CN107635652B - Method for modifying reverse osmosis membrane, method for treating boron-containing water, and method for operating separation membrane - Google Patents

Method for modifying reverse osmosis membrane, method for treating boron-containing water, and method for operating separation membrane Download PDF

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CN107635652B
CN107635652B CN201680011498.9A CN201680011498A CN107635652B CN 107635652 B CN107635652 B CN 107635652B CN 201680011498 A CN201680011498 A CN 201680011498A CN 107635652 B CN107635652 B CN 107635652B
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reverse osmosis
bromine
osmosis membrane
oxidizing agent
chlorine
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CN107635652A (en
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吉川浩
中村勇规
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Organo Corp
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Organo Corp
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Priority claimed from JP2015034048A external-priority patent/JP6506987B2/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/56—Polyamides, e.g. polyester-amides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/025—Reverse osmosis; Hyperfiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis

Abstract

Provided is a method for modifying a reverse osmosis membrane, which is for improving the quality of permeate water of the reverse osmosis membrane while suppressing deterioration of the reverse osmosis membrane. A method for modifying a reverse osmosis membrane, comprising contacting a polyamide reverse osmosis membrane with: a bromine-based oxidizing agent or a reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound; or a reaction product of a bromine-based oxidizing agent, a reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound.

Description

Method for modifying reverse osmosis membrane, method for treating boron-containing water, and method for operating separation membrane
Technical Field
The invention relates to a method for modifying a polyamide reverse osmosis membrane; a reverse osmosis membrane modified by the modification method; a method for treating boron-containing water using the reverse osmosis membrane; and a method for operating the separation membrane.
Background
There are many modification methods for improving the quality of permeate water of a reverse osmosis membrane (RO membrane). Among these methods, there is a method of improving performance by bringing free chlorine containing bromine into contact with a reverse osmosis membrane for a predetermined time.
For example, patent document 1 describes a method of treating a reverse osmosis membrane element, which comprises: in a membrane separation device equipped with a reverse osmosis membrane element having a polyamide surface layer, the reverse osmosis membrane element is filled in a pressure vessel in the membrane separation device, and then a free chlorine aqueous solution containing bromine is brought into contact with the reverse osmosis membrane element.
However, in the method of patent document 1, although the water quality can be temporarily improved, if water is passed through an aqueous solution of free chlorine containing bromine for a long period of time, the reverse osmosis membrane deteriorates and the water quality decreases.
In addition, when various bromine-based oxidizing agents are used for inhibiting slime, for example, during the operation of a polyamide-based separation membrane such as a reverse osmosis membrane (RO membrane) or a nanofiltration membrane (NF membrane), the bromine-based oxidizing agents may flow into the separation membrane. Examples of the bromine-based oxidizing agent include: a reaction product of an oxidizing agent such as hypochlorous acid with bromide ions, hypobromous acid, and the like. However, these bromine-based oxidizing agents are known to have the following problems: the lower the pH of the water to be treated, the more easily the amount of permeated water in the separation membrane decreases (see non-patent document 1).
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2003-088730
Non-patent document
Non-patent document 1: desalination 280(2011)80-86
Disclosure of Invention
Problems to be solved by the invention
An object of the present invention is to provide a method for modifying a reverse osmosis membrane, which is for improving the quality of permeate water of the reverse osmosis membrane while suppressing deterioration of the reverse osmosis membrane; a reverse osmosis membrane modified by the modification method; and a method for treating boron-containing water using the reverse osmosis membrane.
Another object of the present invention is to provide a method for operating a separation membrane, which can suppress a decrease in the amount of permeated water and can stably operate a separation membrane device even when a bromine-based oxidizing agent is brought into contact with the separation membrane.
Means for solving the problems
The invention relates to a method for modifying a reverse osmosis membrane, which comprises the step of contacting a polyamide reverse osmosis membrane with the following substances: a bromine-based oxidizing agent or a reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound; or a reaction product of a bromine-based oxidizing agent, a reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound.
The invention is a reverse osmosis membrane modification method, which comprises contacting a mixture of bromine and sulfamic acid compound with a polyamide reverse osmosis membrane; alternatively, a reaction product of bromine and an aminosulfonic acid compound is brought into contact with a polyamide reverse osmosis membrane.
In the method for modifying a reverse osmosis membrane, the reaction product of bromine and a sulfamic acid compound is preferably obtained by a method comprising the steps of: bromine is added to a mixed solution containing water, a base and a sulfamic acid compound under an inert gas atmosphere and a reaction is performed.
In the method for modifying a reverse osmosis membrane, the contact is preferably performed at a pH of 4 to 6.5.
In the method of modifying a reverse osmosis membrane, it is preferable that the polyamide reverse osmosis membrane is subjected to chlorine treatment using a chlorine-based oxidizing agent.
In the method of modifying a reverse osmosis membrane, the contact is preferably performed at ph5.5 or more.
The invention provides a reverse osmosis membrane modified by the reverse osmosis membrane modification method.
The present invention is a method for treating boron-containing water, which comprises subjecting boron-containing water to reverse osmosis membrane treatment using a reverse osmosis membrane modified by the above-described method for modifying a reverse osmosis membrane.
The present invention is also a method for operating a separation membrane, in which a bromine-based oxidizing agent is brought into contact with a polyamide-based separation membrane that has been subjected to chlorine treatment with a chlorine-based oxidizing agent.
In the method of operating the separation membrane, the pH of the water to be treated when the bromine-based oxidizing agent is brought into contact with the separation membrane is preferably 5.5 or more.
In the method for operating the separation membrane, the bromine-based oxidizing agent preferably contains a bromine-based oxidizing agent or a reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound; or a reaction product of a bromine-based oxidizing agent, a reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound.
In the method for operating the separation membrane, the bromine-containing oxidizing agent preferably contains a mixture of bromine and an aminosulfonic acid compound, or preferably contains a reaction product of bromine and an aminosulfonic acid compound.
In the method for operating the separation membrane, the reaction product of bromine and the sulfamic acid compound is preferably obtained by a method comprising the steps of: bromine is added to a mixed solution containing water, a base and a sulfamic acid compound under an inert gas atmosphere to carry out a reaction.
ADVANTAGEOUS EFFECTS OF INVENTION
The present invention can provide a method for modifying a reverse osmosis membrane for suppressing deterioration of the reverse osmosis membrane and improving the permeate water quality of the reverse osmosis membrane; a reverse osmosis membrane modified by the modification method; and a method for treating boron-containing water using the reverse osmosis membrane.
In the method for operating a separation membrane of the present invention, the separation membrane is subjected to chlorine treatment in advance, and thus, even if the bromine-containing oxidizing agent is brought into contact with the separation membrane thereafter, the reduction in the amount of permeated water can be suppressed, and the separation membrane apparatus can be stably operated.
Detailed Description
Hereinafter, embodiments of the present invention will be described. The present embodiment is merely an example for carrying out the present invention, and the present invention is not limited to the present embodiment.
< method for modifying reverse osmosis membrane and reverse osmosis membrane >
The reverse osmosis membrane modification method of the embodiment of the invention is as follows: contacting a polyamide-based reverse osmosis membrane with: a bromine-based oxidizing agent or a reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound; or a reaction product of a bromine-based oxidizing agent, a reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound. In addition, the reverse osmosis membrane according to the embodiment of the present invention is a reverse osmosis membrane modified by the reverse osmosis membrane modification method. In the present specification, "modification" of a reverse osmosis membrane may mean improvement of permeate water quality and improvement of permeate water quality (i.e., increase in rejection rate), and may mean suppression of reduction in permeate water amount and suppression of reduction in permeate water quality (i.e., suppression of reduction in rejection rate).
A method for modifying a reverse osmosis membrane according to an embodiment of the present invention is a method in which a "bromine-based oxidizing agent" and an "sulfamic acid compound" are present in water or the like supplied to a polyamide-based reverse osmosis membrane as modifiers, and are brought into contact with the polyamide-based reverse osmosis membrane; alternatively, a method of bringing a "reactant of a bromine compound and a chlorine-based oxidizing agent" and an "sulfamic acid compound" into contact with a polyamide-based reverse osmosis membrane as modifiers in water supply to the polyamide-based reverse osmosis membrane or the like. Thus, it is considered that a hypobromous acid stabilizing composition is formed in the feed water or the like.
In addition, a method for modifying a reverse osmosis membrane according to an embodiment of the present invention is a method in which a hypobromous acid stabilizing composition, which is a "reaction product of a bromine-based oxidizing agent and a sulfamic acid compound", is allowed to exist in water supply or the like to a polyamide reverse osmosis membrane as a modifier, and is brought into contact with the polyamide reverse osmosis membrane; alternatively, a hypobromous acid stabilizing composition which is a reaction product of a bromine compound and a chlorine-based oxidizing agent with an aminosulfonic acid compound is allowed to exist in water supply to a polyamide-based reverse osmosis membrane or the like as a modifier, and is brought into contact with the polyamide-based reverse osmosis membrane.
Specifically, the method for modifying a reverse osmosis membrane according to the embodiment of the present invention is a method in which "bromine", "bromine chloride", "hypobromous acid" or "a reaction product of sodium bromide and hypochlorous acid" and "an aminosulfonic acid compound" are allowed to exist in water supply or the like to a polyamide reverse osmosis membrane and are brought into contact with the polyamide reverse osmosis membrane.
In addition, the method for modifying a reverse osmosis membrane according to the embodiment of the present invention is a method in which a hypobromous acid stabilizing composition, which is, for example, a "reaction product of bromine and an aminosulfonic acid compound", a "reaction product of bromine chloride and an aminosulfonic acid compound", or a "reaction product of sodium bromide and hypochlorous acid, a reaction product of a sodium bromide and an aminosulfonic acid compound", is allowed to exist in water supply to a polyamide reverse osmosis membrane or the like, and is brought into contact with the polyamide reverse osmosis membrane. It is not clear what compound is formed as the "reaction product of bromine and a sulfamic acid compound", but it is considered that "bromosulfamic acid (bromosulfonic acid)" is formed as a hypobromous acid-stabilizing compound.
By these methods, deterioration of the reverse osmosis membrane can be suppressed, the rejection of the reverse osmosis membrane can be increased, and the quality of the permeated water can be improved. Since the hypobromous acid stabilizing composition hardly deteriorates the polyamide-based reverse osmosis membrane, deterioration of the reverse osmosis membrane can be suppressed and a decrease in the rejection rate of the reverse osmosis membrane, that is, a decrease in water quality can be suppressed even when water containing the modifier is passed through and contacted with the polyamide-based reverse osmosis membrane for a long period of time without temporarily improving the water quality.
In the method for modifying a reverse osmosis membrane according to the present embodiment, for example, when a reverse osmosis membrane apparatus having a polyamide reverse osmosis membrane is operated, the "bromine-based oxidizing agent" or the "reactant of a bromine compound and a chlorine-based oxidizing agent" and the "sulfamic acid compound" may be injected into the feed water to the reverse osmosis membrane by a chemical injection pump or the like. The "bromine-based oxidizing agent" or the "reactant of the bromine compound and the chlorine-based oxidizing agent" and the "sulfamic acid compound" may be added to the feed water separately, or the raw liquids may be mixed with each other and then added to the feed water. For example, a polyamide reverse osmosis membrane may be immersed in water to which "bromine-based oxidizing agent" or "reaction product of bromine compound and chlorine-based oxidizing agent" and "sulfamic acid compound" are added, and contacted for a predetermined time.
In addition, for example, the "reaction product of a bromine-based oxidizing agent and a sulfamic acid compound" or the "reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound" may be injected into the water supply to the polyamide-based reverse osmosis membrane by a syringe pump or the like. For example, a polyamide reverse osmosis membrane may be immersed in water to which "a reaction product of a bromine-based oxidizing agent and a sulfamic acid compound" or "a reaction product of a bromine compound and a chlorine-based oxidizing agent, and a sulfamic acid compound" is added, and the membrane may be contacted with the membrane for a predetermined time.
The modification with the modifier may be performed, for example, by continuously or intermittently adding the modifier to the water supply to the reverse osmosis membrane when the reverse osmosis membrane apparatus having the polyamide reverse osmosis membrane is in operation, or by continuously or intermittently adding the modifier to the water supply to the reverse osmosis membrane or by immersing the reverse osmosis membrane in the water containing the modifier when the rejection of the reverse osmosis membrane is decreased.
The contact of the modifying agent with the reverse osmosis membrane may be carried out under normal pressure, under pressurized conditions or under reduced pressure, and is preferably carried out under pressurized conditions from the viewpoint that the modification can be carried out without stopping the reverse osmosis membrane apparatus, and the modification of the reverse osmosis membrane can be reliably carried out. The contact of the modifier with the reverse osmosis membrane is preferably performed under a pressure in the range of 0.1MPa to 8.0MPa, for example.
The contact of the modifier with the reverse osmosis membrane can be carried out, for example, under a temperature condition in the range of 5 to 35 ℃.
The ratio of the equivalent of the "sulfamic acid compound" to the equivalent of the "bromine-based oxidizing agent" or the "reactant of the bromine compound and the chlorine-based oxidizing agent" is preferably 1 or more, and more preferably in the range of 1 or more and 2 or less. When the ratio of the equivalent of the "sulfamic acid compound" to the equivalent of the "bromine-based oxidizing agent" or the "reactant of the bromine compound and the chlorine-based oxidizing agent" is less than 1, the reverse osmosis membrane may be deteriorated, and when it exceeds 2, the production cost may be increased.
The effective halogen concentration in contact with the reverse osmosis membrane is preferably 0.01 to 100mg/L in terms of effective chlorine concentration. If the concentration is less than 0.01mg/L, a sufficient reforming effect may not be obtained, and if the concentration is more than 100mg/L, deterioration of the reverse osmosis membrane and corrosion of piping and the like may be caused.
Examples of the bromine-based oxidizing agent include: bromine (liquid bromine), bromine chloride, bromic acid, bromate, hypobromous acid, and the like.
Among these, a formulation using bromine as the "bromine and sulfamic acid compound (mixture of bromine and sulfamic acid compound)" or the "reaction product of bromine and sulfamic acid compound" is preferable because it has less chloride ions, does not further deteriorate the polyamide reverse osmosis membrane, and has a low possibility of causing corrosion of metal materials such as piping, compared with a formulation using hypochlorous acid as the "bromine compound and sulfamic acid" or a formulation using bromine chloride and sulfamic acid.
That is, in the method for modifying a reverse osmosis membrane according to the embodiment of the present invention, it is preferable to contact bromine and an aminosulfonic acid compound with a polyamide reverse osmosis membrane (contact a mixture of bromine and an aminosulfonic acid compound with a polyamide reverse osmosis membrane), or contact a reaction product of bromine and an aminosulfonic acid compound with a polyamide reverse osmosis membrane.
Examples of the bromine compound include: sodium bromide, potassium bromide, lithium bromide, ammonium bromide, hydrobromic acid, and the like. Among these, sodium bromide is preferred from the viewpoint of the cost of the preparation and the like.
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, and the like. Among these, examples of the salt include: alkali metal hypochlorates such as sodium hypochlorite and potassium hypochlorite, alkaline earth metal hypochlorates such as calcium hypochlorite and barium hypochlorite, alkali metal chlorites such as sodium chlorite and potassium chlorite, alkaline earth metal chlorites such as barium chlorite, other metal chlorites such as nickel chlorite, alkali metal chlorites such as ammonium chlorate, sodium chlorate and potassium chlorate, and alkaline earth metal chlorites such as calcium chlorate and barium chlorate. These chlorine-based oxidizing agents may be used alone in 1 kind, or may be used in combination in 2 or more kinds. As the chlorine-based oxidizing agent, sodium hypochlorite is preferably used from the viewpoint of handling properties and the like.
The sulfamic acid compound is a compound represented by the following general formula (1).
R2NSO3H (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, in addition to sulfamic acid (amidosulfuric acid) in which 2R groups are all hydrogen atoms: sulfamic acid compounds in which one of the 2R groups is a hydrogen atom and the other is an alkyl group having 1 to 8 carbon atoms, such as N-methylaminosulfonic acid, N-ethylaminosulfonic acid, N-propylaminosulfonic acid, N-isopropylaminosulfonic acid, N-butylaminosulfonic acid, etc., sulfamic acid compounds in which the 2R groups are alkyl groups having 1 to 8 carbon atoms, such as N, N-diethylaminosulfonic acid, N-dipropylaminosulfonic acid, N-dibutylaminosulfonic acid, N-methyl-N-ethylaminosulfonic acid, N-methyl-N-propylaminosulfonic acid, etc., sulfamic acid compounds in which the 2R groups are alkyl groups having 1 to 8 carbon atoms, sulfamic acid compounds in which one of the 2R groups is a hydrogen atom and the other is an aryl group having 6 to 10 carbon atoms, such as N-phenylaminosulfonic acid, etc., sulfamic acid compounds in which the two R groups are alkyl groups having 1 to 8 carbon atoms, etc., and, Or salts thereof, and the like. Examples of sulfamates include: alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as calcium salt, strontium salt and barium salt, other metal salts such as manganese salt, copper salt, zinc salt, iron salt, cobalt salt and nickel salt, ammonium salt and guanidine salt, etc. The sulfamic acid compound and the salts may be used alone in 1 kind or in combination of 2 or more kinds. As the sulfamic acid compound, sulfamic acid (amidosulfuric acid) is preferably used from the viewpoint of environmental load and the like.
In the method for modifying a reverse osmosis membrane according to the present embodiment, an alkali may be present. Examples of the base include: alkali hydroxides such as sodium hydroxide and potassium hydroxide. From the viewpoint of product stability at low temperature, etc., sodium hydroxide and potassium hydroxide may be used in combination. In addition, the base may be used not in a solid state but in the form of an aqueous solution.
The method of modifying a reverse osmosis membrane according to the present embodiment can be used for a polyamide polymer membrane which is currently the mainstream of reverse osmosis membranes. The polyamide polymer film has low resistance to an oxidizing agent, and when free chlorine or the like is continuously brought into contact with the polyamide polymer film, the film performance is significantly reduced. However, in the method for modifying a reverse osmosis membrane according to the present embodiment, such a significant decrease in membrane performance hardly occurs in the polyamide polymer membrane.
In the method for modifying a reverse osmosis membrane according to the present embodiment, the contacting of the modifier with the polyamide reverse osmosis membrane is preferably performed at a pH exceeding 3 and lower than 8, and more preferably at a pH of 4 to 6.5. When the contacting of the modifier with the polyamide reverse osmosis membrane is performed at a pH of 3 or less, the modifier may deteriorate the reverse osmosis membrane and decrease the barrier ratio when the contacting of the modifier with the polyamide reverse osmosis membrane is performed for a long period of time, and when the contacting is performed at 8 or more, the modification effect may be insufficient. In particular, when the contact is performed at a pH of 4 to 6.5, the deterioration of the reverse osmosis membrane can be suppressed and the permeate quality of the reverse osmosis membrane can be sufficiently improved. In order to bring the modifier into contact with the reverse osmosis membrane within the above pH range, for example, the pH of the feed water to the reverse osmosis membrane may be maintained within the above range, or the pH of the impregnation solution of the reverse osmosis membrane may be maintained within the above range.
In a reverse osmosis membrane apparatus having a polyamide reverse osmosis membrane, when scale is generated at a ph of 5.5 or more in feed water to the reverse osmosis membrane, a dispersant may be used in combination with a bromine-based oxidizing agent or a hypobromous acid stabilizing composition in order to suppress the scale. Examples of the dispersant include: polyacrylic acid, polymaleic acid, phosphonic acid, and the like. The amount of the dispersant added to the feed water is, for example, in the range of 0.1 to 1000mg/L in terms of the concentration in the RO concentrated water.
In order to suppress the generation of scale without using a dispersant, for example, there are: the operating conditions such as the recovery rate of the reverse osmosis membrane apparatus can be adjusted so that the silica concentration in the RO concentrated water is not more than the solubility and the Langerier's index (index) as an index of calcium scale is not more than 0.
In the method for modifying a reverse osmosis membrane according to the present embodiment, it is preferable that the reverse osmosis membrane is subjected to chlorine treatment using a chlorine-based oxidizing agent. That is, a bromine-based oxidizing agent and an aminosulfonic acid compound, or a reaction product of a bromine compound and a chlorine-based oxidizing agent, and an aminosulfonic acid compound are brought into contact with a polyamide-based reverse osmosis membrane that has been subjected to chlorine treatment with a chlorine-based oxidizing agent as modifiers; alternatively, a reaction product of a bromine-based oxidizing agent and a sulfamic acid compound, or a reaction product of a bromine compound and a chlorine-based oxidizing agent and a sulfamic acid compound is brought into contact with a polyamide-based reverse osmosis membrane which has been subjected to chlorine treatment with a chlorine-based oxidizing agent as a modifier.
The method for modifying a reverse osmosis membrane according to an embodiment of the present invention is a method in which a chlorine-based oxidizing agent is present in water supply to a polyamide-based reverse osmosis membrane, washing water, or the like and brought into contact with the water supply to the polyamide-based reverse osmosis membrane, washing water, or the like, and then a modifying agent is present in water supply to the polyamide-based reverse osmosis membrane, washing water, or the like and brought into contact with the water supply. The modifier can be brought into contact with the water supplied to the polyamide reverse osmosis membrane subjected to chlorine treatment with a chlorine-based oxidizing agent.
In these methods, the chlorine-containing oxidizing agent is sufficiently brought into contact with the polyamide-based separation membrane in advance to perform the chlorine treatment, and the modifier is brought into contact with the polyamide-based separation membrane, whereby the deterioration of the separation membrane can be suppressed, and the amount of permeated water and the quality of permeated water can be improved.
The contact of the chlorine-based oxidizing agent and the modifying agent with the reverse osmosis membrane can be performed under normal pressure, under pressurized conditions, or under reduced pressure, and is preferably performed under pressurized conditions from the viewpoint of ensuring the modification of the reverse osmosis membrane. The chlorine-containing oxidizing agent and the modifying agent are preferably brought into contact with the reverse osmosis membrane under a pressure condition in the range of, for example, 0.1 to 10 MPa.
The chlorine-based oxidizing agent and the modifying agent may be contacted with the reverse osmosis membrane at a temperature in the range of 0 to 100 ℃.
The chlorine-based oxidizing agent is preferably contacted with the reverse osmosis membrane at an effective chlorine concentration [ mg-Cl/L ] x time [ hour ] of 0.1 to 1000 mg-Cl/L.multidot.h. If the content is less than 0.1 mg-Cl/L.multidot.h, a sufficient chlorine treatment effect on the membrane cannot be obtained, and if the content exceeds 1000 mg-Cl/L.multidot.h, the membrane may be deteriorated.
The pH of the water to be treated when the chlorine-based oxidizing agent is contacted is preferably in the range of 4 to 13, more preferably in the range of 6 to 12. When the pH is less than 4, the amount of permeated water may decrease, and when the pH exceeds 13, the reverse osmosis membrane may deteriorate.
The pH of the water to be treated when the modifier is brought into contact with the reverse osmosis membrane that has been subjected to chlorine treatment with the chlorine-based oxidizing agent is preferably 5.5 or more, more preferably 6.0 or more, and still more preferably in the range of pH6.5 to 10. When the contact between the modifier and the polyamide reverse osmosis membrane subjected to chlorine treatment with the chlorine-based oxidizing agent is performed at a pH of less than 5.5, if the pH is less than 5.5, the reverse osmosis membrane may be affected by a decrease in the amount of permeated water due to the modifier even if the chlorine treatment is performed in advance. When the pH exceeds 10, the amount of permeated water may excessively increase.
In the method of modifying a separation membrane according to the present embodiment, the modifying agent is a "hypobromous acid-stabilized composition". The hypobromous acid-stabilized composition has a small adverse effect on the barrier ratio of a reverse osmosis membrane, and has a high reforming effect even when continuously added to a chlorine-treated reverse osmosis membrane.
A method for modifying a reverse osmosis membrane according to an embodiment of the present invention is, for example, a method in which a chlorine-based oxidizing agent is present in water supply to a polyamide-based reverse osmosis membrane and is brought into contact with the water supply, and then a "bromine-based oxidizing agent" and a "sulfamic acid compound" are present in water supply to a polyamide-based reverse osmosis membrane and are brought into contact with the polyamide-based reverse osmosis membrane as modifiers; alternatively, a method of bringing a "reactant of a bromine compound and a chlorine-based oxidizing agent" and an "sulfamic acid compound" into contact with a polyamide-based reverse osmosis membrane as modifiers in water supply to the polyamide-based reverse osmosis membrane or the like. Thus, it is considered that a hypobromous acid stabilizing composition is formed in the feed water or the like.
In addition, the reverse osmosis membrane modification method according to the embodiment of the present invention is, for example, a method in which a chlorine-based oxidizing agent is present in water supply to a polyamide-based reverse osmosis membrane and brought into contact with the same, and then a hypobromous acid stabilizing composition that is a "reaction product of a bromine-based oxidizing agent and a sulfamic acid compound" is present in water supply to a polyamide-based reverse osmosis membrane and brought into contact with the same as a modifier, or a method in which a hypobromous acid stabilizing composition that is a "reaction product of a bromine compound and a chlorine-based oxidizing agent and a sulfamic acid compound" is present in water supply to a polyamide-based reverse osmosis membrane and brought into contact with the same as a modifier.
Specifically, the method for modifying a reverse osmosis membrane according to the embodiment of the present invention is, for example, a method in which a chlorine-based oxidizing agent is allowed to exist in water supply to a polyamide-based reverse osmosis membrane and brought into contact with the water supply, and then "bromine", "bromine chloride", or "a reaction product of sodium bromide and hypochlorous acid" and "an aminosulfonic acid compound" are allowed to exist in water supply to a polyamide-based reverse osmosis membrane and brought into contact with the polyamide-based reverse osmosis membrane as modifiers.
In addition, the method for modifying a reverse osmosis membrane according to the embodiment of the present invention is, for example, a method in which a chlorine-based oxidizing agent is allowed to be present in and brought into contact with water supplied to a polyamide-based reverse osmosis membrane, and then a hypobromous acid stabilizing composition, which is a "reaction product of bromine and a sulfamic acid compound", "reaction product of bromine chloride and a sulfamic acid compound", or "reaction product of sodium bromide and hypochlorous acid, reaction product of a sulfamic acid compound", is allowed to be present in water supplied to a polyamide-based reverse osmosis membrane, and brought into contact with the polyamide-based reverse osmosis membrane as a modifying agent.
In the method for modifying a reverse osmosis membrane according to the present embodiment, for example, when a reverse osmosis membrane apparatus having a polyamide reverse osmosis membrane is operated, a chlorine-based oxidizing agent may be injected into water or the like supplied to the polyamide reverse osmosis membrane by a chemical injection pump or the like, and then a "bromine-based oxidizing agent" or a "reaction product of a bromine compound and the chlorine-based oxidizing agent" and an "sulfamic acid compound" may be injected as the modifying agents by the chemical injection pump or the like. The "bromine-based oxidizing agent" or the "reactant of bromine compound and chlorine-based oxidizing agent" and the "sulfamic acid compound" may be added to the feed water or the like, respectively; alternatively, the stock solutions may be mixed with each other and then added to the feed water or the like. For example, a polyamide reverse osmosis membrane may be immersed in water to which a chlorine-based oxidizing agent or a modifier is added, and contacted for a predetermined time.
For example, after a chlorine-based oxidizing agent is injected into water supply or the like to the polyamide-based reverse osmosis membrane by a chemical injection pump or the like, a modifier "a reaction product of a bromine-based oxidizing agent and a sulfamic acid compound" or "a reaction product of a bromine compound and a chlorine-based oxidizing agent and a sulfamic acid compound" may be injected by a chemical injection pump or the like. For example, the polyamide reverse osmosis membrane may be immersed in water to which a chlorine-based oxidizing agent or a modifier is added, and brought into contact with the water for a predetermined time.
The modification with the chlorine-based oxidizing agent or the modifying agent may be performed, for example, by continuously or intermittently adding the chlorine-based oxidizing agent or the modifying agent to the water supply to the reverse osmosis membrane or the like when the reverse osmosis membrane apparatus having the polyamide-based reverse osmosis membrane is in operation.
The bromine-based oxidizing agent, bromine compound, chlorine-based oxidizing agent, and sulfamic acid compound are as described above.
Among bromine-based oxidizing agents, a preparation using bromine as the "bromine and sulfamic acid compound" or the "reaction product of bromine and sulfamic acid compound" is more preferable as a slime inhibitor for reverse osmosis membranes because it has less chloride ions, does not deteriorate the polyamide reverse osmosis membrane, and has less leakage of an effective halogen for membrane permeation water such as RO permeation water, compared with a preparation using hypochlorous acid as the "hypochlorous acid compound and sulfamic acid" or a preparation using bromine chloride and sulfamic acid. Further, corrosion of metal materials such as pipes is less likely to occur, and therefore, this is more preferable.
That is, in the method for modifying a reverse osmosis membrane according to the embodiment of the present invention, it is preferable that after a chlorine-based oxidizing agent is present and brought into contact with a polyamide-based reverse osmosis membrane, bromine and an aminosulfonic acid compound are brought into contact with the polyamide-based reverse osmosis membrane as modifiers, or a reaction product of bromine and an aminosulfonic acid compound is brought into contact with the polyamide-based reverse osmosis membrane as a modifier.
Examples of the use of a reverse osmosis membrane apparatus having a polyamide reverse osmosis membrane modified by the reverse osmosis membrane modification method according to the present embodiment include: sea water desalination, wastewater recovery and the like. In particular, it is preferable to perform reverse osmosis membrane treatment on boron-containing water using a polyamide reverse osmosis membrane modified by the reverse osmosis membrane modification method of the present embodiment. By modifying the polyamide reverse osmosis membrane by the reverse osmosis membrane modification method of the present embodiment, the boron rejection rate is significantly improved.
< method for operating separation Membrane >
The method of operating the separation membrane according to the embodiment of the present invention is a method of contacting a bromine-based oxidizing agent with a polyamide-based separation membrane that has been subjected to chlorine treatment with a chlorine-based oxidizing agent.
The method of operating the separation membrane according to the embodiment of the present invention is a method of bringing a chlorine-based oxidizing agent into contact with water supply to a polyamide-based separation membrane, washing water, or the like, and then bringing a bromine-based oxidizing agent into contact with water supply to a polyamide-based separation membrane, washing water, or the like. The bromine-based oxidizing agent may be brought into contact with the water supplied to the polyamide-based separation membrane subjected to chlorine treatment with the chlorine-based oxidizing agent. In the method of operating the separation membrane according to the present embodiment, the bromine-based oxidizing agent may be brought into contact with the separation membrane in advance, or the chlorine-based oxidizing agent may be brought into contact with the separation membrane in situ and then brought into contact with the bromine-based oxidizing agent.
By these methods, the polyamide-based separation membrane is brought into sufficient contact with the chlorine-based oxidizing agent in advance to perform chlorine treatment, whereby the reduction in the amount of permeated water can be suppressed even when the bromine-based oxidizing agent is brought into contact with the separation membrane, and the separation membrane apparatus can be stably operated. Chlorine can be introduced into the separation membrane material by bringing the chlorine-based oxidizing agent into contact with the separation membrane in advance. In the film into which chlorine is introduced, since bromine is not easily introduced, it is presumed that: is not susceptible to bromine-based oxidizing agents that generally cause a decrease in the amount of permeated water.
The contact of the chlorine-based oxidizing agent and the bromine-based oxidizing agent with the separation membrane may be performed under normal pressure, under pressurized conditions, or under reduced pressure, and is preferably performed under pressurized conditions from the viewpoint of allowing chlorine treatment of the separation membrane to be reliably performed, performing contact treatment while producing treated water, and the like. The contact of the chlorine-based oxidizing agent and the bromine-based oxidizing agent with the separation membrane is preferably performed under a pressurized condition in a range of 0.1MPa to 10MPa, for example.
The contact of the chlorine-based oxidizing agent and the bromine-based oxidizing agent with the separation membrane may be performed, for example, under a temperature condition in the range of 0 to 100 ℃.
The chlorine-based oxidizing agent is preferably in contact with the separation membrane at an effective chlorine concentration [ mg-Cl/L ] x time [ hour ] of 0.1 to 1000 mg-Cl/L.multidot.h. If the content is less than 0.1 mg-Cl/L.multidot.h, a sufficient chlorine treatment effect on the membrane cannot be obtained, and if the content exceeds 1000 mg-Cl/L.multidot.h, the membrane may be deteriorated.
The effective halogen concentration of the bromine-based oxidizing agent in contact with the separation membrane is preferably 0.01 to 100mg/L in terms of effective chlorine concentration. If the concentration is less than 0.01mg/L, a sufficient viscosity-suppressing effect may not be obtained, and if the concentration is more than 100mg/L, the separation membrane may be deteriorated or corrosion of piping or the like may be caused.
The pH of the water to be treated when the chlorine-based oxidizing agent is contacted is preferably in the range of 4 to 13, more preferably in the range of 6 to 12. When the pH is less than 4, the amount of permeated water may decrease, and when the pH exceeds 13, the separation membrane may deteriorate.
The pH of the water to be treated when the bromine-based oxidizing agent is contacted is preferably 5.5 or more, more preferably 6.0 or more, and still more preferably in the range of pH6.5 to 10. When the pH is less than 5.5, the separation membrane may be subjected to chlorine treatment in advance, which may reduce the amount of permeated water by the bromine-based oxidizing agent. When the pH exceeds 10, the amount of permeated water may excessively increase.
In the method of operating the separation membrane of the present embodiment, the bromine-containing oxidizing agent is not particularly limited. Examples of the bromine-based oxidizing agent include: "hypobromite" and the like, "reaction product of chlorine-based oxidizing agent and bromide ion", "hypobromous acid stabilizing composition", and the like, but is preferably a "hypobromous acid stabilizing composition". The hypobromous acid-stabilized composition has a small adverse effect on the barrier ratio of the separation membrane, and can be stably operated for a long period of time even when continuously added to a chlorine-treated separation membrane.
For example, after a chlorine-based oxidizing agent is present in feed water or the like to the polyamide-based separation membrane and brought into contact therewith, a "bromine-based oxidizing agent" and a "sulfamic acid compound" are present and brought into contact with the polyamide-based separation membrane; alternatively, a "reactant of a bromine compound and a chlorine-based oxidizing agent" and a "sulfamic acid compound" are present and brought into contact with a polyamide-based separation membrane. Thus, it is considered that a hypobromous acid stabilizing composition is formed in the feed water or the like.
For example, after a chlorine-based oxidizing agent is present in water supplied to the polyamide-based separation membrane and brought into contact with the water, a hypobromous acid stabilizing composition that is a "reaction product of a bromine-based oxidizing agent and a sulfamic acid compound" may be present and brought into contact with the polyamide-based separation membrane; alternatively, a hypobromous acid-stabilized composition which is a reaction product of a "reaction product of a bromine compound and a chlorine-based oxidizing agent with a sulfamic acid compound" is present and brought into contact with a polyamide-based separation membrane.
Specifically, the separation membrane of the embodiment of the present invention is operated, for example, by bringing a chlorine-based oxidizing agent into contact with water supplied to the polyamide-based separation membrane and then bringing "bromine", "bromine chloride", or "a reaction product of sodium bromide and hypochlorous acid" and "an aminosulfonic acid compound" into contact with the polyamide-based separation membrane.
In addition, the separation membrane of the embodiment of the present invention is operated, for example, by bringing a chlorine-based oxidizing agent into contact with water supplied to the polyamide-based separation membrane, and then bringing a hypobromous acid stabilizing composition, which is a "reaction product of bromine and a sulfamic acid compound", "a reaction product of bromine chloride and a sulfamic acid compound", or "a reaction product of sodium bromide and hypochlorous acid, or a reaction product of a sodium bromide and a sulfamic acid compound", into contact with the polyamide-based separation membrane.
In the operation method of the separation membrane of the present embodiment, for example, when the separation membrane apparatus having the polyamide-based separation membrane is operated, the chlorine-based oxidizing agent is injected into the feed water or the like to the separation membrane by a chemical injection pump or the like, and then the "bromine-based oxidizing agent" or the "reactant of the bromine compound and the chlorine-based oxidizing agent" and the "sulfamic acid compound" are injected by the chemical injection pump or the like. The "bromine-based oxidizing agent" or the "reactant of the bromine compound and the chlorine-based oxidizing agent" and the "sulfamic acid compound" may be added to the feed water separately, or the raw liquids may be mixed with each other and then added to the feed water.
For example, after injecting a chlorine-based oxidizing agent into water supply or the like to the polyamide-based separation membrane by a syringe pump or the like, a "reaction product of a bromine-based oxidizing agent and a sulfamic acid compound" or a "reaction product of a bromine compound and a chlorine-based oxidizing agent and a sulfamic acid compound" may be injected by a syringe pump or the like.
The ratio of the equivalent of the "sulfamic acid compound" to the equivalent of the "bromine-based oxidizing agent" or the "reactant of the bromine compound and the chlorine-based oxidizing agent" is preferably 1 or more, and more preferably in the range of 1 or more and 2 or less. When the ratio of the equivalent of the "sulfamic acid compound" to the equivalent of the "bromine-based oxidizing agent" or the "reactant of the bromine compound and the chlorine-based oxidizing agent" is less than 1, the separation membrane may be deteriorated, and when it exceeds 2, the production cost may be increased.
The bromine-based oxidizing agent, bromine compound, chlorine-based oxidizing agent, and sulfamic acid compound are as described above.
Among bromine-based oxidizing agents, a preparation using bromine as the "bromine and sulfamic acid compound" or the "reaction product of bromine and sulfamic acid compound" is more preferable as a slime inhibitor for separation membranes because it has less chloride ions, does not deteriorate the polyamide separation membrane, and has less leakage of an effective halogen to permeate water such as RO permeate water, compared with a preparation using hypochlorous acid as the "bromine compound and sulfamic acid" or a preparation using bromine chloride as the sulfamic acid. Further, corrosion of metal materials such as pipes is less likely to occur, and therefore, this is more preferable.
That is, in the method of operating the separation membrane according to the embodiment of the present invention, it is preferable that the chlorine-based oxidizing agent is present in the feed water or the like to the polyamide-based separation membrane and then contacted with the polyamide-based separation membrane, and then the bromine and the sulfamic acid compound are contacted with the polyamide-based separation membrane, or the reaction product of the bromine and the sulfamic acid compound is contacted with the polyamide-based separation membrane.
In the method for operating a separation membrane of the present embodiment, the bromine-based oxidizing agent may be present together with a base. Examples of the base include: alkali hydroxides such as sodium hydroxide and potassium hydroxide. From the viewpoint of product stability at low temperature, etc., sodium hydroxide and potassium hydroxide may be used in combination. In addition, the base may be used not in a solid state but in the form of an aqueous solution.
Examples of the separation membrane include: a reverse osmosis membrane (RO membrane), a nanofiltration membrane (NF membrane), a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), and the like. Among these, a reverse osmosis membrane (RO membrane) can be particularly suitably used for the operation method of the separation membrane according to the embodiment of the present invention. The method of operating the separation membrane according to the embodiment of the present invention can be suitably used for a polyamide-based polymer membrane, which is currently the mainstream of a reverse osmosis membrane. The polyamide polymer film is likely to cause a decrease in the amount of permeated water when it is brought into contact with a bromine-based oxidizing agent, and for example, when free chlorine or the like is added in the presence of bromide ions, a hypobromite is generated in water, and when it is temporarily brought into contact with the polyamide polymer film, a significant decrease in the amount of permeated water is caused. However, in the operation method of the separation membrane of the present embodiment, such a significant decrease in membrane performance hardly occurs in the polyamide-based polymer membrane.
In a reverse osmosis membrane apparatus having a polyamide reverse osmosis membrane, when scale is generated at a ph of 5.5 or more in water supply to the reverse osmosis membrane, a dispersant may be used in combination with a bromine-based oxidizing agent or a hypobromous acid stabilizing composition in order to suppress the scale. Examples of the dispersant include: polyacrylic acid, polymaleic acid, phosphonic acid, and the like. The amount of the dispersant added to the feed water is, for example, in the range of 0.1 to 1000mg/L in terms of the concentration in the RO concentrated water.
In order to suppress the generation of scale without using a dispersant, for example, there are: the operating conditions such as the recovery rate of the reverse osmosis membrane apparatus can be adjusted so that the silica concentration in the RO concentrated water is not more than the solubility and the Langerl index as an index of calcium scale is not more than 0.
< modifier composition >
The modifier composition used in the method for modifying a reverse osmosis membrane and the method for operating a separation membrane according to the present embodiment contains a "bromine-based oxidizing agent" or a "reaction product of a bromine compound and a chlorine-based oxidizing agent" and a "sulfamic acid compound", and may further contain an alkali.
The modifier composition of the present embodiment may further contain a base, in addition to the "reaction product of the bromine-based oxidizing agent and the sulfamic acid compound" or the "reaction product of the bromine compound and the chlorine-based oxidizing agent, and the sulfamic acid compound".
The bromine-based oxidizing agent, bromine compound, chlorine-based oxidizing agent, and sulfamic acid compound are as described above.
As the modifier composition of the present embodiment, in order to prevent deterioration of the polyamide-based reverse osmosis membrane or the like and to reduce leakage of effective halogen to RO permeate water, it is preferable to contain bromine and an aminosulfonic acid compound (a mixture containing bromine and an aminosulfonic acid compound), for example, a mixture containing bromine, an aminosulfonic acid compound, a base and water, or a reaction product of bromine and an aminosulfonic acid compound, for example, a reaction product of bromine, an aminosulfonic acid compound, a mixture of a base and water.
The modifier composition of the present embodiment has the modifying effect of a polyamide reverse osmosis membrane or the like as compared with modifiers such as hypochlorous acid and free chlorine containing bromine, and hardly causes significant membrane deterioration such as hypochlorous acid and free chlorine containing bromine. The influence of the usual use concentration on the deterioration of the film can be substantially ignored. Therefore, the modifier is most suitable for a polyamide reverse osmosis membrane and the like.
Unlike hypochlorous acid, free chlorine containing bromine, or the like, the modifier composition of the present embodiment hardly permeates a reverse osmosis membrane or the like, and therefore hardly affects the quality of treated water. Further, since the concentration can be measured on site in the same manner as hypochlorous acid or the like, the concentration can be controlled more accurately.
The pH of the composition is, for example, above 13.0, more preferably above 13.2. If the pH of the composition is 13.0 or less, the available halogen in the composition may become unstable.
The concentration of bromic acid in the modifier composition is preferably less than 5 mg/kg. When the concentration of bromic acid in the modifier composition is 5mg/kg or more, the concentration of bromic acid ions such as RO permeated water may be increased.
< method for producing modifier composition >
The modifier composition of the present embodiment can be obtained by mixing a bromine-based oxidizing agent and a sulfamic acid compound, or by mixing a reaction product of a bromine compound and a chlorine-based oxidizing agent and a sulfamic acid compound, and may further be mixed with a base.
The process for producing a modifier composition containing bromine and a sulfamic acid compound or a modifier composition containing a reaction product of bromine and a sulfamic acid compound preferably comprises the steps of: the method for producing the resin composition comprises a step of adding bromine to a mixed solution containing water, a base and a sulfamic acid compound in an inert gas atmosphere to carry out a reaction, or a step of adding bromine to a mixed solution containing water, a base and a sulfamic acid compound in an inert gas atmosphere. The concentration of the bromic acid ions in the composition can be reduced or the concentration of the bromic acid ions in RO permeate water or the like can be reduced by adding the composition in an inert gas atmosphere to carry out the reaction or adding the composition in an inert gas atmosphere.
The inert gas to be used is not limited, but at least 1 of nitrogen and argon is preferable from the viewpoint of production and the like, and nitrogen is particularly preferable from the viewpoint of production cost and the like.
The oxygen concentration in the reactor when bromine is added is preferably 6% or less, more preferably 4% or less, still more 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 the generated bromic acid in the reaction system may increase.
The addition rate of bromine is preferably 25 wt% or less, more preferably 1 wt% or more and 20 wt% or less, based on the total amount of the composition. When the bromine addition rate exceeds 25% by weight based on the total amount of the composition, the amount of the generated bromic acid in the reaction system may increase. If the amount is less than 1% by weight, the modifying effect may be deteriorated.
The reaction temperature when bromine is added is preferably controlled to be in the range of 0 ℃ to 25 ℃, but is more preferably controlled to be in the range of 0 ℃ to 15 ℃ from the viewpoint of production cost and the like. When the reaction temperature at the time of bromine addition exceeds 25 ℃, the amount of generated bromic acid in the reaction system may increase, and when it is lower than 0 ℃, it may freeze.
Examples
The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.
[ preparation of hypobromous acid-stabilized composition 1]
Liquid bromine was added under nitrogen atmosphere: 16.9 weight% (wt%), sulfamic acid: 10.7 wt%, sodium hydroxide: 12.9 wt%, potassium hydroxide: 3.94 wt%, water: the balance were mixed to prepare hypobromous acid stabilized composition 1. The pH of the hypobromous acid-stabilized composition 1 was 14, and the effective halogen concentration (effective chlorine concentration) was 7.5 wt%. The detailed preparation method of hypobromous acid-stabilized composition 1 is as follows.
A2L 4-neck flask filled with nitrogen gas, into which nitrogen gas was continuously introduced and the flow rate of nitrogen gas was controlled by a mass flow controller so that the oxygen concentration in the reaction vessel was maintained at 1%, 1436g of water and 361g of sodium hydroxide were added and mixed, then 300g of sulfamic acid was added and mixed, and then 473g of liquid bromine and 230g of 48% potassium hydroxide solution were added while maintaining the temperature of the reaction solution at 0 to 15 ℃ and cooling was continued, whereby a target composition was obtained in which the weight ratio of the equivalents of sulfamic acid to the equivalents of bromine was 10.7% and 16.9% based on the total amount of the composition, and the ratio of the equivalents of sulfamic acid to the equivalents of bromine was 1.04. The pH of the resulting solution was measured by a glass electrode method, and found to be 14. The bromine content of the resulting solution was measured by a method in which bromine was converted into iodine by potassium iodide and then redox titration was performed using sodium thiosulfate, and was 16.9%, which was 100.0% of the theoretical content (16.9%). The Oxygen concentration in the reaction vessel at the time of bromine reaction was measured by using "Oxygen Monitor JKO-02 LJDII" manufactured by JIKCO Ltd. Incidentally, the concentration of the bromic acid is less than 5 mg/kg.
< example 1, comparative examples 1 and 2>
A polyamide-based polymeric reverse osmosis membrane ("ES 20" manufactured by ritto electrical corporation, a flat membrane having a diameter of 75mm, and a NaCl rejection rate of 95%) was modified by using the hypobromous acid-stabilized composition 1 (example 1), hypochlorous acid (comparative example 1), and hypobromous acid (a mixture of sodium bromide and hypochlorous acid) (comparative example 2) prepared as described above as modifiers. The modification was carried out by introducing water to which 1ppm of the modifier was added at a pH of 5 and 25. + -. 1 ℃ for 24 hours in a reverse osmosis membrane apparatus having the reverse osmosis membrane under an operating pressure of 0.75 MPa. Then, water to which 500ppm of sodium chloride (NaCl) and 1ppm of the modifier were added was continuously passed at 25 ± 1 ℃ at pH 7 under an operating pressure of 0.75MPa until CT (Concentration Time) value became 1000[ ppm · h ]. The conductivities of the raw water and the permeated water were measured, and the following NaCl rejection was calculated. The CT value was calculated as follows. The results are shown in Table 1. In comparative example 2, sodium bromide: 15 wt%, 12% aqueous sodium hypochlorite solution: 42.4% by weight as modifier.
NaCl rejection [% ] ═ 100- [ transmission water conductivity/supply water conductivity ] × 100)
CT value [ ppm · h ] (free chlorine concentration) × (contact time)
[ Table 1]
Figure GDA0001493254300000201
In this manner, by using the hypobromous acid-stabilized composition 1 of example 1 as a modifier, the deterioration of the reverse osmosis membrane can be suppressed, and the permeate water quality of the reverse osmosis membrane can be improved. When hypochlorous acid of comparative example 1 and free chlorine containing bromine of comparative example 2 were used, although the water quality could be temporarily improved, if water was passed through for a long period of time, the reverse osmosis membrane deteriorated and the NaCl rejection rate decreased.
< example 2>
The hypobromous acid-stabilized composition 1 prepared above was used as a modifier and subjected to modification and continuous water passage under the same conditions as in example 1, and the influence of pH on feed water to a reverse osmosis membrane was examined. The results are shown in Table 2.
[ Table 2]
Figure GDA0001493254300000211
As described above, at pH3, the NaCl rejection rate increases by the modification, but when water is continuously passed until the CT value after the modification becomes 1000[ ppm · h ], the NaCl rejection rate slightly decreases. At pH 8.0, the increase in NaCl rejection by the modification was small, but the decrease in NaCl rejection by continuous water passage was not caused. The NaCl blocking rate is increased by the modification within the pH range of 4 to 6.5, and the NaCl blocking rate is not reduced even when water is continuously passed until the modified CT value becomes 1000[ ppm · h ]. From this, it can be seen that: the modifier is preferably contacted with the polyamide reverse osmosis membrane at a pH of more than 3 and less than 8, more preferably at a pH of 4 to 6.5.
< example 3>
After reverse osmosis membrane treatment of boron-containing water was performed under the following conditions, reverse osmosis membrane treatment was performed by the same method as in example 1, followed by reverse osmosis membrane treatment of boron-containing water. The results are shown in Table 3.
(Experimental conditions)
A polyamide-based polymer reverse osmosis membrane ("SWC 5" 8-inch element manufactured by ritong electrical corporation, reduced to a boron barrier rate of 78%) was modified using the hypobromous acid-stabilized composition 1 prepared above as a modifier. The modification was carried out by introducing water to which the modifier was added at 4ppm at a pH of 6.5 and at 24. + -. 1 ℃ for 300 hours in a reverse osmosis membrane apparatus equipped with the reverse osmosis membrane at an operating pressure of 6.0 MPa. Then, water to which 4ppm of boron and 4ppm of the modifier were added was passed at 24 ± 1 ℃ at a pH of 7 under an operating pressure of 6.0 MPa. The boron concentrations of the raw water, the concentrated water and the permeated water were measured by an ICP emission spectrometry using an ICP emission spectrometer (SPS 3100, manufactured by SII NanoTechnology inc.) to calculate the following boron barrier ratios. The results are shown in Table 3.
Boron barrier rate [% ] 100- [ transmitted water boron concentration { (supplied water boron concentration + concentrated water boron concentration) ÷ 2} × 100]
[ Table 3]
Figure GDA0001493254300000221
In this manner, the reverse osmosis membrane was modified with the hypobromous acid stabilizing composition 1, and as a result, the boron rejection rate was improved.
< example 4>
A polyamide-based polymer reverse osmosis membrane ("ES 15" manufactured by ritto electrical corporation, reduced to a NaCl rejection of 98.5%) was modified using the hypobromous acid-stabilized composition 1 prepared as described above as a modifier. A reverse osmosis membrane was immersed in ultrapure water, and the solution was adjusted to pH 7 by adding 1ppm of the modifier and was carried out at 25. + -. 1 ℃ for 72 hours. Then, 500ppm of sodium chloride (NaCl) solution was passed through water at 25 ± 1 ℃ at pH 7 at an operating pressure of 0.75 MPa. The conductivities of the raw water and the permeated water were measured, and the following NaCl rejection was calculated. The results are shown in Table 4.
NaCl rejection [% ] ═ 100- [ transmission water conductivity/supply water conductivity ] × 100)
[ Table 4]
Figure GDA0001493254300000231
Thus, it was confirmed that: even under immersion conditions, modification of the reverse osmosis membrane occurs by the hypobromous acid stabilizing composition.
[ relationship between the Presence and absence of chlorine treatment and the decrease in the amount of permeated Water when the modifier is passed through Water ]
The behavior of the amount of permeated water when water was passed through the modifier was compared between the separation membrane previously contacted with the chlorine-based oxidizing agent and the separation membrane not contacted with the chlorine-based oxidizing agent.
(conditions of chlorine treatment)
An RO membrane: polyamide polymer reverse osmosis membrane (having a conductivity barrier rate of 95% or more in 2000mg/L NaCl solution at a water temperature of 25 ℃ and an operating pressure of 0.75 MPa)
Chlorine treatment conditions: adding sodium hypochlorite (10 mg-CL/L in terms of available chlorine) to pure water, adjusting pH to 10, and introducing water at 25 deg.C under 0.75MPa for 1 hr
(Water passing Condition of modifier)
Test apparatus: flat membrane test device
Separation membrane: a polyamide-based polymeric reverse osmosis membrane (having a conductivity barrier rate of 95% or more in a 2000mg/L NaCl solution at a water temperature of 25 ℃ and an operating pressure of 0.75 MPa), or a reverse osmosis membrane obtained by subjecting the membrane to the above-mentioned chlorine treatment
Operating pressure: 0.75MPa
Raw water: phase model original city well water (conductivity 240 mu S/cm)
Test water pH: 6.5
An agent: the hypobromous acid-stabilized composition 1 prepared above was added so that the effective halogen concentration (effective chlorine concentration) became 1mg/L
(evaluation method)
Effect of separation membrane on amount of permeate water: retention ratio of amount of permeated Water after 120 hours of Water passage (%)
([ permeation water amount after 120 hours of passing water through the modifier/permeation water amount before passing water through the modifier ]. times.100)
< example 5>
The separation membrane previously subjected to the chlorine treatment was subjected to water-passage of the hypobromous acid-stabilized composition 1 as a modifier under the above conditions. The results are shown in Table 5.
< example 6>
Water was passed through the membrane under the same conditions as in example 5, except that the separation membrane was not subjected to chlorine treatment in advance. The results are shown in Table 5.
[ Table 5]
Effect of chlorine treatment in advance on reduction of the amount of permeated water generated from the modifier in the RO membrane
Figure GDA0001493254300000241
In example 6, the amount of permeated water was reduced to less than 70% of the initial value after passing water through the modifier, but in example 5, the amount of permeated water was maintained at 80% or more.
[ influence of pH when Water is introduced into the modifier ]
(Water passing Condition of modifier)
Test apparatus: flat membrane test device
Separation membrane: polyamide polymer reverse osmosis membrane (having a conductivity barrier rate of 95% or more in 2000mg/L NaCl solution at a water temperature of 25 ℃ and an operating pressure of 0.75 MPa)
Operating pressure: 0.75MPa
Raw water: phase model original city well water (conductivity 240 mu S/cm)
Test water pH: 5.0 to 8.0
An agent: the hypobromous acid-stabilized composition 1 prepared above was added to adjust the effective halogen concentration (effective chlorine concentration) to 1mg/L
(evaluation method)
Effect of separation membrane on amount of permeate water: retention ratio of amount of permeated Water after 120 hours of Water passage (%)
([ permeation water amount after 120 hours of passing water through the modifier/permeation water amount before passing water through the modifier ]. times.100)
< examples 7 to 10>
The separation membrane, which has been subjected to chlorine treatment in advance, is subjected to water passage through hypobromous acid-stabilized composition 1 at a pH of 5.0 to 8.0. The results are shown in Table 6.
< examples 11 to 14>
The separation membrane which has not been subjected to the chlorine treatment in advance is subjected to water passage through the hypobromous acid-stabilized composition 1 at a pH of 5.0 to 8.0. The results are shown in Table 6.
[ Table 6]
Effect of pH on contacting modifier with RO Membrane
Figure GDA0001493254300000251
Therefore, the following steps are carried out: the pH of the water to be treated when the modifier is brought into contact with the separation membrane is preferably 5.5 or more, and more preferably 6.0 or more.
[ influence of the kind of modifier ]
(test conditions)
Test apparatus: flat membrane test device
Separation membrane: a polyamide-based polymeric reverse osmosis membrane (having a conductivity barrier rate in a 2000mg/L NaCl solution of 95% or more) was subjected to chlorine treatment in advance
Operating pressure: 0.75MPa
Raw water: phase model original city well water (conductivity 240 mu S/cm)
Test water pH: 7.0
An agent: the hypobromous acid-stabilized composition 1 prepared above or the hypobromous acid-stabilized composition 2 described below was added to adjust the effective halogen concentration (effective chlorine concentration) to 10mg/L
Test time: 64 days
(evaluation method)
Conductivity barrier ratio (% of RO membrane before and after test)
(hypobromous acid stabilizing composition 2)
Mixing sodium bromide: 11 wt%, 12% aqueous sodium hypochlorite solution: 50 wt%, sodium sulfamate: 14 wt%, sodium hydroxide: 8 wt%, water: the balance were mixed to prepare hypobromous acid stabilized composition 2. The pH of the hypobromous acid-stabilized composition 2 was 14, and the effective halogen concentration (effective chlorine concentration) was 6 wt%. The detailed preparation of the composition of hypobromous acid stabilized composition 2 is as follows.
To a reaction vessel, 17g of water was added, 11g of sodium bromide was added and stirred to dissolve it, then 50g of a 12% aqueous sodium hypochlorite solution was added and mixed, then 14g of sodium sulfamate was added and stirred to dissolve it, then 8g of sodium hydroxide was added and stirred to dissolve it, and thus the objective composition was obtained.
< example 15>
The hypobromous acid-stabilized composition 1 was passed through water, and the conductivity barrier ratio of the separation membrane before and after the test was measured. The results are shown in Table 7.
< example 16>
The hypobromous acid-stabilized composition 2 was passed through water, and the conductivity barrier ratio of the separation membrane before and after the test was measured. The results are shown in Table 7.
[ Table 7]
Influence of the kind of modifier
Figure GDA0001493254300000271
Both examples 15, 16 maintained a conductivity barrier of 90% or more, but example 15 showed a higher barrier.
[ influence of chlorine-based oxidizing agent on degree of contact of separation membrane in chlorine treatment ]
(test conditions)
Test apparatus: flat membrane test device
Separation membrane: polyamide polymer reverse osmosis membrane (having a conductivity barrier rate of 95% or more in 2000mg/L NaCl solution at a water temperature of 25 ℃ and an operating pressure of 0.75 MPa)
Operating pressure: 0.75MPa
Raw water: ultrapure water
Chlorine-based oxidizing agent: sodium hypochlorite
(evaluation method)
Conductivity barrier ratio (%)
< example 17>
The contact degree of the chlorine-based oxidizing agent with the separation membrane was set to 10 mg-CL/L.times.h. The results are shown in Table 8.
< example 18>
The contact degree of the chlorine-based oxidizing agent with the separation membrane was set to 1034 mg-CL/L.times.h. The results are shown in Table 8.
[ Table 8]
Influence of chlorine-based oxidizing agent on degree of contact of dispersion film in chlorine treatment
Figure GDA0001493254300000281
The barrier rate against conductivity was 90% or more in example 17, but was reduced to less than 90% in example 18.
As described above, it is known that: by subjecting the separation membrane to chlorine treatment in advance, it is possible to suppress a decrease in the amount of permeated water and to stably operate the separation membrane apparatus even when the modifier is brought into contact with the separation membrane thereafter. In addition, it is known that: the separation membrane is subjected to chlorine treatment in advance and then brought into contact with a modifier, whereby the amount of permeated water and the quality of permeated water can be improved while suppressing deterioration of the separation membrane.

Claims (6)

1. A method for modifying a reverse osmosis membrane is characterized in that,
contacting a mixture of bromine and a sulfamic acid compound with a polyamide-based reverse osmosis membrane;
or, a reaction product of bromine and an aminosulfonic acid compound is brought into contact with a polyamide reverse osmosis membrane,
the polyamide reverse osmosis membrane is subjected to chlorine treatment using a chlorine-based oxidizing agent,
the contacting is carried out under a pressure condition ranging from 0.1MPa to 8.0MPa, under a temperature condition ranging from 5 ℃ to 35 ℃, at a pH ranging from 6.5 to 10,
the effective halogen concentration in contact with the reverse osmosis membrane is 0.01-100 mg/L calculated by effective chlorine concentration.
2. The method of modifying a reverse osmosis membrane according to claim 1,
the reaction product of bromine and a sulfamic acid compound is obtained by a process comprising the following steps: bromine is added to a mixed solution containing water, a base and a sulfamic acid compound under an inert gas atmosphere and a reaction is performed.
3. A reverse osmosis membrane modified by the method for modifying a reverse osmosis membrane according to claim 1 or 2.
4. A method for treating boron-containing water, characterized in that a reverse osmosis membrane modified by the method for modifying a reverse osmosis membrane according to claim 1 or 2 is used to perform reverse osmosis membrane treatment on the boron-containing water.
5. A method for operating a separation membrane, characterized in that a bromine-based oxidizing agent is brought into contact with a polyamide-based separation membrane subjected to chlorine treatment with a chlorine-based oxidizing agent,
when the bromine-containing oxidizing agent is brought into contact with the separation membrane, the pH of the water to be treated is in the range of 6.5 to 10 under the pressure condition in the range of 0.1MPa to 8.0MPa and under the temperature condition in the range of 5 ℃ to 35 ℃,
the effective halogen concentration in contact with the separation membrane is 0.01 to 100mg/L in terms of effective chlorine concentration,
the bromine-based oxidant contains bromine and sulfamic acid compounds;
or, alternatively, a reaction product of bromine and a sulfamic acid compound.
6. The method of operating a separation membrane according to claim 5,
the reaction product of bromine and a sulfamic acid compound is obtained by a process comprising the following steps: bromine is added to a mixed solution containing water, a base and a sulfamic acid compound under an inert gas atmosphere and a reaction is performed.
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