to the reverse osmosis membrane.

In the method for modifying a reverse osmosis membrane according to this embodiment, for example, a "reaction product of a bromine-based oxidant and an amine sulfonic acid compound" that is a modifier is a stabilized hypobromous acid composition or a "chlorine-based oxidant" The reaction product with the sulfamic acid compound, that is, the stabilized hypochlorous acid composition may be present in the supply water or the like supplied to the reverse osmosis membrane.

Specifically, in the method for modifying a reverse osmosis membrane according to this embodiment, for example, "bromide", "bromine chloride", "hypobromous acid" or "sodium bromide and hypochlorous acid" are reacted as a modifier. What is necessary is just to exist in the supply water etc. which are supplied to the reverse osmosis membrane, and the mixture of "product" and "amine sulfonic acid compound". Alternatively, a mixture of "hypochlorous acid" and "amine sulfonic acid compound" as a modifier may be present in feed water or the like supplied to the reverse osmosis membrane.

In the method for modifying a reverse osmosis membrane according to this embodiment, for example, "reaction product of bromine and sulfamic acid compound", "reaction product of bromine chloride and sulfamic acid compound" as modifiers, "The reaction product of hypobromous acid and amine sulfonic acid compound", or "the reaction product of sodium bromide and hypochlorous acid, and the reaction product of amine sulfonic acid compound" means that the stabilized hypobromous acid composition exists in the supply to It is sufficient to supply the reverse osmosis membrane with water or the like. Alternatively, the "reaction product of hypochlorous acid and sulfamic acid compound" as a modifier, that is, the stabilized hypochlorous acid composition may exist in the supply water or the like supplied to the reverse osmosis membrane.

In the method for modifying the reverse osmosis membrane of this embodiment, the contact of the halogen-based oxidant to the reverse osmosis membrane is preferably performed in a range of more than pH 3 and less than pH 8, and more preferably in a range of pH 4 to 6.5. If the contact between the halogen-based oxidant and the reverse osmosis membrane is performed at pH 3 or less, if the halogen-based oxidant is contacted with the reverse osmosis membrane for a long period of time, the reverse osmosis membrane may be deteriorated and the blocking rate may be reduced. In case of insufficient improvement effect. Especially when it is contacted in the range of pH 4 to 6.5, the deterioration of the reverse osmosis membrane can be suppressed, and the blocking rate of the non-charged substances of the reverse osmosis membrane can be sufficiently improved. In order to perform the contact of the modifier with the above-mentioned pH range, for example, the pH of the supply water or the like supplied to the reverse osmosis membrane may be maintained within the above-mentioned range.

In the method for modifying a reverse osmosis membrane according to this embodiment, for example, when a reverse osmosis membrane device having a reverse osmosis membrane is in operation, a "chlorine-based oxidant", "bromine-based oxidant", or "bromine" "Oxidant" or "chlorine-based oxidant" and "sulfamic acid compound" are injected into the feed water and the like supplied to the reverse osmosis membrane. The "bromine-based oxidant" or "chlorine-based oxidant" and "amine sulfonic acid compound" may be added to the feed water or the like, or the raw liquids may be mixed with each other and added to the feed water or the like supplied to the reverse osmosis membrane.

In addition, for example, a "reaction product of a bromine-based oxidant and a sulfamic acid compound" or a "reaction product of a chlorine-based oxidant and a sulfamic acid compound" may be injected into the supply to the reverse osmosis membrane by using a chemical solution injection pump or the like. In the water.

The halogen-based oxidant is used for modification. For example, when a reverse osmosis membrane device having a reverse osmosis membrane is operated, the halogen-based oxidant can be continuously or intermittently added to the supply water, washing water, etc. supplied to the reverse osmosis membrane. When the barrier ratio of the reverse osmosis membrane is reduced, a halogen-based oxidant may be continuously or intermittently added to the supply water, washing water, and the like supplied to the reverse osmosis membrane.

The contact of the halogen-based oxidant to the reverse osmosis membrane may be performed under normal pressure conditions, pressurized conditions, or reduced pressure conditions. Considering that the reverse osmosis membrane device can be modified without stopping the reverse osmosis membrane, the reverse osmosis membrane can be reliably performed. From the viewpoint of modification and the like, it is suitable to carry out under pressure. The contact of the halogen-based oxidant to the reverse osmosis membrane is preferably performed under a pressure condition in a range of 0.1 to 20 MPa, and more preferably under a pressure condition in a range of 0.1 MPa to 8.0 MPa.

The contact of the halogen-based oxidant to the reverse osmosis membrane may be performed, for example, under a temperature range of 5 ° C to 35 ° C.

In the method for modifying the reverse osmosis membrane of this embodiment, the ratio of the equivalent of the "amine sulfonic acid compound" to the equivalent of the "bromine-based oxidant" or "chlorine-based oxidant" is preferably in the range of 1 or more and 2 or less. Better. If the ratio of the equivalent of the "amine sulfonic acid compound" to the equivalent of the "bromine-based oxidant" or "chlorine-based oxidant" is less than 1, the reverse osmosis membrane may be deteriorated. 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 to 100 mg / L in terms of effective 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, a sufficient modification effect may not be obtained. If it is more than 100 mg / L, it may cause deterioration of the reverse osmosis membrane. , Piping, etc.

Preparations using "bromine and sulfamic acid compounds (mixtures of bromine and sulfamic acid compounds)" or "reaction products of bromine and sulfamic acid compounds" of bromine compared to "hypochlorous acid and bromine compounds and sulfamic acids" "Acid" formulations and "bromine chloride and sulfamic acid" formulations have fewer by-products of bromic acid and do not deteriorate the reverse osmosis membrane. Therefore, they are more suitable as modifiers.

That is, in the method for modifying a reverse osmosis membrane according to this embodiment, it is preferable to change the non-osmosis membrane by contacting a stabilized hypobromous acid composition containing bromine and a sulfamic acid compound with a polyamide-based reverse osmosis membrane. In the case of the blocking rate of the charged substance, the modification treatment is performed based on the measured value of the pure water conversion flux of the reverse osmosis membrane.

At this time, it is preferable that the bromine and the sulfamic acid compound are present (the mixture of the bromine and the sulfamic acid compound is present) in the feed water or the like supplied to the reverse osmosis membrane. Moreover, it is preferable that the reaction product of bromine and a sulfamic acid compound exists in the supply 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 the cost of the preparation.

The sulfamic acid compound is a compound represented by the following general formula (1). R ₂ NSO ₃ H (1) (wherein R is independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.)

Examples of the sulfamic acid compound include amine sulfonic acid (aminosulfonic acid) in which two R groups are both hydrogen atoms. Other examples include N-methylaminesulfonic acid and N-ethylamine. One of the two R groups such as sulfonic acid, N-propylamine sulfonic acid, N-isopropylamine sulfonic acid, and N-butylamine sulfonic acid is a hydrogen atom, and the other is an alkyl group having 1 to 8 carbon atoms. Sulfamic acid compounds; N, N-dimethylaminesulfonic acid, N, N-diethylaminesulfonic acid, N, N-dipropylaminesulfonic acid, N, N-dibutylaminesulfonic acid, N-methyl-N-ethylamine sulfonic acid, N-methyl-N-propylamine sulfonic acid and the other two R groups, both of which are alkyl groups having 1 to 8 carbon atoms; N -One of the two R groups such as phenylsulfamic acid is a hydrogen atom, and the other is an aminesulfonic acid compound having an aryl group having 6 to 10 carbons; or a salt thereof. Examples of the amine sulfonate include alkali metal salts such as sodium and potassium salts; alkaline earth metal salts such as calcium, strontium, and barium salts; manganese, copper, zinc, iron, cobalt, and nickel salts And other metal salts; ammonium and guanidine salts. The sulfamic acid compounds and their salts may be used singly or in combination of two or more kinds. In view of the sulfamic acid compound, amine sulfonic acid (aminosulfonic acid) is preferably used in view of environmental load and the like.

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

The method for modifying the reverse osmosis membrane of this embodiment is applicable to the current mainstream polyamine-based polymer membranes. Polyamine-based polymer membranes have relatively low resistance to oxidants. If free chlorine or the like is continuously contacted with polyamine-based polymer membranes, the membrane performance may decrease significantly. However, in the method for modifying the reverse osmosis membrane of this embodiment, at least one of a stabilized hypobromous acid composition and a stabilized hypochlorous acid composition is used, and in particular, a stabilized hypobromous acid composition is used. Materials, even in polyamidopolymer film, such a significant reduction in film performance will hardly occur.

In a reverse osmosis membrane device equipped with a polyamine-based reverse osmosis membrane, when scale is generated at a pH of 5.5 or higher, such as water supplied to the reverse osmosis membrane, a dispersant and a halogen-based oxidant may be used in order to suppress the scale. . Examples of the dispersant include polyacrylic acid, polymaleic acid, and phosphonic acid. The amount of the dispersant added to the supply water, for example, ranges from 0.1 to 1,000 mg / L in terms of the concentration of the RO concentrated water.

In addition, in order to suppress the generation of scale without using a dispersant, for example, adjusting the operating conditions such as the recovery rate of the reverse osmosis membrane device, so that the concentration of silicon dioxide in the RO concentrated water becomes less than the solubility, and the index of calcium scale is The Lans index is below 0.

The use of a reverse osmosis membrane device provided with a polyamine-based reverse osmosis membrane modified by the method for modifying a reverse osmosis membrane of this embodiment includes, for example, seawater desalination and recovery of discharged water. In particular, it is preferable to use a polyamine-based reverse osmosis membrane modified by the modification method of the reverse osmosis membrane of this embodiment to perform reverse osmosis membrane treatment on water containing non-charged substances such as water containing boron. By using the modification method of the reverse osmosis membrane of this embodiment to modify the polyamine-based reverse osmosis membrane, the blocking rate of non-charged substances is significantly improved.

<Operation Method of Reverse Osmosis Membrane and Reverse Osmosis Membrane Device> An outline of an example of a reverse osmosis membrane device according to an embodiment of the present invention is shown in FIG. 1 and its configuration will be described. The reverse osmosis membrane device 1 of FIG. 1 includes a reverse osmosis membrane treatment device 10 having a modified reverse osmosis membrane that is 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 treated water pipe 12 is connected to the inlet of the reverse osmosis membrane processing device 10. The water-permeable outlet of the reverse osmosis membrane processing device 10 is connected to the water-permeable pipe 14, and the concentrated water outlet is connected to the concentrated water pipe 16.

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

The to-be-treated water is supplied to the reverse osmosis membrane treatment device 10 through the to-be-treated water pipe 12, and the reverse osmosis membrane treatment device 10 is treated by using a modified reverse osmosis membrane that is brought into contact with a bromine-based oxidant for modification. 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 water-permeable pipe 14, and the concentrated water is discharged through the concentrated water pipe 16.

After the treated water is passed through the modified reverse osmosis membrane and the reverse osmosis membrane is treated for a predetermined time, the modified reverse osmosis membrane is subjected to alkaline washing at an pH of 8 or more (alkali washing step). By contacting the polyamine-based reverse osmosis membrane with a bromine-based oxidant and modifying it, it is possible to suppress a decrease in the barrier performance of the modified polyamine-based reverse osmosis membrane with respect to alkali cleaning.

The alkaline washing can be performed, for example, by bringing an alkaline solution such as an alkaline aqueous solution into contact with a modified reverse osmosis membrane. For example, an alkaline solution such as an alkaline aqueous solution may be passed into the modified reverse osmosis membrane for a predetermined time, or the modified reverse osmosis membrane may be immersed in an alkaline solution such as an alkaline aqueous solution for a predetermined time. For example, the alkaline solution is passed into the alkaline solution water piping of the modified reverse osmosis membrane, and the immersion tank for immersing the modified reverse osmosis membrane in the alkaline solution is used to perform alkaline washing of the modified reverse osmosis membrane at pH 8 or higher. It functions by a clean alkaline washing means.

Examples of the base include sodium hydroxide, tetrasodium ethylenediamine tetraacetate, sodium lauryl sulfate, and sodium tripolyphosphate. For the alkali cleaning, an alkali solution such as an aqueous alkali solution may be used.

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

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

In the operation method of the reverse osmosis membrane of this embodiment, the bromine-based oxidant may be brought into contact with the modified reverse osmosis membrane washed with alkali to perform re-modification (re-modification step). Since the degradation of the polyimide-based reverse osmosis membrane is suppressed even after repeated alkaline washing and modification, the reverse osmosis membrane device can still operate stably even after 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 polyamine-based reverse osmosis membrane, and passing in water to be treated to obtain permeate water and concentrated water. Reverse osmosis membrane module.

The polyamide-based reverse osmosis membrane used in the reverse osmosis membrane processing apparatus 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 water permeability, that is, the improvement of the blocking rate. By using a reverse osmosis membrane modified by contacting a bromine-based oxidant with a polyamide-type reverse osmosis membrane, it is possible to perform a reverse osmosis membrane treatment on the water to be treated with a high barrier rate. By this modification method, the deterioration of the reverse osmosis membrane is suppressed, at the same time, the barrier ratio of the reverse osmosis membrane can be improved, and the water permeability can be improved. Since the bromine-based oxidant hardly degrades the polyamine-based reverse osmosis membrane, it is not a temporary improvement in water quality. Even if the water containing the bromine-based oxidant is passed into the polyamine-based reverse osmosis membrane for a long time and brought into contact, It can suppress the deterioration of the reverse osmosis membrane, and can also reduce the reduction of the barrier rate of the reverse osmosis membrane, that is, the reduction of the water quality.

There are no particular restrictions on the bromine-based oxidant used in the modification (and the subsequent modification, the same applies hereinafter). Examples of the bromine-based oxidant include "hypobromite", "reaction product of chlorine-based oxidant and bromide ion", "stabilized hypobromous acid composition", etc., and preferably "stabilized hypobromite composition" ". The "stabilized hypobromous acid composition" has a particularly small adverse effect on the barrier ratio of the reverse osmosis membrane. Even if it is continuously contacted with the reverse osmosis membrane, it can operate stably for a long period of time.

The modified reverse osmosis membrane in the operating method of the reverse osmosis membrane of this embodiment is a membrane modified by the following method: a bromine-based oxidant used as a modifier, for example, a "bromine-based oxidant" and "amine sulfonate" The mixture of "acid compounds" exists in the supply water, washing water, etc. which are supplied to a polyamide-type reverse osmosis membrane, and it is brought into contact with a polyamide-type reverse osmosis membrane. With this, it is thought that a stabilized hypobromous acid composition is generated in the supply water or the like.

In addition, the modified reverse osmosis membrane in the operating method of the reverse osmosis membrane of this embodiment is a membrane modified by the following method: for example, the reaction between a bromine-based oxidant and an amine sulfonic acid compound as a modifier is generated The "substance", that is, the stabilized hypobromous acid composition, is present in the supply water, the washing water, and the like supplied to the polyamide-based reverse osmosis membrane so as to be brought into contact with the polyamide-based reverse osmosis membrane.

Specifically, the modified reverse osmosis membrane in the operating method of the reverse osmosis membrane of this embodiment is a membrane modified by the following methods: for example, "bromide", "bromine chloride", and "hypobromite" Or a mixture of "the reaction product of sodium bromide and hypochlorous acid" and "amine sulfonic acid compound" is present in the supply water or the like supplied to the polyamide-based reverse osmosis membrane to make it reverse osmosis with the polyamide-based reverse osmosis membrane. Membrane contact.

In addition, the modified reverse osmosis membrane in the operating method of the reverse osmosis membrane of this embodiment is a membrane modified by the following methods: for example, "reaction product of bromine and sulfamic acid compound", "bromide chloride" Reaction product with sulfamic acid compound "," reaction product with hypobromous acid and sulfamic acid compound ", or" reaction product between sodium bromide and hypochlorous acid, and reaction product with sulfamic acid compound " The stabilized hypobromous acid composition is present in the feed water or the like supplied to the polyamide-based reverse osmosis membrane so as to be brought into 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 can be used as a modifier when a reverse osmosis membrane device equipped with a polyimide-based reverse osmosis membrane is operated. As the bromine-based oxidant, for example, a "bromine-based oxidant" and an "amine sulfonic acid compound" are injected into the supply water and the like supplied to the reverse osmosis membrane. The "bromine-based oxidant" and the "amine sulfonic acid compound" may be separately added to the supply water or the like, or the raw liquids may be mixed with each other and added to the supply water or the like. Alternatively, for example, a polyamine-based reverse osmosis membrane may be immersed in water to which a bromine-based oxidant as a modifier has been added, for example, a "bromine-based oxidant" and an "amine sulfonic acid compound" to be immersed for a predetermined period of time to make it contact.

In addition, for example, a "reaction product of a bromine-based oxidant and a sulfamic acid compound" or a "reaction product of a bromine compound and a chlorine-based oxidant and a reaction product of a amine sulfonic acid compound" may be injected using a chemical solution injection pump or the like. To feed water or the like supplied to the polyamine-based reverse osmosis membrane. In addition, for example, a polyamine-based reverse osmosis membrane may be added to a reaction product of a bromine-based oxidant and a sulfamic acid compound, or a reaction product of a bromine compound and a chlorine-based oxidant, and a reaction of a sulfamic acid compound. The "product" is immersed in water for a predetermined time and brought into contact.

By using a bromine-based oxidant, for example, when a reverse osmosis membrane device having a polyamine-based reverse osmosis membrane is operated, the bromine-based oxidant can be continuously or intermittently added to the supply water to the reverse osmosis membrane. When the barrier ratio of the reverse osmosis membrane is reduced, the bromine-based oxidant 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 oxidant. For example, an addition pipe for adding a bromine-based oxidant to supply water supplied to the reverse osmosis membrane, an immersion tank for immersing a reverse osmosis membrane or a modified reverse osmosis membrane in water containing a bromine oxidant, etc. are used as The bromine-based oxidant is brought into contact with a reverse osmosis membrane for modification, or the bromine-based oxidant is brought into contact with an alkali-washed modified reverse osmosis membrane for re-modification and re-modification.

The contact of the bromine-based oxidant to the reverse osmosis membrane may be performed under normal pressure conditions, pressurized conditions, or reduced pressure conditions. Considering that the reverse osmosis membrane device can be modified without stopping the reverse osmosis membrane, the reverse osmosis membrane can be reliably performed. From the viewpoint of modification and the like, it is suitable to carry out under pressure. The contact of the bromine-based oxidant to the reverse osmosis membrane is preferably performed under a pressurized condition in a range of 0.1 MPa to 8.0 MPa, for example.

The contact of the bromine-based oxidant to the reverse osmosis membrane may be performed, for example, under a temperature range of 5 ° C to 35 ° C.

When a stabilized hypobromous acid composition is used, the ratio of the equivalent of the "amine sulfonic acid compound" to the equivalent of the "bromine-based oxidant" is preferably 1 or more, and more preferably in the range of 1 or more and 2 or less. If the ratio of the equivalent of the "amine sulfonic acid compound" to the equivalent of the "bromine-based oxidant" is less than 1, the reverse osmosis membrane may be deteriorated. If it exceeds 2, the manufacturing cost may increase.

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

Examples of the bromine-based oxidant used in the stabilized hypobromous acid composition include bromine (liquid bromine), bromine chloride, bromic acid, bromate, hypobromic acid, and the like. Hypobromic acid may be produced by reacting a bromide such as sodium bromide with a chlorine-based oxidant such as hypochlorous acid.

Among these, a preparation using "bromide and sulfamic acid compound (bromide and sulfamic acid compound)" or "reaction product of bromine and sulfamic acid compound" of bromine is compared with "hypochlorous acid" "Bromo compounds and amine sulfonic acid" and "bromine chloride and amine sulfonic acid" preparations, etc., have less chloride ions, and will not degrade the polyimide-based reverse osmosis membrane and cause corrosion of metal materials such as piping. The probability is low, so it is better.

That is, the reverse osmosis membrane in the method of operating the reverse osmosis membrane of this embodiment is preferably a membrane modified by the following method: contacting bromine with a sulfamic acid compound (contacting a mixture of bromine and sulfamic acid compound ) Polyamine-based reverse osmosis membrane, or a reaction product of bromine and a sulfamic acid compound is brought into contact with the polyamine-based reverse osmosis membrane.

The bromine compound, the chlorine-based oxidant, and the sulfamic acid compound are as described above.

In the modification of the reverse osmosis membrane in the method of operating the reverse osmosis membrane of this embodiment, alkali may be further present. Examples of the alkali include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In consideration of the stability of the product at a low temperature, sodium hydroxide and potassium hydroxide may also be used. The alkali can be used in the form of an aqueous solution instead of a solid.

The operation method of the reverse osmosis membrane of this embodiment is applicable to the polyamine-based polymer membrane which is the mainstream of the reverse osmosis membrane at present. Polyamine-based polymer membranes have relatively low resistance to oxidants. If free chlorine or the like is continuously contacted with polyamine-based polymer membranes, a significant decrease in membrane performance may occur. However, using a bromine-based oxidizing agent, particularly a modified method of a reverse osmosis membrane using a stabilized hypobromous acid composition, such a significant reduction in membrane performance would hardly occur even in a polyamide polymer membrane.

In the modification of the reverse osmosis membrane in the method of operating the reverse osmosis membrane of this embodiment, it is preferred that the contact of the bromine-based oxidant with the polyamine-based reverse osmosis membrane is performed at a lower pH than the pH of the water to be treated. After the modification of the reverse osmosis membrane, when the treated water is continuously added as a viscosity inhibitor when the treated water is passed in, the pH of the treated water is higher than the pH at the time of the modification (that is, the pH at the time of the modification is low) At the pH of the water to be treated, the modification effect can be maintained, and the fluctuation of the permeate flow of the water to be treated can be suppressed. After the reverse osmosis membrane is modified, when the bromine-based oxidant is continuously added as a viscosity inhibitor when the treated water is passed in, the pH of the treated water is lower than the pH at the time of the modification (that is, the pH at the time of the modification is high) At the pH of the treated water, the modification effect and the permeate flow rate of the treated water may change. The contact of the bromine-based oxidant to the polyamine-based reverse osmosis membrane is performed, for example, in a range of more than pH 3 and less than pH 8 or in a range of pH 4 to 6.5. The lower the pH of the bromine-based oxidant when it comes into contact, the higher the modification effect of the membrane, the improved the blocking rate, and the better the water permeability.

In the reverse osmosis membrane device, when the supply water supplied to the reverse osmosis membrane has a pH of 5.5 or more to cause fouling, a dispersant and a bromine-based oxidant may be used in order to suppress fouling. Examples of the dispersant include polyacrylic acid, polymaleic acid, and phosphonic acid. The amount of the dispersant added to the supply water is, for example, a range of 0.1 to 1,000 mg / L in terms of the concentration of the RO concentrated water.

In addition, in order to suppress the generation of scale without using a dispersant, for example, adjusting the operating conditions such as the recovery rate of the reverse osmosis membrane device, so that the concentration of silicon dioxide in the RO concentrated water becomes less than the solubility, and the index of calcium scale is The Lans index is below 0.

Applications of the reverse osmosis membrane device include, for example, production of pure water, desalination of seawater, and recovery of discharged water.

The operation method of the reverse osmosis membrane and the reverse osmosis membrane device 1 of this embodiment include at least one of a degassing treatment device, an ion exchange treatment device, and a UV sterilization treatment device for treating the water to be treated in the reverse osmosis membrane treatment device 10. One device can perform at least one of deaeration 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, the method for operating a reverse osmosis membrane according to this embodiment includes an ion exchange treatment device for processing 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, and fine particles. At least one of the removal treatment device and the second reverse osmosis membrane treatment device can perform ion exchange treatment, electric desalination treatment, UV sterilization treatment on permeated water of the reverse osmosis membrane treatment device 10 (reverse osmosis membrane treatment step), At least one of a UV oxidation process, a particulate removal process, and a second reverse osmosis membrane process.

<Modifier for Reverse Osmosis Membrane> The modifier for reverse osmosis membrane according to this embodiment contains a halogen-based oxidant. The modifier for a reverse osmosis membrane of this embodiment is preferably a stabilized hypobromous acid composition containing a mixture of a "bromine-based oxidant" and an "amine sulfonic acid compound", or a "chlorine-based oxidant" and "amine" A "sulfonic acid compound" which stabilizes a hypochlorous acid composition may further contain a base.

The modifier for a reverse osmosis membrane of the present embodiment preferably contains a stabilized hypobromous acid composition containing "a reaction product of a bromine-based oxidant and an amine sulfonic acid compound" or a "chlorine-based oxidant and an amine". The reaction product of the sulfonic acid compound "that stabilizes the hypochlorous acid composition may further contain a base.

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

A commercially available product containing a stabilized hypochlorous acid composition containing a chlorine-based oxidizing agent and an amine sulfonic acid compound includes, for example, "KURIVERTER IK-110" manufactured by Kurita Industry Co., Ltd.

In the modifier for a reverse osmosis membrane of this embodiment, in order not to degrade the polyamine-based reverse osmosis membrane and to reduce the amount of effective halogen leakage to the RO water, it is preferable to contain bromine and A sulfamic acid compound (containing a mixture of bromine and a sulfamic acid compound), such as a mixture of bromine, a sulfamic acid compound, a base, and water; or a reaction product containing bromine and a sulfamic acid compound, such as bromine A mixture of a reaction product with a sulfamic acid compound, a base, and water.

The modifier for a reverse osmosis membrane of the present embodiment includes a modifier containing a stabilized hypobromous acid composition containing a bromine-based oxidant and a sulfamic acid compound, and in particular a stabilized hypobromide containing bromine and a sulfamic acid compound. Compared with modifiers containing chlorinated oxidants and amine sulfonic acid compounds (such as chloramine sulfonic acid), the modifiers of acid composition have higher oxidizing ability, modification effect, sticky suppressive power, and sticky peeling power. Significantly higher, however, it hardly causes significant film degradation like hypochlorous acid, which also has high oxidizing power. In addition, compared with hypochlorous acid, bromine-containing free chlorine and other modifiers, although it has the modification effect of polyamine-based reverse osmosis membrane, it hardly causes significant effects like hypochlorous acid and bromine-free free chlorine. Film deterioration. At normal concentrations, the effect on film degradation can be substantially ignored. Therefore, it is most suitable as a modifier of a polyamine-based reverse osmosis membrane.

Modifiers for reverse osmosis membranes containing a stabilized hypobromous acid composition or a stabilized hypochlorous acid composition are different from hypochlorous acid and free chlorine containing bromine, and hardly pass through the reverse osmosis membrane. Affects the quality of treated water. In addition, since the concentration can be measured on-site like hypochlorous acid and the like, more accurate concentration management can be performed.

The pH of the reverse osmosis membrane modifier containing the stabilized hypobromous acid composition is, for example, more than 13.0, and more preferably more than 13.2. When the pH of the modifier for a reverse osmosis membrane is 13.0 or less, the effective 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 bromic acid concentration in the modifier is 5 mg / kg or more, there may be a case where the bromic acid ion concentration of RO permeate becomes high.

<Manufacturing method of modifier for reverse osmosis membrane> A modifier for reverse osmosis membrane containing a stabilized hypobromous acid composition or a stabilized hypochlorous acid composition can be obtained by combining a bromine-based oxidant or a chlorine-based oxidant with an amine. The sulfonic acid compound is obtained by mixing, and a base may be further mixed.

A method for producing a modifier for a reverse osmosis membrane containing a stabilized hypobromous acid composition containing bromine and a sulfamic acid compound, preferably in a mixed gas containing water, an alkali, and a sulfamic acid compound in a passive gas environment A step of adding bromine and reacting it; or a step of adding bromine in a mixed solution containing water, an alkali and a sulfamic acid compound under an inert gas environment. By adding and reacting in an inert gas environment, or adding in an inert gas environment, the bromide ion concentration in the modifier for reverse osmosis membranes will be lowered, and the bromide ion concentration in RO permeate water will be lower. Go low.

The inert gas to be used is not limited. In consideration of manufacturing, it is preferably at least one of nitrogen and argon. In consideration of manufacturing cost, nitrogen is particularly preferred.

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

The addition rate of bromine is preferably 25% by weight or less, more preferably 1% by weight or more and 20% by weight or less with respect to the entire amount of the modifier. When the addition rate of bromine exceeds 25% by weight based on the total amount of the modifier for the reverse osmosis membrane, the amount of bromic acid produced in the reaction system may increase. If it is less than 1% by weight, the modification effect may be poor.

The reaction temperature when bromine is added should be controlled in the range of 0 ° C to 25 ° C. Considering aspects such as manufacturing costs, it is more preferable to control the range of 0 ° C to 15 ° C. If the reaction temperature during the addition of bromine exceeds 25 ° C, the amount of bromic acid produced in the reaction system may increase, and if it does not reach 0 ° C, it may freeze. [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 environment, liquid bromine: 16.9 wt% (wt%), amine sulfonic acid: 10.7 wt%, sodium hydroxide: 12.9 wt%, potassium hydroxide: 3.94 wt %, Water: The remaining amounts are mixed to prepare a stabilized hypobromous acid composition. The stabilized hypobromous acid composition had a pH of 14 and a total chlorine concentration of 7.5% by weight. The total chlorine concentration is a value (mg / L asCl ₂ ) measured by a total chlorine measurement method (DPD (diethyl-p-phenylene diamine) method) using a multi-item water quality analyzer DR / 4000 of HACH Company. The detailed production method of the stabilized hypobromous acid composition is as follows.

Continuously inject and seal nitrogen while controlling the flow rate with a mass flow controller to maintain the oxygen concentration in the reaction vessel at a 1% 2 L 4-necked flask. Add 1436 g of water and 361 g of sodium hydroxide and mix, then add 300g of amine sulfonic acid was mixed, and then the temperature of the reaction solution was cooled to 0 to 15 ° C. 473g of liquid bromine was added, and 230g of a 48% potassium hydroxide solution was further added to obtain an amount based on the entire composition. By weight ratio, the target stabilized hypobromous acid composition was 10.7% amine sulfonic acid, 16.9% bromine, and the ratio of the equivalent weight of aminesulfonic acid to the equivalent weight of bromine was 1.04. The pH of the produced solution was measured by the glass electrode method, and it was 14. The bromine content of the resulting solution was determined by converting potassium bromide to iodine using potassium iodide and performing a redox titration with sodium thiosulfate. The result was 16.9%, which was 100.0% of the theoretical content (16.9%). The oxygen concentration in the reaction vessel during the bromine reaction was measured using "Oxygen Monitor JKO-02 LJDII" manufactured by Jikco Co., Ltd. The bromic acid concentration was less than 5 mg / kg.

The pH measurement was performed under the following conditions. Electrode type: Glass electrode type pH meter: manufactured by Toya DKK, IOL-30 type electrode calibration: neutral phosphate pH (6.86) standard solution (type 2) manufactured by Kanto Chemical Co., Ltd. 9.18) Two-point calibration of the standard solution (type 2). Measurement temperature: 25 ° C. Measurement 値: The electrode was immersed in the measurement solution and the stabilized 値 was used as the measurement 値.

At pH 4, the test water obtained by using the stabilized hypobromous acid composition prepared as described above as a halogen-based oxidant and adjusting the concentration to 10 ppm was passed to a polyamine-based polymer reverse osmosis membrane (Nitto Denko Corporation) System, SWC5). Use pressure gauges and flow meters to measure the pressure and flow rate during water flow and confirm the change in pure water conversion flux. The relationship between the pure water equivalent flux [m / d / MPa] and the TOC (isopropyl alcohol (IPA)) barrier ratio [%] is shown in FIG. 2. As can be seen from the results in FIG. 2, the relationship is y = 0.9x ² -10x + 100. Regardless of the type of the reverse osmosis membrane and the presence or absence of modification, there is a correlation between the blocking rate of non-charged substances and the pure water conversion flux of the reverse osmosis membrane.

<Examples 1 and 2> Using sodium hypochlorite (Example 1) and the stabilized hypobromous acid composition (Example 2) prepared as described above as modifiers (halogen-based oxidants), polyamine-based polymer inversion was performed. Modification of osmotic membrane (manufactured by Nitto Denko Corporation, SWC5). The modification was carried out at an operating pressure of 2.0 MPa, and 10 ppm of water containing the above-mentioned modifier was introduced into a reverse osmosis membrane device equipped with the reverse osmosis membrane at a pH of 4, 25 ± 1 ° C. The target IPA blocking rate was set to 97%, and the pure water conversion flux was set to 0.28 m / d / MPa based on a pre-made relational expression (Fig. 2). While monitoring the flow rate using a flow meter, water was introduced until the pure water conversion flux obtained by the following formula became 0.28 m / d / MPa. After that, water having an TOC value of 10 ppm of isopropyl alcohol as a non-charged substance was added at an operating pressure of 2.0 MPa, and the mixture was passed under conditions of pH 7, 25 ± 1 ° C. The TOC concentration of raw water and permeated water was measured with a TOC meter (manufactured by GEAI, Siever s M9e series), and the following IPA blocking ratios were calculated. The results are shown in Table 1. Pure water equivalent flux [m / d / MPa] = permeated water volume / membrane area / (supply water pressure-osmotic pressure) IPA blocking rate [%] = 100- {permeate water TOC concentration / [(supply water TOC concentration + TOC concentration of concentrated water) / 2] × 100}

【Table 1】

In this way, in a method for modifying a reverse osmosis membrane by changing a barrier ratio of a non-charged substance by contacting a halogen-based oxidant with a polyamine-based reverse osmosis membrane, the modification process is performed based on the measured value of pure water conversion flux. The blocking rate of the non-charged substance of the reverse osmosis membrane can be adjusted to a predetermined value.

<Examples 3 and 4> Using the stabilized hypobromous acid composition prepared as described above as a modifier, polyamine-based polymer reverse osmosis membranes (manufactured by Nitto Denko Corporation, "SWC4") were implemented (implemented Example 3) Modification of a polyamide-based polymer reverse osmosis membrane (manufactured by Nitto Denko Corporation, "SWC5") (Example 4). The modification is carried out at an operating pressure of 2.0 MPa, to which 10 ppm of the above-mentioned modifier is added, and passed to a reverse osmosis membrane device having the reverse osmosis membrane at a pH of 4, 25 ± 1 ° C. While monitoring the flow using a flow meter, water was introduced until the pure water conversion flux became 0.28 m / d / MPa. Thereafter, at a working pressure of 2.0 MPa, water to which IPA with a TOC value of 10 ppm as a non-charged substance was added was passed at a condition of pH 7, 25 ± 1 ° C. The TOC concentration of raw water and permeated water was measured with a TOC meter, and the IPA blocking rate was calculated. The results are shown in Table 2.

【Table 2】

In this way, even if the membrane type of the polyamine-based polymer reverse osmosis membrane is different, the modification rate of the non-charged substance of the reverse osmosis membrane can be adjusted to a predetermined value by performing a modification process based on the measured value of the pure water conversion flux. value.

<Comparative Examples 1, 2> As described in paragraph [0044] of Patent Document 1, the modification process was performed according to the modification time, instead of the modification process based on the measured value of the pure water conversion flux. Using the stabilized hypobromous acid composition prepared as described above as a modifier, a polyamine-based polymer reverse osmosis membrane ("SW30HR LE" manufactured by FILMTEC) (Comparative Example 1) and a polyamine-based polymer reverse osmosis membrane were respectively implemented. Modification of the permeable membrane (manufactured by Nitto Denko Corporation, "SWC5") (Comparative Example 2). The modification was carried out by operating at a pressure of 2.0 MPa and adding 10 ppm of the above-mentioned modifier to a reverse osmosis membrane device having the reverse osmosis membrane at a pH of 4, 25 ± 1 ° C for a predetermined time. Thereafter, at a working pressure of 2.0 MPa, water to which IPA with a TOC value of 10 ppm as a non-charged substance was added was passed at a condition of pH 7, 25 ± 1 ° C. The TOC concentration of raw water and permeated water was measured with a TOC meter, and the IPA blocking rate was calculated. The results are shown in Table 3.

【table 3】

In this way, when the management time is modified, the TOC barrier performance cannot be achieved, and it depends on the membrane type of the polyamine reverse osmosis membrane. The modification effect is different, so it depends on the membrane type. The difference in the blocking rate of non-charged substances after the modification becomes larger.

As described above, by performing the modification processing based on the measured value of the pure water conversion flux as in the example, the barrier ratio of the non-charged substance of the reverse osmosis membrane can be adjusted to a predetermined value.

<Examples 5, 6, and Comparative Examples 3, 4> The stabilized hypobromous acid composition (Example 5) and hypobromous acid (mixture of sodium bromide and hypochlorous acid) obtained by the above preparation were used respectively (Example 6 ), Hypochlorous acid (Comparative Example 3) was used as a modifier, and a polyamine-based polymer reverse osmosis membrane ("SWC5" manufactured by Nitto Denko Corporation) was implemented. An unmodified polyamido-based polymer reverse osmosis membrane ("SWC5" manufactured by Nitto Denko Corporation) was also prepared (Comparative Example 4). The modification was carried out by operating at a pressure of 2.0 MPa and adding 10 ppm of the above-mentioned modifier to a reverse osmosis membrane device equipped with the reverse osmosis membrane at a pH of 4, 25 ± 1 ° C for one hour. For the modified reverse osmosis membranes of Examples 5, 6, and Comparative Example 3 and the unmodified reverse osmosis membrane of Comparative Example 4, at an operating pressure of 2.0 MPa, a TOC value of 10 ppm of urea (molecular weight 60) was passed under the conditions of pH 7, 25 ± 1 ° C for 1 hour. After that, sodium hydroxide was added as a base in pure water, and each reverse osmosis membrane was immersed in an alkaline aqueous solution adjusted to pH 12 at 20 to 25 ° C overnight (16 hours). This step was performed 5 times, and again under operating pressure. At 2.0 MPa, water to which 10 ppm of urea in terms of TOC value was added was passed under conditions of pH 7, 25 ± 1 ° C for 1 hour. The TOC concentration of the treated water and permeated water was measured with a TOC meter, and the following urea blocking ratios were calculated. The results are shown in Table 4. Urea blocking rate [%] = 100- {Permeate TOC concentration ÷ [(Supply water TOC concentration + Concentrated water TOC concentration) ÷ 2] × 100}

【Table 4】

Compared with a reverse osmosis membrane modified by using a bromine-based oxidant, a reverse osmosis membrane modified by using a chlorine-based oxidant has a significantly reduced barrier performance due to alkali cleaning.

<Examples 7, 8, and Comparative Example 5> The films used in Example 5, Example 6, and Comparative Example 3 were modified again by the method described above, and they became Example 7, Example 8, and Comparative Example 5, respectively. It carried out similarly to Example 5, 6, and comparative example 3, and evaluated the urea blocking rate of the film after re-modification. The results are shown in Table 5.

【table 5】

In Examples 7 and 8, the same barrier performance as before the alkali cleaning was restored by re-modification.

In this way, with the operation method and the reverse osmosis membrane device of the reverse osmosis membrane of the embodiment, it is possible to suppress the reduction of the barrier performance of the modified polyamide reverse osmosis membrane relative to the alkali cleaning.

1‧‧‧ reverse osmosis membrane device

10‧‧‧ reverse osmosis membrane treatment device

12‧‧‧ treated water piping

14‧‧‧ Permeable 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 the pure water conversion flux [m / d / MPa] and the TOC barrier ratio [%] obtained in the examples.

Claims (18)

A method for modifying a reverse osmosis membrane is to change the barrier ratio of non-charged substances by contacting a halogen-based oxidant with a polyamide-type reverse osmosis membrane; it is characterized by: The measured value of the amount is modified. For example, the method for modifying a reverse osmosis membrane according to item 1 of the scope of patent application is based on the relation between the pure water conversion flux of the reverse osmosis membrane and the barrier ratio of the non-charged substance, and the modification process is performed. For example, the method for modifying a reverse osmosis membrane according to item 1 or 2 of the patent application scope, wherein the non-charged substance is a low-molecular substance with a molecular weight of 200 or less. For example, the method for modifying a reverse osmosis membrane in the first or second aspect of the patent application, wherein the contacting is performed within a range of pH 4 to 6.5. For example, the method for modifying a reverse osmosis membrane in the scope of claims 1 or 2, wherein the concentration of the halogen-based oxidant at the time of the contact is in the range of 0.1 to 100 mg / L. For example, the method for modifying a reverse osmosis membrane in the scope of claims 1 or 2 of the patent application, wherein the contacting is performed under a pressure in the range of 0.1 to 20 MPa. A reverse osmosis membrane is modified by a modification method of a reverse osmosis membrane according to any one of claims 1 to 6. A method for treating water containing non-charged substances, using a reverse osmosis membrane modified by a modification method of a reverse osmosis membrane according to any one of claims 1 to 6 of the scope of patent application, The water was treated with reverse osmosis membrane. A method for operating a reverse osmosis membrane includes the following steps: A reverse osmosis membrane treatment step is to pass a treated reverse osmosis membrane through a modified reverse osmosis membrane by contacting a bromine-based oxidant with a polyamine-based reverse osmosis membrane, and Obtaining permeated water and concentrated water; and an alkaline washing step, the modified reverse osmosis membrane is subjected to alkaline washing at a pH of 8 or more. For example, the operation method of the reverse osmosis membrane of item 9 of the patent application scope includes a re-modification step, in which a bromine-based oxidant is brought into contact with the alkali-washed modified reverse osmosis membrane for re-modification. For example, the operating method of the reverse osmosis membrane according to item 9 or 10 of the patent application scope, wherein the contacting of the bromine-based oxidant is performed at a lower pH than the pH of the treated water. For example, the operating method of a reverse osmosis membrane according to item 9 or 10 of the patent application scope, wherein the bromine-based oxidant includes a stabilized hypobromous acid composition containing a bromine-based oxidant and an amine sulfonic acid compound. For example, the operating method of a reverse osmosis membrane according to item 9 or 10 of the patent application scope, wherein the bromine-based oxidant includes a stabilized hypobromous acid composition containing bromine and a sulfamic acid compound. 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 polyamine-based reverse osmosis membrane, and passing treated water into the reverse osmosis membrane; Permeate and concentrated water and alkaline washing means are obtained, and the modified reverse osmosis membrane is subjected to alkaline washing at pH 8 or higher; in the alkaline washing means, the treated water is passed into the modified reverse osmosis After a predetermined time of the membrane, an alkaline solution is brought into contact with the modified reverse osmosis membrane at a pH of 8 or more. For example, the reverse osmosis membrane device under the scope of application for patent No. 14 has a re-modification means, which is to bring the bromine-based oxidant into contact with the alkali-washed modified reverse osmosis membrane for re-modification. For example, the reverse osmosis membrane device according to item 14 or 15 of the application, wherein the contact of the bromine-based oxidant is performed at a lower pH than the pH of the water to be treated. For example, a reverse osmosis membrane device according to item 14 or 15 of the application, wherein the bromine-based oxidant includes a stabilized hypobromous acid composition containing a bromine-based oxidant and an amine sulfonic acid compound. For example, a reverse osmosis membrane device according to item 14 or 15 of the application, wherein the bromine-based oxidant includes a stabilized hypobromous acid composition containing bromine and a sulfamic acid compound.