KR100539332B1 - Metod of Treating Polyamide Membranes to increase Flux - Google Patents

Abstract

The present invention relates to a method for improving the salt removal rate of the reverse osmosis membrane by heating up after the reverse osmosis membrane module processing using a pressurization facility of the membrane module consisting of a pressure pump, a temperature controller, a flow vessel and a pressure vessel membrane vessel Temperature by heating the spiral wound reverse osmosis membrane module having a diameter of 1.8 to 80 inches and a length of 10 to 40 inches for 5 to 120 minutes at a raw water temperature in the range of 30 to 70 degrees and a pressure range of 150 to 1000 psi. Compared with the module before the treatment resulted in an improved salt removal rate of 0.1 ~ 1.0%.

Description

Method of improving the salt removal rate of reverse osmosis membrane {Metod of Treating Polyamide Membranes to increase Flux}

The most important indicators for evaluating the performance of reverse osmosis membranes are the removal rate and production flow rate for contaminants. The method of increasing this is to control the interfacial polymerization of the polyamide layer, which is mainly excluded from reverse osmosis membranes, by changing monomers or additives. Has been used. The present invention is to prepare a polyamide reverse osmosis membrane by the interfacial polymerization reaction, and process it into a reverse osmosis membrane module with a mesh, tricoat, and then post-treatment by pressurizing for more than a predetermined time with a heated raw water to improve the salt removal rate It is about.

In general, dissociated materials are separated from the solvent by membranes having selectivity such as microfiltration, ultrafiltration, and reverse osmosis membranes. Reverse osmosis membranes have been used to desalination with relatively low salinity and large amounts of water such as industrial water, agricultural water and household water by removing salts such as brackish water and seawater. Semi-saline desalination using reverse osmosis membrane or desalination of seawater means that the salt or ions in the aqueous solution cannot be passed through the membrane by pressing an aqueous solution containing salt or ions, and the purified water passes through the membrane and the purified water passes through the membrane. It means to be. At this time, the pressure applied should be more than the osmotic pressure of the aqueous solution, the action is the reverse of the osmotic process, and the higher the concentration of the aqueous solution, the greater the osmotic pressure, the higher the pressure applied to the feed water.

Since water such as brackish water and seawater contain a large amount of salts, reverse osmosis membranes desalination of these solutions should be excellent in salt removal ability (refer to experiments, they should be used as general water only when 97% or more of salt is removed). In order to improve the size of the pump, the resulting noise, and the low energy efficiency problem, it is necessary to reduce the process pressure.

 As another condition that a reverse osmosis membrane should have, the conventional reverse osmosis membrane has a small amount of purified water that actually passes through the reverse osmosis membrane due to the characteristic of filtering out a large amount of salt. Even at a relatively low pressure, a large amount of purified water passes through the membrane, i.e., the characteristics of the high permeate flow rate are indispensable.

Known immediately, passed through the flow rate in the case of sea water desalination at 800 psi 10 gfd be at least (1 ft ² per 24 hours gallon units, gal / ft ² o day of the quantities that can be produced for a) and at 225 psi in the desalination conditions of the rider It should be at least 15 gfd and possibly 22 gfd. Of course, in some cases, for example, when a large flow rate is important, a low salt removal rate may be targeted.

The composite membrane of the reverse osmosis membrane consists of a porous support layer and a polyamide composite thin film on the support layer. Typical polyamide membranes can be obtained by interfacial polymerization of polyfunctional amines and polyfunctional acyl halides.

One example of the aforementioned reverse osmosis composite membrane is U. S. Patent No. filed in Cadette. It was registered in July 1981 at 4,277,34. This patent relates to an aromatic polyamide thin film obtained by interfacial polymerization of an aromatic polyfunctional amine containing two primary amine substituents and an aromatic acyl halide having three or more acyl halide functional groups. In detail, the following process is followed. Meta-phenylenediamine is coated on the microporous polysulfone support. The excess metaphenyl diamine solution is removed on the support layer and then reacted with trimesoyl chloride (TMC) dissolved in Freon (trichlorotrifluoro ethane, Freon TF, DuPont) on this coated support layer. The contact time is about 10 seconds and the actual reaction time takes place within 1 second. At that time, the performance was very good. The polysulfone / polyamide composite membrane is dried in air. Although Caddo's membrane exhibits excellent flow rate and excellent salt removal rate, various improvements have been made to increase the flow rate and improve the salt removal rate of the polyamide reverse osmosis composite membrane. On the other hand, efforts have been made to improve the resistance of the membrane to chemical denaturation. Many of these approaches have involved the addition of various types of additives to solutions in interfacial polymerization.

Another example is Tomashke's U.S. Patent No. 4,872,984 (registered in October 1989) is an aqueous solution consisting of (a) an aromatic polyamine reactant essentially of a monomer having at least two or more amine functional groups and (2) an amine salt of the monomer to form a liquid layer on the microporous support layer. Applying a microporous support layer, (b) the compound capable of reacting with the amine, on average, has at least about 2.2 acyl halides per molecule of the reactant, and reacts with the aromatic amine of the monomer essentially consisting of a polyfunctional acyl halide or mixtures thereof Water permeable, characterized in that it comprises the steps of contacting the liquid layer with an organic solvent solution of the reactant and (c) drying the product of step (B) to form the permeable osmotic membrane. Invented the osmosis membrane.

US Patent No. of Chau 4,983,291 (registered Jan. 1993) also introduced membranes for making polymerization reactants on or in a porous support layer. According to Chow's patent, a membrane is made on a porous support layer in contact with an aqueous polyamine solution comprising a polar aprotic solvent, a polyhydric compound, and an acid acceptor that do not react with the amine. After applying the support layer, the excess nack is removed, and the organic solution in which the polyacyl halide is dissolved is contacted for a sufficient time for polymerization to occur in the support layer yarn. The composite membrane thus obtained was treated with hydroxy polycarboxylic acid, polyamino alkylene polycarboxylic acid, sulfuric acid, amine salt of acid, amino acid, acid inorganic acid of multimer, and the like, followed by drying the membrane.

Hirose US Patent No. 5,614,099 (registered Jan. 1993) is characterized by a reverse osmosis composite membrane in which the average roughness of the polyamide surface layer is at least 55 nm or more. The polyamide type surface layer is a reactant of a compound having an amino functional group and a polyfunctional acid halide having an acyl halide functional group. Was done. For example, in order to form a solution layer on a support layer, a polymer thin film is coated with a solution of m-phenylenediamine and then contacted with a trimesic chloride organic solution to dry the film obtained by high temperature hot air. To form a polymer thin film on the support layer. The polyamide surface layer can be treated with a quaternary amine salt and this crosslinked organic polymer layer can be applied to have a cationic charge.

   In addition to the above patents for controlling the concentration and composition of monomers and additives for forming polyamide layers, methods for controlling physical properties through post-treatment of membranes have also been studied.

In US Patent No.5755964, W. E. Mickols and others invented a method of increasing flux by post-treatment of reverse osmosis membranes or nano membranes with polyamide separation layers with Ammonia or Alkyl Amine. By the above method, Flux and Rejection of the reverse osmosis membrane or the nanomembrane can be controlled, and the reverse osmosis membrane can be changed to the nanomembrane. U.S. Patent No. In 628085 3, polyalkylene oxide was grafted onto polyamide membrane to reduce rejection to NF level and to improve fouling resistance.

The object of the present invention is not a method of adjusting the concentration or type of monomers or the concentration or type of additives in the interfacial polymerization step for making polyamide bonds, which are mainly mentioned in the conventional patent, but the temperature raising treatment after module processing. It is to provide a method for improving the removal rate of the reverse osmosis membrane through.

In order to achieve the above object, in the present invention, as shown in FIG. 1, the diameter of the membrane module is 1.8 inches to 80 inches, using a pressurization device of a membrane module including a pressure pump, a temperature controller, a flow rate and a pressure regulator membrane vessel, The spiral wound reverse osmosis membrane module, between 10 inches and 40 inches in length, is heated to a raw water temperature in the range of 30-70 degrees and a temperature range of 150-1000 psi for 5-240 minutes.

The manufacturing method of the membrane module for the present invention will be described with reference to FIG. First, a polyamide membrane is formed by preparing a support layer coated with polysulfone on a polyester nonwoven fabric and then forming a polyamide membrane interfacially polymerized with a polyfunctional amine and an acyl halide thereon. A polypropylene mesh is placed between two polyamide separation membranes, and a tricot of polyester material with epoxy is placed on one of the polyamide separation membranes, followed by rolling bonding them to prepare a reverse osmosis membrane module.

Next, an aqueous sodium chloride solution having a concentration of 32,000 ppm in the raw water storage tank 1 passes through the high pressure pump 2 and becomes an aqueous solution having a predetermined pressure (in one embodiment, 800 psi) or more, and the high pressure aqueous solution is a temperature control tank (3). After passing through a predetermined temperature (30-70 degrees) is adjusted to a target pressure of 800psi again by the pressure regulator 4 and then passed through the reverse osmosis membrane module 5 produced as described above. By repeating this process for a certain time, the resulting reverse osmosis membrane module is finally obtained.

Membrane module prepared by the present invention was shown to result in improved salt removal rate of 0.1 ~ 1.0% compared to the module before the temperature increase treatment.

In the present invention, the salt removal rate and the production flow rate were measured as follows. After pressing 2,000 ppm aqueous NaCl solution at 225 psi or 32,000 ppm NaCl aqueous solution at 800 psi and sending the membrane to the membrane module, the resulting water was measured with a conductivity meter and a flow meter to measure salt removal rate and flow rate. Here, the recovery rate and the salt removal rate were calculated by the following equation.

Recovery rate = (production flow rate / raw water flow rate) * 100

Salt removal rate = ((Salt concentration of raw water-salt concentration of produced water) / salt concentration of raw water) * 100

This invention is demonstrated in detail based on an Example and a comparative example.

[Example 1 and Comparative Example 1]

A spiral wound polyamide reverse osmosis membrane module 4 inches in diameter and 40 inches in length is mounted in a temperature raising system as shown in FIG. 1, and then pressurized at 40 degrees to 800 psi for 30 minutes. 32,000 ppm sodium chloride solution was passed through the membrane module at a temperature of 25 ° C. and 800 psi pressure. The salt removal rates before and after the temperature increase were measured and recorded in Table 1.

Bakyo Example 1 measured the salt removal rate by passing 32,000ppm aqueous sodium chloride solution through the membrane module at 25 ° C and 800psi pressure in a module treated with raw water at 25 ° C for 30 minutes under the same conditions as in Example 1. It was.

Before temperature increase After heating Example 1 99.3 99.6 Comparative Example 1 99.3 99.3

Example 2-5

The same manner as in Example 1 is carried out to Examples 2-5. However, unlike Example 1, the temperature was changed as shown in Table 2.

Processing temperature Before temperature increase After heating Example 2 30 99.3 99.3 Example 3 35 99.2 99.4 Example 4 45 99.3 99.6 Example 5 50 99.3 99.5

[Example 6-8 and Comparative Example 2-3]

Example 6-8 is carried out in the same manner as in Example 1. However, the treatment time was performed as shown in Table 3, unlike in Example 1. Comparative Example 2-3 was carried out in the same manner, but the treatment time was within 30 minutes.

Processing time Before temperature increase After heating Comparative Example 2 10 99.3 99.3 Comparative Example 3 20 99.3 99.4 Example 6 60 99.3 99.6 Example 7 120 99.3 99.6 Example 8 240 99.3 99.5

Example 9-11

The same manner as in Example 1 is carried out to Examples 9-11. However, the pressure was changed as shown in Table 4 unlike Example 1.

pressure Before temperature increase After heating Example 9 225 99.3 99.5 Example 10 500 99.3 99.6 Example 11 800 99.3 99.6

   As confirmed in the above Examples and Comparative Examples, the reverse osmosis membrane subjected to the elevated temperature according to the present invention was evaluated to have an excellent salt removal rate compared to the conventional reverse osmosis membrane not subjected to the elevated temperature treatment.

   1 is a process of temperature increase treatment of the reverse osmosis membrane

<Description of the symbols for the main parts of the drawings>

      One ; Raw water storage tank

      2 ; High pressure pump

      3; Thermostatic tank

      4 ; Pressure regulator

      5; Membrane module

Claims (4)

A method of improving the salt removal rate of a reverse osmosis membrane, characterized by heating the spiral wound reverse osmosis membrane module consisting of a polyamide membrane, a mesh, and a tricot by passing raw water in a temperature range of 30 to 50 degrees. delete The method of claim 1, wherein the reverse osmosis membrane module is heated for 20 minutes to 120 minutes. According to claim 1, wherein the pressing force of the raw water is characterized in that 225 ~ 800 psi, the method for improving the salt removal rate of the reverse osmosis membrane.