Method for determining phosphorus in phosphate extraction agent

Abstract

The invention relates to a method for determining phosphorus in a phosphate extraction agent. The method comprises the following steps: (1) digesting the phosphate extraction agent with nitric acid at a certain temperature for a certain time; (2) diluting the digested solution with water and fixing the volume to obtain a to-be-detected solution; (3) making a phosphorus standard curve; (4) preparing a blank sample solution; (5) respectively putting the solution to be detected and the blank sample solution into an inductively coupled plasma emission spectrometer, and testing according to a phosphorus characteristic spectral line to obtain equivalent milligrams of phosphorus in each solution; and (6) calculating according to the following formula to obtain the percentage content of phosphorus in the phosphate extraction agent. The method is easy to operate and rapid in analysis process, the problems that in an electric hot plate or microwave digestion method, phosphate extraction agents cannot be completely digested, and insoluble substances exist are solved, the lower detection limit of phosphorus in the phosphate extraction agents is 0.0015 mg / L, the relative standard deviation of phosphorus is lower than 0.40%, and the adding standard recovery rate is 99.91%-101.14%.

Description

Technical Field

[0001] The invention relates to the technical field of testing and analyzing phosphate ester extractants, and in particular to a method for determining phosphorus in phosphate ester extractants. Background Art

[0002] With the rapid development of the new energy industry, battery material companies have higher and higher requirements for product quality. As an excellent battery material, the phosphorus content of cobalt tetroxide has a great influence on the performance of the product. Therefore, the detection of phosphorus is becoming more and more important. This not only reflects the technological level of cobalt tetroxide, but also has an important impact on trade.

[0003] The commonly used phosphate extractant in nickel-cobalt smelting is P 507 , P 204 , P 507 It is 2-ethylhexyl phosphate mono-2-ethylhexyl ester, a colorless or light yellow transparent oily liquid; 204 It is di(2-ethylhexyl) phosphate, which is a colorless, transparent and viscous liquid. At present, the determination of phosphorus in these two phosphate ester organic substances usually adopts the phosphomolybdenum blue photometric method. This method requires the use of a hot plate or microwave digestion to decompose the sample before the test, but it is difficult for the hot plate or microwave to completely digest the sample, and the solution often contains insoluble matter and is not clear, which affects the test results; and during the determination process of the phosphomolybdenum blue spectrophotometric method, the stability of the blank sample is poor, the test results are poorly repeatable, the analysis process is long, and the operation is cumbersome. Therefore, it is of great significance to design and develop a method for the determination of phosphorus in phosphate ester samples with complete sample digestion, accurate test results, and simple operation. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, such as difficulty in completely digesting samples, poor repeatability of test results, long analysis process, and cumbersome test operation, the present invention provides a method for determining phosphorus in phosphate ester extractants. The method is simple to operate and can quickly and accurately determine the phosphorus in phosphate ester samples.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for determining phosphorus in a phosphate ester extractant comprises the following steps:

[0007] (1) Weigh a small amount of phosphate extractant into a reaction kettle, add a small amount of concentrated nitric acid, cover the reaction kettle and put it into an oven, and perform a digestion reaction at a certain temperature for a period of time to obtain a brown solution;

[0008] (2) Cool the brown solution obtained in step (1) until it becomes colorless, dilute it with water, and make up the volume to a 250 mL volumetric flask, shake well, and obtain a test solution;

[0009] (3) Preparation of phosphorus standard curve:

[0010] ①Prepare phosphorus standard solution A: Pipette 10.00mL of 1.0mg / mL phosphorus standard solution into a 100mL volumetric flask, add 1mL of concentrated nitric acid, dilute to the mark with water, and shake well;

[0011] ②Pipette 0.00mL, 0.50mL, 1.00mL, and 2.00mL of phosphorus standard solution A into a set of 100mL volumetric flasks, add a certain amount of nitric acid, dilute to the mark with water, and shake well; the amount of nitric acid added should make the nitric acid concentration in the solution after the volume is fixed to 2%;

[0012] ③ The solutions obtained in step ② were respectively placed in an inductively coupled plasma emission spectrometer, and tested according to the phosphorus characteristic spectrum to prepare a standard curve: the phosphorus standard points were 0.00 mg / L, 0.50 mg / L, 1.00 mg / L, and 2.00 mg / L;

[0013] (4) Prepare a blank sample solution: add a small amount of concentrated nitric acid to a reaction kettle, cover the reaction kettle and place it in an oven, react at a certain temperature for a period of time to obtain a brown solution; after the brown solution is cooled to colorless, dilute it with water and make up to a 250 mL volumetric flask, shake well, and obtain a blank sample solution;

[0014] (5) placing the test solution obtained in step (2) and the blank sample solution obtained in step (4) into an inductively coupled plasma emission spectrometer, respectively, and testing them according to the characteristic spectrum of phosphorus to obtain the equivalent milligram amount of phosphorus in the test solution and the blank sample solution;

[0015] (6) The percentage of phosphorus in the phosphate ester extractant is calculated according to the following formula:

[0016]

[0017] Where ρ 1 is the mass concentration of phosphorus obtained from the standard curve based on the equivalent milligram amount of the test solution, in mg / L; ρ 0 is the mass concentration of phosphorus found on the standard curve based on the equivalent milligram amount measured by the blank sample solution, in mg / L; 0.25 is the solution volume of the test solution, in L; m is the weighed mass of the phosphate ester extractant, in g; 1000 is the conversion rate of mg to g; and 100% is the conversion rate of percentage content.

[0018] Furthermore, the mass of the phosphate extractant weighed in step (1) is 0.1000±0.0002g.

[0019] Furthermore, the amount of concentrated nitric acid added in step (1) is 5-8 mL.

[0020] Furthermore, the reaction temperature in step (1) is 140-160°C.

[0021] Furthermore, the digestion reaction time in step (1) is 7-9 hours.

[0022] Furthermore, the phosphorus characteristic spectral line in step (3) is one of 213.617 nm and 214.914 nm.

[0023] The reaction principle involved in the present invention is as follows:

[0024] P 204 Esterification chemical reaction equation of phosphate extractants:

[0025] (C 8 H 17 O) 2 PO 2 H+24HNO 3 =28H 2 O+6NO 2 ↑+H 3 PO 4 +16CO 2 ↑+9N 2 ↑

[0026] P 507 Chemical reaction equation of phosphate extractant ester:

[0027] C 16 H 35 O 3 P+26HNO 3 =29H 2 O+8NO 2 ↑+H 3 PO 4 +16CO 2 ↑+9N 2 ↑

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention places a phosphate extractant in a high-pressure corrosion-resistant reaction kettle, and puts it into an oven to undergo a digestion reaction with nitric acid at a certain temperature and time, so that the phosphorus in the phosphate extractant can be completely dissolved, thereby solving the problem that the phosphate extractant cannot be completely digested and there are insoluble substances in the electric hot plate or microwave digestion method.

[0030] 2. The present invention adopts inductively coupled plasma emission spectrometry for testing, and the detection limit of phosphorus in phosphate ester extractants is 0.0015 mg / L, which is lower than the detection limit of 0.1 mg / L of phosphorus determined by the traditional phosphomolybdenum blue photometric method, meeting the detection of phosphorus in phosphate ester extractants, and the equipment is low in cost, easy to operate and master, and has a wider range of laboratory applications.

[0031] 3. The present invention adopts inductively coupled plasma emission spectrometry for testing, and the relative standard deviation of phosphorus in the phosphate ester extractant is less than 0.40%, and the spiked recovery rate is 99.91%-101.14%, with good precision and high accuracy.

[0032] 4. The present invention is simple to operate and has a rapid analysis process, which reduces the labor intensity and health hazards of post personnel. It is suitable for the analysis of large quantities of samples in production and provides a reference for the determination of phosphorus in battery materials such as cobalt tetroxide and cobaltous hydroxide. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail by specific embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] A method for determining phosphorus in a phosphate ester extractant comprises the following steps:

[0035] (1) Weigh a small amount of phosphate extractant into a reaction kettle, add a small amount of concentrated nitric acid, cover the reaction kettle and put it into an oven, and perform a digestion reaction at a certain temperature for a period of time to obtain a brown solution;

[0036] (2) Cool the brown solution obtained in step (1) until it becomes colorless, dilute it with water, and make up to the volume in a 250 mL volumetric flask, shake well, and obtain a test solution;

[0037] (3) Preparation of phosphorus standard curve:

[0038] ①Prepare phosphorus standard solution A: Pipette 10.00mL of 1.0mg / mL phosphorus standard solution into a 100mL volumetric flask, add 1mL of concentrated nitric acid, dilute to the mark with water, and shake well;

[0039] ②Pipette 0.00mL, 0.50mL, 1.00mL, and 2.00mL of phosphorus standard solution A into a set of 100mL volumetric flasks, add a certain amount of nitric acid, dilute to the mark with water, and shake well; the amount of nitric acid added should make the nitric acid concentration in the solution after the volume is fixed to 2%;

[0040] ③ The solutions obtained in step ② were respectively placed in an inductively coupled plasma emission spectrometer, and tested according to the phosphorus characteristic spectrum to prepare a standard curve: the phosphorus standard points were 0.00 mg / L, 0.50 mg / L, 1.00 mg / L, and 2.00 mg / L;

[0041] (4) Prepare a blank sample solution: add a small amount of concentrated nitric acid to a reaction kettle, cover the reaction kettle and place it in an oven, react at a certain temperature for a period of time to obtain a brown solution; after the brown solution is cooled to colorless, dilute it with water and make up to a 250 mL volumetric flask, shake well, and obtain a blank sample solution;

[0042] (5) placing the test solution obtained in step (2) and the blank sample solution obtained in step (4) into an inductively coupled plasma emission spectrometer, respectively, and testing them according to the characteristic spectrum of phosphorus to obtain the equivalent milligram amount of phosphorus in the test solution and the blank sample solution;

[0043] (6) The percentage of phosphorus in the phosphate ester extractant is calculated according to the following formula:

[0044]

[0045] Where ρ 1 is the mass concentration of phosphorus obtained from the standard curve based on the equivalent milligram amount of the test solution, in mg / L; ρ 0 is the mass concentration of phosphorus found on the standard curve based on the equivalent milligram amount measured by the blank sample solution, in mg / L; 0.25 is the solution volume of the test solution, in L; m is the weighed mass of the phosphate ester extractant, in g; 1000 is the conversion rate of mg to g; and 100% is the conversion rate of percentage content.

[0046] Furthermore, the mass of the phosphate extractant weighed in step (1) is 0.1000±0.0002g.

[0047] Example 1: Selection of nitric acid amount

[0048] Weigh multiple portions of phosphate extractants into different reactors, add different amounts of nitric acid, cover the reactors and place them in an oven, digest at the same temperature for the same time, cool until the solution is colorless, dilute with water to a 250mL volumetric flask, and shake well. The standard curve method was used for determination on an inductively coupled plasma emission spectrometer according to the set instrument working conditions, and the test results are shown in Table 1.

[0049] Interference investigation of coexisting elements: The coexisting components in the phosphate sample mainly include carbon (59-63%), oxygen (15-30%), and hydrogen (11%). However, after the sample digestion reaction, the coexisting elements present in the test solution are only oxygen and hydrogen, which do not interfere with the determination of phosphorus.

[0050] Table 1 Different amounts of nitric acid added and the corresponding degree of digestion of phosphate extractants

[0051]

[0052] From the test results in Table 1, it can be seen that when the amount of nitric acid added is 5-8 mL, the phosphate ester extractant is completely digested, so the amount of nitric acid added is 5-8 mL.

[0053] Example 2: Selection of digestion reaction temperature

[0054] Weigh multiple portions of phosphate extractants into different reactors, add the same amount of nitric acid, cover the reactor and put it into an oven, digest at different temperatures for the same time, cool until the solution is colorless, dilute with water to a 250mL volumetric flask, and shake well. The standard curve method was used for determination on an inductively coupled plasma emission spectrometer according to the set instrument working conditions. The test results are shown in Table 2.

[0055] Table 2 Different digestion reaction temperatures and corresponding digestion degrees of phosphate extractants

[0056]

[0057] It can be seen from Table 2 that the phosphate ester extractant is completely digested when the digestion reaction temperature is 140-160°C, so the digestion reaction temperature is selected to be 140-160°C.

[0058] Example 3: Selection of digestion reaction time

[0059] Weigh multiple portions of phosphate extractants in different reactors, add the same amount of nitric acid, cover the reactor and put it in an oven, digest for different times at the same temperature, cool until the solution is colorless, dilute with water to a 250mL volumetric flask, and shake well. The standard curve method was used for determination on an inductively coupled plasma emission spectrometer according to the set instrument working conditions. The test results are shown in Table 3.

[0060] Table 3 Different digestion reaction times and corresponding digestion degrees of phosphate extractants

[0061]

[0062] It can be seen from Table 3 that the phosphate ester extractant is completely digested when the digestion reaction time is 7-9h, so the digestion reaction time is selected to be 7-9h.

[0063] Example 4: Selection of test acidity

[0064] A set of 1 μg / mL phosphorus standard solutions were prepared, and different amounts of nitric acid were added to adjust the solutions to different acidities. The solutions were measured on an inductively coupled plasma emission spectrometer under the set instrument working conditions using the standard curve method. The test results are shown in Table 4.

[0065] Table 4 Test results of different test acidities and corresponding phosphorus content

[0066] <![CDATA[HNO 3 (%, volume percent)]]> 0 1 2 3 4 5 P(μg / mL) 0.94 1.01 1.04 1.03 1.01 0.98

[0067] As can be seen from Table 4, nitric acid acidity below 5% has no significant effect on the test results of phosphorus, and the present invention selects a 2% nitric acid test system.

[0068] Example 5: Detection limit and test lower limit

[0069] Under the set instrument working conditions, the blank sample solution was used for continuous measurement 11 times, 3 times the standard deviation of the test results was taken as the detection limit, and 10 times the standard deviation of the test results was taken as the test lower limit. The test results are shown in Table 5.

[0070] Table 5 Detection limit and test lower limit

[0071]

[0072] It can be seen from Table 5 that the detection limit of the present invention is 0.00045 mg / L, and the test lower limit is 0.0015 mg / L, which meets the test requirements.

[0073] Example 6: Precision Test

[0074] Under the set instrument working conditions, the same phosphate ester extractant test solution was tested 9 times independently. The test results are shown in Table 6.

[0075] Table 6 Precision test

[0076]

[0077] As shown in Table 6, the relative standard deviation of phosphorus tested by the present invention is lower than 0.40%, and the precision is good, which meets the detection requirements of the samples.

[0078] Example 7: Spike recovery test

[0079] Weigh several portions of 0.1000g of phosphate ester extractant, add different amounts of phosphorus standard solution, and perform spike recovery test according to the sample analysis steps. The test results are shown in Table 7.

[0080] Table 7 Spike recovery test

[0081]

[0082] As shown in Table 7, the recovery rate of the present invention is 99.91% to 101.14%, which meets the requirements of analytical testing.

[0083] The invention places a phosphate extractant in a high-pressure corrosion-resistant reaction kettle, and puts it into an oven to undergo a digestion reaction with nitric acid at a certain temperature and time, so that phosphorus in the phosphate extractant can be completely dissolved, thereby solving the problem that the phosphate extractant cannot be completely digested and has insoluble matter in a hot plate or microwave digestion method.

[0084] The present invention adopts inductively coupled plasma emission spectrometry for testing, and the detection limit of phosphorus in phosphate ester extractants is 0.0015 mg / L, which is lower than the detection limit of 0.1 mg / L of phosphorus determined by the traditional phosphomolybdenum blue photometric method, and meets the detection requirements of phosphorus in phosphate ester extractants. The equipment is low in cost, easy to operate and master, and has a wider range of laboratory applications.

[0085] The invention adopts inductively coupled plasma emission spectrometry for testing, the relative standard deviation of phosphorus in the phosphate ester extractant is lower than 0.40%, the spiked recovery rate is 99.91%-101.14%, the precision is good, and the accuracy is high.

[0086] The invention has simple operation and rapid analysis process, reduces the labor intensity and health hazards of post personnel, is suitable for the analysis of large batches of samples in production, and provides reference significance for the determination of phosphorus in battery materials such as cobalt tetroxide and cobaltous hydroxide.

[0087] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.

Claims

1. A method for determining phosphorus in a phosphate ester extractant, characterized in that: The following steps are involved: (1) Weigh a small amount of phosphate extractant into a reaction kettle, add a small amount of concentrated nitric acid, cover the reaction kettle and put it into an oven, and perform a digestion reaction at a certain temperature for a period of time to obtain a brown solution; (2) Cool the brown solution obtained in step (1) until it becomes colorless, dilute it with water, and make up the volume to a 250 mL volumetric flask, shake well, and obtain a test solution; (3) Preparation of phosphorus standard curve: ①Prepare phosphorus standard solution A: Pipette 10.00mL of 1.0mg / mL phosphorus standard solution into a 100mL volumetric flask, add 1mL of concentrated nitric acid, dilute to the mark with water, and shake well; ②Pipette 0.00mL, 0.50mL, 1.00mL, and 2.00mL of phosphorus standard solution A into a set of 100mL volumetric flasks, add a certain amount of nitric acid, dilute to the mark with water, and shake well; the amount of nitric acid added should make the nitric acid concentration in the solution after the volume is fixed to 2%; ③ The solutions obtained in step ② were respectively placed in an inductively coupled plasma emission spectrometer, and tested according to the phosphorus characteristic spectrum to prepare a standard curve: the phosphorus standard points were 0.00 mg / L, 0.50 mg / L, 1.00 mg / L, and 2.00 mg / L; (4) Prepare a blank sample solution: add a small amount of concentrated nitric acid to a reaction kettle, cover the reaction kettle and place it in an oven, react at a certain temperature for a period of time to obtain a brown solution; after the brown solution is cooled to colorless, dilute it with water and make up to a 250 mL volumetric flask, shake well, and obtain a blank sample solution; (5) placing the test solution obtained in step (2) and the blank sample solution obtained in step (4) into an inductively coupled plasma emission spectrometer, respectively, and testing them according to the characteristic spectrum of phosphorus to obtain the equivalent milligram amount of phosphorus in the test solution and the blank sample solution; (6) The percentage of phosphorus in the phosphate ester extractant is calculated according to the following formula: Wherein ρ1 is the mass concentration of phosphorus found on the standard curve based on the equivalent milligram amount measured for the test solution, in mg / L; ρ0 is the mass concentration of phosphorus found on the standard curve based on the equivalent milligram amount measured for the blank sample solution, in mg / L; 0.25 is the solution volume of the test solution, in L; m is the mass of the weighed phosphate extractant, in g; 1000 is the conversion rate of mg to g; and 100% is the conversion rate of percentage content.

2. The method for determining phosphorus in a phosphate ester extractant according to claim 1, characterized in that: The mass of the phosphate extractant weighed in the step (1) is 0.1000±0.0002g.

3. The method for determining phosphorus in a phosphate ester extractant according to claim 1, characterized in that: The amount of concentrated nitric acid added in step (1) is 5-8 mL.

4. The method for determining phosphorus in a phosphate ester extractant according to claim 1, characterized in that: The reaction temperature in step (1) is 140-160°C.

5. The method for determining phosphorus in a phosphate ester extractant according to claim 1, characterized in that: The digestion reaction time in step (1) is 7-9 hours.

6. The method for determining phosphorus in a phosphate ester extractant according to claim 1, characterized in that: The phosphorus characteristic spectrum line in the step (3) is one of 213.617 nm and 214.914 nm.

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