Method for measuring content of rare earth elements in single rare earth compound by turbidimetry

Abstract

The invention discloses a method for measuring the content of rare earth elements in a single rare earth compound by turbidimetry. Comprising the following steps: 1, preparing a fluoride solution and a 50% nitric acid aqueous solution; 2, preparing a rare earth element standard solution; step 3, testing the rare earth compound sample by using turbidimetry; and 4, calculating a detection result: calculating the content of the rare earth elements in the sample according to a formula. The method can be used for testing the content of single rare earth with different content levels in the sample. The method has the advantages of wide linear range, high precision, good accuracy, low cost, simplicity in operation, high detection efficiency and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of testing or analyzing materials by means of measuring the chemical or physical properties of the materials, and specifically is a method for measuring the content of rare earth elements in a single rare earth compound by turbidimetry. Background Art

[0002] Rare earth elements refer to the IIIB group in the periodic table, including scandium (21), yttrium (39) and lanthanide elements (57-71), a total of 17 elements. Rare earths are widely used in new energy, new materials, energy conservation and environmental protection, aerospace, electronic information and other fields, and are an indispensable and important element in modern industry. It is called "industrial vitamin" and is a non-renewable strategic resource. China is a country with a large reserve of rare earth resources in the world. It not only has rich reserves, but also has the advantages of complete mineral species and rare earth elements, high rare earth grade and reasonable distribution of mines, which has laid a solid foundation for the development of China's rare earth industry.

[0003] The analysis methods of rare earth elements include oxalate gravimetric method, EDTA titration method, photometry, X-ray fluorescence spectrometry and inductively coupled plasma emission spectrometry. These detection methods all have certain disadvantages. The gravimetric method and titration method have long processes and cumbersome operations. The photometric method requires the addition of a color developer and the selection of appropriate color development conditions. At present, this method has been basically eliminated. X-ray fluorescence spectrometry lacks corresponding standard samples. For the detection of high-content rare earth elements, the accuracy of inductively coupled plasma emission spectrometry is poor. Therefore, it is very necessary to develop a simple, fast and accurate rare earth element analysis method. Summary of the invention

[0004] In view of the problems existing in the background technology, the present invention provides a method for determining the content of rare earth elements in a single rare earth compound by turbidimetry, and the technical solution comprises the following steps:

[0005] Step 1, preparing a fluoride solution and a 50% nitric acid aqueous solution;

[0006] Step 2, preparing a rare earth element standard solution;

[0007] Step 3: Testing the rare earth compounds using turbidimetry, including:

[0008] Step 3.1, sample pretreatment: weigh a rare earth compound and place it in a beaker, the rare earth element content in the rare earth compound is 10w / % to 90w / %; moisten the sample with water, add 20mL of 50% nitric acid aqueous solution, heat to dissolve, cool after complete dissolution, and dilute to a volumetric flask; transfer 5mL of the solution to a colorimetric tube;

[0009] Step 3.2, add 3-10 mL of 50% nitric acid aqueous solution, and then add 1-10 mL of the fluoride solution in step 1. Each reagent needs to be gently mixed, diluted with water, shaken and allowed to stand to form a mixed nitric acid solution;

[0010] Step 3.3, pipette a portion of the mixed nitric acid solution into a cuvette, and measure the absorbance at a fixed wavelength on a spectrophotometer using a reagent blank as a reference;

[0011] Step 3.4, establish a standard working curve: pipette 1-10 mL of the rare earth element standard solution in step 2 into a set of colorimetric tubes; then perform determination according to steps 3.2 and 3.3; establish a standard working curve with the rare earth element concentration as the abscissa and the absorbance as the ordinate;

[0012] Step 3.5, substituting the net absorbance of the solution to be tested into the standard working curve established in step 3.4 to obtain the rare earth element concentration C in the solution;

[0013] Step 4: Calculate the test results: Calculate the content of rare earth elements in the sample according to the following formula:

[0014]

[0015] Wherein, ω-mass fraction of rare earth element in rare earth compound, %; C-concentration of rare earth element in test solution, g / L; V-fixed volume of sample, mL; m-mass of rare earth compound, g.

[0016] Step 2: The raw material for preparing the fluoride solution includes any one of HF, NaF and KF.

[0017] The concentration of HF solution is 1:1, the concentration of NaF solution is 20-25 g / L, and the concentration of KF solution is 25-35 g / L.

[0018] The rare earth compound includes any one of rare earth hydroxide, rare earth chloride, rare earth carbonate and rare earth nitrate.

[0019] The rare earth compound includes any one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc.

[0020] The concentration of the nitric acid solution in the mixed nitric acid solution ranges from 3% to 10%.

[0021] In the standard working curve, the concentration of rare earth elements ranges from 0.1 to 1.0 g / L.

[0022] The fixed wavelength in step 3.3 is in the range of 350-500 nm, and the net absorbance of the sample is obtained by subtracting the absorbance of the blank sample from the absorbance of the sample to be tested.

[0023] The beneficial effects of the present invention are:

[0024] The turbidimetric reagent does not need to add stabilizer during the test process. In the nitric acid medium, the rare earth ion concentration of 0.1-1.0g / L has a good linear relationship with the absorbance value, and can test the single rare earth content at different levels in the sample. It has the advantages of wide linear range, high precision, good accuracy, low cost, simple operation, and high detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a standard curve diagram of Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0027] like Figure 1 The broad embodiment of the present invention shown comprises the following steps:

[0028] Step 1, preparing a fluoride solution and high-grade pure nitric acid (1+1) (i.e., 50% nitric acid aqueous solution);

[0029] Step 2, preparing a rare earth element standard solution;

[0030] Step 3: Testing the rare earth compound to be tested by turbidimetry, including:

[0031] Step 3.1, sample pretreatment: weigh the sample (mass is m) and place it in a 100mL beaker, the rare earth element content in the sample is 10w / % to 90w / %; moisten the sample with a small amount of water, add 20mL of the high-grade pure nitric acid (1+1) in step 1, heat to dissolve, cool after complete dissolution, dilute to a volumetric flask (volume is V), and transfer 5mL of the solution to a 50mL colorimetric tube;

[0032] Step 3.2, add 3-10 mL of the high-grade pure nitric acid (1+1) in step 1, and then add 1-10 mL of the fluoride solution in step 1, gently mix each reagent, dilute with water, shake well, and let stand to prepare a mixed nitric acid solution; the concentration range of the nitric acid solution in the mixed nitric acid solution is 3% to 10%;

[0033] Step 3.3, pipette a portion of the mixed nitric acid solution into a cuvette, and measure the absorbance at a fixed wavelength on a spectrophotometer using a reagent blank as a reference;

[0034] Step 3.4, establish a standard working curve: pipette 1-10 mL of the rare earth element standard solution in step 2 into a set of 50 mL colorimetric tubes; then perform determination according to steps 3.2 and 3.3; establish a standard working curve with the rare earth element concentration as the abscissa and the absorbance as the ordinate; in the standard working curve, the rare earth element concentration range is 0.1-1.0 g / L;

[0035] Step 3.5, substituting the net absorbance of the solution to be tested into the standard working curve established in step 3.4 to obtain the rare earth element concentration C in the solution;

[0036] Step 4: Calculate the test results: Calculate the content of rare earth elements in the sample according to the following formula:

[0037]

[0038] Wherein, ω-mass fraction of rare earth element in single rare earth compound, %; C-concentration of rare earth element in test solution, g / L; V-fixed volume of sample, mL; m-mass of single rare earth compound, g.

[0039] In a broad embodiment, the raw material for preparing the fluoride solution in step 1 includes any one of HF, NaF and KF; the concentration of the HF solution is 1:1, the concentration of the NaF solution is 20-25 g / L, and the concentration of the KF solution is 25-35 g / L.

[0040] In a broad embodiment, the rare earth compound includes any one of rare earth hydroxide, rare earth chloride, rare earth carbonate, and rare earth nitrate; the rare earth compound is a single rare earth compound, including any one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc.

[0041] In a broad embodiment, the fixed wavelength in step 3.3 is in the range of 350 to 500 nm, and the absorbance of the sample to be tested minus the absorbance of the sample blank is the net absorbance of the sample;

[0042] Example 1

[0043] The method for determining the La content in a single rare earth compound lanthanum hydroxide by turbidimetry comprises the following steps:

[0044] Step 1: prepare sodium fluoride solution and high-grade pure nitric acid (1+1); wherein the concentration of the NaF solution is 22 g / L.

[0045] Step 2, prepare a La element standard solution with a concentration of 10 g / L;

[0046] Step 3: Use turbidimetry to test the rare earth compounds to be tested:

[0047] Step 3.1, sample pretreatment: accurately weigh 1g of sample (accurate to 0.001g) and place it in a 100mL beaker. Moisten the sample with a small amount of water, add 20mL of high-grade pure nitric acid (1+1) in step 1, heat to dissolve, cool after complete dissolution, dilute to 100mL volumetric flask, and transfer 5mL of solution to a 50mL colorimetric tube;

[0048] Step 3.2, add 5 mL of the high-grade pure nitric acid (1+1) in step 1, and then add 5 mL of the sodium fluoride solution in step 1. Gently mix each reagent, dilute with water, shake well, and let stand;

[0049] Step 3.3, pipette part of the solution into a cuvette, use the reagent blank as a reference, measure the absorbance at a wavelength of 400 nm on a spectrophotometer, and subtract the sample blank absorbance to obtain the net absorbance of the sample;

[0050] Step 3.4, establish a standard working curve: pipette 0mL, 1mL, 2mL, 3mL, 4mL and 5mL of the La element standard solution in step 2 into a set of 50mL colorimetric tubes. Then perform the determination according to steps 3.2 and 3.3. Establish a standard working curve with La element concentration as the horizontal axis and absorbance as the vertical axis. The test results and standard curves of different concentrations of La standard solutions are shown in Table 1 and Figure 1 As shown:

[0051] Table 1La standard working curve

[0052]

[0053]

[0054] There is a good linear relationship between the element concentration in the range of 0.1-1.0 g / L and the absorbance value, and the correlation coefficient of the linear regression equation is 0.999.

[0055] Step 3.5: Substitute the net absorbance of the solution to be tested into the standard working curve established in step 3.4 to obtain the La element concentration of the sample to be tested.

[0056] Step 4: Calculate the test results: Calculate the La content in the sample according to the following formula:

[0057]

[0058] Wherein, ω-mass fraction of rare earth element in single rare earth compound, %; C-concentration of rare earth element in test solution, g / L; V-fixed volume of sample, mL; m-mass of single rare earth compound, g.

[0059] The rare earth element content in the lanthanum hydroxide in Example 1 was detected by inductively coupled plasma emission spectrometry. The detection results of the two methods are shown in Table 2:

[0060] Table 2 Test results of lanthanum hydroxide

[0061]

[0062] It can be seen from Table 2 that the relative standard deviation of the results of the method used in the present invention is smaller than that of the inductively coupled plasma emission method, which indicates that the precision of this method is better.

[0063] Example 2

[0064] The method for determining the content of Sm element in a single rare earth compound samarium carbonate by turbidimetry comprises the following steps:

[0065] Step 1: prepare hydrofluoric acid solution and high-grade pure nitric acid (1+1); wherein the concentration of the HF solution is 1:1.

[0066] Step 2, prepare a Sm element standard solution with a concentration of 10 g / L;

[0067] Step 3: Use turbidimetry to test the rare earth compounds to be tested:

[0068] Step 3.1, sample pretreatment: weigh 1g of sample (accurate to 0.001g) and place it in a 100mL beaker. Moisten the sample with a small amount of water, add 20mL of high-grade pure nitric acid (1+1) in step 1, heat to dissolve, cool after complete dissolution, dilute to 100mL volumetric flask, and transfer 5mL of solution to a 50mL colorimetric tube;

[0069] Step 3.2, add 5 mL of the high-grade pure nitric acid (1+1) in step 1, and then add 5 mL of the hydrofluoric acid solution in step 1. Each time a reagent is added, it needs to be gently mixed, diluted with water, shaken and allowed to stand;

[0070] Step 3.3, pipette part of the solution into a cuvette, use the reagent blank as a reference, measure the absorbance at a wavelength of 420 nm on a spectrophotometer, and subtract the sample blank absorbance to obtain the net absorbance of the sample;

[0071] Step 3.4, establish a standard working curve: pipette 0mL, 1mL, 2mL, 3mL, 4mL and 5mL of the Sm element standard solution in step 2 into a set of 50mL colorimetric tubes. Then perform the determination according to steps 3.2 and 3.3. Establish a standard working curve with Sm element concentration as the horizontal axis and absorbance as the vertical axis.

[0072] Step 3.5: Substitute the net absorbance of the solution to be tested into the standard working curve established in step 3.4 to obtain the Sm element concentration of the sample to be tested.

[0073] Step 4: Calculate the test results: Calculate the content of Sm in the sample according to the following formula:

[0074]

[0075] Wherein, ω-mass fraction of rare earth element in single rare earth compound, %; C-concentration of rare earth element in test solution, g / L; V-fixed volume of sample, mL; m-mass of single rare earth compound, g.

[0076] The rare earth element content in the samarium carbonate in Example 2 was detected by gravimetric method and inductively coupled plasma emission spectrometry. The detection results of the three methods are shown in Table 3:

[0077] Table 3 Test results of samarium carbonate

[0078] Test Method Samarium carbonate sample 1 Samarium carbonate sample 2 average value / % Gravimetric method 62.36 62.67 62.52 Turbidimetry 62.17 63.65 62.91 Inductively Coupled Plasma Optical Emission Spectroscopy 60.13 62.82 61.48

[0079] It can be seen from Table 3 that the difference between the results of the method used in the present invention and the detection results of the gravimetric method is small, while the difference between the results of the inductively coupled plasma emission spectrometry and the gravimetric method is large, so the detection results of the present invention are highly accurate.

Claims

1. A method for determining the content of rare earth elements in a single rare earth compound by turbidimetry, characterized in that: The following steps are involved: Step 1, preparing a fluoride solution and a 50% nitric acid aqueous solution; Step 2, preparing a rare earth element standard solution; Step 3: Testing the rare earth compounds using turbidimetry, including: Step 3.1, sample pretreatment: weigh a rare earth compound and place it in a beaker, the rare earth element content in the rare earth compound is 10w / % to 90w / %; moisten the sample with water, add 20mL of 50% nitric acid aqueous solution, heat to dissolve, cool after complete dissolution, and dilute to a volumetric flask; transfer 5mL of the solution to a colorimetric tube; Step 3.2, add 3-10 mL of 50% nitric acid aqueous solution, and then add 1-10 mL of the fluoride solution in step 1. Each reagent needs to be gently mixed, diluted with water, shaken and allowed to stand to form a mixed nitric acid solution; Step 3.3, pipette a portion of the mixed nitric acid solution into a cuvette, use the reagent blank as a reference, and measure the absorbance at a fixed wavelength on a spectrophotometer; Step 3.4, establish a standard working curve: pipette 1-10 mL of the rare earth element standard solution in step 2 into a set of colorimetric tubes; then perform determination according to steps 3.2 and 3.3; establish a standard working curve with the rare earth element concentration as the abscissa and the absorbance as the ordinate; Step 3.5, substituting the net absorbance of the solution to be tested into the standard working curve established in step 3.4 to obtain the rare earth element concentration C in the solution; Step 4: Calculate the test results: Calculate the content of rare earth elements in the sample according to the following formula: Wherein, ω-mass fraction of rare earth element in rare earth compound, %; C-concentration of rare earth element in test solution, g / L; V-fixed volume of sample, mL; m-mass of rare earth compound, g.

2. The method for determining the content of rare earth elements in a single rare earth compound by turbidimetry according to claim 1, characterized in that: Step 2: The raw material for preparing the fluoride solution includes any one of HF, NaF and KF.

3. The method for determining the content of rare earth elements in a single rare earth compound by turbidimetry according to claim 1, characterized in that: The concentration of HF solution is 1:1, the concentration of NaF solution is 20-25 g / L, and the concentration of KF solution is 25-35 g / L.

4. The method for determining the content of rare earth elements in a single rare earth compound by turbidimetry according to claim 1, characterized in that: The rare earth compound includes any one of rare earth hydroxide, rare earth chloride, rare earth carbonate and rare earth nitrate.

5. The method for determining the content of rare earth elements in a single rare earth compound by turbidimetry according to claim 1 or 4, characterized in that: The rare earth compound includes any one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc.

6. The method for determining the content of rare earth elements in a single rare earth compound by turbidimetry according to claim 1, characterized in that: The concentration of the nitric acid solution in the mixed nitric acid solution ranges from 3% to 10%.

7. The method for determining the content of rare earth elements in a single rare earth compound by turbidimetry according to claim 1, characterized in that: In the standard working curve, the concentration of rare earth elements ranges from 0.1 to 1.0 g / L.

8. The method for determining the content of rare earth elements in a single rare earth compound by turbidimetry according to claim 1, characterized in that: The fixed wavelength in step 3.3 is in the range of 350-500 nm, and the net absorbance of the sample is obtained by subtracting the absorbance of the blank sample from the absorbance of the sample to be tested.

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