WO2018142904A1 - Method for modifying reverse osmosis membrane, reverse osmosis membrane, method for treating water containing non-charged substance, operation method for reverse osmosis membrane, and reverse osmosis membrane device - Google Patents

Abstract

A method for modifying a reverse osmosis membrane is provided with which it is possible to regulate the reverse osmosis membrane so as to have a given rejection of non-charged substances. The method, which is for modifying a polyamide-based reverse osmosis membrane, comprises bringing a halogen-based oxidant into contact with the reverse osmosis membrane to thereby change the rejection of non-charged substances, the modification being conducted on the basis of found flux values, in terms of pure water, of the reverse osmosis membrane. Furthermore, an operation method for a reverse osmosis membrane is provided in which a modified polyamide-based reverse osmosis membrane can be inhibited from suffering a decrease in rejection performance due to alkali cleaning. The operation method for a reverse osmosis membrane comprises: a reverse osmosis membrane treatment step in which water to be treated is passed through a polyamide-based reverse osmosis membrane that has been modified by contact with a bromine-compound oxidant, thereby obtaining penetrant water and concentrated water; and an alkali cleaning step in which the modified reverse osmosis membrane is cleaned with an alkali at a pH of 8 or higher.

Description

Reverse osmosis membrane modification method, reverse osmosis membrane, treatment method of uncharged substance-containing water, reverse osmosis membrane operation method and reverse osmosis membrane device

The present invention relates to a method for modifying a polyamide-based reverse osmosis membrane, a reverse osmosis membrane modified by the modification method, a method for treating uncharged substance-containing water using the reverse osmosis membrane, a method for operating a reverse osmosis membrane, and The present invention relates to a reverse osmosis membrane device.

In order to use water resources effectively, the introduction of processes that collect wastewater, recycle it, and reuse it is progressing. In order to obtain treated water with high water quality, it is indispensable to use a reverse osmosis membrane (RO membrane) capable of removing electrolytes, removing medium and low molecular weight substances, and the like.

However, when the drainage contains uncharged substances such as urea, isopropyl alcohol, and boron, removal of these uncharged substances is difficult even with a reverse osmosis membrane. For example, even if the rejection rate of sodium chloride, which is a charged substance, is 99% or more, the rejection rate of isopropyl alcohol, which is an uncharged substance, is about 90 to 97%. In some cases, only a rejection rate can be obtained. Therefore, there is a demand for improvement in the rejection rate of uncharged substances in the reverse osmosis membrane.

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

For example, in Patent Document 1, in a membrane separation apparatus equipped with a reverse osmosis membrane element having a polyamide skin layer, after filling the reverse osmosis membrane element into a pressure vessel in the membrane separation apparatus, bromine is added to the reverse osmosis membrane element. A method for treating a reverse osmosis membrane element in which a free chlorine aqueous solution is brought into contact is described.

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

However, in the methods of Patent Documents 1 and 2, since the reforming is managed by time, the blocking rate of the reverse osmosis membrane cannot be adjusted to a predetermined value, and the blocking performance difference after the modification depends on the membrane type. There was a problem that was large. Patent Documents 1 and 2 do not discuss how much the blocking performance of uncharged substances is improved by the contact condition 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 on the acidic side, the amount of permeated water decreases.

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

Non-Patent Document 2 describes that when the pore size of the reverse osmosis membrane is reduced, 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 an uncharged substance.

On the other hand, when the reverse osmosis membrane device is operated for a long period of time, the reverse osmosis membrane is alkali-washed with an alkaline aqueous solution or the like because of biofouling or the like. For example, the reverse osmosis membrane spiral element has a problem in that slime is generated in a mesh-like spacer forming a narrow raw water flow path or concentrated water flow path having a thickness of about 1 mm, thereby blocking the flow path. As a method for removing the accumulated slime, alkali cleaning is generally known.

However, when a polyamide-based reverse osmosis membrane whose performance has been improved by contacting with a chlorine-based oxidant as in the method of Patent Document 1 is alkali-washed, the reverse osmosis membrane is deteriorated and the blocking performance is lowered. In Patent Document 2, the sustainability of the prevention performance improvement effect for alkaline cleaning assuming actual operation is not studied.

JP 2003-088730 A JP 2016-1555067 A

An object of the present invention is to provide a reverse osmosis membrane modification method capable of adjusting the rejection rate of the uncharged substance of the reverse osmosis membrane to a predetermined value, a reverse osmosis membrane modified by the modification method, and the The object is to provide a method for treating uncharged substance-containing water using a reverse osmosis membrane.

It is another object of the present invention to provide a reverse osmosis membrane operating method and a reverse osmosis membrane device capable of suppressing a decrease in the blocking performance against alkali washing in a modified polyamide-based reverse osmosis membrane. .

The present invention provides a method for reforming a reverse osmosis membrane in which a halogen-based oxidant is brought into contact with a polyamide-based reverse osmosis membrane to change the rejection rate of an uncharged substance. This is a method for modifying a reverse osmosis membrane in which a modification treatment is performed based on a measured value.

In the reverse osmosis membrane modification method, it is preferable that the modification treatment is performed based on a correlation formula between a pure water equivalent flux of the reverse osmosis membrane and a blocking rate of the non-charged substance.

In the reverse osmosis membrane modification method, the uncharged substance is preferably a low-molecular substance having a molecular weight of 200 or less.

In the method for modifying a reverse osmosis membrane, it is preferable that the contact is performed in a pH range of 4 to 6.5.

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

In the method for reforming a reverse osmosis membrane, it is preferable that the contact is performed under a pressure in the range of 0.1 to 20 MPa.

Further, the present invention is a reverse osmosis membrane modified by the method for modifying a reverse osmosis membrane.

Further, the present invention is a method for treating uncharged substance-containing water, wherein the uncharged substance-containing water is treated with a reverse osmosis membrane using the reverse osmosis membrane modified by the reverse osmosis membrane modification method.

The present invention relates to a reverse osmosis membrane treatment step in which permeated water and concentrated water are obtained by passing water to be treated through a modified reverse osmosis membrane modified by bringing a bromine-based oxidant into contact with a polyamide-based reverse osmosis membrane. And an alkaline cleaning step of alkali cleaning the modified reverse osmosis membrane at pH 8 or higher.

The operation method of the reverse osmosis membrane preferably includes a re-reforming step of re-modifying the alkali-washed modified reverse osmosis membrane by bringing a bromine-based oxidant into contact therewith.

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

In the reverse osmosis membrane operation method, the bromine-based oxidizing agent preferably contains a stabilized hypobromite composition containing bromine and a sulfamic acid compound.

The present invention also includes a modified reverse osmosis membrane that is modified by bringing a bromine-based oxidant into contact with a polyamide-based reverse osmosis membrane, and passes the water to be treated to obtain permeated water and concentrated water. An osmosis membrane treatment device and an alkali cleaning means for alkali-washing the modified reverse osmosis membrane at pH 8 or more, wherein the alkali cleaning means passed the treated water through the modified reverse osmosis membrane for a predetermined time. Thereafter, the reverse osmosis membrane device is configured to bring an alkaline solution into contact with the modified reverse osmosis membrane at a pH of 8 or more.

In the reverse osmosis membrane device, it is preferable that the apparatus further comprises a re-reformer for re-modifying the alkali-washed modified reverse osmosis membrane by bringing a brominated oxidant into contact therewith.

In the reverse osmosis membrane device, it is preferable that the bromine-based oxidant is contacted 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 hypobromite composition containing a bromine-based oxidant and a sulfamic acid compound.

In the reverse osmosis membrane device, the bromine-based oxidant preferably includes a stabilized hypobromite composition containing bromine and a sulfamic acid compound.

INDUSTRIAL APPLICABILITY According to the present invention, a reverse osmosis membrane modification method capable of adjusting the rejection rate of uncharged substances in a reverse osmosis membrane to a predetermined value, a reverse osmosis membrane modified by the modification method, and a reverse osmosis thereof An uncharged substance-containing water treatment method using a membrane can be provided.

In the reverse osmosis membrane operation method and reverse osmosis membrane apparatus of the present invention, it is possible to suppress a decrease in the ability to prevent alkali washing in a modified polyamide-based reverse osmosis membrane.

It is a schematic block diagram which shows an example of the reverse osmosis membrane apparatus which concerns on embodiment of this invention. It is a figure which shows the relationship between the pure water conversion flux [m / d / MPa] and TOC rejection [%] which were calculated | required in the Example.

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

<Reverse osmosis membrane modification method and reverse osmosis membrane>
A method for modifying a reverse osmosis membrane according to an embodiment of the present invention is a method for modifying a reverse osmosis membrane in which a halogen-based oxidant is brought into contact with a polyamide-based reverse osmosis membrane to change the rejection rate of uncharged substances. This is a method for performing the reforming treatment based on the measured value of the flux of the reverse osmosis membrane in terms of pure water. In this reforming method, it is preferable to perform the reforming process based on a correlation formula between the pure water equivalent flux of the reverse osmosis membrane and the blocking rate of the uncharged substance prepared in advance. Further, the reverse osmosis membrane according to the embodiment of the present invention is a reverse osmosis membrane modified by the method for modifying a reverse osmosis membrane. In the present specification, “reforming” a reverse osmosis membrane refers to an improvement in the rejection rate of uncharged substances.

The present inventors control the flux in terms of pure water (hereinafter sometimes referred to as “pure water equivalent flux”) by bringing a halogen-based oxidant into contact with a reverse osmosis membrane whose membrane material is polyamide. The technology to improve the blocking performance (blocking rate) of any uncharged substance was established. According to the study by the present inventors, it was found that there is a correlation between the blocking rate of the non-charged substance of the reverse osmosis membrane and the pure water equivalent flux regardless of the type of the reverse osmosis membrane or the presence or absence of modification. . Therefore, based on the measured value of the pure water equivalent flux of the reverse osmosis membrane, preferably, based on the correlation formula between the pure water equivalent flux of the reverse osmosis membrane and the blocking rate of the uncharged substance, the reforming treatment is preferably performed in advance. By performing the above, it is possible to adjust the rejection rate of the uncharged substance of the reverse osmosis membrane to a predetermined value.

For example, the reforming is performed by setting the concentration and pH of a predetermined halogen-based oxidant, for example, passing water through a reverse osmosis membrane under pressure, monitoring the flow rate with a flow meter or the like, and calculating the pure water equivalent flux, What is necessary is just to adjust the rejection rate of the uncharged substance of a reverse osmosis membrane to a predetermined value. In addition, for example, set the concentration and pH of a predetermined halogen-based oxidant, for example, pass water through a reverse osmosis membrane under pressure, monitor the flow rate with a flow meter, etc., and create in advance while calculating the pure water equivalent flux Based on the above-described correlation equation, it may be adjusted to a pure water equivalent flux that becomes a target rejection rate of uncharged substances of the reverse osmosis membrane. When a plurality of uncharged substances are targeted, the pure water equivalent flux may be adjusted to a target value based on the uncharged substance having the lowest rejection rate.

</ RTI> By the reverse osmosis membrane modification method according to this embodiment, the rejection rate of uncharged substances in the reverse osmosis membrane can be adjusted to a predetermined value. Depending on the purpose of use of the reverse osmosis membrane and the quality of the water required for the treated water, it is decided how much the reform should be done, that is, what the rejection rate of uncharged substances should be, and the target rejection rate What is necessary is just to modify | reform to such an extent that the pure water conversion flux which becomes is obtained. By this method, for example, even when multiple reverse osmosis membranes are used and the rejection rate of each membrane differs due to the difference in membrane lots, etc., the rejection rate of each membrane is made uniform by reforming to eliminate the membrane lot difference. Can do.

For example, the concentration of uncharged substances at the inlet and outlet to the reverse osmosis membrane device may be monitored and reformed so as to have a predetermined uncharged substance outlet concentration. Since it takes time to measure the concentration (for example, TOC concentration in the case of organic substances, ICP emission analysis in the case of inorganic substances such as boron), the reverse osmosis membrane is It is difficult to adjust the rejection rate of uncharged substances to a predetermined value. However, according to the reforming method of the reverse osmosis membrane according to the present embodiment, the reverse osmosis membrane is instantly obtained by simply monitoring the flow rate with a flow meter or the like and performing the reforming while calculating the pure water equivalent flux. It is possible to adjust the rejection rate of the uncharged substance to a predetermined value.

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

“Pure water equivalent flux (m / d / MPa)” is obtained by dividing the permeated water amount by the membrane area and the operating pressure, and is converted to pure water by the following formula.
Pure water equivalent flux [m / d / MPa] = permeate amount / membrane area / (membrane surface effective pressure−osmotic pressure)

In the reverse osmosis membrane modification method according to the present embodiment, in order to obtain a membrane modified with a halogen-based oxidant, a halogen-based oxidant is present in the water supplied to the reverse osmosis membrane, the washing water, and the like. Then, it may be brought into contact with the reverse osmosis membrane.

The halogen-based oxidant is not particularly limited as long as it contains halogen such as chlorine and bromine and has an oxidizing action. For example, a chlorine-based oxidant, a bromine-based oxidant, and stabilized hypochlorous acid. An acid composition, a stabilized hypobromite composition, etc. are mentioned.

Examples of the chlorine-based oxidizing agent 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, chlorinated isocyanuric acid or a salt thereof. Etc. Among these, examples of the salt include alkali metal hypochlorites such as sodium hypochlorite and potassium hypochlorite, alkaline earth hypochlorite such as calcium hypochlorite and barium hypochlorite. Metal salts, alkali metal chlorites such as sodium chlorite and potassium chlorite, alkaline earth metal chlorites such as barium chlorite, and other metal chlorites such as nickel chlorite , Alkali metal chlorates such as ammonium chlorate, sodium chlorate and potassium chlorate, and alkaline earth metal chlorates such as calcium chlorate and barium chlorate. These chlorine-based oxidants may be used alone or in combination of two or more. As the chlorine-based oxidant, sodium hypochlorite is preferably used from the viewpoint of handleability.

Examples of bromine-based oxidizing agents include bromine (liquid bromine), bromine chloride, bromic acid, bromate, and hypobromite. 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 a chlorine-based oxidizing agent and a sulfamic acid compound. The “stabilized hypochlorous acid composition containing a chlorinated oxidant and a sulfamic acid compound” is a stabilized hypochlorous acid composition containing a mixture of a “chlorine oxidant” and a “sulfamic acid compound”. Alternatively, it may be a stabilized hypochlorous acid composition containing a “reaction product of a chlorinated oxidant and a sulfamic acid compound”.

The stabilized hypobromite composition contains a bromine-based oxidizing agent and a sulfamic acid compound. The “stabilized hypobromite composition containing a bromine-based oxidant and a sulfamic acid compound” is a stabilized hypobromite composition containing a mixture of a “bromine-based oxidant” and a “sulfamic acid compound”. Alternatively, it may be a stabilized hypobromite composition containing a “reaction product of a bromine-based oxidant and a sulfamic acid compound”.

Among these, as the halogen-based oxidant, a stabilized hypochlorous acid composition or a stabilized hypobromite composition is preferable, and a stabilized hypobromite composition is more preferable. Stabilized hypochlorous acid composition or stabilized hypobromite composition, especially stabilized hypobromite composition, also exhibits a modification effect equivalent to or better than chlorine-based oxidizing agents such as hypochlorous acid. Regardless, the deterioration effect on the reverse osmosis membrane is lower than that of the chlorine-based oxidant, and membrane deterioration due to repeated reforming can be suppressed. Therefore, the stabilized hypochlorous acid composition or the stabilized hypobromite composition, particularly the stabilized hypobromite composition used in the method for modifying a reverse osmosis membrane according to the present embodiment is a modifier. Is suitable.

That is, in the reverse osmosis membrane modification method according to the present embodiment, preferably, a stabilized hypobromite composition and a chlorine-based oxidation containing a bromine-based oxidant and a sulfamic acid compound in a polyamide-based reverse osmosis membrane. Measurement of flux of reverse osmosis membrane in terms of pure water when changing the rejection rate of uncharged substances by contacting at least one of the stabilized hypochlorous acid composition containing the agent and the sulfamic acid compound Based on the value, a reforming process is performed.

In the reverse osmosis membrane modification method according to the present embodiment, particularly when the “bromine-based oxidant” is bromine, there is no chlorine-based oxidant, so the deterioration effect on the reverse osmosis membrane is extremely low, and the reverse osmosis membrane It has the reforming effect.

In the method for reforming a reverse osmosis membrane according to the present embodiment, for example, in a water supply to the reverse osmosis membrane, a mixture of “bromine-based oxidant” and “sulfamic acid compound” or “chlorine” A mixture of “system oxidizing agent” and “sulfamic acid compound” may be present. Thereby, it is considered that a stabilized hypobromite composition or a stabilized hypochlorous acid composition is generated in the water supply to the reverse osmosis membrane.

Further, in the method for reforming a reverse osmosis membrane according to the present embodiment, for example, in a water supply to the reverse osmosis membrane, a “reaction product of a bromine-based oxidant and a sulfamic acid compound” is used as a modifier. A stabilized hypochlorous acid composition or a stabilized hypochlorous acid composition that is a “reaction product of a chlorinated oxidant and a sulfamic acid compound” may be present.

Specifically, in the method for modifying a reverse osmosis membrane according to the present embodiment, for example, in the water supply to the reverse osmosis membrane, as a modifier, “bromine”, “bromine chloride”, “hypobromite” Alternatively, a mixture of “reaction product of sodium bromide and hypochlorous acid” and “sulfamic acid compound” may be present. Alternatively, a mixture of “hypochlorous acid” and “sulfamic acid compound” may be present as a modifier in the water supply to the reverse osmosis membrane.

Further, in the reverse osmosis membrane modification method according to the present embodiment, for example, in the water supply to the reverse osmosis membrane, as a modifier, "reaction product of bromine and sulfamic acid compound", "bromine chloride and Reaction product of sulfamic acid compound "," Reaction product of hypobromous acid and sulfamic acid compound ", or" Reaction product of sodium bromide and hypochlorous acid and sulfamic acid compound " The stabilized hypobromite composition, which is a product, may be present. Alternatively, a stabilized hypochlorous acid composition that is a “reaction product of hypochlorous acid and a sulfamic acid compound” may be present as a modifier in the water supply to the reverse osmosis membrane.

In the reverse osmosis membrane modification method according to the present embodiment, the contact of the halogen-based oxidant with the reverse osmosis membrane is preferably performed in the range of more than pH 3 and less than 8, preferably in the range of pH 4 to 6.5. More preferably. If the contact of the halogen-based oxidant with the reverse osmosis membrane is performed at a pH of 3 or less, the reverse osmosis membrane deteriorates when the contact of the halogen-based oxidant with the reverse osmosis membrane is performed over a long period of time, and the blocking rate is reduced. When it is carried out at a pH of 8 or more, the reforming effect may be insufficient. In particular, when contact is made in the pH range of 4 to 6.5, it is possible to sufficiently improve the rejection rate of the uncharged substance of the reverse osmosis membrane while suppressing the deterioration of the reverse osmosis membrane. In order to perform the contact of the modifier in the above pH range, for example, the pH of the water supply to the reverse osmosis membrane may be maintained in the above range.

In the reverse osmosis membrane modification method according to the present embodiment, for example, during the operation of a reverse osmosis membrane device including a reverse osmosis membrane, in the water supply to the reverse osmosis membrane, etc., "chlorine oxidant", " The “bromine-based oxidizing agent”, or “bromine-based oxidizing agent” or “chlorine-based oxidizing agent” and “sulfamic acid compound” may be injected by a chemical injection pump or the like. “Bromine-based oxidizer” or “chlorine-based oxidizer” and “sulfamic acid compound” may be added separately to the water supply, etc., or mixed with stock solutions before supplying water to the reverse osmosis membrane, etc. You may add in.

In addition, for example, in the feed water to the reverse osmosis membrane, the “reaction product of bromine-based oxidant and sulfamic acid compound” or “reaction product of chlorinated oxidant and sulfamic acid compound” is a chemical injection pump, etc. May be injected.

The modification with the halogen-based oxidant is, for example, continuously or intermittently supplying the halogen-based oxidant into the water supplied to the reverse osmosis membrane, the washing water, or the like during the operation of the reverse osmosis membrane device including the reverse osmosis membrane. It may be added, or when the blocking rate of the reverse osmosis membrane is lowered, a halogen-based oxidant may be added continuously or intermittently into the water supplied to the reverse osmosis membrane, washing water or the like.

The contact of the halogen-based oxidant with the reverse osmosis membrane may be performed under normal pressure, pressurized or reduced pressure, but the modification can be performed without stopping the reverse osmosis membrane device. From the viewpoint that the reverse osmosis membrane can be reliably modified, it is preferable to perform the treatment under pressure. The contact of the halogen-based oxidant with the reverse osmosis membrane is preferably performed under a pressure condition in the range of 0.1 to 20 MPa, for example, and is performed under a pressure condition in the range of 0.1 MPa to 8.0 MPa. Is more preferable.

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

In the method for modifying a reverse osmosis membrane according to the present embodiment, the ratio of the equivalent of “sulfamic acid compound” to the equivalent of “bromine-based oxidant” or “chlorine-based oxidant” is preferably 1 or more. A range of 2 or less is more preferable. 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. May increase.

The concentration of the halogen-based oxidant (total chlorine concentration) in contact with the reverse osmosis membrane is preferably in the range of 0.1 to 100 mg / L in terms of effective chlorine concentration. If the concentration of the halogen-based oxidant in contact with the reverse osmosis membrane (total chlorine concentration) is less than 0.1 mg / L, a sufficient modification effect may not be obtained. It may cause deterioration of the osmotic membrane and corrosion of piping.

The formulation of “bromine and sulfamic acid compound (mixture of bromine and sulfamic acid compound)” or “reaction product of bromine and sulfamic acid compound” using bromine is composed of “hypochlorous acid, bromine compound and sulfamic acid”. Compared to preparations and preparations of “bromine chloride and sulfamic acid”, etc., there is less by-product of bromic acid, and the reverse osmosis membrane is not further deteriorated.

That is, in the method for reforming a reverse osmosis membrane according to the present embodiment, preferably, the polyamide-based reverse osmosis membrane is brought into contact with a stabilized hypobromite composition containing bromine and a sulfamic acid compound. When changing the blocking rate of the charged substance, the reforming process is performed based on the measured value of the pure water equivalent flux of the reverse osmosis membrane.

In this case, it is preferable that bromine and a sulfamic acid compound are present (a mixture of bromine and sulfamic acid compound is present) in the water supply to the reverse osmosis membrane. Moreover, it is preferable that a reaction product of bromine and a sulfamic acid compound is present in the water supply to the reverse osmosis membrane.

Examples of bromine compounds include sodium bromide, potassium bromide, lithium bromide, ammonium bromide and hydrobromic acid. Of these, sodium bromide is preferable from the viewpoint of formulation 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 having 1 to 8 carbon atoms.)

Examples of the sulfamic acid compound include sulfamic acid (amidosulfuric acid) in which both two R groups are hydrogen atoms, N-methylsulfamic acid, N-ethylsulfamic acid, N-propylsulfamic acid, N- A sulfamic acid compound in which one of two R groups such as isopropylsulfamic acid and N-butylsulfamic acid is a hydrogen atom and the other is an alkyl group having 1 to 8 carbon atoms, N, N-dimethylsulfamic acid, N, Two R groups such as N-diethylsulfamic acid, N, N-dipropylsulfamic acid, N, N-dibutylsulfamic acid, N-methyl-N-ethylsulfamic acid, N-methyl-N-propylsulfamic acid, etc. One of two R groups such as a sulfamic acid compound, N-phenylsulfamic acid and the like, both of which are alkyl groups having 1 to 8 carbon atoms Is a hydrogen atom and the other sulfamic acid compound or a salt thereof, such as an aryl group having 6 to 10 carbon atoms. Examples of the sulfamate include alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as calcium salt, strontium salt and barium salt, manganese salt, copper salt, zinc salt, iron salt, cobalt salt, Other metal salts such as nickel salts, ammonium salts, guanidine salts and the like can be mentioned. The sulfamic acid compounds and salts thereof may be used alone or in combination of two or more. As the sulfamic acid compound, sulfamic acid (amidosulfuric acid) is preferably used from the viewpoint of environmental load.

In the method for reforming a reverse osmosis membrane according to the present embodiment, at least one of a stabilized hypobromite composition and a stabilized hypochlorous acid composition is used as a modifier in water supply to the reverse osmosis membrane. When present as an alkali, an alkali may be further present. Examples of the alkali include alkali hydroxides such as sodium hydroxide and potassium hydroxide. From the viewpoint of product stability at low temperatures, sodium hydroxide and potassium hydroxide may be used in combination. Further, the alkali is not solid and may be used as an aqueous solution.

The method for reforming a reverse osmosis membrane according to this embodiment is applied to a polyamide-based polymer membrane that is currently mainstream. Polyamide polymer membranes have a relatively low resistance to oxidizing agents, and when free chlorine or the like is continuously brought into contact with the polyamide polymer membrane, the membrane performance may be significantly reduced. However, in the method for modifying a reverse osmosis membrane according to the present embodiment, at least one of a stabilized hypobromite composition and a stabilized hypochlorous acid composition, particularly a stabilized hypobromite composition is used. As a result, even in a polyamide polymer film, such a remarkable decrease in film performance hardly occurs.

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

In addition, in order to suppress the occurrence of scale without using a dispersant, for example, reverse osmosis is performed so that the silica concentration in RO concentrated water is less than the solubility and the Langeria index, which is a calcium scale index, is less than 0. Adjusting the operating conditions such as the recovery rate of the membrane device.

Examples of the use of the reverse osmosis membrane device including the polyamide-based reverse osmosis membrane modified by the reverse osmosis membrane modification method according to this embodiment include seawater desalination and wastewater recovery. In particular, it is preferable to carry out reverse osmosis membrane treatment of uncharged substance-containing water such as boron-containing water using a polyamide-based reverse osmosis membrane modified by the reverse osmosis membrane modification method according to the present embodiment. By modifying the polyamide-based reverse osmosis membrane by the reverse osmosis membrane modification method according to the present embodiment, the rejection rate of uncharged substances is significantly improved.

<Reverse osmosis membrane operation method 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. The reverse osmosis membrane device 1 of FIG. 1 includes a reverse osmosis membrane treatment device 10 having a modified reverse osmosis membrane modified by bringing a bromine-based oxidant into contact with a polyamide-based reverse osmosis membrane.

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

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

The treated water is supplied to the reverse osmosis membrane treatment device 10 through the treated water pipe 12, and the reverse osmosis membrane treatment device 10 uses the modified reverse osmosis membrane modified by contacting with the bromine-based oxidant. A reverse osmosis membrane treatment of treated water is performed (reverse osmosis membrane treatment step). The permeated water obtained by 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 treated water through the modified reverse osmosis membrane for a predetermined time and performing the reverse osmosis membrane treatment, the modified reverse osmosis membrane is alkali washed at pH 8 or more (alkali washing step). By modifying the polyamide-based reverse osmosis membrane by bringing it into contact with a bromine-based oxidant, it is possible to suppress a decrease in the blocking performance against alkali cleaning in the modified polyamide-based reverse osmosis membrane.

Alkali washing can be performed, for example, by bringing an alkaline solution such as an alkaline aqueous solution into contact with the modified reverse osmosis membrane. For example, an alkaline solution such as an alkaline aqueous solution may be passed through 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, an alkaline solution water pipe for passing an alkaline solution through the modified reverse osmosis membrane, an immersion tank for immersing the modified reverse osmosis membrane in the alkaline solution, and the like. It functions as an alkali cleaning means.

Examples of the alkali include sodium hydroxide, tetrasodium ethylenediaminetetraacetate, sodium dodecyl sulfate, sodium tripolyphosphate, and the like. For alkali cleaning, an alkali solution such as an aqueous alkali solution may be used.

The pH in the alkali cleaning step is 8 or more, preferably 8 or more and 13 or less, and more preferably 10 or more and 12 or less. When the pH in the alkali cleaning step is less than 8, the cleaning effect is low, and when it exceeds 13, the reverse osmosis membrane may be deteriorated.

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

In the operation method of the reverse osmosis membrane according to the present embodiment, the reformed reverse osmosis membrane washed with alkali may be contacted with a bromine-based oxidant and re-reformed (re-reforming step). Even if alkali cleaning and modification are repeated, the degradation of the polyamide-based reverse osmosis membrane is suppressed, and therefore the reverse osmosis membrane device can be stably operated even for a long period of operation.

The reverse osmosis membrane treatment apparatus 10 includes, for example, a polyamide-type reverse osmosis membrane filled with a modified reverse osmosis membrane that has been modified by bringing a bromine-based oxidant into contact therewith, and the water to be treated is allowed to pass through to be permeated and concentrated. This is a reverse osmosis membrane module for obtaining water.

The polyamide-based reverse osmosis membrane used in the reverse osmosis membrane treatment apparatus 10 is a modified reverse osmosis membrane modified by bringing a bromine-based oxidant into contact therewith. Here, “reformation” of the reverse osmosis membrane in the present specification refers to improvement of permeated water quality, that is, improvement of the rejection rate. By using a reverse osmosis membrane modified by bringing a bromine-based oxidant into contact with a polyamide-based reverse osmosis membrane, the water to be treated can be treated with a reverse osmosis membrane at a high rejection rate. By this reforming method, it is possible to improve the reverse osmosis membrane rejection rate and improve the permeated water quality while suppressing the deterioration of the reverse osmosis membrane. Because bromine-based oxidants rarely degrade polyamide-based reverse osmosis membranes, it is not a temporary improvement in water quality. Even if it contacts, degradation of a reverse osmosis membrane is suppressed and the fall of the rejection of a reverse osmosis membrane, ie, the fall of water quality, is suppressed.

There are no particular restrictions on the brominated oxidant used for reforming (and re-modification, the same shall apply hereinafter). Examples of bromine-based oxidizing agents include “hypobromite”, “reaction product of chlorine-based oxidizing agent and bromide ions”, “stabilized hypobromite composition”, etc. “Stabilized hypobromite composition”. The “stabilized hypobromite composition” has a particularly small adverse effect on the blocking rate of the reverse osmosis membrane, and can be stably operated for a long period of time even when continuously contacted with the reverse osmosis membrane.

The modified reverse osmosis membrane in the operation method of the reverse osmosis membrane according to the present embodiment includes a bromine-based oxidant, for example, “bromine-based oxidation” as a modifier in water supply to the polyamide-based reverse osmosis membrane, washing water, and the like. It is a membrane modified by a method in which a mixture of an “agent” and a “sulfamic acid compound” is present and brought into contact with a polyamide-based reverse osmosis membrane. Thereby, it is thought that the stabilized hypobromite composition produces | generates in water supply etc.

Further, the modified reverse osmosis membrane in the reverse osmosis membrane operation method according to the present embodiment includes, for example, “bromine-based oxidant and modifier” as a modifier in feed water, washing water, and the like to the polyamide-based reverse osmosis membrane. It is a membrane modified by a method in which a stabilized hypobromite composition, which is a reaction product with a sulfamic acid compound, is present and brought into contact with a polyamide-based reverse osmosis membrane.

Specifically, the modified reverse osmosis membrane in the operation method of the reverse osmosis membrane according to the present embodiment includes, for example, “bromine”, “bromine chloride”, “next” in the water supply to the polyamide-type reverse osmosis membrane. A membrane modified by a method in which a mixture of “bromine acid” or “reaction product of sodium bromide and hypochlorous acid” and “sulfamic acid compound” is present and brought into contact with a polyamide-based reverse osmosis membrane. is there.

Further, the modified reverse osmosis membrane in the reverse osmosis membrane operation method according to the present embodiment includes, for example, “reaction product of bromine and a sulfamic acid compound” in water supply to the polyamide-based reverse osmosis membrane, etc. “Reaction product of bromine chloride and sulfamic acid compound”, “Reaction product of hypobromite and sulfamic acid compound”, or “Reaction product of sodium bromide and hypochlorous acid, and sulfamic acid compound” This is a membrane modified by a method in which a stabilized hypobromite composition, which is a reaction product of, is present and brought into contact with a polyamide-based reverse osmosis membrane.

The modification of the reverse osmosis membrane in the operation method of the reverse osmosis membrane according to the present embodiment is, for example, in the water supply to the reverse osmosis membrane during the operation of the reverse osmosis membrane device including the polyamide-based reverse osmosis membrane. A bromine-based oxidant, for example, “bromine-based oxidant” and “sulfamic acid compound” may be injected as a modifier by a chemical pump or the like. The “bromine-based oxidant” and the “sulfamic acid compound” may be added separately to the water supply or the like, or may be added to the water supply after mixing the stock solutions. Also, for example, a polyamide-based reverse osmosis membrane is immersed in water for a predetermined time in water to which a bromine-based oxidant such as “bromine-based oxidant” and “sulfamic acid compound” is added as a modifier. Also good.

In addition, for example, in the water supply to a polyamide-based reverse osmosis membrane, “reaction product of bromine-based oxidant and sulfamic acid compound” or “reaction product of bromine-based compound and chlorine-based oxidant and sulfamine” You may inject | pour a reaction product of an acid compound "with a chemical injection pump. In addition, for example, in a water to which “reaction product of bromine-based oxidant and sulfamic acid compound” or “reaction product of bromine-based compound and chlorine-based oxidant and sulfamic acid compound” is added. Alternatively, the polyamide-based reverse osmosis membrane may be immersed and contacted for a predetermined time.

The reforming with a bromine-based oxidant is performed, for example, by continuously or intermittently supplying a bromine-based oxidant into the water supply to the reverse osmosis membrane during operation of a reverse osmosis membrane device having a polyamide-based reverse osmosis membrane. It may be added, or when the blocking rate of the reverse osmosis membrane is lowered, a bromine-based oxidant is added continuously or intermittently into the water supply to the reverse osmosis membrane, or a bromine-based oxidant is contained. A reverse osmosis membrane may be immersed in water. For example, reverse osmosis is possible for pipes that add bromine-based oxidants to the water supply to reverse osmosis membranes, immersion tanks for immersing reverse osmosis membranes or modified reverse osmosis membranes in water containing bromine-based oxidants, etc. It functions as a reforming means for reforming by bringing a bromine-based oxidant into contact with the membrane, or as a reforming means for reforming by bringing a bromine-based oxidant into contact with a modified reverse osmosis membrane washed with an alkali.

The contact of the bromine-based oxidant with the reverse osmosis membrane may be performed under normal pressure, pressurized or reduced pressure, but the modification can be performed without stopping the reverse osmosis membrane device. From the viewpoint that the reverse osmosis membrane can be reliably modified, it is preferable to perform the treatment under pressure. The contact of the bromine-based oxidant with the reverse osmosis membrane is preferably performed under a pressurized condition in the range of 0.1 MPa to 8.0 MPa, for example.

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

When the stabilized hypobromite composition is used, the ratio of the equivalent of the “sulfamic acid compound” to the equivalent of the “bromine-based oxidant” is preferably 1 or more, and is preferably in the range of 1 or more and 2 or less. More preferred. If the ratio of the equivalent amount of the “sulfamic acid compound” to the equivalent amount of the “bromine-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 total chlorine concentration in contact with the reverse osmosis membrane is preferably 0.01 to 100 mg / L in terms of effective chlorine concentration. If it is less than 0.01 mg / L, a sufficient reforming effect may not be obtained. If it exceeds 100 mg / L, reverse osmosis membrane deterioration and piping corrosion may occur.

Examples of the bromine-based oxidant used in the stabilized hypobromite composition include bromine (liquid bromine), bromine chloride, bromate, bromate, and hypobromite. Hypobromous acid may be produced by reacting a bromide such as sodium bromide with a chlorine-based oxidizing agent such as hypochlorous acid.

Among these, the preparation of “bromine and sulfamic acid compound (mixture of bromine and sulfamic acid compound)” or “reaction product of bromine and sulfamic acid compound” using bromine is composed of “hypochlorous acid and bromine compound and Compared to sulfamic acid preparations and bromine chloride and sulfamic acid preparations, etc., there is less chloride ion, which does not degrade polyamide reverse osmosis membranes more and may cause corrosion of metal materials such as piping. Since it is low, it is more preferable.

That is, the reverse osmosis membrane in the operation method of the reverse osmosis membrane according to the present embodiment brings bromine and a sulfamic acid compound into contact with a polyamide-based reverse osmosis membrane (contacts a mixture of bromine and a sulfamic acid compound), or A membrane modified by a method of bringing a reaction product of bromine and a sulfamic acid compound into contact with each other is preferable.

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

In the modification of the reverse osmosis membrane in the reverse osmosis membrane operation method according to the present embodiment, an alkali may be further present. Examples of the alkali include alkali hydroxides such as sodium hydroxide and potassium hydroxide. From the viewpoint of product stability at low temperatures, sodium hydroxide and potassium hydroxide may be used in combination. Further, the alkali is not solid and may be used as an aqueous solution.

The operation method of the reverse osmosis membrane according to the present embodiment is applied to a polyamide-based polymer membrane which is currently mainstream as a reverse osmosis membrane. Polyamide polymer membranes have a relatively low resistance to oxidizing agents, and when free chlorine or the like is continuously brought into contact with the polyamide polymer membrane, the membrane performance is significantly reduced. However, in the method for reforming a reverse osmosis membrane using a bromine-based oxidant, particularly a stabilized hypobromite composition, such a significant decrease in membrane performance hardly occurs even in a polyamide polymer membrane.

In the modification of the reverse osmosis membrane in the operation method of the reverse osmosis membrane according to the present embodiment, it is preferable that the contact of the bromine-based oxidant with the polyamide-based reverse osmosis membrane is performed at a pH lower than the pH of the water to be treated. . When the brominated oxidant is continuously added as the slime inhibitor after the reverse osmosis membrane is passed, the pH of the treated water is higher than the pH at the time of reforming (i.e. When the quality is lower than the pH of the water to be treated), the reforming effect is maintained and fluctuations in the permeate flow rate of the water to be treated can be suppressed. When the brominated oxidant is continuously added as the slime inhibitor after the reverse osmosis membrane is passed, the pH of the water to be treated is lower than the pH at the time of reforming (i.e. When the quality is higher than the pH of the water to be treated), the reforming effect and fluctuations in the permeate flow rate of the water to be treated may occur. The contact of the bromine-based oxidant with the polyamide-based reverse osmosis membrane is performed, for example, in the range of more than pH 3 and less than 8, or in the range of pH 4 to 6.5. The lower the pH at the time of contact with the bromine-based oxidant, the higher the membrane modification effect, the higher the rejection rate, and the permeated water quality.

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

In addition, in order to suppress the occurrence of scale without using a dispersant, for example, reverse osmosis is performed so that the silica concentration in RO concentrated water is less than the solubility and the Langeria index, which is a calcium scale index, is less than 0. Adjusting the operating conditions such as the recovery rate of the membrane device.

Examples of the use of the reverse osmosis membrane device include pure water production, seawater desalination, and wastewater collection.

In the reverse osmosis membrane operation method and the reverse osmosis membrane device 1 according to the present embodiment, among the deaeration treatment device, the ion exchange treatment device, and the UV sterilization treatment device that treats the water to be treated of the reverse osmosis membrane treatment device 10. The reverse osmosis membrane treatment apparatus 10 (reverse osmosis membrane treatment step) water to be treated may be subjected to at least one of degassing treatment, ion exchange treatment, and UV sterilization treatment. .

Further, in the reverse osmosis membrane operation method according to the present embodiment, an ion exchange treatment device, an electrical desalination treatment device, a UV sterilization treatment device, and a UV oxidation treatment device that perform treatment on the permeated water of the reverse osmosis membrane treatment device 10. , A fine particle removal treatment device, and at least one of a second reverse osmosis membrane treatment device, the permeated water of the reverse osmosis membrane treatment device 10 (reverse osmosis membrane treatment step), ion exchange treatment, electric desalting At least one of processing, UV sterilization processing, UV oxidation processing, particulate removal processing, and second reverse osmosis membrane processing may be performed.

<Reverse osmosis membrane modifier>
The modifier for reverse osmosis membrane according to this embodiment contains a halogen-based oxidizing agent. The reverse osmosis membrane modifier according to this embodiment is preferably a stabilized hypobromite composition containing a mixture of “bromine-based oxidant” and “sulfamic acid compound”, or “chlorine-based oxidant”. It contains a stabilized hypochlorous acid composition including a mixture with a “sulfamic acid compound”, and may further contain an alkali.

In addition, the reverse osmosis membrane modifier according to this embodiment is preferably a stabilized hypobromite composition containing a “reaction product of a bromine-based oxidant and a sulfamic acid compound”, or a “chlorine-based oxidant”. It contains a stabilized hypochlorous acid composition containing a reaction product of sulfamic acid compound and may further contain an alkali.

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

Examples of commercially available stabilized hypochlorous acid compositions containing a chlorine-based oxidizing agent and a sulfamic acid compound include “Kuriverter IK-110” manufactured by Kurita Kogyo Co., Ltd.

The reverse osmosis membrane modifier according to the present embodiment contains bromine and a sulfamic acid compound because the polyamide-based reverse osmosis membrane is not further deteriorated and the amount of effective halogen leaked into the RO permeate is smaller. (Containing a mixture of bromine and sulfamic acid compound), for example, a mixture of bromine, sulfamic acid compound, alkali and water, or containing a reaction product of bromine and sulfamic acid compound, for example, A mixture of a reaction product of bromine and a sulfamic acid compound, an alkali, and water is preferable.

Among the modifiers for reverse osmosis membranes according to the present embodiment, a modifier containing a stabilized hypobromite composition containing a bromine-based oxidant and a sulfamic acid compound, particularly containing bromine and a sulfamic acid compound. A modifier containing a stabilized hypobromite composition has higher oxidizing power than a modifier (such as chlorosulfamic acid) containing a chlorinated oxidant and a sulfamic acid compound. In spite of remarkably high inhibitory power and slime peeling power, it hardly causes significant film deterioration like hypochlorous acid having high oxidizing power. Compared with modifiers such as hypochlorous acid and free chlorine containing bromine, it has the effect of reforming polyamide-based reverse osmosis membranes, while hypochlorous acid and free chlorine containing bromine. Such remarkable film deterioration is hardly caused. At normal use concentrations, the effect on film degradation can be substantially ignored. Therefore, it is optimal as a modifier for polyamide-based reverse osmosis membranes.

Unlike the hypochlorous acid and free chlorine containing bromine, the reverse osmosis membrane modifier containing the stabilized hypobromite or stabilized hypochlorous acid composition is almost permeable to the reverse osmosis membrane. Therefore, there is almost no impact on the quality of treated water. Further, since the concentration can be measured on site in the same manner as hypochlorous acid or the like, more accurate concentration management is possible.

The pH of the reverse osmosis membrane modifier containing the stabilized hypobromite composition is, for example, more than 13.0, and more preferably more than 13.2. When the pH of the modifier for reverse osmosis membrane is 13.0 or less, the effective halogen in the modifier may become unstable.

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

<Method for producing reverse osmosis membrane modifier>
The modifier for a reverse osmosis membrane containing the stabilized hypobromite composition or the stabilized hypochlorous acid composition is obtained by mixing a bromine-based oxidant or a chlorine-based oxidant and a sulfamic acid compound, Further, an alkali may be mixed.

As a method for producing a reverse osmosis membrane modifier containing a stabilized hypobromite composition containing bromine and a sulfamic acid compound, bromine is an inert gas in a mixed solution containing water, an alkali and a sulfamic acid compound. It is preferable to include a step of adding and reacting under an atmosphere or a step of adding bromine to a mixed solution containing water, an alkali and a sulfamic acid compound under an inert gas atmosphere. By adding and reacting under an inert gas atmosphere, or adding under an inert gas atmosphere, the bromate ion concentration in the reverse osmosis membrane modifier is reduced, and the bromate ion concentration in the RO permeated water Becomes lower.

Although the inert gas to be used is not limited, at least one of nitrogen and argon is preferable from the viewpoint of manufacturing and the like, and nitrogen is particularly preferable from the viewpoint of manufacturing cost and the like.

The oxygen concentration in the reactor during the addition of bromine is preferably 6% or less, more preferably 4% or less, further preferably 2% or less, and particularly preferably 1% or less. If 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 ratio of bromine is preferably 25% by weight or less, more preferably 1% by weight or more and 20% by weight or less, based on the total amount of the modifier. If the bromine addition rate exceeds 25% by weight with respect 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 inferior.

The reaction temperature at the time of bromine addition is preferably controlled in the range of 0 ° C. to 25 ° C., but more preferably in the range of 0 ° C. to 15 ° C. from the viewpoint of production cost. When the reaction temperature at the time of bromine addition exceeds 25 degreeC, the production amount of the bromic acid in a reaction system may increase, and when it is less than 0 degreeC, it may freeze.

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

[Preparation of Stabilized Hypobromite Composition]
Under 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: remaining Minutes were mixed to prepare a stabilized hypobromite composition. The stabilized hypobromite 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-phenylenediamine) method) using a multi-item water quality analyzer DR / 4000 manufactured by HACH. The detailed method for preparing the stabilized hypobromite composition is as follows.

Add 1436 g of water and 361 g of sodium hydroxide to a 2 L four-necked flask sealed by continuous injection while controlling the flow rate of nitrogen gas with a mass flow controller so that the oxygen concentration in the reaction vessel is maintained at 1%. Next, after adding 300 g of sulfamic acid and mixing, 473 g of liquid bromine was added while maintaining cooling so that the temperature of the reaction solution was 0 to 15 ° C., and 230 g of 48% potassium hydroxide solution was added. A target stabilized hypobromite composition having a sulfamic acid 10.7% by weight ratio relative to the total amount of the composition, 16.9% bromine, and an equivalent ratio of sulfamic acid to the equivalent of bromine of 1.04. Obtained. The pH of the resulting solution was 14 as measured by the glass electrode method. The bromine content of the resulting solution was 16.9% as measured by a redox titration method using sodium thiosulfate after bromine was converted to iodine with potassium iodide, and the theoretical content (16.9% ) Of 100.0%. The oxygen concentration in the reaction vessel during the bromine reaction was measured using “Oxygen Monitor JKO-02 LJDII” manufactured by Zico Corporation. The bromic acid concentration was less than 5 mg / kg.

The pH was measured under the following conditions.
Electrode type: Glass electrode type pH meter: IOL-30, manufactured by Toa DKK Corporation Electrode calibration: Neutral phosphate pH (6.86) standard solution (type 2) manufactured by Kanto Chemical Co., boric acid manufactured by the same company Salt temperature (9.18) Standard solution (type 2) was measured by two-point calibration Measurement temperature: 25 ° C
Measurement value: Immerse the electrode in the measurement solution and use the value after stabilization as the measurement value.

Using the stabilized hypobromite composition prepared above as a pH 4 and halogen-based oxidant, the test water with a concentration of 10 ppm was passed through a polyamide polymer reverse osmosis membrane (Nitto Denko Corporation, SWC5). did. While measuring the pressure and flow rate during water flow with a pressure gauge and a flow meter, the change in pure water equivalent flux was confirmed. The relationship between pure water equivalent flux [m / d / MPa] and TOC (isopropyl alcohol (IPA)) rejection rate [%] is shown in FIG. From the result of FIG. 1, the correlation equation is y = 0.9x ² -10x + 100. Regardless of the type of reverse osmosis membrane and the presence or absence of modification, it was found that there is a correlation between the blocking rate of uncharged substances in the reverse osmosis membrane and the pure water equivalent flux.

<Examples 1 and 2>
Polyamide-based polymer reverse osmosis membrane using sodium hypochlorite (Example 1) and the stabilized hypobromite composition prepared above (Example 2) as a modifier (halogen-based oxidant), respectively. (Nitto Denko Corporation, SWC5) was modified. In the modification, water with 10 ppm of the above modifier added at an operating pressure of 2.0 MPa was passed through the reverse osmosis membrane apparatus including the reverse osmosis membrane at pH 4 and 25 ± 1 ° C. The target IPA rejection was set to 97%, and the set pure water equivalent flux was set to 0.28 m / d / MPa based on the correlation equation (FIG. 1) prepared in advance. While monitoring the flow rate with a flow meter, it was carried out by passing water until the pure water equivalent flux determined by the following formula reached 0.28 m / d / MPa. Thereafter, water to which 10 ppm of isopropyl alcohol as an uncharged substance was added at a TOC value at an operating pressure of 2.0 MPa was passed at pH 7 and 25 ± 1 ° C. The TOC concentration of raw water and permeated water was measured using a TOC meter (manufactured by GEAI, Sievers M9e series), and the following IPA rejection was calculated. The results are shown in Table 1.
Pure water equivalent flux [m / d / MPa] = permeate amount / membrane area / (feed water pressure-osmotic pressure)
IPA rejection [%] = 100− [permeated water TOC concentration / {(feed water TOC concentration + concentrated water TOC concentration) / 2}] × 100)

Thus, in the reverse osmosis membrane modification method in which the blocking rate of uncharged substances is changed by bringing the halogen-based oxidant into contact with the polyamide-based reverse osmosis membrane, the modification is based on the measured value of the pure water equivalent flux. By performing the quality treatment, the rejection rate of the uncharged substance of the reverse osmosis membrane could be adjusted to a predetermined value.

<Examples 3 and 4>
Using the stabilized hypobromite composition prepared above as a modifier, a polyamide polymer reverse osmosis membrane (“SWC4” manufactured by Nitto Denko Corporation) (Example 3), polyamide polymer reverse osmosis Each of the membranes (“SWC5” manufactured by Nitto Denko Corporation) was modified (Example 4). The reforming was carried out on a reverse osmosis membrane device equipped with this reverse osmosis membrane at an operating pressure of 2.0 MPa, water added with 10 ppm of the above modifier at pH 4, 25 ± 1 ° C. while monitoring the flow rate with a flow meter. It carried out by passing water until the water equivalent flux became 0.28 m / d / MPa. Thereafter, water with 10 ppm of IPA added as an uncharged substance at an operating pressure of 2.0 MPa was added at pH 7 and 25 ± 1 ° C. The TOC concentration of raw water and permeated water was measured using a TOC meter, and the above IPA rejection was calculated. The results are shown in Table 2.

In this way, even if the membrane type of the polyamide polymer reverse osmosis membrane is different, by performing the modification treatment based on the measured value of the pure water equivalent flux, the rejection rate of the non-charged substance of the reverse osmosis membrane is set to a predetermined value. The value could be adjusted.

<Comparative Examples 1 and 2>
Instead of performing the reforming process based on the measured value of the pure water equivalent flux, the reforming process was performed based on the reforming time as described in paragraph [0044] of Patent Document 1. Using the stabilized hypobromite composition prepared above as a modifier, a polyamide polymer reverse osmosis membrane (manufactured by FILMTEC, “SW30HRLE”) (Comparative Example 1), a polyamide polymer reverse osmosis membrane (Nitto) Reform of “SWC5” (Comparative Example 2) manufactured by Denko Co., Ltd. was performed. The reforming was carried out by passing water added with 10 ppm of the above modifier at a pH of 4 and 25 ± 1 ° C. for a predetermined time in a reverse osmosis membrane apparatus equipped with this reverse osmosis membrane. . Thereafter, water with 10 ppm of IPA added as an uncharged substance at an operating pressure of 2.0 MPa was added at pH 7 and 25 ± 1 ° C. The TOC concentration of raw water and permeated water was measured using a TOC meter, and the above IPA rejection was calculated. The results are shown in Table 3.

Thus, when managed by the modification time, the target TOC blocking performance is not achieved, and the modification effect varies depending on the type of polyamide polymer reverse osmosis membrane. The difference in the rejection rate of substances has increased.

As described above, the rejection rate of the uncharged substance in the reverse osmosis membrane could be adjusted to a predetermined value by performing the reforming treatment based on the measured value of the pure water equivalent flux as in the example.

<Examples 5 and 6, Comparative Examples 3 and 4>
Stabilized hypobromite composition (Example 5) prepared above, hypobromite (mixture of sodium bromide and hypochlorous acid) (Example 6), hypochlorous acid (Comparative Example 3) The polyamide polymer reverse osmosis membrane (“SWC5” manufactured by Nitto Denko Corporation) was modified by using each as a modifier. Further, a polyamide polymer reverse osmosis membrane (“SWC5” manufactured by Nitto Denko Corporation) (Comparative Example 4) without modification was also prepared. The reforming was carried out by passing water added with 10 ppm of the above-mentioned modifier at pH = 4 and 25 ± 1 ° C. for 1 hour to the reverse osmosis membrane device provided with this reverse osmosis membrane. . For each of the modified reverse osmosis membranes of Examples 5 and 6 and Comparative Example 3 that were modified, and the non-modified reverse osmosis membrane of Comparative Example 4, urea (molecular weight 60) was TOC value at an operating pressure of 2.0 MPa. As a result, water added at 10 ppm was passed through at pH = 7 and 25 ± 1 ° C. for 1 hour. After that, the process of immersing each reverse osmosis membrane at 20 to 25 ° C. overnight (16 hours) in an alkaline aqueous solution adjusted to pH 12 by adding sodium hydroxide as an alkali to pure water was performed five times, and again the operation pressure Water with 2.0 ppm of urea added as a TOC value at 2.0 MPa was passed for 1 hour at pH = 7 and 25 ± 1 ° C. The TOC concentration of the water to be treated and the permeated water was measured with a TOC meter, and the following urea rejection rate was calculated. The results are shown in Table 4.
Urea rejection rate [%] = 100− [permeated water TOC concentration ÷ {(feed water TOC concentration + concentrated water TOC concentration) ÷ 2} × 100]

In contrast to reverse osmosis membranes modified with bromine-based oxidants, reverse osmosis membranes modified with chlorine-based oxidants showed a significant reduction in blocking performance due to alkali cleaning.

<Examples 7 and 8, Comparative Example 5>
The membranes used in Example 5, Example 6, and Comparative Example 3 were modified again by the above-described method to give Example 7, Example 8, and Comparative Example 5, respectively. The urea rejection rate of the film after re-modification was evaluated in the same manner as in Examples 5 and 6 and Comparative Example 3. The results are shown in Table 5.

In Examples 7 and 8, the blocking performance recovered to the same level as before alkali washing by re-reforming.

Thus, by the reverse osmosis membrane operation method and reverse osmosis membrane apparatus of the example, it was possible to suppress a decrease in the blocking performance against alkali washing in the modified polyamide-based reverse osmosis membrane.

1 reverse osmosis membrane device, 10 reverse osmosis membrane treatment device, 12 treated water piping, 14 permeate piping, 16 concentrated water piping.

Claims (18)

1. In a method for modifying a reverse osmosis membrane in which the blocking rate of uncharged substances is changed by bringing a halogen-based oxidant into contact with a polyamide-based reverse osmosis membrane,
   A method for reforming a reverse osmosis membrane, characterized in that a reforming treatment is performed based on a measured value of pure water equivalent flux of the reverse osmosis membrane.
2. A method for modifying a reverse osmosis membrane according to claim 1,
   A method for reforming a reverse osmosis membrane, characterized in that the reforming treatment is performed based on a correlation equation between a pure water equivalent flux of the reverse osmosis membrane and a blocking rate of the uncharged substance, which is prepared in advance.
3. A method for modifying a reverse osmosis membrane according to claim 1 or 2,
   The method for reforming a reverse osmosis membrane, wherein the uncharged substance is a low molecular substance having a molecular weight of 200 or less.
4. A method for reforming a reverse osmosis membrane according to any one of claims 1 to 3,
   A method for modifying a reverse osmosis membrane, wherein the contact is performed in a pH range of 4 to 6.5.
5. A method for modifying a reverse osmosis membrane according to any one of claims 1 to 4,
   The method for modifying a reverse osmosis membrane, wherein the concentration of the halogen-based oxidizing agent in the contact is in the range of 0.1 to 100 mg / L.
6. A method for modifying a reverse osmosis membrane according to any one of claims 1 to 5,
   A method for modifying a reverse osmosis membrane, wherein the contact is performed under a pressure in a range of 0.1 to 20 MPa.
7. A reverse osmosis membrane, which is modified by the reverse osmosis membrane modification method according to any one of claims 1 to 6.
8. An uncharged substance characterized by subjecting uncharged substance-containing water to a reverse osmosis membrane treatment using the reverse osmosis membrane modified by the reverse osmosis membrane modification method according to any one of claims 1 to 6. Treatment method of contained water.
9. A reverse osmosis membrane treatment step for obtaining permeated water and concentrated water by passing water to be treated to a modified reverse osmosis membrane modified by bringing a bromine-based oxidant into contact with a polyamide-based reverse osmosis membrane;
   an alkali washing step of washing the modified reverse osmosis membrane with an alkali at a pH of 8 or more;
   A method for operating a reverse osmosis membrane, comprising:
10. A method for operating a reverse osmosis membrane according to claim 9,
    A method for operating a reverse osmosis membrane, comprising a re-reforming step in which a brominated oxidant is brought into contact with the modified reverse osmosis membrane washed with alkali to re-reform.
11. A method for operating a reverse osmosis membrane according to claim 9 or 10,
    The method for operating a reverse osmosis membrane, wherein the bromine-based oxidizing agent is contacted at a pH lower than the pH of the water to be treated.
12. A method for operating a reverse osmosis membrane according to any one of claims 9 to 11,
    The method for operating a reverse osmosis membrane, wherein the bromine-based oxidant includes a stabilized hypobromite composition containing a bromine-based oxidant and a sulfamic acid compound.
13. A method for operating a reverse osmosis membrane according to any one of claims 9 to 11,
    The method for operating a reverse osmosis membrane, wherein the brominated oxidant includes a stabilized hypobromite composition containing bromine and a sulfamic acid compound.
14. A reverse osmosis membrane treatment apparatus having a modified reverse osmosis membrane modified by bringing a bromine-based oxidant into contact with a polyamide-based reverse osmosis membrane, and obtaining permeated water and concentrated water by passing water to be treated;
    alkaline washing means for washing the modified reverse osmosis membrane with alkali at pH 8 or higher;
    With
    A reverse osmosis membrane device, wherein the alkali cleaning means causes the water to be treated to flow through the modified reverse osmosis membrane for a predetermined time, and then contacts an alkaline solution with the modified reverse osmosis membrane at a pH of 8 or more. .
15. The reverse osmosis membrane device according to claim 14,
    The reverse osmosis membrane device further comprising a re-modification means for bringing a bromine-based oxidant into contact with the alkali-washed modified reverse osmosis membrane for re-modification.
16. The reverse osmosis membrane device according to claim 14 or 15,
    The reverse osmosis membrane device, wherein the bromine-based oxidizing agent is contacted at a pH lower than the pH of the water to be treated.
17. The reverse osmosis membrane device according to any one of claims 14 to 16,
    The reverse osmosis membrane device, wherein the bromine-based oxidant includes a stabilized hypobromite composition containing a bromine-based oxidant and a sulfamic acid compound.
18. The reverse osmosis membrane device according to any one of claims 14 to 16,
    The reverse osmosis membrane device, wherein the brominated oxidant includes a stabilized hypobromite composition containing bromine and a sulfamic acid compound.

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