Direct complexometric titration of zirconium in sulphuric acid medium with yttrium zirconium complex oxide

Abstract

The application relates to the field of chemical detection methods, and particularly discloses a direct complexing titration method for zirconium in yttrium-zirconium composite oxide in a sulfuric acid medium. The direct complexing titration method for zirconium in yttrium-zirconium composite oxide in a sulfuric acid medium is as follows: ZrO2 is fused by using concentrated sulfuric acid to generate zirconium sulfate, water is added for dilution, concentrated sulfuric acid is added dropwise to increase the acidity of a test solution, EDTA solution is added dropwise under high-acidity high-[ZrO 2+ ] conditions to complex and mask a large amount of ZrO 2+ ; water is further added for dilution to reduce the acidity of the test solution, EDTA solution is added dropwise under low-acidity low-[ZrO 2+ ] conditions to complex ZrO 2+ , and obvious bright yellow jumps of dimethylphenol orange indicator appear at the end point. The method can be used for rapid detection of various yttrium-zirconium composite oxides, and has the advantages of strong operability, high recovery rate and sensitive titration end point.

Description

Technical Field

[0001] The present invention relates to the field of chemical detection methods, and more specifically, to a direct complexometric titration method for zirconium in a sulfuric acid medium of a yttrium-zirconium composite oxide. Background Art

[0002] Yttria-zirconia composites are used in the manufacture of structural ceramics or functional ceramics. Due to their high strength, toughness, and hardness, they are widely used in aerospace, military, electronics, new energy, smart wearables, and other applications.

[0003] The commonly used method for determining zirconium oxide in yttria-composite zirconium oxide is as follows: first, 0.25g of yttria-composite zirconium oxide sample is dissolved at high temperature with 2g of potassium pyrosulfate, the reaction product is dissolved with hydrochloric acid, and the mixture is diluted to 250ml with water. 50ml of the diluted solution is placed in a 250ml beaker, 4 drops of phenolphthalein indicator are added, and ammonia water is added dropwise until the solution is completely precipitated (the solution turns red) and a few drops are added in excess to obtain a ZrO(OH)2 precipitate; then, the mixture is covered with a watch glass and heated to boiling, filtered while hot, and washed with hot water until the phenolphthalein indicator solution no longer turns red. The precipitate and the filter paper are returned to the original beaker, 150ml of water and 15ml of hydrochloric acid are added, and the precipitate is heated to boil to dissolve the precipitate; then, 0.5g of hydroxylamine hydrochloride is added, the mixture is boiled for 2-3 minutes, 0.1g of xylenol orange indicator is added, and the mixture is titrated with an EDTA standard solution until the solution no longer turns red after boiling, which is the titration endpoint. The zirconium oxide content in the sample can be calculated based on the EDTA consumption at the titration endpoint.

[0004] However, during the titration process with EDTA standard solution, the color of the indicator often shows chromaticity graded decay without color jump, the titration end point is difficult to judge, and the titration volume is difficult to count, which affects the accuracy of the test results and needs to be improved. Summary of the Invention

[0005] In order to improve the reliability and accuracy of the detection results, the present application provides a direct complexometric titration method for zirconium in a sulfuric acid medium of yttrium-zirconium composite oxide, which adopts the following technical solution.

[0006] A direct complexometric titration method for zirconium in a sulfuric acid medium of a yttrium-zirconium composite oxide comprises the following steps:

[0007] Step 1: Take 0.2-0.8g of yttrium oxide composite zirconia sample and 5g of ammonium sulfate and add them to a beaker, add 5mL of concentrated sulfuric acid, cover with a watch glass, heat and melt until clear, cool to room temperature, add water to dissolve to obtain a solution, then rinse the watch glass with water 5 times, collect the washing liquid, transfer the solution and washing liquid into a 200mL volumetric flask to the 200mL mark, add water to the 200mL mark, shake well, and let it stand for 15 minutes to obtain a test solution;

[0008] Step 2: Preliminary test: Pipette 25 mL of the test solution obtained in the first step into a flask, add 0.5 mL of concentrated sulfuric acid, boil, add 50 mL of boiling water, add 2 drops of xylenol orange, and titrate with 0.022 mol / L EDTA solution until the color of the solution decays from purple-red to pink. The amount of EDTA solution added is recorded as v1 (mL);

[0009] Step 3: Pipette 25 mL of the test solution obtained in the first step into a flask, add 0.5 mL of concentrated sulfuric acid and 0.5 g of hydroxylamine hydrochloride, and boil; then add 1 mL of 0.022 mol / L EDTA solution and boil again;

[0010] Step 4: Add 100 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and then add EDTA solution until the test solution turns bright yellow. The amount of EDTA added at this time is recorded as v2 (mL). If the solution does not change color after boiling for 30 seconds, it is the titration end point;

[0011] The actual mass percentage m% of zirconium oxide in the sample is:

[0012] m%=(cV EDTA M / 1000m 分 )×100%,m 分 =(v 分 / v 总 )×m 样品 ; V EDTA =v1+v2;

[0013] m 样品 is the total mass of the sample (g); V 总 is the total volume of the test solution after the first step, i.e. 200 mL; V 分 is the amount of test solution transferred in the third step, i.e. 25 mL;

[0014] c is the molar concentration of EDTA (mol / L); M is the molar mass of zirconium oxide (g / mol).

[0015] By adopting the above technical solution, concentrated sulfuric acid is used to melt ZrO2 to generate zirconium sulfate in the first step, and ammonium sulfate is used as a flux. The reaction equation of the first step is:

[0016] ZrO2+2H2SO4→Zr(SO4)2+2H2O, Zr(SO4)2+H2O→ZrOSO4+H2SO4;

[0017] In the second step, the preliminary test was conducted to determine the complexation of most of the ZrO 2+ The volume of EDTA solution required, after adding v1 of EDTA solution, the solution color decays from purple-red to pink. At this time, the color decays, but the titration endpoint is not reached, that is, ZrO2+ It is not completely complexed by EDTA;

[0018] In the third step, concentrated sulfuric acid is added. Under the condition of high acidity of the test solution, EDTA solution with a volume of v1 is added to make most of the ZrO 2+ Complexation with EDTA to form [ZrO(EDTA)] 2+ , reduce the free ZrO in the test solution 2+ concentration, reducing the high concentration of ZrO 2+ The possibility of hydrolysis or hybridization with sulfate groups affecting the titration results;

[0019] In the fourth step, water is added to dilute and adjust the acidity of the test solution. + ]、Low [ZrO 2+ ] In the case of adding xylenol orange indicator, xylenol orange and free ZrO 2+ In acidic solution, a red complex is generated, ZrO 2+ +XO→[ZrO(XO)] 2+ , while ZrO 2+ The stability constant of the complex with EDTA is higher than that of the complex with xylenol orange, so the ZrO 2+ It does not complex with xylenol orange, and the subsequent addition of EDTA can convert ZrO 2+ Stripped from xylenol orange complex, [ZrO(XO)] 2+ +EDTA → [ZrO(EDTA)] 2+ +XO, the color of the solution will show the bright yellow of xylenol orange in its free state at this acidity;

[0020] This application adopts the method of twice acid adjustment and twice complexation, high acidity and high [ZrO 2+ ] is masked by EDTA complexation, low acidity and low [ZrO 2+ ] and EDTA complex titration to avoid low acidity, high [ZrO 2+ ] Titration produces ZrO 2+ Hydrolysis phenomenon, increasing the EDTA and ZrO 2+ The complex stability of EDTA [ZrO(XO)] 2+ ZrO 2+ The deprivation effect of the titration endpoint is obvious, and the bright yellow jump is shown, which is convenient for observing the reaction endpoint and making the test results more accurate.

[0021] Preferably, in the third step, the boiling step comprises: heating the solution until it boils and maintaining the boiling time for 10s-30s.

[0022] By adopting the above technical solution, multiple heating and boiling can reduce the ZrO 2+Polymerize into [ZrO]2 4+ Or the possibility of forming polyhydroxy complexes.

[0023] Preferably, in the third step, after the first boiling and before the addition of EDTA, the solution [H + ] is 1.50-1.57mol / L.

[0024] By adopting the above technical solution, concentrated sulfuric acid is added to increase the [H + ] to 1.50-1.57 mol / L. Under this acidity condition, more EDTA and ZrO 2+ Complexation to shield a large amount of ZrO 2+ , reduce the free ZrO in the test solution 2+ ; Reduce the ZrO caused by adding more EDTA when the acidity is low 2+ The possibility of hydrolysis to form ZrO(OH)2 precipitate also avoids the possibility that the acidity after dilution in the fourth step due to high acidity is not reduced to the applicable acidity of the indicator, thereby affecting the color change sensitivity of the indicator.

[0025] Preferably, in the fourth step, after adding boiling water to dilute, the solution [H + ] is 0.26-0.27mol / L.

[0026] By adopting the above technical solution, the acidity of the solution is adjusted to be within the above reasonable range. During the titration process, the possibility of the indicator color change being not sensitive due to excessive acidity is reduced, and the possibility of ZrO being not sensitive due to excessive acidity is avoided. 2+ The possibility of hydrolysis to generate ZrO(OH)2 precipitate and affect the titration result is eliminated, thus ensuring the accuracy and reliability of the determination results.

[0027] Preferably, in the first to fourth steps, the zirconium in the test solution exists in the form of ZrO 2+ .

[0028] By adopting the above technical solution, EDTA and ZrO 2+ The molar ratio is 1:1 complexation.

[0029] All water used in this application is deionized water, and all chemicals used are of analytical grade or above. Sulfuric acid or concentrated sulfuric acid has a content of 98% and a specific gravity of 1.84 g / cm 3 Analytical grade concentrated sulfuric acid and 0.3% aqueous solution of xylenol orange.

[0030] Preferably, the test error of the direct complexometric titration method is ±0.2%.

[0031] By adopting the above technical solution, the error caused by the balance, volumetric flask, pipette, visual angle difference and other systems is ±0.2%.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. Since this application uses high acidity and high [ZrO 2+ ] complexation masking, low acidity and low [ZrO 2+ ] complexometric titration method, which improves the 2+ The complexation stability of the product can achieve better titration effect, simplify the analysis steps and improve the recovery rate of the analysis method;

[0034] 2. This application defines [H + ] and [H + ] interval, ensuring a large amount of ZrO before titration 2+ Can be masked by EDTA complexation, only a small amount of free ZrO is present during titration 2+ , improve the EDTA and ZrO 2+ The complex stability of ZrO is ensured by adding a small amount of EDTA solution in a certain acid buffer zone. 2+ It is stripped from the xylenol orange complex, reducing the possibility of the indicator changing color due to excessive acidity in the fourth step, and reducing the ZrO 2+ The possibility of hydrolysis to form precipitation and affect the titration results;

[0035] 3. This application makes full use of the dual functions of EDTA as a masking agent and titrant, and cleverly avoids the addition of ZrO 2+ The time-dependent rigidification produced by the combination of sulfate and xylenol orange ensures the color change sensitivity of the xylenol orange indicator, providing a titration method with sensitive color change and high accuracy. DETAILED DESCRIPTION

[0036] The present application is further described in detail below with reference to the embodiments.

[0037] Example

[0038] Example 1

[0039] The direct complexometric titration method of zirconium in a sulfuric acid medium of yttrium-zirconium composite oxide comprises the following steps:

[0040] Step 1: Weigh 0.6g of reference zirconium oxide and place it in a 100ml beaker containing 5g of ammonium sulfate. Add 5ml of sulfuric acid, cover with a watch glass, heat and melt until clear, remove the molten sample beaker, cool to room temperature, add water and dissolve until clear, rinse the watch glass 5 times with 10ml water, wash the beaker 5 times with 20ml water, collect the washing liquid, transfer the dissolved test solution and washing liquid into a 200ml volumetric flask, dilute to the scale with water, shake well, and let it stand for 15 minutes;

[0041] Step 2: Preliminary test: Pipette 25 mL of the test solution obtained in the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, boil, add 50 mL of boiling water, add 2 drops of 0.3% xylenol orange indicator, and titrate with 0.022 mol / L EDTA solution until the solution color decays from purple-red to pink. At this point, the amount of EDTA solution added is 21 mL;

[0042] Step 3: Use a pipette to transfer 25 mL of the test solution from the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, add 0.5 g of hydroxylamine hydrochloride, boil, and dropwise add 21 mL of 0.022 mol / L EDTA solution, and boil;

[0043] Step 4: Add 100 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and continue titrating with 0.022 mol / L EDTA until the solution changes from red to bright yellow. Boil for 30 seconds without changing color. The amount of EDTA added is 6.67 mL.

[0044] In this embodiment, the reference zirconium oxide is a zirconium oxide reference reagent, that is, the purity is ≥99.95%.

[0045] V EDTA =v1+v2=21+6.67=27.67mL;

[0046] m 分 =(v 分 / v 总 )×m 样品 =(25 / 200)×0.6=0.075g;

[0047] m%=(cV EDTA M / 1000m 分 )×100%=(0.022(mol / L)×27.67(mL)×123.22(g / mol))÷1000÷

[0048] 0.075(g)×100%=100.01%;

[0049] That is, the actual mass fraction of the zirconium oxide sample measured in this embodiment is: m%=100.01%±0.2%.

[0050] Example 2

[0051] The difference between this embodiment and embodiment 1 is that the direct complexometric titration method of zirconium in a sulfuric acid medium of yttrium-zirconium composite oxide comprises the following steps:

[0052] Step 1: Weigh 0.8g of reference zirconium oxide and place it in a 100ml beaker containing 5g of ammonium sulfate. Add 5ml of sulfuric acid, cover with a watch glass, heat and melt until clear, remove the molten sample beaker, cool to room temperature, add water and dissolve until clear, rinse the watch glass 5 times with 10ml water, wash the beaker 5 times with 20ml water, collect the washing liquid, transfer the dissolved test solution and washing liquid into a 200ml volumetric flask, dilute to the mark with water, shake well, and let it stand for 15 minutes;

[0053] Step 2: Preliminary test: Pipette 25 mL of the test solution obtained in the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, boil, add 50 mL of boiling water, add 2 drops of 0.3% xylenol orange indicator, and titrate with 0.022 mol / L EDTA solution until the solution color decays from purple-red to pink. At this time, the amount of EDTA solution added is 32 mL;

[0054] Step 3: Use a pipette to transfer 25 mL of the test solution from the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, add 0.5 g of hydroxylamine hydrochloride, boil, add 32 mL of 0.022 mol / L EDTA solution dropwise, and boil;

[0055] Step 4: Add 100 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and continue titrating with 0.022 mol / L EDTA until the solution changes from red to bright yellow. Boil for 30 seconds without changing color. The amount of EDTA added is 5.86 mL.

[0056] V EDTA =v1+v2=32+5.86=36.86mL;

[0057] m 分 =(v 分 / v 总 )×m 样品 =(25 / 200)×0.8=0.1g;

[0058] m%=(cV EDTA M / 1000m 分 )×100%=(0.022(mol / L)×36.86(mL)×123.22(g / mol))÷1000÷0.1(g)

[0059] ×100%=99.92%

[0060] That is, the actual mass fraction of the zirconium oxide sample measured in this embodiment is: m%=99.92%±0.2%.

[0061] Example 3

[0062] The only difference between this embodiment and embodiment 1 is that the direct complexometric titration method of zirconium in a sulfuric acid medium of yttrium-zirconium composite oxide comprises the following steps:

[0063] Step 1: Weigh 0.2g of reference zirconium oxide and place it in a 100ml beaker containing 5g of ammonium sulfate. Add 5mL of sulfuric acid, cover with a watch glass, heat and melt until clear, remove the molten sample beaker, cool to room temperature, add water and dissolve until clear, rinse the watch glass 5 times with 10mL of water, wash the beaker 5 times with 20mL of water, collect the washing liquid, transfer the dissolved test solution and washing liquid into a 200ml volumetric flask, dilute to the mark with water, shake well, and let it stand for 15 minutes;

[0064] Step 2: Preliminary test: Pipette 25 mL of the test solution obtained in the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, boil, add 50 mL of boiling water, add 2 drops of 0.3% xylenol orange indicator, and titrate with 0.022 mol / L EDTA solution until the solution color decays from purple-red to pink. At this time, the amount of EDTA solution added is 8 mL;

[0065] Step 3: Use a pipette to transfer 25 mL of the test solution from the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, add 0.5 g of hydroxylamine hydrochloride, boil, add 8 mL of 0.022 mol / L EDTA solution dropwise, and boil;

[0066] Step 4: Add 100 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and continue titrating with 0.022 mol / L EDTA until the color of the solution changes from red to bright yellow. Boil for 30 seconds without changing color. The amount of EDTA added is 1.2 mL.

[0067] V EDTA =v1+v2=8+1.2=9.2mL;

[0068] m 分 =(v 分 / v 总 )×m 样品 =(25 / 200)×0.2=0.025g;

[0069] m%=(cV EDTA M / 1000m 分 )×100%=(0.022(mol / L)×9.2(mL)×123.22(g / mol))÷1000÷0.025(g)

[0070] ×100%=99.76%

[0071] That is, the actual mass fraction of the zirconium oxide sample measured in this embodiment is: m%=99.76%±0.2%.

[0072] Example 4

[0073] The only difference between this embodiment and embodiment 1 is that the direct complexometric titration method of zirconium in a sulfuric acid medium of yttrium-zirconium composite oxide comprises the following steps:

[0074] Step 1: Weigh 0.6 g of 3Y-ZrO2 sample and place it in a 100 ml beaker containing 5 g of ammonium sulfate. Add 5 ml of concentrated sulfuric acid, cover with a watch glass, heat and melt until clear, remove the molten sample beaker, cool to room temperature, add water and dissolve until clear, rinse the watch glass 5 times with 10 ml of water, wash the beaker 5 times with 20 ml of water, collect the washing liquid, transfer the dissolved test solution and washing liquid into a 200 ml volumetric flask, dilute to the mark with water, shake well, and let it stand for 15 minutes;

[0075] Step 2: Preliminary test: Pipette 25 mL of the test solution obtained in the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, boil, add 50 mL of boiling water, add 2 drops of xylenol orange indicator, and titrate with 0.022 mol / L EDTA solution until the solution color decays from purple-red to pink. At this time, the amount of EDTA solution added is 20 mL;

[0076] Step 3: Use a pipette to transfer 25 mL of the test solution from the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, add 0.5 g of hydroxylamine hydrochloride, boil, add 20 mL of 0.022 mol / L EDTA solution dropwise, and boil;

[0077] Step 4: Add 100 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and continue titrating with 0.022 mol / L EDTA until the solution changes from red to bright yellow. Boil for 30 seconds without changing color. The amount of EDTA added is 6.15 mL.

[0078] In this embodiment, the model of 3Y-zirconia is HN-R30N, and the particle size is 30 nm. According to the factory information of HN-R30N, the theoretical mass fraction of zirconium oxide in HN-R30N is 94.64%.

[0079] V EDTA =v1+v2=20+6.15=26.15mL;

[0080] m 分 =(v 分 / v 总 )×m 样品 =(25 / 200)×0.6=0.075g;

[0081] m%=(cV EDTA M / 1000m 分)×100%=(0.022(mol / L)×26.15(mL)×123.22(g / mol))÷1000÷

[0082] 0.075(g)×100%

[0083] That is, the actual mass fraction of the zirconium oxide sample measured in this embodiment is: m%=94.52%±0.2%.

[0084] Comparative Example

[0085] Comparative Example 1

[0086] The only difference between this comparative example and Example 1 is that the direct complexometric titration method of zirconium in a sulfuric acid medium of yttrium-zirconium composite oxide comprises the following steps:

[0087] Step 1: Weigh 0.6g of reference zirconium oxide and place it in a 100ml beaker containing 5g of ammonium sulfate. Add 5ml of sulfuric acid, cover with a watch glass, heat and melt until clear, remove the molten sample beaker, cool to room temperature, add water and dissolve until clear, rinse the watch glass 5 times with 10ml water, wash the beaker 5 times with 20ml water, collect the washing liquid, transfer the dissolved test solution and washing liquid into a 200ml volumetric flask, dilute to the scale with water, shake well, and let it stand for 15 minutes;

[0088] Step 2: Use a pipette to transfer 25 mL of the test solution from the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, add 0.5 g of hydroxylamine hydrochloride, boil, add 3 drops of 0.3% xylenol orange indicator, and add 0.022 mol / L EDTA solution for titration. The color of the solution gradually becomes lighter, but no bright yellow jump is observed.

[0089] Comparative Example 2

[0090] The only difference between this comparative example and Example 1 is that the direct complexometric titration method of zirconium in a zirconium composite oxide sulfuric acid medium comprises the following steps:

[0091] Step 1: Weigh 0.6g of reference zirconium oxide and place it in a 100ml beaker containing 5g of ammonium sulfate. Add 5ml of sulfuric acid, cover with a watch glass, heat and melt until clear, remove the molten sample beaker, cool to room temperature, add water and dissolve until clear, rinse the watch glass 5 times with 10ml water, wash the beaker 5 times with 20ml water, collect the washing liquid, transfer the dissolved test solution and washing liquid into a 200ml volumetric flask, dilute to the scale with water, shake well, and let it stand for 15 minutes;

[0092] Step 2: Use a pipette to transfer 25 mL of the test solution from step 1 into a 300 mL flask. Add 0.5 mL of concentrated sulfuric acid and 0.5 g of hydroxylamine hydrochloride, bring to a boil, then add 21 mL of 0.022 mol / L EDTA solution and boil again.

[0093] Step 3: Add 3 drops of 0.3% xylenol orange indicator and continue to add 0.022 mol / L EDTA solution. The color of the solution gradually becomes lighter, but no bright yellow jump is observed.

[0094] Comparative Example 3

[0095] The only difference between this comparative example and Example 1 is that the direct complexometric titration method of zirconium in a zirconium composite oxide sulfuric acid medium comprises the following steps:

[0096] Step 1: Weigh 0.6g of reference zirconium oxide and place it in a 100ml beaker containing 5g of ammonium sulfate. Add 5ml of sulfuric acid, cover with a watch glass, heat and melt until clear, remove the molten sample beaker, cool to room temperature, add water and dissolve until clear, rinse the watch glass 5 times with 10ml water, wash the beaker 5 times with 20ml water, collect the washing liquid, transfer the dissolved test solution and washing liquid into a 200ml volumetric flask, dilute to the scale with water, shake well, and let it stand for 15 minutes;

[0097] Step 2: Use a pipette to transfer 25 mL of the test solution from the first step into a 300 mL flask, add 0.5 mL of concentrated sulfuric acid, boil, add 0.5 g of hydroxylamine hydrochloride, add 100 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and add 0.022 mol / L EDTA solution for titration. The solution gradually becomes turbid without a bright yellow jump.

[0098] Comparative Example 4

[0099] The only difference between this comparative example and comparative example 1 is that concentrated sulfuric acid is not added in the third step, that is:

[0100] Step 3: Use a pipette to transfer 25 mL of the test solution from the first step into a 300 mL flask, add 0.5 g of hydroxylamine hydrochloride, boil, and dropwise add 21 mL of 0.022 mol / L EDTA solution. The solution becomes turbid. After boiling, the turbidity of the solution becomes even greater, and ZrO(OH)2 floccules are precipitated.

[0101] Step 4: Add 100 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and continue titrating by adding 0.022 mol / L EDTA. The solution is still turbid without a bright yellow color jump.

[0102] Comparative Example 5

[0103] The only difference between this comparative example and comparative example 1 is that 3 mL of concentrated sulfuric acid is added in the third step, namely:

[0104] Step 3: Use a pipette to transfer 25 mL of the test solution from the first step into a 300 mL flask, add 3 mL of concentrated sulfuric acid, add 0.5 g of hydroxylamine hydrochloride, boil, add 20 mL of 0.022 mol / L EDTA solution dropwise, and boil;

[0105] Step 4: Add 100 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and add 0.022 mol / L EDTA for titration. The color of the solution gradually becomes lighter without a sudden change to bright yellow.

[0106] Comparative Example 6

[0107] The only difference between this comparative example and Example 1 is that, in the fourth step, 150 mL of boiling water is added for dilution, namely:

[0108] Step 4: Add 150 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and continue titrating with 0.022 mol / L EDTA. The solution becomes turbid.

[0109] Comparative Example 7

[0110] The only difference between this comparative example and Example 1 is that, in the fourth step, 50 mL of boiling water is added for dilution, namely:

[0111] Step 4: Add 50 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and continue titrating with 0.022 mol / L EDTA. The solution should not show a bright yellow color jump.

[0112] Combined with Examples 1-3, it can be seen that the direct complexometric titration method disclosed in this application is used to determine the ZrO 2+ The titration is carried out, and the endpoint is clearly visible with an obvious bright yellow color jump, which is convenient for the operator to observe, and the accuracy and reliability of the titration result are excellent. The direct complexometric titration method of the present application is excellent in the control of raw materials, intermediates and actual production, or is added to the teaching syllabus as a special case of the volumetric method of university analytical chemistry, and the application effect is excellent.

[0113] In combination with Example 1 and Example 4, it can be seen that the method disclosed in the present application can be applied to the determination of the zirconium content in yttrium-zirconium composite oxide, and the determination results have excellent reliability and accuracy.

[0114] Combining Example 1 and Comparative Example 1, in Comparative Example 1, in a high acidity environment, high [ZrO 2+ ] conditions, the indicator was directly added dropwise, and then the EDTA solution was added dropwise for complexometric titration. No color jump was observed. This may be because the color change sensitivity of the xylenol orange indicator was suppressed under high acidity and could not show an obvious color change.

[0115] In combination with Example 1 and Comparative Example 2, in Comparative Example 2, under high acidity conditions, EDTA solution was first added for complexation masking, then xylenol orange indicator was added, and then EDTA was added dropwise for complexometric titration. The test did not show an obvious bright yellow jump; this may be because the high acidity environment reduced the color change sensitivity of the xylenol orange indicator, resulting in no color jump at the titration endpoint.

[0116] Combined with Example 1 and Comparative Example 3, in Comparative Example 3, under high acidity conditions, boiling water was first added to dilute the test solution, and then xylenol orange indicator was added, and complexometric titration was performed with EDTA test solution. The test solution was turbid and there was no color jump; this may be because directly adding a large amount of boiling water to dilute will cause ZrO 2+ It hydrolyzes and forms ZrO(OH)2 precipitate, causing the test solution to become turbid.

[0117] Combining Example 1 and Comparative Example 4, in Comparative Example 4, concentrated sulfuric acid was not added in the third step, so that the acidity of the test solution was too low when the EDTA solution was added for complexation masking, and the test solution became turbid when the complexation calibration was performed in the fourth step; this may be because, at high [ZrO 2+ ], When the acidity is low, adding a large amount of EDTA solution for complexation and masking will cause ZrO 2+ It hydrolyzes and generates ZrO(OH)2 precipitate, which affects the accuracy of the titration results.

[0118] In combination with Example 1 and Comparative Example 5, in Comparative Example 5, an excess of concentrated sulfuric acid was added in the third step, and no color jump occurred at the titration endpoint during the complexometric titration in the fourth step. This may be because the acidity in the third step was too high, so that after dilution with 100 ml of boiling water was added in the fourth step, the acidity failed to be reduced to the applicable acid-base environment of the indicator, thereby affecting the color change sensitivity of the xylenol orange indicator, resulting in no color jump at the titration endpoint.

[0119] Combining Example 1 and Comparative Example 6, in the fourth step of Comparative Example 6, excessive boiling water was added to dilute the test solution, resulting in turbidity. This may be because the acidity of the test solution after excessive boiling water dilution in the fourth step was too low, resulting in the free ZrO 2+ Hydrolysis and formation of ZrO(OH)2 precipitate will make the test solution turbid and affect the measurement accuracy;

[0120] In combination with Example 1 and Comparative Example 7, in Comparative Example 7, a small amount of boiling water was added for dilution in the fourth step, and no color jump occurred at the titration endpoint; this may be because the acidity of the test solution after dilution with a small amount of boiling water in the fourth step was relatively high, which suppressed the color change sensitivity of the xylenol orange indicator, resulting in no obvious bright yellow color jump.

[0121] In summary, referring to the method disclosed in this application, in high acidity and high [ZrO 2+ ] under the conditions of adding EDTA solution for complexation masking, low acidity and low [ZrO2+ ] under the condition of adding EDTA solution for complex calibration, twice acid adjustment and twice titration, to ensure that EDTA and ZrO 2 The excellent complex stability and the color change sensitivity of the xylenol orange indicator make the titration endpoint easy to observe and the measurement results have excellent reliability and accuracy.

[0122] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A direct complexometric titration method for zirconium in a sulfuric acid medium of a yttrium-zirconium composite oxide, characterized in that: For the following steps: Step 1: Take 0.2-0.8g of yttrium oxide composite zirconia sample and 5g of ammonium sulfate and add them to a beaker, add 5mL of concentrated sulfuric acid, cover with a watch glass, heat and melt until clear, cool to room temperature, add water to dissolve to obtain a solution, then rinse the watch glass with water 5 times to collect the washing liquid, transfer the solution and washing liquid into a 200mL volumetric flask to the volume, add water to dilute to the 200mL mark, shake well, and let it stand for 15 minutes to obtain a test solution; Step 2: Preliminary test: Pipette 25 mL of the test solution obtained in the first step into a flask, add 0.5 mL of concentrated sulfuric acid, boil, add 50 mL of boiling water, add 2 drops of xylenol orange, and titrate with 0.022 mol / L EDTA solution until the color of the solution decays from purple-red to pink. The amount of EDTA solution added is recorded as v1; Step 3: Pipette 25 mL of the test solution obtained in the first step into a flask, add 0.5 mL of concentrated sulfuric acid and 0.5 g of hydroxylamine hydrochloride, and boil; then add 0.022 mol / L EDTA solution v1 and boil again; Step 4: Add 100 mL of boiling water, add 3 drops of 0.3% xylenol orange indicator, and then add 0.022 mol / L standard EDTA solution until the test solution turns bright yellow. The amount of EDTA added at this time is recorded as v2. If the solution does not change color after boiling for 30 seconds, it is the titration endpoint. The actual mass percentage m% of zirconium oxide in the sample is: V EDTA = v1+v2; m 分 =(in 分 / in 总 )×m 样品 ; m%=(cV EDTA M / 1000m 分 )×100%; m 样品 is the total mass of the sample, in g; V 总 V is the total volume of the test solution after the first step, i.e. 200 mL; 分 is the volume of test solution transferred in the third step, i.e., 25 mL; v1 is in mL; v2 is in mL; c is the molar concentration of EDTA, in mol / L; M is the molar mass of zirconium oxide, in g / mol; V EDTA The unit is mL; In the third step, the boiling step includes: heating the solution to boiling and maintaining it for 10s-30s; In the third step, after the first boiling and before adding EDTA, the solution [H + ]1.50-1.57mol / L; In the fourth step, after adding boiling water to dilute, the solution [H + ]is 0.26-0.27mol / L.

2. The direct complexometric titration method of zirconium in a sulfuric acid medium of a yttrium-zirconium composite oxide according to claim 1, characterized in that: From the first to the fourth step, the zirconium in the test solution exists in the form of ZrO 2+ .

3. The direct complexometric titration method of zirconium in a sulfuric acid medium of a yttrium-zirconium composite oxide according to claim 1, characterized in that: The test error of the direct complexometric titration method is ±0.2%.