KR20200092793A - Metal-organic framework for adsorption of organic contaminant material and method of making the same - Google Patents

Abstract

The present invention relates to a method for fabricating a metal-organic framework and a method for adsorbing organic pollutants by using the same. The method comprises the steps of (A1) preparing a solution by dissolving a metal precursor and an organic ligand in a solvent; and (A2) irradiating ultrasonic waves to the prepared solution. According to the present invention, it is expected that the synthesis time of the metal-organic skeleton can be reduced compared to a fabrication method using a general oven, and organic pollutants can be effectively removed from water contaminated with organic pollutants and easily separated in water.

Description

Metal-organic framework for adsorption of organic contaminants and method of making the same{Metal-organic framework for adsorption of organic contaminant material and method of making the same}

The present invention relates to a method for manufacturing a metal-organic frame work (MOF) for the removal of organic pollutants and to the MOF produced through the method. The method can be utilized as an organic pollutant adsorbent capable of efficiently removing organic pollutants by reducing the synthesis time by applying the method of ultrasonic irradiation.

Recently, as environmental damage continues, environmentally friendly methods (LOHAS, Lifestyles of Health and Sustainability) and environmental pollution prevention technologies have attracted attention, and technologies for adsorbing or detecting various environmental pollutants have been actively studied. In particular, research on the removal of organic pollutants is an area that is actively being researched as interest in environmental pollution and human welfare increases.

In general, organic pollutants in water are generated from industrial wastewater and industrial water, and discharged organic pollutants act as a fatal danger to humans and ecosystems through various channels. Many of the organic pollutants in water are substances called phenolic compounds, and typical examples include so-called'endocrine disruptors' called'environment hormones', diethylhexyl phthalate (DEHP) and bisphenol A. (bisphenol A, BPA). These organic pollutants inhibit or interfere with the essential chemical action of cells or biomolecules present in the body, and pose a fatal risk to the biochemical functions of biological species, such as damage to nerves and organs or cancer. It is known to bring (Guidelines for drinking water quality, World Health Organization).

Existing processes for removing such organic pollutants include adsorption method, electrochemical treatment, microbial degradation, membrane filtration, etc. It is widely used due to its advantages such as convenience, economy, and efficiency. Looking at the conditions required as an adsorbent used in the adsorption method, it should basically have a high specific surface area and a porous structure for high adsorption performance and fast adsorption speed, and should be easily separated in water in a batch-type water treatment process and pressure loss in a column-type water treatment process. It should not be too small, because it has to be reduced. In order to satisfy these conditions, it can be said that a porous material having a size of about 1 µm or more and having a high specific surface area is more suitable than simply using nanoparticles having a high specific surface area as an adsorbent.

A metal-organic framework (MOF) is a substance that forms a framework of a certain structure by connecting organic ions or clusters of metal ions with a cluster of metal ions or metal ions. It is a porous material present. Since this material can be synthesized only by reaction of a metal ion and an organic ligand, there is an advantage that the synthesis process is simple compared to a general porous material, but there is a problem that it takes a long time to synthesize.

Recently, studies on adsorption and removal of organic pollutants present in water using some metal-organic frameworks have been recently conducted. During the synthesis process, metal ions (copper, chromium ions, etc.) harmful to the human body are used or hydrofluoric acid is used. In most cases, it is added as mineralizers, and its synthesis time is long. (Journal of Materials Chemistry A 2013, 1, 8534-8537.)

In addition, the use of substances harmful to the human body during the synthesis process, such as the use of mineralizers, conflicts with the reason for developing an adsorbent for water purification, and the longer the synthesis time, the greater the energy consumption and the lower the economical efficiency. Research is needed.

Iron is an essential element for the human body and is the most abundant metal in the universe and can be used to develop eco-friendly and economical metal-organic framework-based adsorbents. However, because synthesis takes a long time in general, research on the synthesis of iron-based metal-organic skeletal bodies using ultrasonic waves is ongoing, and several cases have been reported. However, in the reported case, MOF was synthesized using ultrasound, but its application to water treatment has not been studied. In addition, the synthetic MOFs reported to date are up to several hundred nm in size and are not suitable for water treatment (Microporous and Mesoporous Materials 2012, 162, 36~43.).

An object of the present invention is to provide a metal-organic framework-based adsorbent capable of efficiently removing harmful substances in water and a method for manufacturing the same. The manufacturing method is characterized in that it is in accordance with the ultrasonic chemical synthesis method and has low human toxicity. In addition, the adsorbent is characterized in that it has the appropriate size of the micron level so that the adsorption performance of organic pollutants in water can be maximized and the adsorbent can be easily separated from the polluted water.

The first aspect of the present invention relates to a method of manufacturing an iron-based metal-organic framework (Fe-MOF), wherein the manufacturing method includes (S10) a metal precursor and an organic ligand ( preparing a precursor solution by dissolving an organic ligand) in a solvent; And (S20) irradiating ultrasonic waves to the precursor solution.

In the second aspect of the present invention, in the first aspect, the concentration of metal (iron) ions in the precursor solution is 0.0001 mol/liter to 0.3 mol/liter.

In a third aspect of the present invention, in the first or second aspect, the organic ligand includes an organic acid.

In addition, the present invention relates to an adsorbent for removing pollutants from water, wherein the adsorbent for removing pollutants from water is an iron-based metal-organic framework obtained by a manufacturing method according to at least one of the first to fourth aspects ( Fe metal-organic framework, Fe-MOF), wherein the Fe-MOF has a MIL-53 crystal structure and has a horizontal and vertical length of 1 µm or more.

The Fe-MOF manufacturing method according to the present invention can be synthesized simply and economically through ultrasonic irradiation, and can reduce the synthesis time. In addition, the method does not use substances harmful to the human body, so the manufacturing process is environmentally friendly.

Fe-MOF prepared by the method according to the present invention has a size on the order of several micrometers, and can effectively adsorb organic pollutants by using a large number of pores present in the skeleton. In addition, the batch adsorption process for removing organic contaminants in water has the advantage of being easy to separate in water, and in the column adsorption process, it has the advantage of less pressure loss, thereby improving the economic efficiency of the adsorption process.

1A is a schematic diagram showing a method of manufacturing Fe-MOF according to an embodiment of the present invention.
Figure 1b is a schematic view showing a method for confirming the adsorption performance of organic pollutants in water using Fe-MOF obtained by the method according to the present invention.
Figure 2 shows the results of FT-IR analysis for Fe-MOF obtained in Example 1 and Example 2.
Figure 3 shows the results of confirming the crystal structure using X-ray diffraction analysis for Fe-MOF obtained in Example 1 and Example 2.
Figure 4 shows the results of the field emission scanning electron microscope analysis to confirm the macrostructure and morphology (morphology) of Fe-MOF obtained in Example 1 and Example 2.
Figure 5 shows the results of measuring the adsorption performance of the organic pollutants of Fe-MOF obtained in Example 1 and Example 2.
6 shows the results of measuring the adsorption performance according to various adsorption time and the concentration of various pollutants using the Fe-MOF obtained in Example 1.
7 is a Fe-MOF prepared according to the production method of the present invention It shows schematically the crystal structure.
8 is a schematic view showing the reaction between Fe-MOF and contaminants according to the present invention.

The objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments associated with the accompanying drawings. In addition, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. In addition, in describing the present invention, detailed descriptions of related well-known technologies that may unnecessarily obscure the subject matter of the present invention will be omitted.

The present inventors have conceived that the size of the iron-based metal-organic framework (Fe-MOF) needs to grow to several tens to several tens of micro levels in consideration of industrial and technical applications of the adsorbent for water treatment for removing organic pollutants in water. Considering the basic material generation-growth mechanism, in order to increase the size of the material, it is desirable to suppress nucleation to induce a small number of nuclei to grow, and for this, it is necessary to lower the concentration of the reactant or lower the density of the irradiated energy. Do. Accordingly, the present inventors could lower the concentration of the reactant or increase the amount of the reaction solution irradiated with ultrasonic waves to lower the irradiation density of ultrasonic energy and to grow the size of Fe-MOF therefrom.

Accordingly, the present invention relates to a method for manufacturing an iron-based metal organic framework (Fe-MOF) and an iron-based metal organic framework (Fe-MOF) prepared therefrom.

Figure 1a is a schematic diagram showing a method for producing an iron-based metal-organic framework (Fe-MOF) according to the present invention. The Fe-MOF obtained according to the production method of the present invention has a micro-level diameter. On the other hand, Figure 1b is a schematic view showing the flow of the organic pollutant adsorption experiment in water using Fe-MOF obtained by the method according to the present invention.

Next, a method of manufacturing an iron-based metal organic framework (Fe-MOF) will be described. In one embodiment of the present invention, the method comprises preparing a precursor solution by introducing a metal precursor and an organic ligand into a solvent (S10); And irradiating the precursor solution with ultrasonic waves (S20).

In particular, the manufacturing method of the present invention does not need to add hydrofluoric acid or nitric acid, and since Fe-MOF is produced without adjusting the pH, it is possible to provide a safe working environment for workers compared to the prior art. Hereinafter, each step will be described in more detail.

First, a precursor solution is prepared by introducing a metal precursor and an organic ligand into a solvent (S10). The precursor solution may be prepared by dissolving an iron precursor in the form of a metal salt, a metal chloride, nitride, bromide, sulfide, or the like in a solvent. Non-limiting examples of the iron precursor include, but are not limited to, iron(III) nitratenonahydrate, iron(III) bromide, iron(III) sulfate, and the like. In one embodiment of the invention, the precursor solution may be prepared by introducing FeCl ₃ .6H ₂ O into a solvent.

In one embodiment of the present invention, the concentration of metal (iron) ions in the precursor solution may be included in the range of 0.0001 mol/liter to 0.3 mol/liter, preferably 0.02 mol/liter to 0.2 mol/liter.

In one embodiment of the present invention, the organic ligand may include an organic acid. The organic acid is not particularly limited, for example, fumaric acid, terephthalic acid, Naphthalenedicarboxylic acid, benzenetricarboxylic acid, naphthalenetricarboxylic acid, pyridinedicarboxylic acid, bipyridyldicarboxylic acid, formic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, hexanedioic acid, and heptanediic acid. have. In one embodiment of the present invention, terephthalic acid may be used as the organic acid.

In this way, a metal precursor and an organic ligand are dissolved in a solvent in this step to prepare a precursor solution . In an embodiment of the present invention, the metal precursor and the organic acid may be mixed at a ratio of 0.1 mol to 10 organic acids relative to 1 mol of the metal precursor, and specific ratios may be appropriately adjusted according to the type of the metal precursor and the organic acid. For example, in one embodiment of the present invention, the organic acid may be added in excess of the same mole number or more than the metal ion charged in the solution. That is, it may be added in the same amount as the concentration (molar number) of the iron ions added, or may be added in an excessive amount. For example, terephthalic acid may be added in an amount of 320 g or 2 mol with respect to 1 mol of FeCl ₃ .6H ₂ O. In one embodiment of the present invention, the solvent includes water, alcohol having 1 to 10 carbons. , Dimethylformamide, pyridine, dimethylsulfoxide, methyl pyrrolidone, dimethylacetamide, chlorobenzene, acetonitrile, chloroform, tetrahydrofuran and acetone, and the like, or a mixture of two or more may be used, preferably Dimethyl formamide can be used. In one specific embodiment of the present invention, the precursor solution may be introduced in a stirring process. The stirring may be performed at room temperature, or may be performed while maintaining the temperature of the precursor solution at a temperature of about 30°C to 50°C. In addition, the stirring may be performed for 30 minutes or more.

Next, the precursor solution is irradiated with ultrasonic waves (S20). Fe-MOF is obtained by the method of ultrasonic chemical synthesis by the ultrasonic irradiation.

In one embodiment of the present invention, ultrasonic irradiation may be performed using a range of 10% to 33% of the maximum ultrasonic power (750 W, 20 kHz) of an ultrasonic device (VCX-750, Sonics & Materials). Preferably, 33% of the maximum ultrasonic power can be used. Ultrasonic irradiation may be performed for about 10 minutes to 120 minutes, and the longer the irradiation time, the more preferable in terms of obtaining a particle size on the order of several microns. Most preferably, the ultrasonic irradiation may be performed for 120 minutes.

Next, Fe-MOF is obtained from the reaction solution. The filtration method of Fe-MOF can be separated by sedimentation of Fe-MOF in the reaction solution, for example, or Fe-MOF can be separated from the reaction solution using a filter having an appropriate pore size. In one embodiment of the present invention, the filter may have a pore size of 1 μm or more. Fe-MOF separated from the reaction solution may be washed with a cleaning solution. The cleaning solution may be a mixture of at least one or two or more of water and alcohol. Meanwhile, a drying process of drying the Fe-MOF obtained after the washing may be further performed. The drying process is not limited to a specific method as long as the physical and chemical properties of the obtained Fe-MOF are not changed. In one embodiment of the present invention, the drying may be applied by selecting one or more appropriate methods among methods of natural drying, blow drying, hot air drying, cold air drying, room temperature vacuum drying and high temperature vacuum drying.

In addition, the present invention relates to an iron-based metal-organic framework (Fe-MOF) produced by the above-described method. The Fe-MOF according to the present invention has the same crystal structure as the conventional MIL-53 and shows the shape of a hexagonal bipyramid as shown in FIG. 4. 7 schematically shows the crystal structure of Fe-MOF according to the present invention. According to this also, Fe-MOF obtained by the production method according to the present invention is The horizontal and vertical lengths are 1 µm or more when confirmed by an electron microscope image.

Hereinafter, examples and the like will be described in detail to help understanding of the present invention. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the following embodiments. The embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

One. Fe-MOF synthesis

Example 1

In a 50 mL vial, 30 mL of dimethylforamide was added, and 2.5 mmol of iron chloride (FeCl ₃ 6H ₂ O) and terephthalic acid were added respectively, followed by stirring at room temperature for 1 hour to prepare a uniform precursor solution. . The precursor solution was irradiated with ultrasound for 2 hours to perform sonochemical synthesis. Then dimethylformamide and After washing through repeated washing with ethanol and acetone three times, drying was performed in a vacuum oven at 100°C for 24 hours to obtain an iron-based metal-organic framework (Fe-MOF). Figure 1a is a schematic view showing a method of manufacturing Fe-MOF of the present invention.

Example 2

An iron-based metal-organic framework (Fe-MOF) was obtained in the same manner as in Example 1, except that the concentration of terephthalic acid was 6 mmol.

2. Characterization of Fe-MOF

(1) Infrared spectroscopy (FT-IR)

Figure 2 shows the results of FT-IR analysis for Fe-MOF obtained in Example 1 and Example 2. The Fe-MOF obtained in Example 1 and Example 2 exhibited a characteristic stretch corresponding to the carboxylic groups of the terephthalic acid, an organic ligand, at about 1685 cm ^-1 , and carbohydrate in a form bound to iron ions Symmetric and asymmetric stretches of carboxylate appear at about 1400 cm ^-1 and 1600 cm ^-1 . In addition, the CH band (bend) occurring in the benzene ring of terephthalic acid appears at 750 cm ^-1 .

Through this, it was confirmed that the organic ligand terephthalic acid binds well with metal ions to form a metal-organic framework.

(2) X-ray powder diffraction analysis (PXRD)

Figure 3 shows the results of confirming the crystal structure using X-ray diffraction analysis for the Fe-MOF obtained in Example 1 and Example 2, Cu κα radiation (λ = 0.1541 nm) as an X-ray source 2θ value It was measured by changing to 5°/min in the 5° to 30° region. The peaks identified in each example were consistent with the specific peaks of the Fe-MIL-53 structure reported as the metal organic framework. (Chemistry-A European Journal 2010, 16, 1046-1052., Microporous and Mesoporous Materials 2012, 162, 36~43.)

(3) Field emission scanning electron microscope (FE-SEM)

To confirm the macroscopic structure and morphology of Fe-MOF obtained in Examples 1 and 2, field emission scanning electron microscope analysis was performed, and FIG. 4 shows the results. As shown in Figure 4, the Fe-MOF obtained in each example was confirmed to have a shape characteristic of a hexagonal bipyramid, and it was confirmed to have a horizontal and vertical length of 1 μm or more. As can be seen in Figure 4, in the case of the particles obtained in Example 1, it was confirmed that the horizontal length is about 1.5 μm, and the vertical length has a size of about 1.5 μm, in the case of the particles obtained in Example 2 It was confirmed that the length of the horizontal was about 1 μm and the length of the vertical was about 1.3 μm.

From the above analysis results, it was confirmed that the iron-based metal-organic framework according to the present invention has a crystal structure of MIL-53 and a hexagonal bipyramid shape of about 1 μm.

3. Evaluation of removal performance for organic pollutants

Using the Fe-MOF obtained in Example 1 and Example 2 was conducted to evaluate the organic pollutant removal performance. Methyl orange (methyl orange, MO), methylene blue (MB), and bisphenol A (bisphenol A, BPA) were added to deionized water in 200 mg, 200 mg, and 100 mg, respectively, to prepare 1 L of contaminated water. . Two 20 mL samples of contaminated water containing the methyl orange were prepared, and 5 mg of Fe-MOF obtained in Examples 1 and 2 were added to each sample, respectively, and stirred at 30°C for 14 hours. The methylene blue and bisphenol A-containing contaminated water were treated in the same manner. That is, a total of six samples were prepared. Thereafter, Fe-MOF was separated from the six contaminated waters through filtering.

For each sample, the concentration of organic pollutants before and after Fe-MOF captures the organic pollutants is analyzed and compared with the concentration of the organic pollutants removed by ultraviolet-visible spectroscopy (UV-vis.spectroscopy). The removal performance was calculated. As a result, it was confirmed that Fe-MOF of Example 1 having a large particle size as shown in FIG. 5 has higher organic pollutant removal performance than Fe-MOF of Example 2.

Using the Fe-MOF obtained in Example 1, the adsorption performance according to various adsorption times and the concentrations of various pollutants were measured and summarized as in FIG. 6. According to this, it can be seen that the rate of adsorption to Fe-MOF in Example 1 is slow in the order of bisphenol A, methylene blue, and methyl orange, because the higher the molecular weight, the slower the diffusion rate into the pores of Fe-MOF. I think. In addition, it can be seen that the adsorption performance of Fe-MOF decreases in the order of methyl orange, bisphenol A, and methylene blue, which is different from bisphenol A, which has a neutral charge, and methylene blue, which has a positive charge and methyl orange, which has a negative charge, Fe-MOF. In addition to the π-π interaction with the organic ligand of terephthalic acid, it is considered that the electrostatic repulsive force and the electrostatic attraction force with iron ions having a positive charge act respectively (see FIG. 8).

Claims (4)

(S10) preparing a precursor solution by dissolving a metal precursor and an organic ligand in a solvent; And
(S20) irradiating ultrasonic waves to the precursor solution;
Method for producing an iron-based metal-organic framework (Fe based metal-organic framework, Fe-MOF) comprising a.
According to claim 1,
The concentration of metal (iron) ions in the precursor solution is 0.0001 mol / liter to 0.3 mol / liter of iron-based metal-organic framework (Fe-based metal-organic framework, Fe-MOF) method of manufacturing.
According to claim 1,
The organic ligand is a method of manufacturing an iron-based metal-organic framework (Fe-based metal-organic framework, Fe-MOF) containing an organic acid.
It consists of an iron-based metal-organic framework (Fe-MOF) obtained by the production method according to any one of claims 1 to 4, wherein the Fe-MOF is a MIL-53 crystal structure The adsorbent for removing pollutants in water having a horizontal and vertical length of 1 µm or more.

Images