WO2018056242A1

WO2018056242A1 - Reverse osmosis membrane rejection rate-improving agent and rejection rate-improving method

Info

Publication number: WO2018056242A1
Application number: PCT/JP2017/033644
Authority: WO
Inventors: 孝博川勝
Original assignee: 栗田工業株式会社
Priority date: 2016-09-20
Filing date: 2017-09-19
Publication date: 2018-03-29
Also published as: JP2018047406A

Abstract

Provided are a RO membrane rejection rate-improving agent capable of improving the rejection rate, particularly the boron rejection rate, without significantly reducing permeation flux, and a rejection rate-improving method using said rejection rate-improving agent. A reverse osmosis membrane rejection rate-improving agent comprises pyrogallol and/or a pyrogallol derivative with a molecular weight of less than 500. For the pyrogallol derivative, a gallic acid ester with a molecular weight of less than 300 is preferred. A reverse osmosis membrane rejection rate-improving method treats a reverse osmosis membrane using said reverse osmosis membrane rejection rate-improving agent.

Description

Reverse osmosis membrane rejection rate improver and rejection rate improvement method

The present invention relates to a rejection improving agent that can effectively improve the rejection of a reverse osmosis membrane (RO) membrane, particularly an aromatic polyamide-based RO membrane. Specifically, in view of the fact that the permeated water of the RO membrane is used as drinking water and domestic water, the present invention ensures a high desalination rate and significantly improves the boron removal rate without significantly reducing the amount of permeated water. The present invention relates to an RO membrane rejection rate improver. The present invention also relates to a RO membrane rejection rate improving method using the RO membrane rejection rate improving agent, and a water treatment method using the RO membrane subjected to the rejection rate improving treatment.

In order to make up for the shortage of water supply, seawater and brine desalination and water recovery are performed using RO membrane systems. Seawater desalination is used in areas where river water, lake water, or groundwater is not available, such as the Middle East and remote islands. Seawater contains 5-10 mg / L boron. The WHO drinking water quality guideline 4th edition stipulates that the boron concentration be 2.4 mg / L or less. The boron standard was 0.5 mg / L or less in the third edition. According to domestic tap water standards, the boron concentration is 1 mg / L or less. In addition, in the US Environmental Protection Agency agricultural water standard, the boron concentration is 0.75 mg / L or less.

Boron in seawater exists mainly in the form of boric acid. Since boric acid in seawater hardly deviates in the neutral region and the molecular weight is as small as 62, it is difficult to remove with RO membrane. For this reason, there is a process in which the RO film is provided in two stages in series, and the boron concentration is reduced to about 1 to 2 mg / L with the first stage RO film, and then the pH is increased to further reduce boron with the second stage RO film. Has been made. Increasing the pH of the second stage RO membrane water supply leads to increased processing costs and risk of scale generation.

For this reason, seawater desalination RO membranes are required to improve the boron removal rate in addition to the desalination rate.

If the desalination rate and boron removal rate of the RO membrane are improved in the ultrapure water production process, it is possible to reduce the processing cost by reducing the load on the ion exchange resin and the electric regenerative pure water device at the subsequent stage of the RO membrane. it can.

In the RO membrane system, an oxidizing agent such as chlorine (sodium hypochlorite) or hydrogen peroxide is added to the raw water (water to be treated for the RO membrane) in the pretreatment process to suppress biofouling. .

Since these oxidizing agents have a strong oxidative decomposition action, when raw water is supplied to the RO membrane in a state where the reduction treatment is insufficient after the addition of these oxidizing agents, the RO membrane is deteriorated.

In order to decompose the oxidizing agent in the raw water, when a reducing agent such as sodium bisulfite is added to the raw water and supplied to the RO membrane, in a reducing environment where sodium bisulfite is excessively added, Cu, When a metal such as Co coexists, the RO membrane deteriorates and the rejection rate decreases (Patent Document 1, Non-Patent Document 1).

Conventionally, the following methods have been proposed as methods for improving the RO membrane rejection rate.

Patent Document 2: A method for improving the RO membrane rejection by attaching an anionic or cationic polymer compound to the surface of the RO membrane. This method can improve the desalting rate, but it is difficult to improve the removal rate of solutes with low chargeability such as boron.

Patent Document 3: Permeation flux is in the proper range (at the start of use) by attaching a nonionic surfactant to the membrane surface against nanofiltration membranes or RO membranes with anion charge that have deteriorated and increased permeation flux In the range of +20 to -20%), and prevents membrane contamination and permeated water quality deterioration. The nonionic surfactants used here are known as membrane contaminants and greatly reduce the permeation flux when applied to undegraded RO membranes.

Patent Document 4: A method of improving the RO membrane rejection by attaching a compound having a polyalkylene glycol chain to the surface. Although this method can improve the desalination rate, it is difficult to improve the boron removal rate.

Non-patent document 2: A method of improving the desalination rate by attaching tannic acid or the like to a deteriorated film. The effect of improving the rejection rate by this method is not sufficient. For example, the permeated water conductivity of ES20 (manufactured by Nitto Denko) and SUL-G20F (manufactured by Toray Industries), which are deteriorated RO membranes, are 82% → 88% and 92% → 94%, respectively, before and after treatment. The blocking rate cannot be increased until the solute concentration of the permeated water is halved.

Non-Patent Document 3: A method of improving the RO membrane rejection rate by adding polyvinyl methyl ether (PVME) to tannic acid. Although this method can improve the desalination rate, no study has been made on improving the boron removal rate.

Japanese Unexamined Patent Publication No. 7-308671 JP 2006-110520 A JP 2008-86945 A JP 2007-289922 A

The above prior art has the following problems.
(1) The recovery and improvement of the desalination rate is the main, and the improvement of the boron removal rate has not been studied.
(2) The effect of improving the rejection rate is small.
(3) The permeation flux is greatly reduced.

The present invention solves these problems.
The present invention provides an RO membrane rejection rate improver that can improve the rejection rate, particularly the boron removal rate, without significantly reducing the permeation flux, and a rejection rate improving method using the rejection rate improver. To do.

As a result of extensive studies, the present inventor has found that pyrogallol or a low molecular weight pyrogallol derivative can solve the above problems.

The gist of the present invention is as follows.

[1] A reverse osmosis membrane rejection rate improver comprising pyrogallol and / or a pyrogallol derivative having a molecular weight of less than 500.

[2] The reverse osmosis membrane rejection rate improver according to [1], comprising at least the pyrogallol derivative, wherein the pyrogallol derivative has a molecular weight of less than 300.

[3] The reverse osmosis membrane rejection rate improver according to [1] or [2], which contains at least the pyrogallol derivative, and the pyrogallol derivative is a gallic acid ester.

[4] The reverse osmosis membrane rejection rate improver according to any one of [1] to [3], wherein the reverse osmosis membrane is a polyamide-based reverse osmosis membrane.

[5] The reverse osmosis membrane rejection improving agent according to any one of [1] to [4], wherein the reverse osmosis membrane is a reverse osmosis membrane for seawater desalination.

[6] The reverse osmosis membrane rejection rate improver according to any one of [1] to [5], further comprising a polyamino acid.

[7] A reverse osmosis membrane rejection rate improving method, comprising treating the reverse osmosis membrane with the reverse osmosis membrane rejection rate improving agent according to any one of [1] to [6].

[8] After treating the reverse osmosis membrane with the reverse osmosis membrane rejection rate improver according to any one of [1] to [6], the reverse osmosis membrane further contains a polyamino acid, A method for improving the rejection of a reverse osmosis membrane, characterized by treating the osmosis membrane.

[9] A water treatment method using a reverse osmosis membrane treated by the inhibition rate improving method according to [7] or [8].

According to the RO membrane rejection rate improver of the present invention, the rejection rate, particularly the boron removal rate, can be improved without greatly reducing the permeation flux.
According to the present invention, the following effects can be industrially obtained by improving the RO membrane rejection rate, particularly the boron removal rate.

Conventionally, when producing drinking water by desalination of seawater, a process of increasing the pH of the second stage RO supply water by assembling a multistage RO has been required, but by improving the boron removal rate of the RO membrane, This process can be reduced to a low cost.
In the ultrapure water production process, by improving the RO membrane rejection rate, the load on the ion exchange resin and the electric regenerative deionized water device downstream of the RO membrane can be reduced, and the processing cost can be reduced.

It is a schematic diagram which shows the flat film test apparatus used by the test example.

Hereinafter, embodiments of the present invention will be described in detail.

[mechanism]
The examination process that the inventor has conceived of the present invention is as follows.

i) In order to enhance the removal effect of uncharged small molecules to which charge repulsion such as boron cannot be applied, it is necessary to make the gaps small by adsorbing low molecular substances in the gaps of the dense layer of the RO membrane.
ii) As described in Non-Patent Documents 2 and 3, tannic acid is known to have an effect of improving the desalination rate, and is considered to be a substance having a high affinity with the RO membrane. However, since tannic acid has a high molecular weight of 500 or more, it is difficult to adsorb in the gap between the dense layers of the RO membrane. As a result, it is difficult to improve the removal rate of uncharged small molecules such as boron.
iii) The present inventor has made the following hypothesis.
By using the low molecular weight constituting the tannic acid as the low molecular weight adsorbing material, the low molecular weight material with high affinity to the RO membrane is adsorbed in the gap of the dense layer of the membrane, and this gap is reduced, The effect of removing uncharged small molecules such as boron can be enhanced.
iv) Based on this hypothesis, the present inventor paid attention to a pyrogallol skeleton in which three hydroxy groups were added to the benzene ring as a component of tannic acid that has increased affinity for the membrane, and obtained the following knowledge .
By adsorbing pyrogallol and its derivatives on the RO membrane, there is an effect of improving the desalting rate. Not only the desalting rate but also the boron removal rate can be improved.

The structural formulas of tannic acid types (hydrolyzed type and condensed type) and the virogallol structure constituting it are shown below.

The structural formulas of pyrogallol and typical pyrogallol derivatives used in the present invention are shown below. Examples of pyrogallol derivatives include methyl gallate (MW: 184) and ethyl gallate (MW: 198) in which the propyl group of propyl gallate shown below is replaced with a methyl group, an ethyl group, a butyl group, an octyl group, and a lauryl group, respectively. ), Butyl gallate (MW: 226), octyl gallate (MW: 282), gallic acid alkyl esters such as lauryl gallate (MW: 338).

The catechol or catechol derivative in which two hydroxy groups are added to the benzene ring represented by the structural formula below is also a low molecular weight organic compound having a high affinity for the RO membrane, and an effect of improving the blocking rate can be obtained. However, catechol and catechol derivatives are less effective in improving the rejection rate than pyrogallol and its derivatives.

The mechanism for improving the rejection rate and the boron removal rate according to the present invention is as follows.
(1) Tannic acid has an effect of improving the desalination rate and has a high affinity for the membrane.
(2) Three hydroxy groups are added to pyrogallol constituting tannic acid, which increases the affinity for the membrane.
(3) Since tannic acid is a substance having a molecular weight of 500 or more, it is difficult to adsorb in the gap between the dense layers of the film. In contrast, pyrogallol and pyrogallol derivatives include substances having a molecular weight of less than 500, and by adsorbing them to the film, the polymer gap in the film can be filled.
(4) As a result, not only the desalting rate but also the boron removal rate can be improved.

[Rejection rate improver]
The RO membrane rejection rate improver of the present invention contains pyrogallol (molecular weight: 126) and / or a pyrogallol derivative having a molecular weight of less than 500.

The pyrogallol derivative having a molecular weight of less than 500 is not particularly limited, but the aforementioned gallic acid (molecular weight: 170), methyl gallate (molecular weight: 184), ethyl gallate (molecular weight: 198), propyl gallate (molecular weight: 212). ), Butyl gallate (molecular weight: 226), octyl gallate (molecular weight: 282), gallic acid alkyl esters such as lauryl gallate (molecular weight: 338) (the carbon number of the alkyl group is preferably 1 to 12), epigallo Catechin (molecular weight: 306), epigallocatechin gallate (molecular weight: 458), methyl 3,4,5-trimethoxybenzoate (molecular weight: 226), and the like. Among these, pyrogallol or a pyrogallol derivative having a molecular weight of less than 300 is preferable, and gallic acid ester is particularly preferable from the viewpoints of the affinity for RO membrane, the desalination rate improvement effect, and the boron removal rate improvement effect.

These pyrogallol and pyrogallol derivatives may be used alone or in combination of two or more.

The blocking rate improver of the present invention may further contain a polyamino acid, and by containing the polyamino acid, a further excellent blocking rate improving effect can be obtained.

As the polyamino acid used in the blocking rate improver of the present invention, one or two or more amino acids are polymerized. Examples of polyamino acids include polylysine, polyglycine, polyglutamic acid, polyarginine, polyhistidine and the like. Of these, polylysine, polyarginine, and polyhistidine, which are polymers of basic amino acids, are particularly suitable. In particular, polylysine is preferable because it has a strong electrostatic interaction with pyrogallol and a pyrogallol derivative, and can be used in combination with pyrogallol and / or a pyrogallol derivative to obtain a high treatment rate improvement treatment effect.

These polyamino acids may be used alone or in combination of two or more.

The molecular weight of the polyamino acid used in the present invention is not particularly limited, but a polyamino acid having a molecular weight of 1,000 or more and 1,000,000 or less is preferably used from the viewpoint of the adsorptivity to the RO membrane and the influence on water permeability. be able to.

The content of the polyamino acid contained in the blocking rate improver of the present invention is preferably 10% by weight or more, particularly 30 to 300% by weight with respect to pyrogallol and / or pyrogallol derivative in the blocking rate improver. If the content of the polyamino acid is not less than the above lower limit, the effect of improving the inhibition rate by using the polyamino acid can be more effectively obtained. However, if the content of the polyamino acid is excessively large, there is a possibility that the adsorption of pyrogallol and / or pyrogallol derivatives may be inhibited, and the water permeability will be affected.

The inhibitory rate improver of the present invention may be one in which pyrogallol and / or a pyrogallol derivative and a polyamino acid are combined into one agent, and two agents in which pyrogallol and / or a pyrogallol derivative and a polyamino acid are separately supplied. It may be of a type.

[Prevention rate improvement method]
The RO membrane rejection rate improving method of the present invention performs RO membrane rejection rate improving treatment using the rejection rate improving agent of the present invention. Specifically, in the RO membrane rejection rate improving method of the present invention, by passing an aqueous solution of the rejection rate improving agent of the present invention through the RO membrane, the desalination rate of the deteriorated RO membrane is improved and boron is added. Improve the removal rate. Hereinafter, the aqueous solution of the blocking rate improver that passes through the RO membrane for the RO membrane blocking rate improving process is referred to as “blocking rate improving treated water”.

The concentration of pyrogallol and / or pyrogallol derivative, which is an active ingredient of the rejection rate improver in the treatment rate improvement treated water, is preferably 0.01 to 100 mg / L, more preferably 0.1 to 10 mg / L. If the concentration of the active ingredient in the water for improving the rejection rate is lower than the lower limit, a sufficient effect for improving the rejection rate cannot be obtained. When the concentration of the active ingredient in the treatment rate improving treated water is higher than the upper limit, the permeation flux is greatly lowered and the treatment cost is also increased.

When the rejection improving agent further contains a polyamino acid, the concentration of the polyamino acid in the rejection improving water is preferably 0.001 to 300 mg / L for the same reason as the concentration of pyrogallol and / or pyrogallol derivative. The total concentration of pyrogallol and / or pyrogallol derivative and polyamino acid is preferably 0.02 to 300 mg / L, particularly preferably 0.2 to 300 mg / L. The content ratio of the polyamino acid with respect to pyrogallol and / or pyrogallol derivatives is as described above.

The pH of the water for improving the rejection rate is preferably about 5 to 10 from the viewpoint of the adsorptivity of the rejection rate improving agent.

In the water for improving the rejection rate, an inorganic electrolyte such as sodium chloride (NaCl), a neutral organic substance such as isopropyl alcohol or glucose, or a low molecular polymer such as polymaleic acid may be added as a tracer. By adding the tracer, the degree of permeation of salt and glucose into the permeated water of the RO membrane can be analyzed to confirm the treatment effect.

If the water supply pressure when passing the treated water with improved rejection rate through the RO membrane is excessively high, the adsorption to the membrane gap proceeds too much, and if it is too low, the adsorption to the membrane gap does not advance. The water supply pressure when the blocking rate improving treated water is passed through the RO membrane is preferably 20 to 150%, particularly 50 to 130% of the normal operating pressure of the RO membrane. When the RO membrane is an ultra-low pressure membrane, the inlet pressure of the apparatus is preferably 0.1 to 1.0 MPa. When the RO membrane is a low pressure membrane, the inlet pressure of the apparatus is preferably 0.1 to 2.0 MPa. When the RO membrane is a seawater desalination membrane, the inlet pressure of the apparatus is preferably 0.1 to 7.0 MPa.

The linear velocity of RO membrane permeated water during the rejection improvement process is related to pressure, water temperature, membrane shape, and the like. The permeation flux during the rejection improvement process is preferably 0.1 to 5 m ³ / (m ² · d). The reason is that, like the feed water pressure, if the pressure is excessively high, the adsorption proceeds too much, and if the pressure is excessively low, the contact efficiency to the membrane gap deteriorates.

The water temperature of the rejection rate improving treated water during the rejection rate improvement treatment is preferably room temperature, for example, about 10 to 35 ° C. If the water temperature is too low, the amount of permeated water is lowered and the contact efficiency is deteriorated. If the temperature of the water for improving the rejection rate is too high, the membrane material may be denatured.

It is preferable that the time for passing the treated water for improving the rejection rate to be sufficient to allow the pyrogallol and / or pyrogallol derivative, or the pyrogallol and / or pyrogallol derivative and the polyamino acid, which are active ingredients, to sufficiently pass through the RO membrane. When the RO membrane device is not in steady operation, it is preferable to pass water for about 0.5 to 500 hours, particularly about 1 to 150 hours, when the treated water with improved rejection rate is passed. If the water passage time is excessively short, the treatment is terminated without sufficiently fixing the active ingredient, and the attached active ingredient may be peeled off.

In the present invention, a first rejection rate improving process using pyrogallol and / or a pyrogallol derivative as a first rejection rate improving agent, and a second rejection rate improving process using a polyamino acid as a second rejection rate improving agent, By performing the two-stage rejection improvement process, it is possible to obtain a better rejection improvement process effect.

In this case, the first rejection rate improving treatment is preferably performed using the first rejection rate improving treatment water containing pyrogallol and / or pyrogallol derivative and not containing polyamino acid. The second inhibition rate improving treatment may be carried out using a prevention rate improving treatment water that contains a polyamino acid and does not contain pyrogallol and / or a pyrogallol derivative. Preferably, pyrogallol and / or a pyrogallol derivative and a polyamino acid are added. It implements using the 2nd rejection rate improvement processed water containing with the above-mentioned suitable density | concentration.

As for the first rejection rate improvement treatment with the first rejection rate improvement treated water and the second rejection rate improvement treatment with the second rejection rate improvement treated water, the treatment conditions are the same as those described above. Can be adopted.

The rejection rate improvement process may be performed during the steady operation of the RO membrane device. For example, you may carry out by adding the aqueous solution prepared from the blocking rate improvement processing agent to RO water supply at the time of steady operation of a RO membrane apparatus. The time for adding the aqueous solution of the inhibition rate improving agent to the RO water supply is preferably about 0.5 to 500 hours. You may always add the aqueous solution of a blocking rate improvement processing agent to RO water supply.

When the RO membrane device is operated for a long time and membrane permeation occurs and the permeation flux is reduced, the blocking rate improvement treatment may be performed after the membrane cleaning.

As the film cleaning agent used in this case, in acid cleaning, mineral acids such as hydrochloric acid, nitric acid and sulfuric acid, and organic acids such as citric acid and oxalic acid can be mentioned. Examples of alkali cleaning include sodium hydroxide and potassium hydroxide. In general, the pH is about 2 for acid cleaning and about 12 for alkali cleaning.

[RO membrane]
In the present invention, the membrane structure of the RO membrane to be subjected to the rejection improvement processing includes polymer membranes such as asymmetric membranes and composite membranes. Examples of the RO membrane material include aromatic polyamides, aliphatic polyamides, polyamide materials such as composite materials thereof, and cellulose materials such as cellulose acetate. Among these, the RO membrane made of an aromatic polyamide material has high affinity with the blocking rate improver of the present invention, and therefore the blocking rate improver and blocking rate improving method of the present invention are particularly preferably applied. Can do.

The form of the RO membrane module is not particularly limited, and examples thereof include a tubular membrane module, a planar membrane module, a spiral membrane module, and a hollow fiber membrane module.

The present invention may be applied to a new RO membrane, or may be applied to an RO membrane having a reduced rejection rate due to use.

[Water treatment method]
The water treatment method of the present invention uses an RO membrane that has been subjected to a rejection improvement process by the rejection improvement method of the present invention. The water treatment method of the present invention is a water treatment for recovering and reusing high-concentration or low-concentration TOC-containing wastewater discharged in the electronic device manufacturing field, semiconductor manufacturing field, and other various industrial fields, or seawater / brine water. It is effectively applied to desalination, ultrapure water production from industrial and municipal water, and water treatment in other fields.

According to the present invention, not only the RO membrane desalination rate but also the boron removal rate can be improved, so the water treatment method of the present invention is effectively applied to seawater desalination processes where boron removal is important. The

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

In the following test examples, the flat membrane test apparatus shown in FIG. 1 was used as the test apparatus.
In this flat membrane test apparatus, a flat membrane cell 2 is provided at an intermediate position in the height direction of a cylindrical container 1 having a bottom and a lid, and the inside of the container is divided into a raw water chamber 1A and a permeate water chamber 1B. The container 1 is installed on the stirrer 3, and the water to be treated is supplied to the raw water chamber 1 </ b> A through the pipe 11 by the pump 4, and the stirrer 5 in the container 1 is rotated to stir the inside of the raw water chamber 1 </ b> A. The permeated water is taken out from the permeated water chamber 1B through the pipe 12, and the concentrated water is taken out from the raw water chamber 1A through the pipe 13. The concentrated water outlet pipe 13 is provided with a pressure gauge 6 and an opening / closing valve 7.

[Test Example I]
Using the following RO membrane and the flat membrane test apparatus shown in FIG. 1, the feed water (1) was passed under the following operating conditions, and then the feed water (2) was passed (the test water of the feed water (2) was passed. Water time is 4.5 hours).

RO membrane: Aromatic polyamide ultra-low pressure RO membrane "ES20" manufactured by Nitto Denko Corporation
Feed water (1) (blank): An aqueous solution in which boric acid (Kishida Chemical) was added to pure water so that the boron concentration was 5 mg / L to pH 6.5. Feed water (2) (test water): blank A 10 mg / L additive was added to the aqueous solution to adjust the pH to 6.5. Operating conditions: Permeation flux 1 m ³ / (m ² · d), recovery rate 80%, temperature 24 ° C. ± 2 ° C.

From the above water flow test, the boron removal rate, the decrease rate of the boron permeability, and the permeation flux ratio were determined by the following formulas (1) to (4).
Boron permeability = boron concentration in permeated water / boron concentration in concentrated water (1)
Boron removal rate = 1-boron permeability (2)
Reduction rate of boron permeability =
1-Boron permeability of test water / Boron permeability of blank (3)
Permeation flux ratio = blank operating pressure / test water operating pressure (4)

<Additives>
The following were used as the additive in each case.
Comparative Example I-1: Catechol (molecular weight 110, manufactured by Kishida Chemical Co., Ltd.)
Comparative Example I-2: Chlorogenic acid (molecular weight 354, manufactured by Tokyo Chemical Industry Co., Ltd.)
Example I-1: pyrogallol (molecular weight 126, manufactured by Wako Pure Chemical Industries, Ltd.)
Example I-2: Propyl gallate (molecular weight 212, manufactured by Kishida Chemical Co., Ltd.)
Example I-3: Ethyl gallate (molecular weight 198, manufactured by Tokyo Chemical Industry Co., Ltd.)
Example I-4: Methyl gallate (molecular weight 184, manufactured by Tokyo Chemical Industry Co., Ltd.)
Example I-5: Methyl 3,4,5-trimethoxybenzoate (molecular weight 226, manufactured by Wako Pure Chemical Industries, Ltd.)
Example I-6: Epigallocatechin gallate (molecular weight: 458, manufactured by Wako Pure Chemical Industries, Ltd.)

Table 1 shows the test results.
As is apparent from Table 1, in the examples, the decrease rate of the boron permeability exceeds 0.1. On the other hand, the permeation flux ratio can maintain 0.8 or more.

[Test Example II]
Using the following RO membrane and the flat membrane test apparatus shown in FIG. 1, the feed water (1) was passed under the following operating conditions, and then the feed water (2) was passed (the test water of the feed water (2) was passed. Water time is 1 hour).

RO membrane: Toray Industries aromatic polyamide seawater desalination RO membrane "TM820V"
Feed water (1) (blank): An aqueous solution in which boric acid is added to pure water so that the boron concentration is 5 mg / L, and 32 g / L NaCl (Kishida Chemical) is added to adjust the pH to 8. 2) (Test water): Aqueous solution in which 10 mg / L of added drug was added to the blank to adjust the pH to 8 Operating conditions: Operating pressure 5.5 MPa, temperature 24 ° C. ± 2 ° C.

From the water flow test, the boron removal rate and the decrease rate of the boron permeability were obtained from the formulas (1) to (3) in the same manner as in Test Example I. The permeation flux ratio was determined by the following equation (5).
Permeation flux ratio = test water permeation flux / blank permeation flux (5)

<Additives>
The following were used as the additive in each case.
Comparative Example II-1: Catechin (molecular weight 110, manufactured by Sigma-Aldrich)
Comparative Example II-2: Ploidy tannin (molecular weight of 500 or more, manufactured by Fuji Chemical Industry Co., Ltd.)
Comparative Example II-3: Mimosatanine (molecular weight of 500 or more, manufactured by Kawamura Tsusho)
Example II-1: Propyl gallate (molecular weight 212, manufactured by Kishida Chemical Co., Ltd.)

Table 2 shows the test results.
As is clear from Table 2, in the examples, the decrease rate of the boron permeability exceeds 0.2. On the other hand, the permeation flux ratio can also be maintained at 0.95 or more.

[Test Example III]
Using the following RO membrane and the flat membrane test apparatus shown in FIG. 1, the feed water (1) was passed under the following operating conditions, and then the feed water (2) was passed (the test water of the feed water (2) was passed. Water time is 2 hours).

RO membrane: Aromatic polyamide-based seawater desalination RO membrane “SWC5-MAX” manufactured by Nitto Denko Corporation
Feed water (1) (blank): An aqueous solution in which boric acid was added to pure water so that the boron concentration was 5 mg / L and 32 g / L NaCl was added to adjust the pH to 8. Feed water (2) (test Water): Aqueous solution in which 2 mg / L of added drug was added to the blank to adjust the pH to 8 Operating conditions: Operating pressure 5.5 MPa, temperature 24 ° C. ± 2 ° C.

From the above water flow test, the boron removal rate and the reduction rate of the transmittance were obtained from the formulas (1) to (3) in the same manner as in Test Example I. The permeation flux ratio was determined from Equation (5) in the same manner as in Test Example II. Further, the removal rate of NaCl and the decrease rate of transmittance were obtained by the following formulas (6) to (8).
NaCl permeability =
NaCl concentration in permeated water / NaCl concentration in concentrated water (6)
NaCl removal rate = 1-NaCl permeability (7)
Decrease rate of NaCl permeability =
1-NaCl permeability of test water / NaCl permeability of blank (8)

<Additives>
The following were used as the additive in each case.
Example III-1: Propyl gallate (molecular weight 212, manufactured by Kishida Chemical Co., Ltd.)
Example III-2: Butyl gallate (molecular weight 226, manufactured by Wako Pure Chemical Industries, Ltd.)

Table 3 shows the test results.
As can be seen from Table 3, even when 2 mg / L of propyl gallate or butyl gallate was added, the removal rate of boron and NaCl was improved, and the permeation flux decreased slightly.

[Test Example IV]
Using the following RO membrane and flat membrane test apparatus, the feed water (1) to (3) was passed under the following operating conditions. The flat membrane test apparatus used has the same basic configuration as the flat membrane test apparatus shown in FIG. 1, but unlike the flat membrane test apparatus shown in FIG. 1, the supply water flows at high speed on the membrane surface and is removed by concentration polarization. The flat membrane cell is configured so that the flow path height on the membrane surface is low so that the rate reduction can be suppressed.

<RO membrane>
The following was used as the RO membrane.
Example IV-1: Aromatic polyamide seawater desalination RO membrane “TM820V” manufactured by Toray Industries, Inc.
Example IV-2: A membrane obtained by drying an aromatic polyamide-based seawater desalination RO membrane “TM820V” manufactured by Toray Industries, Inc. at room temperature. Example IV-3: An aromatic polyamide-based seawater desalination RO membrane, manufactured by Toray Industries, Inc. Membrane whose performance was degraded by immersing TM820V in sodium hypochlorite aqueous solution with 20 mg / L of effective chlorine for 24 hours Example IV-4: Aromatic polyamide-based seawater desalination RO membrane “TM820V” manufactured by Toray Industries, Inc. Membrane with performance degraded by immersion in 100 mg / L sodium hypochlorite aqueous solution for 24 hours

<Supply water>
As the feed water, the following feed waters (1) to (3) were used.
Feed water (1) (blank): An aqueous solution in which boric acid was added to pure water so that the boron concentration was 5 mg / L and 32 g / L NaCl was added to adjust the pH to 8. Feed water (2) (test Water): 100 mg / L propyl gallate (molecular weight 212, manufactured by Kishida Chemical Co., Ltd.) added to pure water Feed water (3) (test water): 100 mg / L polylysine (molecular weight 4500) in feed water (2) To 5000, manufactured by JNC)

<Operating conditions>
The operation was performed according to the following procedures 1) to 6).
1) Feed water (1) was passed through the flat membrane test apparatus at an operating pressure of 5.5 MPa and a temperature of 25 ° C. ± 2 ° C., and the permeation flux, boron removal rate, and NaCl removal rate were measured.
2) The flat membrane test apparatus was rinsed with pure water.
3) Supply water (2) was passed through the flat membrane test apparatus for 3 hours at an operating pressure of 0.3 MPa and a temperature of 25 ° C. ± 2 ° C.
4) Feed water (3) was passed through the flat membrane test apparatus for 3 hours at an operating pressure of 0.3 MPa and a temperature of 25 ° C. ± 2 ° C.
5) The flat membrane test apparatus was rinsed with pure water.
6) Feed water (1) was passed at an operating pressure of 5.5 MPa and a temperature of 25 ° C. ± 2 ° C., and the permeation flux, boron removal rate, and NaCl removal rate were measured.

From the above water flow test, the boron removal rate, the decrease rate of the boron permeability, the NaCl removal rate, the decrease rate of the NaCl permeability, and the permeation flux ratio were obtained from the following equations.
Boron permeability = boron concentration in permeated water × 2 /
(Boron concentration in supply water + Boron concentration in concentrated water) (9)
Boron removal rate = 1-boron permeability (10)
Reduction rate of boron permeability = 1-Boron permeability under operating condition 6) / Boron permeability under operating condition 1) (11)
NaCl permeability = NaCl concentration in permeated water × 2 /
(NaCl concentration in supply water + NaCl concentration in concentrated water) (9)
NaCl removal rate = 1-NaCl permeability (10)
Decrease rate of NaCl permeability = 1−NaCl permeability under operating condition 6) / NaCl permeability under operating condition 1) (11)
Permeation flux ratio = permeation flux under operation condition 6) / permeation flux under operation condition 1)

Table 4 shows the results. As is clear from Table 4, the removal rate of boron and NaCl is not affected by batch treatment at low pressure, rather than adding a rejection rate improver to the RO feed water to improve the rejection rate in parallel with fresh water. Is improving. Overall, the removal rate is higher than that of the flat membrane test apparatus used in Test Examples I to III. Even in the deteriorated film, the boron removal rate is improved and the decrease rate of the boron permeability is large. In the case of a deteriorated membrane, the permeation flux ratio is slightly high. However, in the case of Example IV-3 and Example IV-4, the permeation flux is increased due to the deterioration, and thus the value is sufficiently large compared with the permeation flux in the case where the deterioration is not caused.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2016-183082 filed on September 20, 2016, which is incorporated by reference in its entirety.

1 container 1A raw water chamber 1B permeate water chamber 2 flat membrane cell 3 stirrer

Claims

A reverse osmosis membrane blocking rate improver comprising pyrogallol and / or a pyrogallol derivative having a molecular weight of less than 500.
The reverse osmosis membrane blocking rate improver according to claim 1, comprising at least the pyrogallol derivative, wherein the pyrogallol derivative has a molecular weight of less than 300.
The reverse osmosis membrane inhibition rate improver according to claim 1 or 2, comprising at least the pyrogallol derivative, wherein the pyrogallol derivative is a gallic acid ester.
The reverse osmosis membrane blocking rate improver according to any one of claims 1 to 3, wherein the reverse osmosis membrane is a polyamide-based reverse osmosis membrane.
The reverse osmosis membrane rejection rate improving agent according to any one of claims 1 to 4, wherein the reverse osmosis membrane is a reverse osmosis membrane for seawater desalination.
The reverse osmosis membrane rejection improvement agent according to any one of claims 1 to 5, further comprising a polyamino acid.
A reverse osmosis membrane blocking rate improving method, comprising treating the reverse osmosis membrane with the reverse osmosis membrane blocking rate improving agent according to any one of claims 1 to 6.
After the reverse osmosis membrane is treated with the reverse osmosis membrane rejection rate improver according to any one of claims 1 to 6, the reverse osmosis membrane is further treated with a second rejection rate improver containing a polyamino acid. A method for improving the rejection of a reverse osmosis membrane, characterized by comprising:
A water treatment method using a reverse osmosis membrane treated by the inhibition rate improving method according to claim 7 or 8.