KR20120048378A - Measuring method of fouling of membrane containing fluorescent nano particle - Google Patents

Abstract

PURPOSE: A method for measuring the contaminated degree of a separating membrane is provided to monitor the variation of fluorescence peak intensity on the surface of a separating membrane carrying fluorescence nano particles. CONSTITUTION: A method for measuring the contaminated degree of a separating membrane carrying fluorescence nano particles includes the following: a separating membrane carrying fluorescence nano particles is prepared; contaminants are generated on the surface of the separating membrane by lapse of time; and the contaminated degree of the surface of the separating membrane is measured by monitoring the variation of fluorescence peak intensity on the surface of the separating membrane based on a spectrum analyzer. The fluorescence particles are quantum dots with the center composed of CdSe, CdTe, or CdS or fluorescent brightener. The separating membrane is polysulfone, polyvinylidenefluoride, polyetherimide, polyethersulfone, or polypropylene.

Description

Measuring method of pollution degree of membrane carrying fluorescent nanoparticles {Measuring method of fouling of membrane containing fluorescent nano particle}

The present invention relates to a method for measuring the degree of contamination of a separator, and more particularly, to a method for measuring the degree of contamination of a separator in real time by monitoring the change in fluorescence peak intensity on the surface of the membrane carrying fluorescent nanoparticles.

At present, the water treatment process for treating water mainly uses a membrane process due to its high efficiency and productivity, thereby stably producing high quality water. In the case of membrane processes, however, the need for physical / chemical cleaning due to membrane fouling and the need for periodic replacement are pointed out as technical and economic limitations for the widespread application of water treatment methods through such membranes. Membrane contamination is therefore the most important factor to be addressed in order to achieve technical and economic efficiency in water treatment processes.

Much of the contamination of membranes over the last few decades has used indirect measurements using flux or transmembrane pressure measurements. However, these methods are not suitable for the operation of the process because they degrade performance due to membrane contamination and then indirectly predict the extent of membrane contamination. In particular, recently, process researches to collect and control information through the ubiquitous system for efficient operation and safety of the process, that is, accurate operation conditions and information on control elements thereof through real-time bidirectional communication have been conducted. It is done. Therefore, it is required to develop a monitoring analysis method through the real-time accurate detection and measurement of the degree of membrane contamination. This requires a new technology that can detect and observe a cake layer formed on the surface of the membrane without damaging the membrane and measuring and analyzing the contamination of the membrane in real time.

Several existing studies have used laser triangulometry, optical laser sensors, ultrasonic time-domain reflectometry, and electrical impedance spectroscopy to monitor and visualize film surfaces. Although electrical impedence spectroscopy or optical microscope are used, these methods are merely an experimental method for the study of membrane fouling, which is inadequate to be applied to a water treatment process using a real membrane.

Therefore, the present inventors have researched and tried to measure the degree of contamination on the surface of the membrane more easily and in real time. As a result, when preparing a separation membrane containing fluorescence nanoparticles and using it in a water treatment process, By discovering that the degree of contamination can be easily measured in real time with only a reduction measurement, the present invention has been completed.

Accordingly, an object of the present invention is to provide a method for measuring in real time the degree of contamination of a membrane carrying fluorescent nanoparticles.

The present invention comprises the steps of preparing a separator supporting the fluorescent nanoparticles; Forming contaminants on the surface of the separator over time; And measuring the degree of contamination by monitoring a change in fluorescence peak intensity on the surface of the separator through a spectroscopic analyzer.

When using the membrane contamination measurement method of the present invention it is possible to detect, measure and analyze the degree of fouling (fouling) of the membrane surface by the fluorescent signal. Therefore, it is expected to be useful for the measurement of membrane contamination in the future water treatment process because it is possible to collect accurate information such as real-time operating condition control related to pressure and permeability of water treatment separation process using membrane and diagnosing cleaning cycle and replacement time of membrane. .

1 is a photograph showing the surface structure of a separator including a fluorescent nanoparticles prepared according to the present invention.
2 is a graph showing the intensity of a fluorescence signal of a membrane carrying a fluorescent substance upon pure transmission.
Figure 3 is a graph showing the fluorescence signal intensity of the membrane loaded with a fluorescent material when the feed water containing 1,000 ppm PEG 100K as a pollutant.
FIG. 4 is a graph showing a comparison of changes in fluorescence signal intensity and water permeability due to membrane fouling according to water treatment operation time.

Hereinafter, the present invention will be described in detail.

The present invention comprises the steps of preparing a separator supporting the fluorescent nanoparticles; Forming a contaminant layer on the surface of the separator according to an operation time; And measuring a degree of contamination by monitoring a change in fluorescence peak intensity on the surface of the separator through a spectroscopic analyzer.

First, the first step is to prepare a separator supporting the fluorescent nanoparticles. In this case, as the fluorescent nanoparticles (FNP), a quantum dot (QD) or a fluorescent brightener may be used. The quantum dots may be composed of, for example, a shell composed of a core having a size of about 2 to 10 nm and mainly zinc sulfide (ZnS), but are not limited thereto. It is preferable to use CdSe, CdTe, CdS, etc. as the center body, and to have a polymer coating on the outer surface of the shell in order to disperse it in an aqueous solution, it is preferable to use one having a nano size of 10 to 15 nm. The quantum dot generates strong fluorescence in a narrow wavelength band, the smaller the particles of the quantum dot is characterized in that the shorter wavelength of light, the larger the particle is characterized in that the longer wavelength of light is generated. In addition, as the optical brightener, for example, powders and liquid forms of OB, FP, KCB, etc. may be used (manufactured by THREETEX ^™ ), but is not limited thereto. In the case of using the fluorescent nanoparticles selected in the present invention, the fluorescence signal analysis is easy even with a small amount of support, and is most suitable because it has a minimal effect on the shape and performance of the film.

In the present invention, the separator may be used without limitation in the art, preferably, PSf (polysufone), PVDF (polyvinylidenefluoride), PEI (polyetherimide), PES (polyethersulfone), PP (polypropylene) water treatment membrane material It is preferable to prepare a separator in which fluorescent nanoparticles are loaded using a polymer used as a polymer having similar performances, such as permeability and solute rejection rate, to a conventional water treatment separator. This is because membrane fouling occurring on the surface and pores of the membrane is different depending on the permeation characteristics such as the permeability and the solute rejection rate of the membrane. The separator may be prepared using a known method.

In the present invention, the content of the fluorescent nanoparticles included in the separator is not limited, but preferably the use of the fluorescent nanoparticles in the range of 0.01 to 20 parts by weight based on 100 parts by weight of the separator may be considered in consideration of the permeation characteristics of the separator. It is preferable because it is a content suitable for minimizing and detecting contaminant layers, and more preferably in the range of 0.5 to 10 parts by weight.

The method for preparing a separator including the fluorescent nanoparticles may be prepared using a known method. For example, a coating solution may be added by adding a predetermined amount of PVDF as a separator, NMP as a solvent, PEG as a pore forming agent, and fluorescent nanoparticles. After the manufacturing process, the bubble is removed and then coated on a non-woven fabric using a casting knife to a certain thickness, and is prepared by a phase inversion method, which is directly immersed in a precipitation tank containing non-solvent water. Then, it may be prepared by removing the solvent and the pore-forming agent remaining in the separator through the hot water treatment. The membrane containing the fluorescent nanoparticles prepared as described above has a permeability similar to that of conventional water treatment membranes such as microfiltration membranes and ultrafiltration membranes, and may be usefully used as a membrane for measuring the degree of contamination of the membrane module for water treatment.

The second step of the present invention is a step in which contaminants are formed in the pores and the surface of the separator according to the operating time of the water treatment membrane, and membrane contamination occurs. More specifically, a contaminant layer such as a gel layer or a cake layer is continuously stacked on the surface of the separator according to the operation time, and thus the fluorescence of the fluorescent nanoparticles supported on the membrane surface is It is a step that gradually decreases. This is a phenomenon caused by membrane contamination, such as an increase in operating pressure when maintaining a certain transmittance or a decrease in transmittance when operating at a certain operating pressure, and exhibits the same result as a decrease in fluorescence although there is a time variation.

The final step is to measure the degree of contamination by monitoring the change in fluorescence peak intensity on the surface of the separator through a spectroscopic analyzer.

In order to monitor the change in the fluorescence peak intensity, a spectroscopic analyzer is used, and UV and visible light having a wavelength range of 350 nm or more is preferably used as a light source. Deuterium lamps (UV) and tungsten halogen lamps ( VIS) is recommended. The spectrometer consists of a lamp and a spectrometer, and the lamp and the spectrometer are connected to an optical fiber to a probe tip, and the UV-Vis ray from a light source lamp located at the edge of the probe end. Is irradiated and the signal absorbed / transmitted and reflected from the membrane surface is configured to be collected by a spectroscopic detector located at the center of the probe tip.

The method of measuring the contamination level of the membrane carrying the fluorescent nanoparticles using the spectroscopic analyzer is applicable to a general water treatment process, and also has the advantage of measuring the degree of contamination in real time.

In addition, the pollution degree measuring method of the present invention may use a flat membrane-type permeation cell instead of the actual water treatment process. The structure of the flat-film transmission cell is largely composed of a supply part and a transmission part. The supply part consists of a lid of the cell, a feed port into which the feed water is introduced into the cell, a discharge port that is permeated through some membranes of the excessively introduced feed water and is discharged from the rest, and a probe. The permeation part is composed of a discharge port for fixing the separation membrane to the body portion of the permeation cell and at the same time discharge the permeate material transmitted through the separation membrane out of the cell. That is, the upper end of the separation membrane (side of the membrane) is positioned in the supply portion of the permeation cell, and the lower end of the separation membrane (the support side of the separation membrane) is positioned in the permeation portion. In addition, it is designed to maintain a constant distance from the surface of the probe and the separator mounted on the supply. After fixing the separation membrane in which the fluorescent nanoparticles are loaded in the permeable cell, the feed water containing contaminants in any concentration is supplied at a constant flow rate and pressure through the supply port of the cell. At the same time, the permeation rate is measured at the permeate side and the signals absorbed / transmitted and reflected from the membrane surface are collected by the spectroscopic detector located at the center of the probe and monitored in real time. As described above, changes in the fluorescence signal collected in real time along with changes in water permeability are measured.

As a result, when using the method of measuring the contamination level of the membrane of the present invention, it is possible to detect a cake layer formed on the surface of the membrane for water treatment with an accuracy within 5% of an error range, and the thickness detection range of the contamination layer is also 100 nm. It is characterized by the sophisticated detection possible below. In addition, unlike the conventional method, it is possible to observe in real time.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the following examples are intended to illustrate the invention and are not intended to limit the invention.

< Manufacturing example  1> fluorescent nanoparticles Supported PSf - FP  Preparation of Membrane

A membrane carrying fluorescent nanoparticles was prepared by the following process.

A coating solution was prepared by stirring at a temperature of 60 ° C. for 24 hours at a composition of 15 wt% of PSf, 5 wt% of PEG (MW 600) as a pore forming agent, 1.5 wt% of FP as a fluorescent nanoparticle, and 78.5 wt% of solvent NMP. . The prepared coating solution was stored at room temperature without stirring for 24 hours to remove bubbles. The coating solution prepared in this way is coated on a polyester (PS) nonwoven fabric using an applicator having a predetermined thickness, and then immersed in a precipitation tank containing non-solvent water, that is, a phase inversion method. After the preparation, the separator was prepared by removing solvent and pore-forming agent remaining in the separator by hot water treatment using 80 ° C. hot water. This is summarized in Table 1 below.

< Manufacturing example  2> fluorescent nanoparticles Supported PSf - KCB  Preparation of Membrane

Except that KCB was used as the fluorescent nanoparticles, a separator was prepared in the same manner as in Preparation Example 1. This is summarized in Table 1 below.

< Manufacturing example  3> fluorescent nanoparticles Supported PSf - OB  Preparation of Membrane

Except that OB was used as the fluorescent nanoparticles, a separator was prepared in the same manner as in Preparation Example 1. This is summarized in Table 1 below.

< Manufacturing example  4> fluorescent nanoparticles Supported PVDF - FP  Preparation of Membrane

A separator was prepared in the same manner as in Preparation Example 1, except that PVDF was used as the separator material polymer. This is summarized in Table 1 below.

< Manufacturing example  5> fluorescent nanoparticles Supported PVDF - KCB  Preparation of Membrane

A separation membrane was manufactured in the same manner as in Preparation Example 4, except that KCB was used as the fluorescent nanoparticles. This is summarized in Table 1 below.

< Manufacturing example  6> fluorescent nanoparticles Supported PVDF - OB  Preparation of Membrane

A separation membrane was manufactured in the same manner as in Preparation Example 4, except that OB was used as the fluorescent nanoparticle. This is summarized in Table 1 below.

division Furtherance Composition (weight ratio)
(Fluorescent Nanoparticles: Separator) Preparation Example 1 PSf-FP 1: 10 Production Example 2 PSf-KCB 1: 10 Production Example 3 PSf-OB 1: 10 Preparation Example 4 PVDF-FP 1: 10 Preparation Example 5 PVDF-KCB 1: 10 Preparation Example 6 PVDF-OB 1: 10

< Experimental Example  1> Fluorescence measurement experiment of separator

The fluorescence signal was measured by the fluorescence analysis method for each separator while performing permeation experiments on the conditions of supplying ultrapure water at a pressure of 1 atm and 1 L / min to the separator prepared in Preparation Example.

For monitoring, UV and visible light with a wavelength of 350 nm or more were used as a light source. Deuterium lamps (UV) and tungsten halogen lamps (VIS) were used for this purpose. The lamp of the spectrometer was used as DH lamp 2000 of KMAC, and the CCD array detector (2048pixel) of Ocean optics was used as the spectrometer.

The measurement results are shown in FIG. 3. As a result, the PSf and the PVDF were detected in a high fluorescence signal in the membrane carrying the fluorescent material as compared to the membrane not carrying the fluorescent material. In the wavelength range of 450 to 550 nm, regardless of the presence of phosphor, the difference in signal intensity was observed for each phosphor, especially in PVDF separators.

< Experimental Example  2> Fluorescence signal change due to membrane contamination

Using the same method as Experimental Example 1, using a feed water containing PEG 100K 1,000ppm as a contaminant in ultrapure water was examined for the change in fluorescence signal intensity according to the water transmission to the PSf membrane. As a result, after 1.5 hours, the fluorescent signal rapidly decreased from T ₁ to T ₂ .

The measurement results are shown in FIG. 3, and as can be seen from the measurement results, in the case of PSf and PSf_PEG100K which do not carry fluorescent nanoparticles, the intensity of the fluorescence signal decreases from 1000 to 300. In the case of PSf_OB and PSf_OB_PEG100K loaded with particles, the result is reduced from 3000 to 900, and when the measurement method of the present invention is used to measure the degree of contamination of the separation membrane for water treatment, the degree of contamination is precisely reduced by using a decrease in fluorescence intensity. It was found that it can be measured.

Claims (5)

Preparing a separator supporting the fluorescent nanoparticles;
Forming contaminants on the surface of the separator over time; And
Measuring the degree of contamination by monitoring the change in fluorescence peak intensity on the surface of the separator using a spectroscopic analyzer
Pollution degree measuring method of the separation membrane comprising a.
The method of claim 1, wherein the fluorescent particles are quantum dots consisting of CdSe, CdTe or CdS the core; Or a degree of contamination of the separation membrane, characterized in that the fluorescent brightener.
The method of claim 1, wherein the separation membrane is PSf, PVDF, PEI, PES, or PP.
The method of measuring contamination of the separator according to any one of claims 1 to 3, wherein the separator is a separator for water treatment.
The method of measuring the contamination level of the separator according to any one of claims 1 to 3, wherein the contamination layer measurement of the separator is performed in real time.

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