JP6484460B2 - Separation membrane operation method and separation membrane modification method - Google Patents

Description

  The present invention relates to a method for operating a separation membrane such as a reverse osmosis membrane, a method for modifying a separation membrane, and a separation membrane.

  In the operation of polyamide-based separation membranes such as reverse osmosis membranes (RO membranes) and nanofiltration membranes (NF membranes), for example, when various bromine-based oxidants are used for the purpose of slime suppression, bromine-based oxidants are used as separation membranes. May flow into. Examples of the bromine-based oxidizing agent include a reaction product of an oxidizing agent such as hypochlorous acid and bromide ions, and hypobromite. However, these brominated oxidants are known to have a problem that the lower the pH of the water to be treated, the easier it is to reduce the amount of permeated water of the separation membrane (see Non-Patent Document 1).

Desalination 280 (2011) 80-86

  An object of the present invention is to provide a method for operating a separation membrane in which a decrease in the amount of permeate is suppressed even when a bromine-based oxidant comes into contact with the separation membrane, and the separation membrane device is stably operated. Another object of the present invention is to provide a method for modifying a separation membrane for improving the amount of permeated water and the quality of permeated water while suppressing deterioration of the separation membrane, and a reverse osmosis membrane modified by the modifying method. It is in.

According to the present invention, a stabilized hypobromite composition is brought into contact with a polyamide separation membrane that has been chlorinated with a chlorine-based oxidant, and the stabilized hypobromite composition is a bromine-based oxidant or a bromine compound. Contains a reaction product of a chlorinated oxidant and a sulfamic acid compound, or a reaction product of a brominated oxidant or a reaction product of a bromine compound and a chlorinated oxidant, and a sulfamic acid compound. and, wherein the pH of the water to be treated when the contacting stabilized hypobromous acid composition on the separation membrane is a driving method of 6.0 or more der Ru separation membrane.

In the operation method of the separation membrane, the stabilized hypobromite composition preferably contains bromine and a sulfamic acid compound, or contains a reaction product of bromine and a sulfamic acid compound.

  In the method for operating the separation membrane, the reaction product of bromine and a sulfamic acid compound includes a step of reacting a mixed liquid containing water, an alkali and a sulfamic acid compound by adding bromine in an inert gas atmosphere. It is preferable that it was obtained by.

According to the present invention, a stabilized hypobromite composition is brought into contact with a polyamide separation membrane that has been chlorinated with a chlorine-based oxidant, and the stabilized hypobromite composition is a bromine-based oxidant or a bromine compound. Contains a reaction product of a chlorinated oxidant and a sulfamic acid compound, or a reaction product of a brominated oxidant or a reaction product of a bromine compound and a chlorinated oxidant, and a sulfamic acid compound. and, wherein the pH of the water to be treated when the contacting stabilized hypobromous acid composition on the separation membrane is a method of modifying a separation membrane Ru der 6.0 or more.

In the separation membrane modification method, it is preferable that the stabilized hypobromite composition contains bromine and a sulfamic acid compound or a reaction product of bromine and a sulfamic acid compound.

  In the method for reforming the separation membrane, the reaction product of bromine and a sulfamic acid compound includes a step of adding bromine to a mixed liquid containing water, an alkali, and a sulfamic acid compound in an inert gas atmosphere to cause a reaction. It is preferable that it is obtained by the method.

  The present invention is a separation membrane modified by the separation membrane modification method.

  In the operation method of the separation membrane of the present invention, the separation membrane is subjected to chlorination in advance, so that even if the bromine-based oxidant comes into contact with the separation membrane thereafter, a decrease in the amount of permeate is suppressed, and the separation membrane is stably provided. The device can be operated. Further, the present invention can provide a method for modifying a separation membrane for improving the amount of permeated water and the quality of permeated water while suppressing deterioration of the separation membrane, and a separation membrane modified by the modifying method.

  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.

<Operation method of separation membrane>
The operation method of the separation membrane according to the embodiment of the present invention is a method in which a bromine-based oxidizing agent is brought into contact with a polyamide-based separation membrane that has been chlorinated with a chlorine-based oxidizing agent.

  In the operation method of the separation membrane according to the embodiment of the present invention, after bringing the chlorinated oxidant into contact with the supply water or the washing water to the polyamide-based separation membrane, the bromine-based oxidant is present. It is a method of making contact. A bromine-based oxidant may be present in contact with the polyamide-type separation membrane chlorinated with a chlorine-based oxidant, for example. In addition, the operation method of the separation membrane according to this embodiment may use a separation membrane that has been contacted with a chlorine-based oxidant in advance, and may contact the bromine-based oxidant on-site, or the separation membrane on-site. After contacting the chlorine-based oxidizing agent, the bromine-based oxidizing agent may be contacted.

  By these methods, a chlorine-based oxidant is sufficiently brought into contact with a polyamide-based separation membrane in advance to perform chlorination, and even if a bromine-based oxidant comes into contact with the separation membrane, a decrease in the amount of permeated water is suppressed and stable. The separation membrane device can be operated. Chlorine is introduced into the material of the separation membrane by previously contacting the separation membrane with a chlorine-based oxidant. In a membrane into which chlorine has been introduced, bromine is less likely to be introduced, so it is generally assumed that the membrane is less susceptible to the influence of a bromine-based oxidant that causes a reduction in the amount of permeated water.

  The contact of the chlorine-based oxidant and bromine-based oxidant to the separation membrane may be performed under normal pressure, pressurized or reduced pressure conditions, but the separation membrane can be reliably chlorinated. In view of being able to perform contact treatment while producing water, it is preferable to carry out under pressure. The contact of the chlorine-based oxidant and the bromine-based oxidant with the separation membrane is preferably performed under a pressure condition in the range of 0.1 MPa to 10 MPa, for example.

  The contact of the chlorine-based oxidant and the bromine-based oxidant with the separation membrane may be performed, for example, under temperature conditions in the range of 0 ° C to 100 ° C.

  The contact of the chlorine-based oxidizing agent with the separation membrane is preferably 0.1 to 1000 mg-Cl / L · hr as a value of effective chlorine concentration [mg-Cl / L] × time [hr]. If the amount is less than 0.1 mg-Cl / L · hr, a sufficient chlorination effect cannot be obtained for the membrane, and if it exceeds 1000 mg-Cl / L · hr, the membrane may be deteriorated.

  The effective halogen concentration by the bromine-based oxidizing agent that contacts the separation 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 slime-inhibiting effect may not be obtained. If it is more than 100 mg / L, there is a possibility of causing deterioration of the separation membrane and corrosion of the piping.

  The pH of the water to be treated when the chlorine-based oxidizing agent comes into contact is preferably in the range of 4 to 13, and 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 oxidant comes into contact is preferably 5.5 or more, more preferably 6.0 or more, and even more preferably in the range of pH 6.5 to 10. When the pH is less than 5.5, even if the separation membrane has been subjected to chlorination in advance, it may be affected by a decrease in the amount of permeated water due to the bromine-based oxidizing agent. If the pH exceeds 10, the amount of permeated water may increase too much.

  In the operation method of the separation membrane according to the present embodiment, there is no particular limitation on the chlorinated oxidant. 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.

  In the operation method of the separation membrane according to the present embodiment, the bromine-based oxidant is not particularly limited. 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 little adverse effect on the rejection of the separation membrane, and can be stably operated for a long time even when continuously added to the chlorinated separation membrane.

  For example, in a feed water to a polyamide-based separation membrane, a chlorinated oxidant is present and contacted, and then a “bromine-based oxidant” and a “sulfamic acid compound” are present to form a polyamide-based separation membrane. Or “reactant of bromine compound and chlorinated oxidant” and “sulfamic acid compound” are present in contact with the polyamide separation membrane. Thereby, it is thought that the stabilized hypobromite composition produces | generates in water supply etc.

  In addition, for example, in the water supply to a polyamide-based separation membrane, after the presence of a chlorine-based oxidant and contact, a stabilization reaction that is a “reaction product of a bromine-based oxidant and a sulfamic acid compound” Stabilized hypobromite in the presence of a bromite composition in contact with a polyamide separation membrane or “reaction product of a reaction product of a bromine compound and a chlorine-based oxidant and a sulfamic acid compound” An acid composition may be present and contacted with the polyamide separation membrane.

  Specifically, in the operation method of the separation membrane according to the embodiment of the present invention, for example, in the water supply to the polyamide-type separation membrane, after bringing the chlorinated oxidant into contact therewith, “bromine”, In this method, “bromine chloride” or “reaction product of sodium bromide and hypochlorous acid” and “sulfamic acid compound” are present and brought into contact with a polyamide separation membrane.

  Further, the operation method of the separation membrane according to the embodiment of the present invention is, for example, a method in which a bromine and a sulfamic acid compound are contacted in the presence of a chlorine-based oxidizing agent in water supply to a polyamide-based separation membrane. A reaction product of “a reaction product of sulfamic acid compound with sodium bromide and hypochlorous acid” or “a reaction product of a reaction product of sodium bromide with hypochlorous acid”. This is a method in which a hypobromite composition is present and brought into contact with a polyamide separation membrane.

  In the operation method of the separation membrane according to the present embodiment, for example, when operating a separation membrane device including a polyamide-based separation membrane, a chlorine-based oxidant is supplied to the separation membrane by using a chemical injection pump or the like. After injection, “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” and “sulfamic acid compound” may be injected by a chemical injection pump or the like. “Brominated oxidant” or “reaction product of bromine compound and chlorinated oxidant” and “sulfamic acid compound” may be added separately to the feed water, or mixed with the stock solution before feeding water. It may be added inside.

  In addition, for example, after injecting a chlorine-based oxidant into a water supply to a polyamide-based separation membrane with a chemical pump or the like, a “reaction product of a bromine-based oxidant and a sulfamic acid compound” or “bromine A reaction product of a reaction product of a compound and a chlorine-based oxidant and a sulfamic acid compound ”may be injected by a chemical injection pump or the like.

  The ratio of the equivalent of “sulfamic acid compound” to the equivalent of “bromine-based oxidizing agent” or “reaction product of bromine compound and chlorine-based oxidizing agent” is preferably 1 or more, and is in the range of 1 or more and 2 or less. It is more preferable. If the ratio of the equivalent amount of the “sulfamic acid compound” to the equivalent amount of the “bromine-based oxidant” or “reaction product of the bromine compound and the chlorine-based oxidant” is less than 1, the separation membrane may be deteriorated. If it exceeds, the manufacturing cost may increase.

  Examples of bromine-based oxidizing agents include bromine (liquid bromine), bromine chloride, bromic acid, bromate, and hypobromite.

  Among these, the preparations of “bromine and sulfamic acid compound” or “reaction product of bromine and sulfamic acid compound” using bromine are the preparations of “hypochlorous acid, bromine compound and sulfamic acid” and “bromine chloride”. Compared with ”and sulfamic acid” preparations, etc., there is less chloride ion, the polyamide-based separation membrane is not further deteriorated, and the amount of effective halogen leaked into membrane permeated water such as RO permeated water is smaller. It is more preferable as a slime inhibitor. Further, it is more preferable because it is less likely to cause corrosion of metal materials such as piping.

  That is, in the operation method of the separation membrane according to the embodiment of the present invention, after bringing the chlorinated oxidant into contact with water or the like to the polyamide separation membrane, bromine and It is preferable to contact the sulfamic acid compound or to contact the reaction product of bromine and the sulfamic acid compound.

  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 and N-phenylsulfamic acid, both of which are alkyl groups having 1 to 8 carbon atoms, An atom, the other is 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 operation method of the separation membrane according to the present embodiment, an alkali may be further present together with the bromine-based oxidizing agent. 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.

  Examples of the separation membrane include a reverse osmosis membrane (RO membrane), a nanofiltration membrane (NF membrane), a microfiltration membrane (MF membrane), and an ultrafiltration membrane (UF membrane). Among these, the operation method of the separation membrane according to the embodiment of the present invention can be preferably applied to a reverse osmosis membrane (RO membrane). Moreover, the operation method of the separation membrane which concerns on embodiment of this invention is suitably applicable to the polyamide-type polymer membrane which is mainstream these days as a reverse osmosis membrane. Polyamide polymer membranes tend to decrease the amount of permeated water when they come into contact with bromine-based oxidants. For example, when free chlorine or the like is added in the presence of bromide ions, hypobromite is generated in water. When contacted with the polymer polymer membrane even temporarily, the permeated water amount significantly decreases. However, in the operation method of the separation membrane according to the present embodiment, such a remarkable decrease in membrane performance hardly occurs even in the polyamide polymer membrane.

  In a reverse osmosis membrane apparatus equipped with a polyamide-based reverse osmosis membrane, when scale is generated at pH 5.5 or higher of water supplied to the reverse osmosis membrane, a dispersant may be used as a bromine-based oxidant or a stabilizing agent to suppress the scale. You may use together with a bromite composition. 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.

<Method for reforming separation membrane and separation membrane>
The method for modifying a separation membrane according to an embodiment of the present invention is a method in which a bromine-based oxidizing agent is brought into contact with a polyamide-based separation membrane that has been chlorinated with a chlorine-based oxidizing agent. The modification method of the separation membrane according to the present embodiment includes, for example, a method in which a chlorine-based oxidizing agent is brought into contact with a polyamide-based separation membrane, or a chlorine-based oxidizing agent and a bromine-based oxidizing agent in a chlorine-based oxidizing agent The bromine-based oxidizing agent is contacted in this order. Further, the separation membrane according to the embodiment of the present invention is a separation membrane modified by the method for modifying the separation membrane. Here, “reformation” of the separation membrane in this specification may refer to an improvement in the amount of permeated water and an improvement in the quality of the permeated water (that is, an improvement in the rejection rate). In some cases, it refers to the suppression of the reduction (that is, the suppression of the decrease in the blocking rate).

  In the method for reforming a separation membrane according to an embodiment of the present invention, a bromine-based separation membrane is brought into contact with a polyamide-based separation membrane in the presence of a chlorine-based oxidizing agent in the feed water or washing water. In this method, an oxidizing agent is present and contacted. A bromine-based oxidant may be present in contact with the polyamide-type separation membrane chlorinated with a chlorine-based oxidant, for example.

  By these methods, the amount of permeated water and the quality of permeated water are controlled by sufficiently contacting a chlorinated oxidant with a polyamide-based separation membrane in advance and then treating the chlorinated chlorinating agent with the bromine-based oxidant, and further suppressing the deterioration of the separation membrane. Is improved.

  The contact of the chlorine-based oxidant and bromine-based oxidant to the separation membrane may be performed under normal pressure, pressurized or reduced pressure conditions, but the separation membrane can be reliably modified, etc. From the viewpoint, it is preferable to carry out under a pressurized condition. The contact of the chlorine-based oxidant and the bromine-based oxidant with the separation membrane is preferably performed under a pressure condition in the range of 0.1 MPa to 10 MPa, for example.

  The contact of the chlorine-based oxidant and the bromine-based oxidant with the separation membrane may be performed, for example, under a temperature condition in the range of 0 ° C to 100 ° C.

  The contact of the chlorine-based oxidizing agent with the separation membrane is preferably 0.1 to 1000 mg-Cl / L · hr as a value of effective chlorine concentration [mg-Cl / L] × time [hr]. If the amount is less than 0.1 mg-Cl / L · hr, a sufficient modification effect cannot be obtained for the membrane, and if it exceeds 1000 mg-Cl / L · hr, the membrane may be deteriorated.

  The effective halogen concentration by the bromine-based oxidizing agent that contacts the separation 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 slime-inhibiting effect may not be obtained. If it is more than 100 mg / L, there is a possibility of causing deterioration of the separation membrane and corrosion of the piping.

  The pH of the water to be treated when the chlorine-based oxidizing agent comes into contact is preferably in the range of 4 to 13, and 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 oxidant comes into contact is preferably 5.5 or more, more preferably 6.0 or more, and even more preferably in the range of pH 6.5 to 10. If the above-mentioned modifier is brought into contact with the polyamide-based separation membrane at a pH of less than 5.5, even if the separation membrane has been previously subjected to chlorination, it may be affected by a decrease in the amount of permeated water due to the bromine-based oxidizing agent. . If the pH exceeds 10, the amount of permeated water may increase excessively.

  In the separation membrane reforming method according to the present embodiment, the bromine-based oxidizing agent is not particularly limited. 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 little adverse effect on the rejection of the separation membrane, and has a high reforming effect even when continuously added to a chlorinated separation membrane.

  The separation membrane reforming method according to the embodiment of the present invention includes, for example, supplying a bromine-based separation agent in the presence of a chlorinated oxidant as a modifying agent in, for example, feed water to a polyamide-based separation membrane. A method in which an “oxidant” and a “sulfamic acid compound” are present and brought into contact with a polyamide separation membrane, or a “reaction product of a bromine compound and a chlorine-based oxidizing agent” and a “sulfamic acid compound” are present in a polyamide. This is a method of contacting with a separation membrane of the system. Thereby, it is thought that the stabilized hypobromite composition produces | generates in water supply etc.

  In addition, the method for reforming the separation membrane according to the embodiment of the present invention includes, for example, supplying a chlorinated oxidizing agent as a modifying agent in water supply to a polyamide-based separation membrane and bringing it into contact. A method of contacting a polyamide-based reverse osmosis membrane with a stabilized hypobromite composition that is a reaction product of a bromine-based oxidant and a sulfamic acid compound; In this method, a stabilized hypobromite composition which is a reaction product of a reactant and a sulfamic acid compound is present and brought into contact with a polyamide separation membrane.

  Specifically, the method for reforming a separation membrane according to an embodiment of the present invention is, for example, after bringing a chlorinated oxidant as a modifier into contact with water or the like to supply a polyamide-based separation membrane. , “Bromine”, “bromine chloride” or “reaction product of sodium bromide and hypochlorous acid” and “sulfamic acid compound” are present in contact with the polyamide separation membrane.

  In addition, the method for reforming the separation membrane according to the embodiment of the present invention includes, for example, supplying a chlorinated oxidizing agent as a modifying agent in water supply to a polyamide-based separation membrane and bringing it into contact. Reaction product of bromine and sulfamic acid compound "," Reaction product of bromine chloride and sulfamic acid compound "or" Reaction product of sodium bromide and hypochlorous acid and sulfamic acid compound " This is a method in which a stabilized hypobromite composition, which is a product, is present and brought into contact with a polyamide separation membrane.

  In the method for reforming a separation membrane according to the present embodiment, for example, during operation of a separation membrane device including a polyamide-based separation membrane, water is supplied to the polyamide-based separation membrane and the like as a modifier. After injecting the oxidizer with a chemical injection pump, etc., use a chemical injection pump or the like to add “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” and “sulfamic acid compound” as modifiers. Just inject. The “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” and the “sulfamic acid compound” may be added separately to the feed water or the like, or mixed with the stock solution. May be added to the water supply. Further, for example, the polyamide separation membrane may be immersed and contacted in water to which a modifier is added.

  Further, for example, after injecting a chlorinated oxidant as a modifier into a water supply to a polyamide-based separation membrane by a chemical pump or the like, the modifier is “a bromine oxidant and a sulfamic acid compound. “Reaction product” or “reaction product of bromine compound and chlorine-based oxidizing agent and sulfamic acid compound” may be injected by a chemical injection pump or the like. Further, for example, the polyamide separation membrane may be immersed and contacted in water to which a modifier is added.

  The modification with the modifying agent may be performed by, for example, adding the modifying agent continuously or intermittently into the water supply to the separation membrane during the operation of the separation membrane device including the polyamide separation membrane. .

  The ratio of the equivalent of “sulfamic acid compound” to the equivalent of “bromine-based oxidizing agent” or “reaction product of bromine compound and chlorine-based oxidizing agent” is preferably 1 or more, and is in the range of 1 or more and 2 or less. It is more preferable. If the ratio of the equivalent of “sulfamic acid compound” to the equivalent of “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” is less than 1, the reverse osmosis membrane may be deteriorated, If it exceeds 2, the production cost may increase.

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

  Among the bromine-based oxidants, the preparation of “bromine and sulfamic acid compound” or “reaction product of bromine and sulfamic acid compound” using bromine is the preparation of “hypochlorous acid, bromine compound and sulfamic acid” and Compared to “bromine chloride and sulfamic acid” preparations, etc., it has less chloride ions, does not deteriorate the polyamide separation membrane, and has less leakage of effective halogen into membrane permeated water such as RO permeated water. More preferable as a slime inhibitor for separation membranes. Further, it is more preferable because it is less likely to cause corrosion of metal materials such as piping.

  That is, in the method for modifying a separation membrane according to the embodiment of the present invention, after bringing a polyamide-based separation membrane into contact with a chlorinated oxidizing agent as a modifying agent, bromine and a sulfamic acid compound are brought into contact with each other. Alternatively, it is preferable to contact a reaction product of bromine and a sulfamic acid compound.

  In the method for reforming the separation membrane according to the present embodiment, an alkali may be further present together with the bromine-based oxidizing agent. 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.

  Examples of the separation membrane include a reverse osmosis membrane (RO membrane), a nanofiltration membrane (NF membrane), a microfiltration membrane (MF membrane), and an ultrafiltration membrane (UF membrane). Of these, the separation membrane modification method according to the embodiment of the present invention can be suitably applied to a reverse osmosis membrane (RO membrane). In addition, the method for reforming a separation membrane according to the embodiment of the present invention can be suitably applied to a polyamide-based polymer membrane, which is currently mainstream as a reverse osmosis membrane. Polyamide polymer membranes tend to decrease the amount of permeated water when they come into contact with bromine-based oxidants. For example, when free chlorine or the like is added in the presence of bromide ions, hypobromite is generated in water. When contacted with the polymer polymer membrane even temporarily, the permeated water amount significantly decreases. However, in the method for modifying a separation membrane according to the present embodiment, such a remarkable decrease in membrane performance hardly occurs even in a polyamide polymer membrane.

  Examples of the use of the reverse osmosis membrane device including the polyamide-based reverse osmosis membrane modified by the separation membrane modification method according to the present embodiment include seawater desalination and wastewater recovery.

<Composition for separation membrane operation, Composition for modification of separation membrane>
Separation membrane operation composition or separation membrane modification composition used in the separation membrane operation method and separation membrane modification method according to the present embodiment (hereinafter referred to as “separation membrane operation / modification composition” Is a product containing “bromine-based oxidizing agent” or “reaction product of bromine compound and chlorine-based oxidizing agent” and “sulfamic acid compound”, and may further contain an alkali. .

  Further, the separation membrane operation / modification composition according to the present embodiment includes a “reaction product of a bromine-based oxidant and a sulfamic acid compound” or a “reaction product of a bromine compound and a chlorine-based oxidant, and a sulfamine. It contains "reaction product of an 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.

  As the separation membrane operation / modification composition according to this embodiment, since the polyamide separation membrane is not further deteriorated and the amount of effective halogen leaked to RO permeate is smaller, bromine, sulfamic acid compound, Or those containing a reaction product of bromine and a sulfamic acid compound are preferred.

  The composition for operation / reformation of the separation membrane according to the present embodiment has higher oxidizing power, slime suppressing power, and slime peeling power significantly higher than those of bonded chlorine-based slime inhibitors such as chlorosulfamic acid. Also, it hardly causes significant film deterioration like hypochlorous acid having high oxidizing power. At normal use concentrations, the effect on film degradation can be substantially ignored. Therefore, it is optimal as a slime inhibitor and modifier for separation membranes such as polyamide-based reverse osmosis membranes (RO membranes).

  Unlike the hypochlorous acid, the separation membrane operation / modification composition according to the present embodiment hardly permeates the reverse osmosis membrane (RO membrane) or the like, and therefore has little influence 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 composition is, for example, more than 13.0, more preferably more than 13.2. When the pH of the composition is 13.0 or less, the effective halogen in the composition may become unstable.

  The bromic acid concentration in the separation membrane operation / modification composition is preferably less than 5 mg / kg. When the bromate concentration in the separation membrane operation / modification composition is 5 mg / kg or more, the concentration of bromate ions such as RO permeate may increase.

<Production Method for Separation Membrane Operation and Separation Membrane Modification Composition>
The separation membrane operation composition or the separation membrane modification composition used in the separation membrane operation method and the separation membrane modification method according to the present embodiment is a mixture of a bromine-based oxidizing agent and a sulfamic acid compound, or It is obtained by mixing a reaction product of a bromine compound and a chlorine-based oxidant and a sulfamic acid compound, and an alkali may be further mixed.

  As a method for producing a separation membrane operation / modification composition containing bromine and a sulfamic acid compound, or a separation membrane operation / modification composition containing a reaction product of bromine and a sulfamic acid compound, It is preferable to include a step of adding bromine to a mixed liquid containing water, an alkali and a sulfamic acid compound in an inert gas atmosphere and reacting them. By adding and reacting under an inert gas atmosphere, the bromate ion concentration in the composition is lowered, and the bromate ion concentration in the RO permeate and the like is lowered.

Used but are not limited to inert gas, at least one and preferably one in terms of nitrogen and argon, such as production, nitrogen is particularly preferred from the viewpoint of production cost and the like.

  The oxygen concentration in the reactor upon 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 composition. If the bromine addition rate exceeds 25% by weight relative to the total amount of the composition, the amount of bromic acid produced in the reaction system may increase. If it is less than 1% by weight, the sterilizing power and the reforming effect may be inferior.

  The reaction temperature during the addition of bromine 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 and the like. 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, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

[Relationship between presence / absence of chlorination and decrease in permeate volume when bromine-based oxidant is passed]
The behavior of the amount of permeated water when a bromine-based oxidant was passed through a separation membrane previously contacted with a chlorine-based oxidant and a separation membrane not contacted with a chlorine-based oxidant were compared.

(Chlorine treatment conditions)
RO membrane: polyamide polymer reverse osmosis membrane (water temperature: 25 ° C., operating pressure: 0.75 MPa, conductivity rejection of 2000 mg / L NaCl solution is 95% or more)
Chlorine treatment conditions: 10 mg-CL / L of sodium hypochlorite as effective chlorine was added to pure water, adjusted to pH 10, and passed for 1 hr at a pressure of 0.75 MPa and a water temperature of 25 ° C.

(Brominated oxidant flow conditions)
Test device: Flat membrane test device Separation membrane: Polyamide polymer reverse osmosis membrane (water temperature: 25 ° C., operating pressure: 0.75 MPa, conductivity rejection of 2000 mg / L NaCl solution is 95% or more ), Or reverse osmosis membrane with the above chlorination treatment and operating pressure: 0.75 MPa
・ Raw water: Sagamiharai water (conductivity 240μS / cm)
Test water pH: 6.5
・ Drug: Stabilized hypobromite composition 1 is added so that the effective halogen concentration (effective chlorine equivalent concentration) is 1 mg / L.

(Evaluation method)
・ Effect on the amount of permeated water of the separation membrane: Permeated water retention rate after passing through 120 hours (%)
([Permeated water amount after 120 hours of bromine-based oxidant flow / Amount of permeated water before flow of bromine-based oxidant] × 100)

(Preparation of Stabilized Hypobromite Composition 1)
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 stabilized hypobromite composition 1. The pH of the stabilized hypobromite composition 1 was 14, and the effective halogen concentration (effective chlorine equivalent concentration) was 7.5% by weight. The detailed preparation method of the stabilized hypobromite composition 1 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. The target stabilized hypobromite composition 1 having a sulfamic acid ratio of 10.7% by weight 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. Got. 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%. In addition, 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.

<Example 1>
The stabilized hypobromite composition 1 as a bromine-based oxidant was passed through the separation membrane subjected to the chlorination in advance under the above conditions. The results are shown in Table 1.

<Comparative Example 1>
Water was passed under the same conditions as in Example 1 except that the above separation membrane not subjected to chlorination was used. The results are shown in Table 1.

  In Comparative Example 1, the permeated water amount decreased to less than 70% of the initial value after passing the bromine-based oxidizing agent, but in Example 1, the permeated water amount was maintained at 80% or more.

[Effect of pH when bromine-based oxidant passes]
(Brominated oxidant flow conditions)
Test device: Flat membrane test device Separation membrane: Polyamide polymer reverse osmosis membrane (water temperature: 25 ° C., operating pressure: 0.75 MPa, conductivity rejection of 2000 mg / L NaCl solution is 95% or more )
・ Operating pressure: 0.75 MPa
・ Raw water: Sagamiharai water (conductivity 240μS / cm)
Test water pH: 5.0 to 8.0
・ Drug: Stabilized hypobromite composition 1 is added so that the effective halogen concentration (effective chlorine equivalent concentration) is 1 mg / L.

(Evaluation method)
・ Effect on the amount of permeated water of the separation membrane: Permeated water retention rate after passing through 120 hours (%)
([Permeated water amount after 120 hours of bromine-based oxidant flow / Amount of permeated water before flow of bromine-based oxidant] × 100)

< Reference Examples 2 and 3, Examples 4 and 5>
The stabilized hypobromite composition 1 was passed through the separation membrane that had been previously chlorinated under conditions of pH 5.0 to 8.0. The results are shown in Table 2.

<Comparative Examples 2-5>
The stabilized hypobromite composition 1 was passed through the separation membrane that had not been previously chlorinated under conditions of pH 5.0 to 8.0. The results are shown in Table 2.

  It was found that 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, and more preferably 6.0 or more.

[Influence of the type of bromine-based oxidant]
(Test conditions)
・ Test equipment: Flat membrane test equipment ・ Separation membrane: Polyamide-based polymer reverse osmosis membrane (conductivity rejection in a 2000 mg / L NaCl solution is 95% or more) in advance. Chlorine treatment ・ Operating pressure: 0 .75 MPa
・ Raw water: Sagamiharai water (conductivity 240μS / cm)
Test water pH: 7.0
-Drug: Stabilized hypobromite composition 1 or stabilized hypobromite composition 2 is added so that the effective halogen concentration (effective chlorine equivalent concentration) is 10 mg / L.-Test time: 64 days

(Evaluation method)
-Conductivity rejection rate (%) in RO membrane before and after the test

(Stabilized hypobromite composition 2)
Sodium bromide: 11% by weight, 12% sodium hypochlorite aqueous solution: 50% by weight, sodium sulfamate: 14% by weight, sodium hydroxide: 8% by weight, water: the remainder is mixed to stabilize hypochlorous acid Bromic acid composition 2 was prepared. The pH of the stabilized hypobromite composition 2 was 14, and the effective halogen concentration (effective chlorine equivalent concentration) was 6% by weight. The detailed preparation method of the composition of the stabilized hypobromite composition 2 is as follows.

  17 g of water was put into a reaction vessel, 11 g of sodium bromide was added and dissolved by stirring, 50 g of 12% aqueous sodium hypochlorite solution was added and mixed, and then 14 g of sodium sulfamate was added and stirred. After dissolution, 8 g of sodium hydroxide was added, stirred and dissolved to obtain the desired composition.

<Example 6>
The stabilized hypobromite composition 1 was passed through and the conductivity rejection rate in the separation membrane before and after the test was measured. The results are shown in Table 3.

<Example 7>
The stabilized hypobromite composition 2 was passed through, and the conductivity rejection rate in the separation membrane before and after the test was measured. The results are shown in Table 3.

  In both Examples 6 and 7, the conductivity rejection rate of 90% or more was maintained, but Example 6 showed a higher rejection rate.

[Effect of contact degree of chlorinated oxidant on separation membrane in chlorination]
(Test conditions)
Test device: Flat membrane test device Separation membrane: Polyamide polymer reverse osmosis membrane (water temperature: 25 ° C., operating pressure: 0.75 MPa, conductivity rejection of 2000 mg / L NaCl solution is 95% or more )
・ Operating pressure: 0.75 MPa
・ Raw water: Ultrapure water ・ Chlorine oxidizer: Sodium hypochlorite

(Evaluation method)
-Conductivity rejection rate (%) in the separation membrane before and after the test

<Example 8>
The contact degree of the chlorine-based oxidizing agent to the separation membrane was 10 mg-CL / L × hr. The results are shown in Table 4.

<Comparative Example 6>
The degree of contact of the chlorine-based oxidizing agent with the separation membrane was 1034 mg-CL / L × hr. The results are shown in Table 4.

  The conductivity rejection was 90% or more in Example 8, but decreased to less than 90% in Comparative Example 6.

  As described above, since the separation membrane is preliminarily treated with chlorine, even if a bromine-based oxidant comes into contact with the separation membrane thereafter, a decrease in the amount of permeate is suppressed, and the separation membrane device can be operated stably. I knew it was possible. Further, it was found that the permeated water amount and the permeated water quality can be improved while the deterioration of the separation membrane is suppressed by bringing the separation membrane into contact with a bromine-based oxidant in advance after chlorination.

Claims (6)

The stabilized hypobromite composition is brought into contact with a polyamide separation membrane that has been chlorinated with a chlorinated oxidant ,
The stabilized hypobromite composition contains a bromine-based oxidant, a reaction product of a bromine compound and a chlorine-based oxidant, and a sulfamic acid compound, or a bromine-based oxidant, or a bromine compound and chlorine. Containing a reaction product with a oxidant and a reaction product with a sulfamic acid compound,
The method of operating the separation membrane, characterized in der Rukoto pH 6.0 or more water to be treated when the contacting stabilized hypobromous acid composition to the separation membrane. A method for operating the separation membrane according to claim 1 ,
The method for operating a separation membrane, wherein the stabilized hypobromite composition contains bromine and a sulfamic acid compound or contains a reaction product of bromine and a sulfamic acid compound. A method for operating the separation membrane according to claim 2 ,
The reaction product of bromine and a sulfamic acid compound is obtained by a method including a step of reacting a mixed liquid containing water, an alkali and a sulfamic acid compound by adding bromine in an inert gas atmosphere. A method of operating a separation membrane characterized by the above. The stabilized hypobromite composition is brought into contact with a polyamide separation membrane that has been chlorinated with a chlorinated oxidant ,
The stabilized hypobromite composition contains a bromine-based oxidant, a reaction product of a bromine compound and a chlorine-based oxidant, and a sulfamic acid compound, or a bromine-based oxidant, or a bromine compound and chlorine. Containing a reaction product with a oxidant and a reaction product with a sulfamic acid compound,
Modification method of the separation membrane, characterized in der Rukoto pH 6.0 or more treated water upon contacting the stabilized hypobromous acid composition to said separation membrane. A method for reforming a separation membrane according to claim 4 ,
The method for reforming a separation membrane, wherein the stabilized hypobromite composition contains bromine and a sulfamic acid compound or contains a reaction product of bromine and a sulfamic acid compound. A method for modifying a separation membrane according to claim 5 ,
The reaction product of bromine and a sulfamic acid compound is obtained by a method including a step of reacting a mixed liquid containing water, an alkali and a sulfamic acid compound by adding bromine in an inert gas atmosphere. A method for reforming a separation membrane characterized by the above.