KR100338123B1 - Rapid measuring method of soil cation exchangeable capacity using copper adsorption and spectrophotometer - Google Patents

Abstract

The present invention relates to a method for measuring the soil cation substitution capacity using copper adsorption and spectrophotometer, and when dissolved in distilled water naturally compared to the conventional method of causing a water pollution and a complex analysis process using a large amount of reagents By adsorbing a copper solution with a certain concentration of blue to the negative charge of the soil, the concentration of unadsorbed copper is measured by spectrophotometer, so that the cation substitution capacity of the soil can be measured easily, accurately and quickly within a short time. There is a significant cost savings.

Description

Rapid measuring method of soil cation exchangeable capacity using copper adsorption and spectrophotometer

The present invention relates to a method for measuring the soil cation substitution capacity using copper adsorption and spectrophotometer. More specifically, the present invention relates to a copper solution which is blue when dissolved in distilled water. Method of measuring cation substitution capacity of soil easily in a short time without using reagents that cause environmental pollution by measuring spectrophotometer quantitatively decrease of blue chromaticity by the amount adsorbed on soil surface It is about.

The cation substitution capacity of soil is the total amount of negative charge of soil, and it is ammonium nitrogen (NH ₄ ⁺ ), potassium (K ⁺ ), calcium (Ca ²⁺ ), magnesium (Mg ²⁺ ), etc. Refers to the capacity of the cationic component of the adsorbed soil. Components added as fertilizer are adsorbed by electrical attraction under the negative charge of the soil and then moved to the place where the crops can be used. As the cation substitution capacity increases, more fertilizer components can be adsorbed to the soil. Since the cation substitution capacity serves as an important criterion for determining the amount of fertilizer used, the method has been proposed by various researchers.

The ammonium acetate method, used as an international standard method, has been proposed and improved by several researchers. In this method, ammonium acetate solution is added to the soil to saturate the negative charge of the soil with ammonium ions, and the excess ammonium acetate solution is removed by washing with ethanol or isopropyl alcohol, and then ammonium adsorbed on the soil. The amount of ammonium produced by leaching ions with acidified sodium chloride (NaCl) is used to determine the amount of cation substitution, the total amount of negative charge in the soil.

This ammonium acetate solution is used for the determination of ammonium acetate solution used for saturation process, 80% (v / v) ethyl alcohol or isopropyl alcohol used for washing process, sodium chloride used for leaching process, and boric acid solution used for the determination of ammonium ion. Many reagents, such as boric acid solution, sulfuric acid (H ₂ SO ₄ ) or hydrochloric acid (HCl) and bromocresol green, are consumed and most of them can contaminate water quality. In addition, an expensive cation exchange capacity measuring device made of glassware and a distillation device for quantitating ammonium ions are required separately to advance the leaching process, and the analysis process is complicated and time consuming. It is inconvenient and inadequate to measure the cation substitution capacity of soil.

Polemio and Rhoades (1977) developed a method of using sodium acetate (CH ₃ COONa) instead of ammonium acetate (CH ₃ COONH ₄ ) because the ammonium acetate method used excessive amounts of ammonium ions as water pollution components. This method, improved by several researchers, added sodium acetate (NaOAc.3H ₂ O), a solution of sodium chloride and ethanol to the soil, adsorbed sodium to the soil with negative charge, saturated, and magnesium nitrate (MgNO ₃ ). It is a method of measuring the sodium leaching out by adding it. However, the method needs to repeat the saturation process and leaching process several times, and requires a laboratory apparatus such as a sonicator and a centrifuge, and requires a separate device for analyzing sodium and chlorine as well as time-consuming and complicated operation. Do. In addition, acetate (CH ₃ COOH) and nitric acid (NO ₃ ) that may contaminate the water quality has the disadvantage that occurs as a waste reagent.

Gillman (1979) also measured the amount of magnesium that was reduced by adding barium chloride (BaCl ₂ ) solution to saturate the soil negative charge and add magnesium sulfate (MgSO ₄ ) to leach the negatively charged barium with magnesium to leach it. This paper suggests a method to measure the cation substitution capacity of soil and has been developed by many researchers. However, this method is not suitable for the simple and rapid analysis of cation substitution capacity of soil at the required time because the analysis operation is complicated and a large amount of water pollutant reagent is used.

As mentioned above, the conventional method for measuring the cation substitution capacity of the soil is a saturation process of adsorbing ammonium ions or sodium ions on the soil negative charge using a large amount of reagents that may contaminate water quality, and excess reagents with alcohol. The process of washing to remove, leaching saturated ammonium or sodium, and measuring leaching components are essential. This process is complicated and requires a number of analysis tools, which requires a lot of analysis time, a lot of reagents, which is inexpensive, and has a common disadvantage of not being able to analyze quickly when needed.

Therefore, an object of the present invention is to measure the cation substitution capacity of soil economically, quickly and simply by shortening the complicated experiment process such as the conventional saturation process, washing process, leaching process, quantification process and significantly reducing the amount of reagent. In providing.

The above object of the present invention is a copper compound of blue color (CuSO ₄ · 5H ₂ O), copper acetate [Cu (COO) ₂ · H ₂ O], copper chloride (CuCl ₂ · 2H ₂ O), copper nitrate [Cu (NO ₃ ) ₂ ], copper chloride (I) (CuCl), copper acetylacetonate [Cu (C ₅ H ₇ O ₂ )], etc. were dissolved in distilled water to prepare a copper solution, added to the soil and shaken. This is achieved by adsorbing copper ions to the negative charge of the soil and then comparing the cation substitution capacity measured by spectrophotometer with the decrease in blue absorbance according to the substitution reaction and the cation substitution capacity quantified by the ammonium acetate method. It was.

Hereinafter, the configuration of the present invention will be described.

1 shows the equivalent adsorption of negative charges and cationic components on the soil surface.

Figure 2 shows the substitution reaction of cations and copper ions adsorbed on the soil.

3 shows the change in absorbance of unabsorbed copper with shaking time.

Figure 4 shows the absorbance of the copper solution according to the wavelength.

5 is a standard curve showing the relationship between absorbance and copper solution concentration measured at 720 nm with a spectrophotometer.

FIG. 6 is a standard curve showing the relationship between absorbance and copper solution concentration measured at 812 nm with a spectrophotometer. FIG.

Figure 7 shows a graph comparing the average content of three repeated measurements of the present invention and the conventional method.

8 shows a graph comparing the coefficient of variation between repetitions by measuring three iterations according to the present invention and the conventional method.

9 shows a graph comparing the standard deviation between repetitions by measuring three iterations according to the present invention and the conventional method.

The present invention comprises the steps of dissolving a copper compound in distilled water to prepare a copper solution of 0.02 ~ 2 N; Placing a soil sample in an Erlenmeyer flask and adsorbing copper ions to the soil negative charge by adding the copper solution; Measuring the absorbance of the filtrate by filtration or centrifugation of the mixed solution of the copper solution and the soil; Preparing a standard curve by measuring the absorbance of the copper solution having a known concentration with a spectrophotometer; Calculating the cation substitution capacity of the soil by substituting the absorbance of the sample into a standard curve; Comparing the cation substitution capacity quantified by the method of the present invention and the cation substitution capacity quantified by the conventional ammonium acetate method.

In the present invention, the reaction of adsorbing copper ions to the negative charge of the soil by adding a copper solution to the soil is based on the principle of the cation substitution reaction of the soil. As shown in Figure 1, the surface of the soil is a component added as a fertilizer or the cation produced while the soil is weathered is adsorbed by reacting with the negative charge of the soil surface in equivalent weight equivalent, the cation substitution capacity means the total amount of negative charge of the soil This is equivalent to the total amount of cations adsorbed on the negative charge. As shown in Fig. 2, the surface of the soil before the addition of copper sulfate solution is adsorbed by other cations, so the copper sulfate solution becomes dark blue. However, when copper sulfate solution is added to the soil and shaken, it is adsorbed on the soil in an equivalence-equivalent ratio. The cations displace and flow out into the solution, whereas the copper ions in the solution adsorb with the negative charge of the soil, so the chromaticity of the solution gradually becomes pale blue.

Hereinafter, the specific configuration of the present invention will be described in detail with reference to step-by-step description and embodiments, but the scope of the present invention is not limited to these embodiments.

First step: preparation of copper solution for adsorption reaction

The copper solution for the adsorption reaction is prepared using a copper compound so as to have a concentration of 0.02 to 2 N. Copper acetate is 1.9965 to 199.65 g, copper sulfate is 4.9978 to 499.78 g, copper chloride is 1.705 to 170.5 g, and copper nitrate is dissolved in distilled water to make 1 L. Prepare a copper solution. Since copper solution for adsorption reaction is to adjust the concentration of copper, copper chloride (I) and copper acetylacetonate may be used instead of the above copper compound, and in the case of hydrate or anhydride, the concentration calculation method generally used in this regard Manufacture according to The concentration of the copper solution depends on the size of the cation substitution capacity of the soil and the amount of soil sample to be taken. The optimum concentration of copper solution is 0.2 N.

Step 2: adsorption of copper to soil negative charge

Place 0.1-20 g of soil in a glass apparatus such as a Erlenmeyer flask, add 2 to 250 mL of the copper solution prepared in the first step, and shake the copper in the solution for 1 to 60 minutes using a shaker. Saturate. The amount of soil taken and the amount of copper added can be arbitrarily adjusted according to the size of the cation substitution capacity of the soil. The larger the cation substitution capacity, the smaller the amount of soil and the higher the concentration or addition of copper solution. For normal soils, it is appropriate to add 25 mL of 0.2 N copper solution per 5 g of soil. Shaking process is the reaction of copper in the solution to saturate the adsorption of cations that are saturated and adsorbed to the soil negative charge, can be determined by the preliminary experiment according to the nature of the soil, shake for 5 minutes in the general soil.

Step 3: Determination of Copper in Solution

The concentration of copper in the solution is quantified by measuring the absorbance with a spectrophotometer. Since the copper solution, which is blue when dissolved in distilled water, absorbs in the range of 600-1,100 nm, the concentration of copper is quantified by measuring the absorbance at an arbitrary wavelength.

Step 4: prepare a standard curve

In order to saturate the copper solution in the soil and measure the concentration of unadsorbed copper, first prepare a copper standard solution for each concentration and measure the absorbance. Then, prepare a standard curve showing the correlation between the concentration of the copper solution and the absorbance. The absorbance measurement wavelength for creating a standard curve can be arbitrarily selected from 600 to 1,100 nm.

Step 5: Calculate Soil Cation Replacement Capacity

The cation substitution capacity of the soil is calculated from the difference between the concentration of copper solution added to the soil and the unadsorbed concentration using the following formula [1].

Soil cation substitution capacity (meq or cmol ⁺ / kg) =

{(Concentration of added copper solution (meq)-concentration of copper solution remaining after adsorption (meq)} ×

Amount of copper solution added (mL) / weight of soil (g) x 1/10 ---------------- [1]

Where 1/10 is a unit conversion factor for expressing units of cation substitution capacity in meq / 100 g or cmol ⁺ / kg.

Step 6: Compare the Analytical Precision with Conventional Methods

According to the present invention, the correlation between the cation substitution capacity calculated in the fifth step and the cation substitution capacity quantified by the conventional ammonium acetate method, the variation coefficient between repetitions, and the standard deviation between repetitions are plotted and compared. do.

Hereinafter, the specific structure of this invention is given and mentioned an Example.

Example 1 Preparation of Standard Curves

As a result of investigating the effect of shaking time on the adsorption of copper, as shown in FIG. 3, the longer the shaking time, the better the copper adsorption reaction, and the shorter the shaking time, the complete adsorption reaction did not occur. If the shaking time is short, the cation substitution capacity may be measured low, and the shaking time was more than 5 minutes. As shown in FIG. 4, the absorption wavelength of the copper solution was distributed in the range of 600-1,100 nm, and the maximum absorption wavelength was 812 nm.

The standard curve was prepared by varying the concentration of the copper standard solution in the range of 0-1,200 milli equivalents (meq) and measuring the absorbance at 720 nm selected as the representative wavelength. 5 is a standard curve of the copper standard solution measured at 720 nm, and there was a high correlation (r = 0.9994) between the absorbance and the concentration of the copper solution. Therefore, the concentration of the copper solution was converted from the absorbance value using the formula of the standard curve. 6 is a standard curve measured at 812 nm, the maximum absorption wavelength, and the correlation coefficient (r = 0.9996) is very high as at 720 nm.

Example 2 Determination of Cation Replacement Capacity of Soil Sample

5 g of air-dried soil was added to a Erlenmeyer flask, shaken for 5 minutes by adding 25 mL of 0.2 N copper solution, filtered, and measured the absorbance of the filtrate with a spectrophotometer. This was substituted into Equation [1] of the fifth step to calculate the cation substitution capacity. The cation substitution capacity of 33 soil samples measured three times by the method of the present invention and the conventional standard ammonium acetate method is shown in Table 1.

Example 3 Comparison of Analytical Accuracy of Methods of the Present Invention and Conventional Methods

Soils used as test samples were 33 soils with cation substitution capacity ranging from 6.7 to 30.5 cmol ⁺ / kg and were collected from cleared land, paddy fields, fields and plantation soils. 7 is a comparison of the average content of the cation substitution capacity measured by the method of the present invention and the cation substitution capacity measured by three repeated methods according to the conventional method, and there is a high correlation (r = 0.977) of 1: 1 between the two methods. It was confirmed that there was no difference between the two methods.

Comparison of cation substitution capacity of three repetitive quantifications according to the present invention method and conventional ammonium acetate method Sample Number Method of the invention Conventional ammonium acetate method 1 repetition 2 repetitions 3 repetitions Average 1 repetition 2 repetitions 3 repetitions Average One 5.30 5.20 5.40 5.30 6.90 6.50 6.70 6.7 2 6.20 6.30 6.18 6.23 7.60 7.50 7.30 7.5 3 28.30 27.60 28.90 28.27 26.50 27.20 26.80 26.8 4 8.60 8.50 8.70 8.60 8.20 8.50 8.90 8.5 5 19.30 19.10 18.90 19.10 18.60 17.90 18.20 18.2 6 20.30 20.60 20.10 20.33 21.20 20.60 21.00 20.9 7 29.80 29.40 30.00 29.73 29.60 28.90 29.30 29.3 8 25.60 25.60 26.00 25.73 24.60 25.30 24.80 24.9 9 24.30 24.10 23.80 24.07 23.60 22.60 23.00 23.1 10 12.50 12.00 13.00 12.50 11.80 12.60 11.50 12.0 11 6.90 7.20 7.10 7.07 8.90 8.10 8.50 8.5 12 20.30 20.40 20.90 20.53 21.20 20.50 20.80 20.8 13 22.50 22.50 21.60 22.20 23.60 23.40 23.90 23.6 14 28.10 29.00 28.50 28.53 26.20 25.90 26.00 26.0 15 27.30 27.90 27.10 27.43 25.90 26.10 25.70 25.9 16 8.80 8.70 8.50 8.67 9.50 10.60 9.80 10.0 17 9.60 9.50 9.10 9.40 11.20 11.60 11.90 11.6 18 11.30 11.40 10.90 11.20 13.20 13.50 13.90 13.5 19 23.60 23.80 22.90 23.43 26.90 25.80 26.20 26.3 20 15.60 15.90 15.40 15.63 15.70 14.90 15.00 15.2 21 20.00 20.50 21.10 20.53 21.30 21.50 21.00 21.3 22 18.80 18.40 18.90 18.70 18.80 18.20 19.00 18.7 23 26.30 26.40 26.10 26.27 27.50 27.30 27.90 27.6 24 6.70 6.70 6.10 6.50 8.20 8.60 8.00 8.3 25 7.80 7.90 7.20 7.63 9.80 9.20 9.60 9.5 26 9.20 9.60 9.30 9.37 11.10 10.90 11.40 11.1 27 25.90 26.50 26.10 26.17 26.50 26.80 26.00 26.4 28 30.00 30.50 31.10 30.53 29.80 30.60 31.10 30.5 29 26.20 26.80 26.90 26.63 26.60 26.80 27.00 26.8 30 15.20 15.30 15.80 15.43 18.20 19.20 19.10 18.8 31 13.30 13.60 13.90 13.60 15.20 15.60 16.20 15.7 32 15.20 15.20 16.10 15.50 18.40 18.60 19.10 18.7 33 8.20 8.60 8.90 8.57 10.20 10.90 10.50 10.5

Figure 8 shows the coefficient of variation of the cation substitution capacity measured in three iterations by the method of the present invention and the conventional method, the variation coefficient of both methods is 5% or less, both methods were accurate. Figure 9 shows the standard deviation of the cation substitution capacity measured in three iterations by the method of the present invention and the conventional method, it was confirmed that the standard deviation of both methods is 1 cmol ⁺ / kg or less, there is no difference between the two methods. Therefore, it was confirmed that the method of the present invention can obtain the same analytical accuracy as the conventional method while being able to quickly measure the cation substitution capacity of the soil with significantly less reagent and simple operation than the conventional method.

As described above in detail with reference to the step-by-step description and examples, the present invention uses a large amount of expensive reagents that can contaminate water quality by adsorbing copper solution to the soil and quantifying the cation substitution capacity, which is the total amount of negative soil charge. Compared with the conventional method, which is very complicated and requires a lot of analysis time, it uses only inexpensive copper solution. By measuring the absorbance using a phosphorus spectrophotometer, it is possible to measure the cation substitution capacity in the soil by a simple operation in a short time, and it is a very useful invention in the soil analysis industry to grasp the exact usage of fertilizer because it has a significant cost saving effect. .

Claims (4)

Preparing a copper solution by dissolving the copper compound in distilled water; Placing a soil sample in an Erlenmeyer flask and adsorbing copper ions to the soil negative charge by adding the copper solution; Measuring the absorbance of the filtrate by filtration or centrifugation of the mixed solution of the copper solution and the soil; Preparing a standard curve by measuring the absorbance of the copper solution having a known concentration, using a spectrophotometer; Calculating the cation substitution capacity of the soil by substituting the absorbance of the sample into a standard curve; A method for measuring the attribution of a soil cation exchange capacity using a spectrophotometer and adsorption of copper, characterized in that it comprises the step of comparing the cation substitution capacity quantified by the method of the present invention and the cation substitution capacity quantified by the conventional ammonium acetate method. The copper adsorption and spectroscopy of claim 1, wherein the copper solution is selected from the group consisting of copper acetate, copper sulfate, copper chloride (II), copper phosphate, copper acetylacetonate, copper nitrate, and copper oxide. Property Measurement Method of Soil Cation Replacement Capacity Using Photometer. 2. The adsorption and spectroscopy of copper according to claim 1, wherein the copper solution is prepared at a concentration of 0.02 to 2 N and added to 0.1 to 20.0 g of soil, followed by shaking to adsorb copper ions in a saturated state to the negative charge of the soil. Property Measurement Method of Soil Cation Replacement Capacity Using Photometer. The method according to claim 1, wherein the absorbance of the filtrate is measured at a wavelength of 600 to 1100 nm by using a spectrophotometer, and then a standard curve is prepared to convert the absorbance to a concentration of copper solution and substituting the following equation into the soil. A method for measuring the property of soil cation exchange capacity using copper adsorption and spectrophotometer, characterized in that to calculate the cation exchange capacity of. Soil cation substitution capacity (meq or cmol ⁺ / kg) = {(Concentration of added copper solution (meq)-concentration of copper solution remaining after adsorption (meq)} × Amount of copper solution added (mL) / soil weight (g) x 1/10 Here, 1/10 is a unit conversion coefficient for expressing the unit of cation substitution capacity as meq / 100g or cmol ⁺ / kg.