KR102225373B1 - Method for preparing a composition for adsorbing cesium using chitin - Google Patents

Abstract

The disclosed content relates to a method of preparing a composition for adsorption of cesium using chitin, and more particularly, a chitin mixing step of mixing and stirring chitin in an aqueous metal chloride solution, a solid content separation step of separating the solid content prepared through the chitin mixing step , Separation washing step of separating and washing the solids subjected to the reaction step of potassium hexacyanoferrate in which the solid content separated through the solid content separation step is added to an aqueous solution of potassium hexacyanoferrate, and the separation It consists of a drying step of drying the solids washed through the washing step.
The composition for adsorption of cesium prepared through the above process exhibits excellent adsorption power for cesium ions contained in water.

Description

Method for preparing a composition for adsorption of cesium using chitin {METHOD FOR PREPARING A COMPOSITION FOR ADSORBING CESIUM USING CHITIN}

The disclosed content relates to a method of preparing a composition for adsorption of cesium using chitin, and more particularly, to a method of preparing a composition for adsorption of cesium using chitin, which exhibits excellent adsorption power for cesium ions contained in water.

Nuclear power is used not only in power plants, but also in various fields such as medicine, agriculture, and industrial fields, and radioactive wastewater generated in this process is different from general industrial wastewater and household wastewater, so care must be taken in treatment.

In 2011, a nuclear accident occurred in Fukushima, Japan, and a large amount of radioactive material leaked into the sea, soil and atmosphere, and concerns about the removal of radioactive elements such as cesium, strontium and selenium have rapidly increased. Interest in this is increasing. Since radioactive substances in wastewater generated from nuclear power plants can cause diseases such as skin disease and leukemia when introduced into the body, an effective treatment technology is required to remove radioactive ions in water.

In particular, cesium 137 is the most dangerous fission product due to its high fission yield and long half-life, and many researchers have studied the removal of toxic metals, precipitation, membrane filtration, reverse osmosis, solvent extraction and electrolysis, biological treatment, ion exchange processes and adsorption. And other methods have been successfully applied to water and wastewater treatment systems. Among them, the adsorption process has advantages such as high efficiency, adsorption properties and cost efficiency compared to other technologies, and its applicability at very low concentrations, suitability for batch and continuous process use, ease of operation, less sludge generation, possibility of regeneration and reuse. There are such advantages.

In general, there are various treatment methods such as adsorption/ion exchange, chemical precipitation, coagulation flocculation, and membrane separation as methods for treating radioactive waste liquid. Based on this, researches for effective treatment of radioactive waste solutions are still being actively conducted.However, although the radioactivity of highly radioactive waste solutions is high, the actual chemical concentration of radionuclides is very small, so treatment methods such as adsorption and ion exchange are the most effective.

As adsorbents used to remove radioactive ions in water, activated carbon, biomass, fly ash, bentonite, and zeolite are generally used. Many types of adsorbents such as these have been used to remove harmful metals, and various wastes such as crab shells, sawdust, coffee grounds, and industrial wastes are recently used as economical adsorbents in terms of recycling of wastes. In addition, a method of using non-living algal biomass was studied. In particular, for example, chitin, a material that is abundantly present in the shells of animals such as crabs, shrimp, and crayfish, has been in the spotlight as a material that can be applied to various fields. Chitin has a structure similar to that of cellulose, exists in a relatively stable state, and is insoluble in water, dilute acids, alkalis and most organic solvents, and is widely used in cold stabilizers, recovery accelerators, wet strength improvers and water treatment coagulants. Such chitin is an amino polysaccharide containing about 7% nitrogen and can be applied in various fields, and has high utility value in terms of recycling aquatic waste using shrimp and crab shells.

In addition, hexacyanoferrate (HCF) containing a transition metal is also being studied as an effective adsorbent for cesium, and the synthesis of hexacyanoferrate and other compounds can increase the efficiency of cesium adsorption.

Korean Patent Registration No. 10-1708708 (2017.02.15) Korean Patent Registration No. 10-1589905 (2016.01.25)

Disclosed is to provide a method for preparing a composition for adsorption of cesium using chitin, which provides a composition for adsorption showing excellent adsorption power for cesium ions contained in water.

As an embodiment, the content of this disclosure is a chitin mixing step of mixing and stirring chitin in an aqueous metal chloride solution, a solid content separation step of separating the solid content prepared through the chitin mixing step, and the solid content separated through the solid content separation step. Potassium hexacyanoferrate reaction step in which potassium hexacyanoferrate is added to an aqueous solution of potassium hexacyanoferrate, a separation washing step of separating and washing the solids subjected to the potassium hexacyanoferrate reaction step, and drying the washed solids It describes a method for producing a composition for adsorption of cesium using chitin, characterized in that it consists of a drying step.

Preferably, the chitin mixing step may be performed by mixing 0.5 to 1.5 parts by weight of chitin with 100 parts by weight of an aqueous metal chloride solution.

More preferably, the metal chloride aqueous solution has a concentration of 0.05 to 0.15 mol/L, and the metal chloride may be made of one selected from the group consisting of copper chloride, nickel chloride, and iron chloride.

More preferably, the potassium hexacyanoferrate reaction step may be performed at a temperature of 25 to 35° C. for 10 to 15 hours.

Even more preferably, the aqueous solution of potassium hexacyanoferrate may have a concentration of 0.05 to 0.15 mol/L.

The method for preparing a composition for adsorption of cesium using chitin as described above has an excellent effect of providing a composition for adsorption that exhibits excellent adsorption power for cesium ions contained in water.

1 is a flow chart showing a method for preparing a composition for adsorption of cesium using chitin disclosed.
Figure 2 is a photograph showing a scanning electron microscope to determine the surface change of the composition for adsorption of cesium of Example 1 and Comparative Example 1 disclosed.
3 is a graph showing an EDX analysis to confirm whether the composition for adsorption of cesium using chitin of Example 1 and the composition for adsorption of cesium prepared through Comparative Example 1 are synthesized.
Figure 4 is a graph showing the results of XRD analysis of the composition for adsorption of cesium prepared through the disclosed Example 1 and Comparative Example 1.
5 is a graph showing the measurement of Cs(I) adsorption rate according to pH of the composition for adsorption of cesium prepared through the disclosed Examples 1 to 3 and Comparative Example 1. FIG.
6 is a graph showing the measurement of Cs(I) adsorption rate over time of the composition for adsorption of cesium prepared through the disclosed Example 1 and Comparative Example 1. FIG.
7 is a graph showing the measurement of adsorption power according to the ionic strength of the composition for adsorption of cesium using chitin of Example 1 and the composition for adsorption of cesium prepared through Comparative Example 1. FIG.

Hereinafter, a preferred embodiment of the present invention and the physical properties of each component will be described in detail, but this is for explaining in detail enough that one of ordinary skill in the art can easily carry out the invention, This does not mean that the technical spirit and scope of the present invention are limited.

The method for preparing a composition for adsorption of cesium using chitin is a chitin mixing step (S101) of mixing and stirring chitin in an aqueous metal chloride solution, and a solid content separation step (S103) of separating the solid content prepared through the chitin mixing step (S101). , The solid content separated through the solid content separation step (S103) is added to the potassium hexacyanoferrate aqueous solution, the reaction step of potassium hexacyanoferrate (S105), and the solid content through the potassium hexacyanoferrate reaction step (S105) is separated. And a separate washing step (S107) of washing and a drying step (S109) of drying the solids washed through the separate washing step (S107).

The chitin mixing step (S101) is a step of mixing and stirring chitin in an aqueous metal chloride solution, and is made by mixing 0.5 to 1.5 parts by weight of chitin to 100 parts by weight of an aqueous metal chloride solution having a concentration of 0.05 to 0.15 mol/L.

At this time, the chitin is derived from the shell of shrimp, and can be used by Sigma Aldrich in the United States, has a structure similar to cellulose, exists in a relatively stable state, and exhibits excellent adsorption performance for cesium ions contained in water. .

In addition, as the metal chloride, the aqueous metal chloride solution may have a concentration of 0.05 to 0.15 mol/L, and it is preferable to use a metal chloride of 0.1 mol/L, in the group consisting of copper chloride, nickel chloride, and iron chloride. It is more preferable to consist of the selected one.

When chitin is mixed and stirred in an aqueous metal chloride solution as described above, copper, nickel and iron components contained in metal chlorides such as copper chloride, nickel chloride, and iron chloride are synthesized with chitin.

The solid content separation step (S101) is a step of separating the solid content prepared through the chitin mixing step (S101), and is performed by separating the solid content from the mixture prepared through the chitin mixing step (S101). It consists of a process of separating solids in the mixture through a method such as manure.

In the reaction step of potassium hexacyanoferrate (S105), the solid content separated through the solid content separation step (S103) is added to an aqueous solution of _{potassium hexacyanoferrate (K 3} [Fe(CN) _{6]) for reaction.} As a step, the solid content separated through the solid content separation step (S103) is added to an aqueous solution of potassium hexacyanoferrate having a concentration of 0.05 to 0.15 mol/L, and reacted at a temperature of 25 to 35° C. for 10 to 15 hours.

Through the above process, the solid content separated in the solid content separation step (S103) and potassium hexacyanoferrate react to produce various types of hexacyanoferrate in the mixture, and the metal chloride used in the chitin mixing step (S101) In the case of copper chloride, copper hexacyanoferrate (CuHCF) is produced, and when the metal chloride used in the chitin mixing step (S101) is nickel, nickel hexacyanoferrate (NiHCF) ) Is generated, and when the metal chloride used in the chitin mixing step (S101) is iron, iron hexacyanoferrate (FeHCF) is generated.

The separation and washing step (S107) is a step of separating and washing the solid content that has been subjected to the potassium hexacyanoferrate reaction step (S105), and copper hexacyanoferrate prepared through the potassium hexacyanoferrate reaction step (S105). Solids generated from salt, nickel hexacyanoferrate, iron hexacyanoferrate, etc. are separated by filtration through a filter, and the separated solids are washed 1 to 3 times with distilled water to remove impurities remaining on the surface of the solids. This is the step of removing.

The drying step (S107) is a step of drying the solids washed through the separation and washing step (S107), and drying by heating the solids washed through the separation and washing step (S107) to a temperature of 65 to 75°C. All.

After the drying step (S107) consisting of the above process is performed, the preparation of the composition for adsorption of cesium using the disclosed chitin is completed.

Hereinafter, a method for preparing a composition for adsorption of cesium using chitin and physical properties of a composition for adsorption of cesium prepared through the method will be described with reference to examples.

<Example 1>

10 g of chitin (Shrimp shells, Sigma Aldrich, USA) was added to 1000 mL of a 0.1 mol/L copper chloride aqueous solution and stirred at room temperature at 150 rpm for 24 hours to separate the solid content, and the separated solid content was mixed with a concentration of 0.1 mol/l. L potassium hexacyanoferrate (>98%, Hayashi Pure Chemical, Japan) was added to 1000 mL of aqueous solution and stirred at 30°C for 12 hours to produce copper hexacyanoferrate, and the produced copper hexacyanoferric acid The salt was separated by filtration, and the separated copper hexacyanoferrate was washed twice with distilled water and then dried at a temperature of 70° C. to prepare a composition for adsorption of cesium using chitin.

<Example 2>

Proceeding in the same manner as in Example 1, a composition for adsorption of cesium using chitin was prepared by using an aqueous nickel chloride solution instead of an aqueous copper chloride solution.

<Example 3>

Proceeding in the same manner as in Example 1, a composition for adsorption of cesium using chitin was prepared using an aqueous iron chloride solution instead of an aqueous copper chloride solution.

<Comparative Example 1>

A composition for adsorption of cesium made of chitin (Shrimp shells, Sigma Aldrich, USA).

SEM analysis was performed to determine the surface change of the composition for adsorption of cesium of Example 1 and Comparative Example 1, and the results are shown in FIG. 2 below.

As shown in Figure 2 below, the composition for adsorption of cesium (CuHCF) prepared through Example 1 has fine particles evenly bonded to the surface through HCF synthesis, whereas the composition for adsorption of cesium prepared through Comparative Example 1 You can see that the surface is smooth.

In addition, EDX analysis was performed to confirm whether the composition for adsorption of cesium using chitin of Example 1 and the composition for adsorption of cesium prepared through Comparative Example 1 were synthesized, and the results are shown in FIG. 3 below.

As shown in FIG. 3 below, the main components of the composition for adsorption of cesium of Comparative Example 1 were carbon and oxygen, and the composition for adsorption of cesium (CuHCF) prepared through Example 1 contained K and Fe through HCF synthesis. It was synthesized, and it can be seen that Cu was also synthesized by 1.17%.

In addition, the composition for adsorption of cesium prepared through Example 1 and Comparative Example 1 was analyzed by XRD, and the results are shown in FIG. 4 below.

As shown in FIG. 4 below, the composition for adsorption of cesium showed similar diffraction peaks, but the relative intensity of the peaks was different. A peak of C appeared at 22~23.5° and 39~40°, and a peak of O at 25~27°. Fe peaks due to HCF synthesis appear at 36.5°, and Cu synthesis can be confirmed at 44.2° and 51.5°.

In addition, the Cs(I) adsorption rate according to the pH of the composition for adsorption of cesium prepared through Examples 1 to 3 and Comparative Example 1 was measured and shown in FIG. 5 below.

{However, the Cs(I) adsorption rate was conducted by adjusting 100 mL of a Cs(I) 10ppm solution to pH 2 to 10, and the composition for adsorption of cesium was injected under the condition of 2g/L and stirred for 24 hours. Analyzed.}

As shown in FIG. 5 below, it was found that the pH was slightly increased after 24 hours as a whole. In the case of chitin prepared through Comparative Example 1, it showed a removal rate of about 30% at pH 2, about 46% at pH 4, and about 65% at pH 6 or higher, and the composition for adsorption of cesium prepared through Example 1 was at pH 2 When increasing from to 6, the removal rate gradually increased from about 82% to 95%, and the removal rate slightly decreased as the pH increased, showing a removal rate of about 90% at pH 10. In the case of the composition for adsorption of cesium (NiHCF) prepared in Example 2, the removal rate was about 74% at pH 2, 87% at pH 6, and about 85% at pH 10.

In the case of the composition for adsorption of cesium (FeHCF) prepared in Example 3, the removal rate was about 84% at pH 2, 93% at pH 6, and about 90% at pH 10. Overall, the removal rate was highest at neutral pH, and the removal rate was lower as pH increased or decreased in the neutral region.

In particular, it can be seen that the Cs(I) removal rate of the composition for adsorption of cesium prepared through Example 1 was the highest.

The reason why the removal rate decreases when the pH is less than 4 is that when the pH decreases as shown in Scheme 1, the H ⁺ concentration in the aqueous solution increases rapidly, and H ⁺ acts as a competing ion for Cs ions, resulting in a decrease in the removal amount.

[Scheme 1]

MOH ⁰ + H ⁺ ↔ MOH ₂ ⁺

In addition, the Cs(I) adsorption rate according to time of the composition for adsorption of cesium prepared through Example 1 and Comparative Example 1 was measured and shown in FIG. 6 below.

{However, the change of adsorption of pollutants from aqueous medium over time is one of the most important features to be studied in the adsorption process, and adsorption experiments were conducted for Cs(I) at various time intervals between 5 and 400 minutes. }

As shown in Figure 6 below, as a result of an experiment by injecting a composition for adsorption of cesium into 100 mL of a 10 ppm Cs(I) solution under the condition of 2 g/L, the composition for adsorption of cesium of Comparative Example 1 (Chitin) was about 11% 5 minutes after the start of the experiment, It showed a removal rate of about 55% after 180 minutes and about 64% after 300 minutes, and the removal rate of the composition for adsorption of cesium (CuHCF) of Example 1 was about 55% after 5 minutes of the experiment, about 91% after 180 minutes, and 240 minutes. It was found to be about 96%. When all the cesium adsorption compositions were used, there was no significant change in the reduction rate with increasing time after 240 minutes. This phenomenon is because in the initial stage of adsorption, the adsorption rate is high due to the large number of empty active sites on the surface of the adsorption composition, but the adsorption rate decreases as the number of empty active sites decreases as adsorption proceeds. As a result of the experiment, it was determined that the equilibrium state was reached after 300 minutes, so the experiment was conducted with the optimum time set to 5 hours.

In addition, Cs(I) adsorption power according to the concentration of the composition for adsorption of cesium using chitin of Example 1 and the composition for adsorption of cesium prepared through Comparative Example 1 was measured and shown in Table 1 below.

{However, the adsorption power of Cs(I) according to the concentration was confirmed by conducting an adsorption experiment for each concentration of Cs(I) using each cesium adsorption composition. After adding 2g/L of the composition and stirring for 5 hours, an analysis method was used.}

As shown in Table 1 below, the results of adsorption experiments obtained to investigate the adsorption behavior of the prepared cesium adsorption composition were analyzed using Langmuir adsorption isotherm and Freundlich adsorption isotherm. Langmuir adsorption isotherm is mainly used when adsorption occurs in a single molecular layer, and the general form of liquid phase adsorption is as follows.

Where qe is the amount of solute adsorbed per gram of adsorbent in adsorption equilibrium (mg/g), qm is the maximum adsorption amount (mg/g), Ce is the equilibrium concentration of the aqueous solute in the adsorption equilibrium (mg/L), K Means the Langmuir constant related to the adsorption energy.

Freundlich adsorption isotherm is mainly used to describe the adsorption of a multimolecular layer between an adsorbent and an adsorbent molecule, and is expressed as the following equation.

Where qe is the amount of solute adsorbed per gram of adsorbent in adsorption equilibrium (mg/g), C (mg/L) is the equilibrium concentration in aqueous solution, Kf (mg/g) and n are Freundlich constants. Kf represents the adsorption capacity of the solid phase at a certain concentration of a solute in an aqueous solution, and the index n represents the magnitude and non-uniformity of the energy during the adsorption process.

The isothermal adsorption results for Cs(I) of the composition for adsorption of cesium (Chitin) prepared in Comparative Example 1 and the composition for adsorption of cesium (CuHCF) prepared in Example 1 are shown in Table 1 below, Langmuir adsorption When isotherm was applied, the R ^{2 values of chitin and CuHCF were 0.65 and 0.976, respectively, and the R 2} values when the Freundlich adsorption isotherm was applied were 0.992 and 0.98, respectively. Therefore, it can be expected that cesium ions are adsorbed on the surface of the composition for adsorption of cesium in the form of a single molecular layer, and the maximum adsorption amounts of chitin and CuHCF are 2.72 mg/g and 18.5 mg/g, respectively. When synthesized with HCF, the maximum adsorption amount was improved about 6 times.

<Table 1>

In addition, for comparison of adsorption of cesium, the maximum adsorption amount for each adsorbent is shown in Table 2 below. The difference in adsorption capacity by each adsorbent may be due to differences in the physicochemical properties of the adsorbent as well as experimental factors including the concentration range of Cs(I), pH, temperature, ionic strength, etc. It can be seen that it shows a fairly high efficiency for removal.

<Table 2>

In addition, the adsorption power according to the ionic strength of the composition for adsorption of cesium using chitin of Example 1 and the composition for adsorption of cesium prepared through Comparative Example 1 were measured and shown in FIG. 7 below.

{However, for the adsorption power according to the ionic strength, proceed with the experiment by injecting 0.001 M~0.1 M of NaCl into 100 mL of a 10 ppm Cs(I) solution, but the adsorbent is injected under the condition of 2 g/L, stirred for 5 hours, and then analyzed. Was used.}

As shown in Figure 7 below, the removal rate according to the ionic strength is about 67 to 61% in the case of the cesium adsorption composition (Chitin) prepared through Comparative Example 1, and the cesium adsorption composition prepared through Example 1 (CuHCF) In the case of, it was found to be about 93%. As the ionic strength increased, chitin decreased by about 4%, but there was no significant change in the case of CuHCF.

The results of ionic strength on the removal of pollutants are essential to investigate specific adsorption and non-specific adsorption of pollutants by adsorbents. In non-specific adsorption, toxic ions form hydration spheres, are adsorbed on the adsorbent surface through electrostatic attraction, and metal ions form external sphere complexes. In specific adsorption, contaminants bind directly to the surface of the adsorbent and finally form a complex with functional groups present in the material. Therefore, non-specific adsorption is greatly affected by changes in ionic strength, whereas specific adsorption is not affected by ionic strength. Therefore, adsorption in the above process is judged as specific adsorption. It can be seen that the functional group of the substance formed an inner sphere complex.

Accordingly, the disclosed method for preparing a composition for adsorption of cesium using chitin provides a composition for adsorption that exhibits excellent adsorption power for cesium ions contained in water.

S101; Chitin mixing step
S103; Solid content separation step
S105; Potassium hexacyanoferrate reaction step
S107; Separation washing step
S109; Drying stage

Claims (5)

Chitin mixing step of mixing and stirring chitin in an aqueous metal chloride solution;
A solid content separation step of separating the solid content prepared through the chitin mixing step;
Potassium hexacyanoferrate reaction step of introducing the solids separated through the solids separation step into an aqueous solution of potassium hexacyanoferrate;
Separation washing step of separating and washing the solids that have gone through the potassium hexacyanoferrate reaction step; And
Consists of; a drying step of drying the solid content washed through the separation washing step,
The method for producing a composition for adsorption of cesium using chitin, wherein the reaction step of potassium hexacyanoferrate is performed at a temperature of 25 to 35° C. for 10 to 15 hours.
The method according to claim 1,
The chitin mixing step is a method of producing a composition for adsorption of cesium using chitin, characterized in that 0.5 to 1.5 parts by weight of chitin are mixed with 100 parts by weight of an aqueous metal chloride solution.
The method according to claim 1 or 2,
The metal chloride aqueous solution has a concentration of 0.05 to 0.15 mol/L,
The metal chloride is a method for producing a composition for adsorption of cesium using chitin, characterized in that consisting of one selected from the group consisting of copper chloride, nickel chloride, and iron chloride.
delete The method according to claim 1,
The method for producing a composition for adsorption of cesium using chitin, wherein the aqueous solution of potassium hexacyanoferrate has a concentration of 0.05 to 0.15 mol/L.

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