KR102556035B1 - A method of chitosan-based 4-hydroxybenzoic acid hydrogel synthesis and the application for ammonium ions adsorption and quantitative detection - Google Patents

Abstract

The present invention is related to a technology for measuring the concentration of ammonium ions, which cause disease and death of aquatic organisms at high concentrations. It relates to a novel chitosan-based 4-hydroxybenzoic acid hydrogel that can be easily measured, a method for synthesizing the hydrogel, and a method for measuring the ammonium ion concentration using the hydrogel.

Description

A method of chitosan-based 4-hydroxybenzoic acid hydrogel synthesis and the application for ammonium ions adsorption and quantitative detection}

The present invention is related to a technology for measuring the concentration of ammonium ions, which cause disease and death of aquatic organisms at high concentrations. It relates to a novel chitosan-based 4-hydroxybenzoic acid hydrogel that can be easily measured, a method for synthesizing the hydrogel, and a method for measuring the ammonium ion concentration using the hydrogel.

Due to high-density aquaculture, large-scale crop cultivation, and the use of livestock manure or excessive fertilizer, a large amount of nutrients are leaked into the aquatic ecosystem, resulting in eutrophication and mortality of farmed fish in the aquaculture industry. In particular, ammonia, the most frequently found substance in polluted wastewater, can cause bleeding in the fins and gills of farmed fish even at a low concentration of 0.10 mg/L, and may cause death at a high concentration of 2.00 mg/L.

Ammonium ion, which is an ionized form of ammonia, is generated when most of the excrement discharged from farmed fish and lost feed that has not been fed are decomposed by aerobic microorganisms. When ammonium ion touches the mucous membrane of farmed fish, it dissolves the cell membrane through a saponification reaction, and when it enters the body fluid, it makes the body fluid basic and inhibits enzyme activity in organs. In particular, when the concentration of ammonium ion is high, tricarboxylic acid (TCA) Because it inhibits the reaction of the cycle, there is a setback in energy production in the body.

As a method for measuring ammonium ion, an absorbance photometry method is mainly used, and there are Indophenol Blue Method and Nessler's method. The indophenol method is used by measuring the blue color of indophenol produced by reacting phenol and sodium nitroprusside with ammonium ion in the sample solution with an absorbance photometer. The Nessler method is a colorimetric method for measuring the yellowish-brown solution obtained by reacting Nessler reagent, which is a solution of mercury iodide (?) and potassium iodide in an aqueous solution of potassium hydroxide, with ammonia.

Biological treatment, chemical coagulation, oxidation reaction, steam stripping, microwave radiation, ion exchange method, adsorption treatment method, etc. are being studied for ammonia removal. Among them, the adsorption treatment method is an economical method in that it is efficient in terms of treatment time, does not use many chemicals, and requires low energy. Hydrogel is one of the materials used in representative adsorption treatment methods, and has advantages such as fast adsorption, high contaminant capacity, and use in a wide pH range. is used with

However, the method of measuring the concentration of ammonia adsorbed by the hydrogel remains only in the method of measuring and investigating the difference in ammonia concentration in the influent and outlet water, so it takes a long time and is inefficient. Unlike the fields of biomaterials and biomedical engineering, which are other areas where hydrogels are applied, many applications of polymers have not been studied.

Domestic Patent Registration No. 10-2351290

Therefore, the object of the present invention is to develop a chitosan-based 4 with a new structure that has excellent ammonium ion adsorption capacity and has the ability to adsorb and sense ammonium ions because the content of ammonium ions adsorbed as well as whether or not ammonium ions are adsorbed is measured by fluorescence analysis. - To provide a hydroxybenzoic acid hydrogel and a method for synthesizing the hydrogel.

Another object of the present invention is to measure the concentration of ammonium ions present in various liquids, including water systems, by using the characteristics of chitosan-based 4-hydroxybenzoic acid hydrogel, in which the content of adsorbed ammonium ions is measured by fluorescence analysis. It is to provide a method for measuring ammonium ion concentration using a hydrogel that is environmentally friendly because it does not use heavy metals and can be measured quickly and simply at low cost.

Another object of the present invention is to provide an ammonium ion adsorbent comprising a chitosan-based 4-hydroxybenzoic acid hydrogel having a better ammonium ion adsorption capacity than the previously known chitosan hydrogel.

The objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the description below.

In order to achieve the above object of the present invention, first, the present invention provides a chitosan-based 4-hydroxybenzoic acid hydrogel having the following Chemical Formula 1.

[Formula 1]

Here, n is a real number between 200 and 50000, and m is a real number between 50 and 1000.

In a preferred embodiment, the ammonium ion adsorption capacity of chitosan hydrogel is improved by 1.5 times or more.

In a preferred embodiment, the ammonium ion adsorption capacity is enhanced by the 4-hydroxybenzoic acid.

In a preferred embodiment, when the ammonium ion is adsorbed, green fluorescence is emitted by the 4-hydroxybenzoic acid.

In a preferred embodiment, the adsorbed amount of the ammonium ion is measured by the intensity of the emitted green fluorescence.

In a preferred embodiment, in a hydrogel in which m is a real number between 150 and 500 in Chemical Formula 1, the amount of adsorption of ammonium ions and the intensity of the green fluorescence are inversely proportional.

In addition, the present invention comprises the steps of preparing a reaction solution 1 by dissolving chitosan in an acid solution at a constant temperature; preparing a reaction solution 2 in which a plurality of radicals are formed in chitosan by adding an initiator to the reaction solution 1 to generate a chemical radical of chitosan; preparing a reaction solution 3 in which chitosan and 4-hydroxybenzoic acid are combined through an amide reaction generated by adding 4-hydroxybenzoic acid to the reaction solution 2; It provides a chitosan-based 4-hydroxybenzoic acid hydrogel synthesis method comprising adding a hydrogel inducing agent to the reaction solution 3 and then stirring it at a constant temperature to form a hydrogel.

In a preferred embodiment, a washing step of removing residual chemicals from the hydrogel; and a drying step of drying the formed hydrogel or the washed hydrogel; further includes one or more of

In a preferred embodiment, the acid solution is at least one selected from the group consisting of a hydrochloric acid solution, a nitric acid solution, and a sulfuric acid solution.

In a preferred embodiment, the initiator is ammonium sulfate, 2,2-azobis (2-methylpropionitrile), 2,2-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2 - At least one selected from the group consisting of bromopropanenitrile and toluenesulfonyl chloride.

In a preferred embodiment, the 4-hydroxybenzoic acid is added to the reaction solution 2 at a concentration of 0.1 to 1 mM.

In a preferred embodiment, the hydrogel inducer is at least one selected from the group consisting of polyethylene glycol, acrylic acid, polyacrylamide, polyvinyl alcohol, collagen, and gelatin.

In a preferred embodiment, the constant temperature is 60 ℃ to 80 ℃.

In addition, the present invention provides an ammonium adsorbent comprising any one of the above-described chitosan-based 4-hydroxybenzoic acid hydrogels or the chitosan-based 4-hydroxybenzoic acid hydrogel synthesized by any one of the above-described synthesis methods.

In a preferred embodiment, the amount of ammonium ion adsorption is reduced when it is out of the range of pH 5 to pH 8.

In a preferred embodiment, when n is 18000 and m is a real number between 150 and 500 in the chitosan-based 4-hydroxybenzoic acid hydrogel, the adsorbed amount of ammonium ion at pH 6 is 19.2 mg/g.

In addition, the present invention comprises the steps of diluting ammonia water in tertiary distilled water to prepare a plurality of standard solutions in the concentration range of 9.00-900μM; immersing the chitosan-based 4-hydroxybenzoic acid hydrogel of claim 1 in a standard solution according to each concentration; Maintaining for 60 minutes to 120 minutes while shaking at 150 to 300 rpm conditions in a state in which the hydrogel is immersed; Separating the hydrogels immersed in each of the standard solutions and measuring the fluorescence intensity of the hydrogels; Ammonium in a liquid using a hydrogel comprising; and matching the fluorescence intensity measured per hydrogel with the concentration of the standard solution in which the hydrogel is immersed, thereby creating a library so that the concentration of ammonium ions adsorbed to the hydrogel is specified. A method for forming a reference library for measuring ion concentration is provided.

In a preferred embodiment, in the chitosan-based 4-hydroxybenzoic acid hydrogel, n is 18000 and m is a real number between 150 and 500.

In a preferred embodiment, the step of measuring the fluorescence intensity is performed by measuring the absorbance intensity of the hydrogel at a wavelength of 390 nm to 420 nm.

In a preferred embodiment, the step of creating a library is performed by matching the calculated value by changing the absorbance or ammonium ion concentration of the hydrogel at regular intervals using Equation 1 below.

[Equation 1]

y=-147x + 4601

Here, y is the measured fluorescence intensity, x is the ammonium ion concentration, and R ² is greater than or equal to 0.9.

In addition, the present invention provides a reference library for measuring the ammonium ion concentration in a liquid using a hydrogel formed by any one of the methods described above.

In addition, the present invention comprises the steps of immersing the above-described chitosan-based 4-hydroxybenzoic acid hydrogel or the chitosan-based 4-hydroxybenzoic acid hydrogel synthesized by any one of the above-described synthesis methods in a target liquid; Maintaining the hydrogel immersed in the liquid for 60 to 120 minutes while shaking at 150 to 300 rpm; Separating the hydrogel from the target liquid and measuring fluorescence intensity; and determining the concentration of ammonium ions corresponding to the measured fluorescence intensity according to the reference library of claim 21 or Equation 1 below.

[Equation 1]

y=-147x + 4601

Here, y is the measured fluorescence intensity, x is the ammonium ion concentration, and R ² is greater than or equal to 0.9.

In a preferred embodiment, a step of removing adsorbed ammonium ions from the chitosan-based 4-hydroxybenzoic acid hydrogel in which the step of measuring the fluorescence intensity is performed is further performed.

In a preferred embodiment, the step of removing the ammonium ion is performed by immersing the chitosan-based 4-hydroxybenzoic acid hydrogel in a strong basic solution.

In a preferred embodiment, the chitosan-based 4-hydroxybenzoic acid hydrogel from which ammonium ions are removed is reused up to 5 times.

According to the above-described chitosan-based 4-hydroxybenzoic acid hydrogel and its synthesis method of the present invention, it has excellent ammonium ion adsorption capacity, and since the content of adsorbed ammonium ions as well as whether or not ammonium ions are adsorbed is measured by fluorescence analysis, ammonium ion adsorption It is possible to provide a hydrogel with a new structure that has characteristics capable of sensing and sensing.

In addition, according to the ammonium ion concentration measurement method using the hydrogel of the present invention, the content of adsorbed ammonium ions is measured by fluorescence analysis, using the characteristics of chitosan-based 4-hydroxybenzoic acid hydrogel to various liquids, including aqueous systems. The concentration of ammonium ion present can be measured quickly and simply at low cost and environmentally friendly without using harmful chemicals or heavy metals.

In addition, according to the ammonium ion adsorbent of the present invention, it has an excellent ammonium ion adsorption capacity compared to the conventionally known chitosan hydrogel.

Effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

1A shows the bonding relationship between chitosan and 4-hydroxybenzoic acid and the function of 4-hydroxybenzoic acid in the chemical formula of chitosan-based 4-hydroxybenzoic acid hydrogel according to various embodiments of the present invention, and FIG. Fluorescence is generated by 4-hydroxybenzoic acid in the hydrogel having the structure shown in , and it is a schematic diagram showing that fluorescence intensity decreases when ammonium ions are adsorbed.
Figure 2 is a schematic diagram showing the change in fluorescence intensity according to the chitosan-based 4-hydroxybenzoic acid hydrogel synthesis method according to various embodiments of the present invention, the adsorption of ammonium, and the chemical change in the hydrogel according to the ammonium adsorption.
3a is a chitosan-based 4-hydroxybenzoic acid hydrogel prepared by adding 4-hydroxybenzoic acid at various concentrations according to the synthesis method according to various embodiments of the present invention in a solution containing various concentrations of ammonium ions. It is a result graph obtained by numerically quantifying the maximum adsorption amount and the binding affinity between the adsorbent and the adsorbent using the Langmuir isothermal adsorption model, and FIG. 3B is a graph showing the result of deriving the adsorption rate by evaluating the ammonium adsorption amount over time.
FIG. 4 shows 365 nm ultraviolet rays after adsorbing concentrations of 0, 0.1, 0.2, 1.0, and 5.0 mM ammonium ions to chitosan-based 4-hydroxybenzoic acid hydrogels synthesized according to the synthesis method according to various embodiments of the present invention, respectively. These are the resulting photographs showing the fluorescence intensity emitted by each irradiation.
Figure 5a is a graph showing a standard calibration curve obtained by displaying the fluorescence intensity measured per ammonium ion concentration of a standard solution with the ammonium ion concentration as the x-axis and the fluorescence intensity as the y-axis, and Figure 5b is a graph showing the standard calibration curve used in FIG. It is a graph showing the results of measuring the hydrogel adsorbed at various ammonium ion concentrations (0.1-5.0 mM) with a fluorescence spectrophotometer.
Figure 6a is a graph showing the results of experiments on whether chitosan-based 4-hydroxybenzoic acid hydrogel and chitosan hydrogel according to various embodiments of the present invention can be reused by removing adsorbed ammonium ions after adsorbing ammonium ions; , Figure 6b is a graph showing the ammonium ion removal efficiency of chitosan-based 4-hydroxybenzoic acid hydrogel and chitosan hydrogel according to various embodiments of the present invention.

The terms used in the present invention have been selected from general terms that are currently widely used as much as possible while considering the functions in the present invention, but these may vary depending on the intention of a person skilled in the art or precedent, the emergence of new technologies, and the like. In addition, in a specific case, there is also a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the invention.

When 'includes,' 'has,' or 'consists of' mentioned in the present invention is used, other parts may be added unless 'only' is used. In the case where a component is expressed in the singular, the case including the plural is included unless otherwise explicitly stated.

In interpreting the components, even if there is no separate explicit description, it is interpreted as including the error range.

Characteristic parts of each of the various embodiments of the present invention can be partially or entirely combined or combined with each other, technically various interlocking and driving are possible, and each embodiment can be implemented independently of each other or in an association relationship. may be performed together.

Hereinafter, the technical configuration of the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Like reference numbers used to describe the invention throughout the specification indicate like elements.

The technical feature of the present invention is that it has an excellent ammonium ion adsorption capacity compared to conventionally known chitosan hydrogels, and unlike chitosan hydrogels, the adsorption of ammonium ions as well as the content of adsorbed ammonium ions is measured through fluorescence analysis through fluorescence analysis Therefore, a new structure of chitosan-based 4-hydroxybenzoic acid hydrogel having the characteristics of enabling ammonium ion adsorption and sensing and the method for synthesizing the hydrogel, the ammonium ion adsorbent including the hydrogel, and the hydrogel present in various liquids It is in the method of measuring the ammonium ion concentration.

That is, when using absorbance spectrophotometric methods such as the Indophenol Blue method and the Nessler's method, which measure the concentration of ammonium ions present in known liquids, the Indophenol method is phenol, and the Nessler method is mercury. This is because this essential use is harmful to the environment, and the process is also extremely complex, so it takes a long time and is inefficient. In addition, the conventionally known chitosan hydrogel has an ability to adsorb ammonium ions and can be used as an adsorbent to remove ammonium ions present in liquid, but does not generate specific fluorescence during fluorescence analysis, so the concentration of ammonium ions in the liquid to be measured can be measured. This is because, in order to measure, the difference in ammonia concentration between the inflow water before and after the introduction of chitosan hydrogel and the ammonia concentration in the discharge water was measured by absorbance photometric method and was limited to the method of investigation.

Accordingly, the present invention provides a chitosan-based 4-hydroxybenzoic acid hydrogel having Formula 1 below.

[Formula 1]

Here, n is a real number between 200 and 50000, and m is a real number between 50 and 1000.

The chitosan-based 4-hydroxybenzoic acid hydrogel of the present invention has an ammonium ion adsorption capacity, which is 1.5 times higher than the ammonium ion adsorption capacity of chitosan hydrogel, and the ammonium ion adsorption capacity is improved by 4-hydroxybenzoic acid. .

When ammonium ions are adsorbed on the chitosan-based 4-hydroxybenzoic acid hydrogel of the present invention, green fluorescence can be emitted by 4-hydroxybenzoic acid. That is, 4-hydroxybenzoic acid can be decomposed into 4-hydroxybenzoate by removing the hydrogen atom of the hydroxy group by receiving photon energy (hv). demonstrated the occurrence of green fluorescence emission.

As a result, since the amount of adsorption of ammonium ion is measured by the intensity of green fluorescence emitted from the chitosan-based 4-hydroxybenzoic acid hydrogel of the present invention, it can be seen that it has characteristics capable of simultaneously adsorbing and sensing ammonium ion.

As an embodiment, a hydrogel in which m is a real number between 150 and 500 in Chemical Formula 1 exhibits characteristics in which the adsorbed amount of ammonium ions and the intensity of green fluorescence are inversely proportional.

As shown in FIG. 1A, chitosan and 4-hydroxybenzoic acid are bonded to each other by an amide bond, and ammonium ion adsorption capacity is formed by 4-hydroxybenzoic acid, as well as ammonium as schematically shown in FIG. 1B. It can be seen that it has the ability to sense ions.

Next, the chitosan-based 4-hydroxybenzoic acid hydrogel synthesis method of the present invention comprises the steps of preparing a reaction solution 1 by dissolving chitosan in an acid solution at a certain temperature; preparing a reaction solution 2 in which a plurality of radicals are formed in chitosan by adding an initiator to the reaction solution 1 to generate a chemical radical of chitosan; preparing a reaction solution 3 in which chitosan and 4-hydroxybenzoic acid are combined through an amide reaction generated by adding 4-hydroxybenzoic acid to the reaction solution 2; and forming a hydrogel by adding a hydrogel inducing agent to the reaction solution 3 and stirring at a constant temperature.

If necessary, a washing step of removing residual chemicals from the hydrogel; and a drying step of drying the formed hydrogel or the washed hydrogel; One or more of them may be further included. In particular, the washing step needs to be performed when a material containing ammonium ions is used as an initiator and/or a hydrogel inducer.

Here, the acid solution included in the reaction solution 1 is not limited as long as the pH is less than 5, but as an embodiment, it may be any one or more selected from the group consisting of a hydrochloric acid solution, a nitric acid solution, and a sulfuric acid solution.

As an initiator, any known material can be used as long as it can form a large number of radicals in chitosan with low reactivity. As an embodiment, ammonium sulfate, 2,2-azobis(2-methylpropionitrile), 2,2- It may be at least one selected from the group consisting of azobis(4-methoxy-2,4-dimethylvaleronitrile), 2-bromopropanenitrile, and toluenesulfonyl chloride.

4-hydroxybenzoic acid may be added to the reaction solution 2 at a concentration of 0.1 to 1 mM. If the concentration is less than 0.1 mM, there is a problem in that the amount of ammonium ions adsorbed is reduced, and if the concentration exceeds 1 mM, there is a problem in that synthesis is not possible.

Any known hydrogel inducing agent can be used as long as it can induce hydrogelation in reaction solution 3 in which chitosan and 4-hydroxybenzoic acid are combined. As an embodiment, polyethylene glycol, acrylic acid, polyacrylamide, and polyvinyl alcohol can be used. At least one selected from the group consisting of , collagen, and gelatin may be used.

In the step of preparing the reaction solution 1 or the step of forming the hydrogel, the constant temperature may be 60 ° C to 80 ° C. If the temperature exceeds 80 ° C, there is a problem of boiling the solution in the step of preparing the reaction solution 1, and the hydrogel In the forming step, there is a problem in that the hydrogel is formed while burning and the quality deteriorates. If the temperature is less than 60 ° C, there is a problem in that chitosan does not dissolve in the step of preparing reaction solution 1, and in the step of forming the hydrogel, the synthesis time is long. There was a problem with taking

Next, the ammonium adsorbent of the present invention includes any one of the above-described chitosan-based 4-hydroxybenzoic acid hydrogels or the chitosan-based 4-hydroxybenzoic acid hydrogel synthesized by any one of the above-described methods.

Compared to the ammonium adsorbent containing chitosan hydrogel, it was more stable in a fairly wide pH range of pH 2-8, but exhibited a characteristic that the adsorption amount of ammonium ions decreased when it was out of the range of pH 5 to pH 8.

In particular, when n is 18000 and m is a real number between 150 and 500 in the chitosan-based 4-hydroxybenzoic acid hydrogel, the adsorbed amount of ammonium ion at pH 6 was 19.2 mg/g.

Next, the method for forming a standard library for measuring the concentration of ammonium ions in a liquid using the hydrogel of the present invention includes preparing a plurality of standard solutions in the concentration range of 9.00-900 μM by diluting ammonia water in tertiary distilled water; immersing the chitosan-based 4-hydroxybenzoic acid hydrogel of claim 1 in a standard solution according to each concentration; Maintaining for 60 minutes to 120 minutes while shaking at 150 to 300 rpm conditions in a state in which the hydrogel is immersed; Separating the hydrogels immersed in each of the standard solutions and measuring the fluorescence intensity of the hydrogels; And matching the fluorescence intensity measured per hydrogel with the concentration of the standard solution in which the hydrogel is immersed to create a library so that the concentration of ammonium ions adsorbed to the hydrogel is specified.

Here, in the step of constructing a plurality of standard solutions, a plurality of standard solutions having a required concentration are prepared using ammonium chloride and tertiary distilled water. As an embodiment, an ammonium stock solution of 1000 mg/L is prepared. Then, the concentration is calculated and diluted with tertiary distilled water to prepare each standard solution having a concentration of the required concentration range, in one embodiment, 0.1, 0.2, 0.5, 0.8, 1, 2, 3. 4 and 5 mM. can

The chitosan-based 4-hydroxybenzoic acid hydrogel of claim 1 is not limited as long as it corresponds to the above-mentioned Chemical Formula 1, but as an embodiment, n is 18000 and m is a real number between 150 and 500, and chitosan-based 4-hydroxybenzoic acid Hydrogels may be used.

The step of measuring the fluorescence intensity may be performed by measuring the fluorescence intensity of the hydrogel in a wavelength range of 390 to 420 nm, and a wavelength suitable for the fluorescence meter used may be used. As one embodiment, it can be measured at a wavelength of 390 to 400 nm if it is a fluorescence spectrophotometer, and it will be able to be measured at a wavelength of 420 nm if it is an ultraviolet spectrophotometer.

The shaking intensity and time in the holding step are experimentally determined, and if the adsorption is less than 150 rpm, there is a problem of weakening the adsorption, if it exceeds 300 rpm, there is a problem of rapid shaking of the solution, and if it is less than 60 minutes, ammonium ions on the adsorption sites of all hydrogels There is a problem of not sticking, and there is a problem that adsorbed ammonium ions fall off after 120 minutes.

As an embodiment, the step of libraryizing may be performed by matching the fluorescence intensity measured per ammonium ion concentration of the standard solution as shown in Table 1 below.

Dissolved Ammonium-ions (mM) Fluorescence Intensities at 396.5nm 0.1 4682 0.2 4613 0.5 4516 0.8 4423 One 4364 2 4339 3 4093 4 4067 5 3876

Fluorescence intensity measurement conditions for forming the reference library of Table 1 are as follows.

-Amount of standard solution used: 50mg

-Hydrogel type: Cht-0.3PHBA-HG 100mg used

Shake at -200 rpm and hold for 60 minutes

-Use a fluorescence spectrophotometer for absorbance measurement

On the other hand, it is also possible to subdivide the ammonium ion concentration per 0.01uM, measure the fluorescence intensity, and then match and make the library. As shown, a standard calibration curve is prepared by displaying the fluorescence intensity measured per ammonium ion concentration of the standard solution with the ammonium ion concentration as the x-axis and the fluorescence intensity as the y-axis, and using this, the following Equation 1 was completed.

[Equation 1]

y=-147x + 4601

Here, y is the measured fluorescence intensity, x is the ammonium ion concentration, and R ² is greater than or equal to 0.9. At this time, R ² is a coefficient of determination, and the closer to 1, the higher the accuracy.

Equation 1 may be used to form a reference library per desired ammonium ion interval or fluorescence intensity interval.

Next, the reference library for measuring the ammonium ion concentration in liquid using the hydrogel of the present invention can be obtained by the above-described reference library formation method.

As an embodiment, the library may be created by matching the fluorescence intensity calculated per ammonium ion concentration at a certain interval using Equation 1 in the manner shown in Table 1.

Next, the method for measuring the ammonium ion concentration in the liquid using the hydrogel of the present invention is any one of the above-described chitosan-based 4-hydroxybenzoic acid hydrogel or chitosan-based 4-hydroxybenzoic acid synthesized by any of the above-described synthesis methods immersing the hydrogel in a target liquid; Maintaining the hydrogel immersed in the liquid for 60 to 120 minutes while shaking at 150 to 300 rpm; Separating the hydrogel from the target liquid and measuring fluorescence intensity; and determining the concentration of ammonium ions corresponding to the measured fluorescence intensity based on the aforementioned reference library.

If necessary, removing ammonium ions adsorbed from the chitosan-based 4-hydroxybenzoic acid hydrogel in which the measuring the fluorescence intensity was performed may be further performed. This can be done by immersing the 4-hydroxybenzoic acid hydrogel in a strong basic solution. Chitosan-based 4-hydroxybenzoic acid hydrogel from which ammonium ions have been removed can be reused up to 5 times to measure the concentration of ammonium ions in the liquid.

The shaking intensity and time in the holding step are experimentally determined, and if the adsorption is less than 150 rpm, there is a problem of weakening the adsorption, if it exceeds 300 rpm, there is a problem of rapid shaking of the solution, and if it is less than 60 minutes, ammonium ions are attached to the adsorption sites of all hydrogels. There is a problem of not sticking, and there is a problem that adsorbed ammonium ions fall off after 120 minutes.

If necessary, the step of determining the ammonium ion concentration may be calculated and performed by inserting the measured fluorescence intensity value into Equation 1 above.

Example 1

As shown in FIG. 2, a chitosan-based 4-hydroxybenzoic acid hydrogel was synthesized as follows.

1. Preparing reaction solution 1

Reaction solution 1 was prepared by dissolving 1.0 g of chitosan in 50 mL of a 1 M hydrochloric acid solution and dissolving the mixture while rotating it with a magnetic bar at 65° C. for 30 minutes.

2. Preparing reaction solution 2

766 mg of ammonium sulfate was added to reaction solution 1 for initiation, which is a chemical radical generation reaction of chitosan, and reaction solution 2 in which formation of a large number of radicals was induced in chitosan was prepared.

3. Preparing Reaction Solution 3

0.1 mM of 4-hydroxybenzoic acid was added to reaction solution 2, and an amide reaction, which is a bonding reaction between 4-hydroxybenzoic acid and chitosan, proceeded for 1 hour to obtain reaction solution 3.

4. Formation of hydrogel

After adding 0.1 g of N,N'-methylene-bisacrylamide and 14 g of acrylic acid as a hydrogel inducing agent to reaction solution 3, the reaction was performed by heating and rotating at 65 ° C for about 30 minutes to obtain chitosan-based 4-hydroxybenzoic acid. Hydrogel 1 (Cht-0.1PHBA-HG) was synthesized.

5. Washing step

The synthesized hydrogel was sequentially washed with methanol, ethanol, and 1M aqueous sodium hydroxide solution to remove residual chemicals.

6. Drying step

The washed hydrogel was dried at 60 °C for 3 hours.

Example 2

Chitosan-based 4-hydroxybenzoic acid hydrogel 2 (Cht-0.3PHBA-HG) was synthesized in the same manner as in Example 1, except that 0.3 mM 4-hydroxybenzoic acid was added to reaction solution 2.

Example 3

Chitosan-based 4-hydroxybenzoic acid hydrogel 3Cht-0.5HBA-HG) was synthesized in the same manner as in Example 1, except that 0.5 M of 4-hydroxybenzoic acid was added to reaction solution 2.

Example 4

Chitosan-based 4-hydroxybenzoic acid hydrogel 4Cht-0.7HBA-HG) was synthesized in the same manner as in Example 1, except that 0.7 M of 4-hydroxybenzoic acid was added to reaction solution 2.

Example 5

Chitosan-based 4-hydroxybenzoic acid hydrogel 5Cht-1.0HBA-HG) was synthesized in the same manner as in Example 1, except that 1 mM 4-hydroxybenzoic acid was added to reaction solution 2.

Example 6

As follows, a reference library for measuring the concentration of ammonium ions in a liquid using a hydrogel was formed.

1. Preparing multiple standard solutions

Ammonia water was diluted in tertiary distilled water to prepare standard solutions of 0.1, 0.2, 0.5, 0.8, 1, 2, 3. 4, and 5 mM each in a volume of 50 ml.

2. Step of soaking Cht-0.3PHBA-HG

100 mg of Cht-0.3PHBA-HG was immersed in each of the prepared standard solutions.

3. The stage of maintaining

It was maintained for 60 minutes while shaking at 200 rpm.

4. Measuring fluorescence intensity

Ammonium ion-adsorbed Cht-0.3PHBA-HG was separated from each standard solution and fluorescence intensity was measured.

5. Libraries step

The measured fluorescence intensity was matched with the ammonium ion concentration and adsorbed ammonium ion content of the standard solution to form a library, and a standard library for measuring the ammonium ion concentration in liquid was formed as shown in Table 1 above. If necessary, using Equation 1 as an embodiment, the fluorescence intensity interval is set to 3000 a.u. as a starting value and 1 a.u. After calculating the ammonium ion concentration at intervals, it may be possible to form a reference library by matching.

Example 7

Ammonium ion concentration in liquid was measured using a standard library for measuring ammonium ion concentration in liquid using hydrogel as follows.

1. Step of immersing chitosan-based 4-hydroxybenzoic acid hydrogel in target liquid

100 mg of Cht-0.3PHBA-HG was immersed in 50 ml of effluent from the fish farm.

2. The stage of maintaining

It was maintained for 60 minutes while shaking at 200 rpm.

3. Measuring fluorescence intensity

Ammonium ion-adsorbed Cht-0.3PHBA-HG was separated from fish farm effluent and measured with a fluorescence spectrophotometer, and the result was 4272a.u.

4. Determining the concentration of ammonium ion corresponding to the measured fluorescence intensity

1a.u. When a reference library matching the ammonium ion concentration at intervals is constructed, when the fluorescence intensity measured from the reference library is 4272a.u., the corresponding ammonium ion concentration is determined and confirmed, and if not constructed, y in Equation 1 When the value of x is calculated by putting 4272 in , it is 2.238, so it was confirmed that the ammonium ion concentration of the effluent of the fish farm is 2.24 mg/L.

comparative example

Comparative example chitosan hydrogel (Cht-HG) was synthesized in the same manner as in Example 1, except that 4-hydroxybenzoic acid was not added to reaction solution 2.

Experimental Example 1

Chitosan-based 4-hydroxybenzoic acid hydrogels 1 to 5 synthesized in Examples 1 to 5 (Cht-0.1PHBA-HG, Cht-0.3PHBA-HG, Cht-0.5PHBA-HG, Cht-0.7PHBA-HG , Cht-1.0PHBA-HG) and the comparative chitosan hydrogel (Cht-HG) synthesized in Comparative Example were examined by scanning electron microscopy (SEM).

Relatively small honeycomb pores of various sizes were observed on the surface of Cht-HG, while larger, integrated pores were observed on the surface of Cht-PHBA-HG. Specifically, Cht-0.3PHBA-HG and Cht-0.5PHBA-HG had 3 to 5 pores on each surface, whereas a lower number of 1 to 2 pores was observed on the surface of Cht-0.1PHBA-HG. In addition, several scattered pores were observed on the surfaces of Cht-0.7PHBA-HG and Cht-1.0PHBA-HG that were not effective for ammonium adsorption, which showed the same values as the adsorption results described later. The pore diameters of Cht-HG and Cht-0.3PHBA-HG were 260-370 and 600-800 nm, respectively, and these differences in pore size were attributed to the amide bond and benzene-benzene electrostatic interaction caused by the addition of PHBA. Finally, the pore size was increased by a factor of 2.2.

Experimental Example 2

The effect of pH on the ammonium ion adsorption capacity of Cht-HG and Cht-0.3PHBA-HG was investigated under the conditions of pH 2 to 12 adjusted with 1M hydrochloric acid and sodium hydroxide solution.

Under acidic conditions (pH2-4), both Cht-HG and Cht-PHBA-HG had lower ammonium ion adsorption capacity than neutral pH, but the adsorption capacity gradually increased as the pH increased, reaching the optimum values at pH 6 and 8, respectively. In the solution containing ammonium ions, Cht-0.3PHBA-HG reached an adsorption amount of 19.2 mg/g at pH 6, while Cht-HG at pH 8 reached an adsorption amount of 12.3 mg/g under optimal conditions. In addition, as a result of comparing Cht-0.3PHBA-HG and Cht-HG, the chitosan-based 4-hydroxybenzoic acid hydrogel 2 (Cht-0.3PHBA-HG) of the present invention is 1.56 times higher than Cht-HG under optimal conditions. It was confirmed that the ammonium ion adsorption capacity was shown. On the other hand, both Cht-0.3PHBA-HG and Cht-HG showed a sharp decrease in ammonium ion adsorption capacity under strong alkaline conditions in the pH range of 9-12.

Ammonium ions and numerous cations in seawater, such as Na+, K+, Ca2+ and Mg2+, compete for adsorption on the negatively charged surface of the adsorbent.

Na ⁺ (0.1–0.5 mM) reduced the ammonium ion adsorption capacities of Cht-HG-NH ⁴⁺ and Cht-PHBA-HG-NH ⁴⁺ from 89.5% to 78.9% and from 94.7% to 81.9%, respectively. In addition, the ammonium ion adsorption rate decreased as the Na ⁺ concentration increased (1.0-10.0 mM). In addition, Ca ²⁺ was a strong inhibitor for ammonium ion adsorption in both Cht-HG and Cht-PHBA-HG, and 1.0 mM Ca ²⁺ reduced the ammonium ion adsorption capacity by about 40%, while 10.0 mM Ca ²⁺ reduced the original ammonium ion adsorption capacity. Only 11.0% of the ion adsorption capacity was retained. Mg ²⁺ and K ⁺ showed the most contradictory results for ammonium ion adsorption. In particular, Cht-HG maintained 99.0% of ammonium adsorption efficiency at 1 mM of Mg ²⁺ , but K ⁺ decreased the ammonium ion adsorption rate by about 20% to 54.4% at 0.5 to 10 mM, respectively. Conversely, Cht-0.3PHBA-HG was not significantly affected by K ⁺ , but the ammonium adsorption rate at 1 mM Mg ²⁺ decreased to 83.2%.

Experimental Example 3

Chitosan-based 4-hydroxybenzoic acid hydrogels 1 to 5 (Cht-0.1PHBA-HG, Cht-0.3PHBA-HG, Cht-0.5PHBA-HG, Cht -0.7PHBA-HG, Cht-1.0PHBA-HG) and Comparative Chitosan Hydrogel (Cht-HG) synthesized in Comparative Example were investigated at ammonium concentrations of 0.15-25.0mM, and the results are shown in Figure 3a and Table 2. For the adsorbed ammonium concentration, the Langmuir model, which is an adsorption curve for an adsorbent composed of homogeneous components and composed of a single layer, was used.

As shown in FIG. 3a, rapid ammonium adsorption was observed on the surface of the adsorbent when a low ammonium concentration of 0.15 to 2.00 mM was introduced. However, the slope of the isotherm curve gradually decreased as the ammonium concentration increased, and the maximum adsorption amount (qm) was shown at 5 mM. The measured ammonium capacity parameters were calculated for the Langmuir model, and K _L (L/mg), q _m (mg/g) and R ² are shown in Table 1. The correlation coefficients (R ² ) of the Langmuir model exceeded 0.920 for both Cht-HG and Cht-0.3PHBA-HG, indicating that the adsorption mechanisms of these materials are in strong agreement with this model.

As shown in Table 2, as a result of comparing the adsorption capacities of Cht-HG and Cht-PHBA-HGs, it was found that the maximum adsorption capacity ( q _m ) of Cht-0.3PHBA-HG had the optimal value (19.9mg /g). The adsorption capacities of the other hydrogels were 11.6, 14.3, 19.6, 17.4, and 13.3 mg for Cht-HG, Cht-0.1PHBA-HG, Cht-0.5PHBA-HG, Cht-0.7PHBA-HG, and Cht-1.0PHBA-HG, respectively. It was /g. The results obtained indicate that the adsorption capacity of the adsorbent is improved when various PHBA concentrations are mixed with Cht-HG. In addition, the Langmuir constant K _L (L/mg) representing binding affinity is Cht-HG, Cht-0.1PHBA-HG, Cht-0.3PHBA-HG, Cht-0.5PHBA-HG, Cht-0.5PHBA-HG, Cht- 0.7PHBA-HG and Cht-1.0 PHBA-HG were 1.48, 1.94, 2.18, 1.47, 1.20 and 1.34 mol/L, respectively (see Table 1). As a result, Cht-0.3PHBA-HG showed the highest ammonium-hydrogel binding affinity value of 2.18 L/mg, indicating that ammonium can be more effectively attached to the surface of Cht-0.3PHBA-HG than other hydrogels. means

Experimental Example 4

Chitosan-based 4-hydroxybenzoic acid hydrogels 1 to 5 synthesized in Examples 1 to 5 (Cht-0.1PHBA-HG, Cht-0.3PHBA-HG, Cht-0.5PHBA-HG, Cht-0.7PHBA-HG , Cht-1.0PHBA-HG), that is, Cht-PHBA-HGs and Comparative Example synthesized in Comparative Example Chitosan Hydrogel (Cht-HG) to know the ammonium ion adsorption rate at various adsorption time intervals ranging from 5 minutes to 240 minutes It was investigated in 5 mM ammonium solution and the results are shown in Figure 3b. Then, the adsorption rate constants ( k ₁ and k ₂ ), equilibrium adsorption capacities ( q _e1 and q _e2 ) and equilibration time ( q _t ) of the adsorbent were calculated, and the results are shown in Table 3.

As shown in Fig. 3b, both Cht-HG and Cht-PHBA-HGs in ammonium solution showed a rapid growth of q _t from initial adsorption to 60 min from the start of the reaction. Due to the high surface area of Cht-HG and Cht-PHBA-HGs, a large concentration of ammonium ion was adsorbed at the initial site. However, after the initial point (0 to 60 min), the ammonium ion reached an equilibrium state and was no longer adsorbed in both Cht-HG and Cht-PHBA-HGs. These data are depicted in the pseudo-first-order (PFO) and pseudo-second-order (PSO) chemisorption kinetic models and presented in Table 2, which, as can be seen from Table 3, reached R ² values greater than 0.930. As a result of comparing the k ₁ and k ₂ values of Cht-HG and Cht-PHBA-HGs, the overall ammonium adsorption rate of Cht-PHBA-HGs was higher than that of Cht-HG. In particular, the k ₁ values of Cht-HG and Cht-PHBA-HGs were 0.049 min ^-1 and 0.066-0.109 min ^-1 , respectively.

Among all the hydrogels investigated, Cht-0.3PHBA-HG showed the fastest adsorption rate of 0.109 min ^-1 . This means that the adsorption rate of Cht-0.3PHBA-HG was improved by 2.24 times compared to Cht-HG. This k1 result is consistent with the k2 result and shows the same trend when the PSO kinetics model is applied. In addition, the ammonium equilibrium adsorption capacities of Cht-HG and Cht-0.3PHBA-HG were 11.1 and 19.9 mg/g, respectively. These results indicate that the addition of PHBA enhanced the ammonium adsorption capacity due to the effective introduction of anionic functional groups on the adsorbent surface. In particular, the ammonium ion adsorption rate and capacity of Cht-0.3PHBA-HG are superior to those of Cht-HG, so the ammonium ion adsorbent containing the chitosan-based 4-hydroxybenzoic acid hydrogel of the present invention can be used as a promising material for ammonium ion treatment. suggests

Experimental Example 5

Chitosan-based 4-hydroxybenzoic acid hydrogels 1 to 5 (Cht-0.1PHBA-HG, Cht-0.3PHBA-HG, Cht-0.5PHBA-HG, Cht-0.7PHBA-HG) synthesized in Examples 1 to 5 , Cht-1.0PHBA-HG) was adsorbed at concentrations of 0, 0.1, 0.2, 1.0, and 5.0 mM, respectively, and then irradiated with 365 nm ultraviolet rays to investigate the fluorescence intensity emitted through fluorescence microscopy. The fluorescence emission of Cht-HG, Cht-0.1PHBA-HG, Cht-0.5PHBA-HG, Cht-0.7PHBA-HG and Cht-1.0PHBA-HG is due to the total epifluorescence effect, whereas that of Cht-0.3PHBA-HG was weaker than To evaluate the effect of PHBA (4-hydroxybenzoic acid) on ammonium ion adsorption, Cht-0.3PHBA-HG adsorbed ammonium ions by immersing in ammonium solutions of various ammonium ion concentrations (0.1-5.0 mM) at pH 8.0 Ammonium ion fluorescence was detected for and the resulting photograph is shown in FIG. 4 .

Although not shown, it was confirmed that Cht-0.1PHBA-HG, Cht-0.3PHBA-HG, Cht-0.5PHBA-HG, Cht-0.7PHBA-HG and Cht-1.0 gradually darkened as the adsorbed ammonium ion concentration increased. 4 shown as an example, it can be seen that the higher the ammonium ion concentration of the immersed ammonium solution, the higher the adsorption amount and the lower the fluorescence intensity quantitatively.

Experimental Example 6

The effect of ammonium ions adsorbed on Cht-0.3PHBA-HG on the fluorescence intensity was investigated using a fluorescence spectrophotometer under UV light, and the results are shown in FIG. 5B.

As shown in FIG. 5B, it was confirmed that the higher the adsorbed ammonium ion concentration, the lower the fluorescence intensity quantitatively. That is, when immersed in a solution having a higher and higher ammonium ion concentration, the amount of ammonium ion adsorbed increased, resulting in a quantitative decrease in fluorescence emission at 396.5 nm. Therefore, it can be seen that Cht-0.3PHBA-HG can be used as an ammonium ion sensor. The correlation coefficient ( R ² ) for the fluorescence emission assay was 0.951 for measurements of hydrogels adsorbed with ammonium ranging from 0.1 to 5.0 mM and the limit of detection (LOD) was 0.1 mM. In addition, different fluorescence intensities of Cht-0.3PHBA-HG exposed to various ammonium concentrations (0, 0.1, 0.5, 1.0 and 5.0 mM) under a 365 nm UV lamp were observed. Cht-0.3PHBA-HG without ammonium ion adsorption showed the brightest fluorescence, and fluorescence at 0.1 and 0.5 mM ammonium slightly faded, while Cht-0.3PHBA-HG at 1.0 mM ammonium became darker. Finally, the morphology of the hydrogel was no longer fluorescent at 5.0 mM ammonium. In this result, the fluorescence intensity of Cht-0.3PHBA-HG decreased as the adsorbed ammonium increased, resulting in a decrease in fluorescence. For analysis according to UV irradiation, various ammonium concentrations were investigated under UV irradiation of various wavelengths. The initial absorbance intensity of Cht-0.3PHBA-HG was obtained at 224 nm. However, the absorbance intensity increased as the ammonium concentration increased from 0.1 to 2.0 mM, indicating that the added ammonium caused dehydrogenation of PHBA. Combined with the aforementioned results, the standard curve of ammonium fluorescence quenching and absorbance intensity at 224 nm showed a high correlation coefficient ( R ² ) of 0.995 based on the 0.1-2.0 mM ammonium concentration range. In addition, to prepare for experiments on real natural waters, the disturbance of ammonium ion detection by electrolytes of 2 mM Ca ²⁺ , K ⁺ , Mg ²⁺ , Na ⁺ and PO ^{4 3-} in Cht-0.3PHBA-HG was identical to the experimental UV evaluated under irradiation conditions. The relative absorbance intensity in the presence of these electrolytes (Ca ²⁺ , K ⁺ , Mg ²⁺ , Na ⁺ and PO4 ^3- ) did not show a significant change at 224 nm, a wavelength related to the adsorption of ammonium ions. This means that the ammonium ion is the only factor interacting with the fluorophore of the PHBA conjugate structure. Therefore, it was found that ammonium ion can be sensitively detected in the presence of salt, and Cht-0.3PHBA-HG can be used as an effective ammonium ion adsorbent and sensor.

Experimental Example 7

The reusability of Cht-HG and Cht-0.3PHBA-HG was investigated for 5 repetition cycles as follows, and the results are shown in FIG. 6a.

As a result of evaluating the reusability including adsorption of Cht-HG and Cht-PHBA-HG in a saturated ammonium solution and ammonium removal by 1M sodium hydroxide solution, the ammonium removal efficiency of Cht-HG and Cht-0.3PHBA-HG was 77.1% and 73.9%. Therefore, it was found that PHBA slightly improved the structural durability of the adsorbent.

Experimental Example 8

In order to evaluate the applicability of adsorbents for actual wastewater treatment, 50 mL of effluent samples from local fish farms were treated with 0.2 g of Cht-HG and Cht-0.3PHBA-HG, and the results are shown in Fig. 6b.

The initial ammonium concentration of the actual wastewater was 2.24 mg/L as demonstrated by Nessler's reagent method, but after removal using Cht-HG and Cht-0.3PHBA-HG, the residual ammonium concentration was 0.896 mg/L and 1.50 mg, respectively. /L showed a decrease. Therefore, it can be seen that the chitosan-based 4-hydroxybenzoic acid hydrogel of the present invention can be used in practical applications. In particular, Cht-PHBA-HGs, a hydrogel modified with PHBA, showed a removal rate of 60.1% in the actual farm effluent, which was significantly higher than the 33.0% adsorption efficiency of Cht-HG, showing a difference in adsorption capacity and about 1.82 times It was found that the adsorption capacity of ammonium ions was improved.

Although the present invention has been shown and described with preferred embodiments as described above, it is not limited to the above embodiments, and to those skilled in the art within the scope of not departing from the spirit of the present invention Various changes and modifications will be possible.

Claims (25)

Chitosan-based 4-hydroxybenzoic acid hydrogel having Formula 1 below.
[Formula 1]

Here, n is an integer between 200 and 50000, and m is an integer between 50 and 1000.
According to claim 1,
Chitosan-based 4-hydroxybenzoic acid hydrogel, characterized in that the ammonium ion adsorption capacity of chitosan hydrogel is improved by more than 1.5 times.
According to claim 2,
Chitosan-based 4-hydroxybenzoic acid hydrogel, characterized in that the ammonium ion adsorption capacity is improved by the 4-hydroxybenzoic acid.
According to claim 2,
Chitosan-based 4-hydroxybenzoic acid hydrogel, characterized in that when the ammonium ion is adsorbed, green fluorescence is emitted by the 4-hydroxybenzoic acid.
According to claim 4,
Chitosan-based 4-hydroxybenzoic acid hydrogel, characterized in that the amount of adsorption of the ammonium ion is measured by the intensity of the emitted green fluorescence.
According to claim 5,
Chitosan-based 4-hydroxybenzoic acid hydrogel, characterized in that the adsorption amount of the ammonium ion and the intensity of the green fluorescence are inversely proportional in the hydrogel where m is an integer between 150 and 500 in Formula 1.
preparing a reaction solution 1 by dissolving chitosan in an acid solution at a constant temperature;
preparing a reaction solution 2 in which a plurality of radicals are formed in chitosan by adding an initiator to the reaction solution 1 to generate a chemical radical of chitosan;
preparing a reaction solution 3 in which chitosan and 4-hydroxybenzoic acid are combined through an amide reaction generated by adding 4-hydroxybenzoic acid to the reaction solution 2;
A method for synthesizing a chitosan-based 4-hydroxybenzoic acid hydrogel comprising adding a hydrogel inducing agent to the reaction solution 3 and stirring at a constant temperature to form a hydrogel.
According to claim 7,
A washing step of removing residual chemicals from the hydrogel; and
A drying step of drying the formed hydrogel or the washed hydrogel; Chitosan-based 4-hydroxybenzoic acid hydrogel synthesis method, characterized in that it further comprises one or more of.
According to claim 7,
The acid solution is a chitosan-based 4-hydroxybenzoic acid hydrogel synthesis method, characterized in that at least one selected from the group consisting of a hydrochloric acid solution, a nitric acid solution and a sulfuric acid solution.
According to claim 7,
The initiator is ammonium sulfate, 2,2-azobis (2-methylpropionitrile), 2,2-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2-bromopropanenitrile, Chitosan-based 4-hydroxybenzoic acid hydrogel synthesis method, characterized in that at least one selected from the group consisting of toluenesulfonyl chloride.
According to claim 7,
Chitosan-based 4-hydroxybenzoic acid hydrogel synthesis method, characterized in that the 4-hydroxybenzoic acid is added to the reaction solution 2 at a concentration of 0.1 to 1 mM.
According to claim 7,
The hydrogel inducer is a chitosan-based 4-hydroxybenzoic acid hydrogel synthesis method, characterized in that at least one selected from the group consisting of polyethylene glycol, acrylic acid, polyacrylamide, polyvinyl alcohol, collagen, and gelatin.
According to claim 7,
Chitosan-based 4-hydroxybenzoic acid hydrogel synthesis method, characterized in that the constant temperature is 60 ℃ to 80 ℃.
Ammonium containing the chitosan-based 4-hydroxybenzoic acid hydrogel according to any one of claims 1 to 6 or the chitosan-based 4-hydroxybenzoic acid hydrogel synthesized by the synthesis method according to any one of claims 7 to 13 absorbent.
15. The method of claim 14,
Ammonium adsorbent, characterized in that the amount of ammonium ion adsorption is reduced when it is out of the pH 5 to pH 8 range.
It comprises the chitosan-based 4-hydroxybenzoic acid hydrogel of any one of claims 1 to 6,
When n is 18000 and m is an integer between 150 and 500 in the chitosan-based 4-hydroxybenzoic acid hydrogel, the ammonium ion adsorption amount at pH 6 is 19.2 mg/g.
Preparing a plurality of standard solutions in the concentration range of 9.00-900 μM by diluting ammonia water with tertiary distilled water;
immersing the chitosan-based 4-hydroxybenzoic acid hydrogel of claim 1 in a standard solution according to each concentration;
Maintaining for 60 minutes to 120 minutes while shaking at 150 to 300 rpm conditions in a state in which the hydrogel is immersed;
Separating the hydrogels immersed in each of the standard solutions and measuring the fluorescence intensity of the hydrogels; and
Ammonium ions in a liquid using a hydrogel comprising; matching the fluorescence intensity measured per hydrogel with the concentration of the standard solution in which the hydrogel is immersed, and creating a library so that the concentration of ammonium ions adsorbed to the hydrogel is specified. A method for forming a reference library for concentration measurement.
18. The method of claim 17,
The chitosan-based 4-hydroxybenzoic acid hydrogel is a standard library formation method for measuring the ammonium ion concentration in a liquid using a hydrogel, characterized in that n is 18000 and m is a real number between 150 and 500.
18. The method of claim 17,
The step of measuring the fluorescence intensity of the hydrogel, respectively, is performed by measuring the absorbance of the hydrogel at a wavelength of 390 nm to 420 nm.
18. The method of claim 17,
The step of libraryizing is performed by matching the calculated value by changing the absorbance or ammonium ion concentration of the hydrogel at regular intervals using Equation 1 below. Ammonium ion concentration measurement in liquid using a hydrogel, characterized in that A method for forming a reference library for use.
[Equation 1]
y=-147x + 4601
where y is the measured fluorescence intensity and x is the ammonium ion concentration. A standard library for measuring the concentration of ammonium ions in a liquid using the hydrogel formed by the method of any one of claims 17 to 20.
The chitosan-based 4-hydroxybenzoic acid hydrogel according to any one of claims 1 to 6 or the chitosan-based 4-hydroxybenzoic acid hydrogel synthesized by the synthesis method according to any one of claims 7 to 13 is added to the target liquid. immersion;
maintaining the hydrogel immersed in the liquid for 60 to 120 minutes while shaking at 150 to 300 rpm;
Separating the hydrogel from the target liquid and measuring fluorescence intensity; and
A method for measuring the concentration of ammonium ions in a liquid using a hydrogel comprising: determining the concentration of ammonium ions corresponding to the measured fluorescence intensity according to the reference library formed by the method of claim 17 or Equation 1 below.
[Equation 1]
y=-147x + 4601
where y is the measured fluorescence intensity and x is the ammonium ion concentration.
23. The method of claim 22,
Removing ammonium ions adsorbed from the chitosan-based 4-hydroxybenzoic acid hydrogel in which the step of measuring the fluorescence intensity was performed; Ammonium ion concentration measurement method in a liquid using a hydrogel, characterized in that further performed.
24. The method of claim 23,
The step of removing the ammonium ion is performed by immersing the chitosan-based 4-hydroxybenzoic acid hydrogel in a strong basic solution.
24. The method of claim 23,
A method for measuring the concentration of ammonium ions in a liquid using a hydrogel, characterized in that the chitosan-based 4-hydroxybenzoic acid hydrogel from which the ammonium ions are removed is reused up to 5 times.

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