JP2020165863A - Tungsten quantitative analysis method - Google Patents

Abstract

To provide a quantitative analysis method with which it is possible to accurately and easily carry out the quantitative analysis of W in a metal compound.SOLUTION: Provided is a tungsten quantitative analysis method comprising: a mixing step for mixing the oxide of a metal element, nitric acid, a hydrogen peroxide solution and perchloric acid and obtaining a mixture; a white smoke treatment step for heating the mixture for white smoke treatment and obtaining a white smoke treated liquid; a dissolving step for adding nitric acid and hydrofluoric acid to the white smoke treated liquid and decomposing these to obtain a dissolved liquid; a masking step for adding boric acid to the dissolved liquid and obtaining a dissolved liquid in which free hydrofluoric acid is masked; and a quantitative measurement step for quantitatively measuring a tungsten amount in the dissolved liquid in which free hydrofluoric acid is masked.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for quantitative analysis of tungsten in a metal compound.

There are many types of metal compounds such as metal oxides, metal hydroxides, and metal nitrides, all of which are important as various industrial materials. There are many types of metals contained in the metal compound, including iron, copper, and nickel.
In recent years, in the fields of various catalyst materials, optical materials, and the like, tungsten (sometimes referred to as "W" in the present invention) is increasingly used as a component of a metal compound. In view of the importance of W, which is a component of metal compounds used in each of the fields, there is a demand in the industrial world for a quantitative analysis method that enables accurate and easy quantitative analysis of W in the metal compound. There is.
Here, Non-Patent Documents 1, 2 and 3 are known as W quantitative analysis methods, Non-Patent Document 1 describes iron and steel-tungsten quantitative analysis methods, and Non-Patent Document 2 describes in ore. The method for quantitative analysis of tungsten in Tungsten is described, and Non-Patent Document 3 describes the method for quantitative analysis of tungsten in an iron-tungsten alloy.

JIS G 1220 JIS M 8128 BUNSEKI KAGAKU Vol. 19, pp. 207-212 (1970)

The gist of the iron and steel-tungsten quantitative analysis method described in Non-Patent Document 1 is that the sample is decomposed with an appropriate acid, W is made into tungstic acid, and cinchonine is added to completely precipitate W. After squeezing the precipitate and igniting it, it is treated with sulfuric acid and hydrofluoric acid to remove silicon dioxide, and ignited again to measure the mass of impure tungsten oxide (VI). Next, the impure tungsten oxide is melted with sodium carbonate, dissolved in warm water and strained, and the insoluble residue is heated to a high mass to measure the mass and subtract it from the mass of the impure tungsten oxide (VI).

The gist of the W quantitative analysis method in ore described in Non-Patent Document 2 is that the sample is decomposed with hydrochloric acid and nitric acid, synconin is added, the precipitate of the generated tungstic acid is squeezed out, and then dissolved in aqueous ammonia. , Separate undecomposed products. Then, magnesium chloride and ammonium chloride are added to the obtained filtrate to precipitate phosphorus or niobium, and the mixture is separated by filtration. Then, hydrochloric acid, nitric acid and cinchonine are added to the obtained filtrate again to regenerate a precipitate of tungstic acid and strain it. The obtained precipitate is ignited to obtain tungsten oxide (VI), treated with sulfuric acid and hydrofluoric acid to remove silicon dioxide, and ignited again, and then the mass of tungsten oxide (VI) is measured. Next, this tungsten oxide (VI), the previously filtered undecomposed product, and the precipitate of phosphorus or niobium are melted with sodium carbonate and boric acid, and hydrogen peroxide solution, hydrochloric acid, and tartrate acid are added to dissolve the precipitate. The ICP emission spectroscopy is used to quantitatively analyze molybdenum and undecomposed products contained in tungsten oxide (VI) and W contained in the precipitate of phosphorus or niobium.

The gist of the W quantification method in an iron-tungsten alloy described in Non-Patent Document 3 is that a sample is decomposed with phosphoric acid, hydrochloric acid and nitric acid, and the decomposed product is filtered using a filter paper, and is insoluble in a solution. Get the ingredients. Insoluble components are washed with ammonia and warm water. Combine the dissolved solution and the cleaning solution of the insoluble component, and set the volume. ICP emission spectroscopy is applied to the obtained volumetric solution to quantify W. The insoluble component on the filter paper is melted with sodium carbonate, and then the obtained molten salt is dissolved in water and the volume is adjusted. ICP emission spectroscopy is applied to the obtained volumetric solution to quantify W. The W concentration in the sample is obtained from the above two W quantification results.

As is clear from the above description, it is considered that the quantitative analysis methods described in Non-Patent Documents 1 to 3 according to the prior art are not easily feasible quantitative analysis methods because the operation steps are long.
The present invention has been made under the above circumstances, and the problem to be solved thereof is to provide a method for quantitative analysis of W, which enables accurate and easy quantitative analysis of W in a metal compound. It is to be.

In order to solve the above-mentioned problems, the present inventors conducted research. Then, when the metal compound to be the target of the quantitative analysis is an oxide of a metal element and further contains one or more selected from W metal and W oxide, the quantitative analysis of W in the metal compound is performed. We came up with a quantitative analysis method that can be carried out accurately and easily, and were able to solve the above-mentioned problems.

That is, the first invention for solving the above-mentioned problems is
A method for quantitative analysis of tungsten in oxides of metal elements.
A decomposition step of mixing the oxide of the metal element, nitric acid, hydrogen peroxide solution, and perchloric acid to obtain a mixture.
A white smoke treatment step of heating the mixture to treat white smoke to obtain a liquid after the white smoke treatment,
A dissolution step of adding nitric acid and hydrofluoric acid to the solution after white smoke treatment and decomposing it to obtain a solution.
A masking step of adding boric acid to the solution to obtain a solution in which free fluoride ions are masked.
A method for quantitative analysis of tungsten, which comprises a tungsten quantification step of quantitatively measuring the amount of tungsten in a solution in which free fluoride ions are masked.
The second invention is
Quantitative analysis of tungsten according to the first invention, wherein the oxide of the metal element contains two or more kinds of metal elements, and the tungsten is one or more kinds selected from tungsten metal and tungsten oxide. The method.
The third invention is
The method for quantitative analysis of tungsten according to the first or second invention, which comprises solubilizing the liquid after white smoke treatment in the dissolution step.
The fourth invention is
The method for quantitative analysis of tungsten according to any one of the first to third inventions, which comprises adding boric acid equal to or more than the equivalent of hydrofluoric acid added in the dissolution step in the masking step. ..
Is.

According to the present invention, quantitative analysis of W in a metal compound can be carried out accurately and easily.

It is a flow chart which shows the quantitative analysis operation of W.

In the fields of various catalyst materials, optical materials, and the like, W is increasingly used as a component of metal compounds. In view of the importance of W, which is a component of the metal compound used in each of the fields, there is a demand in the industrial world for a quantitative analysis method that enables accurate and easy quantitative analysis of W in the metal compound. There is.

When the present inventors examined the quantitative analysis methods of W according to the conventional techniques such as Non-Patent Documents 1, 2 and 3, the analysis steps were long and the analysis operations were complicated in each method. Here, as a result of research by the present inventors, the quantitative analysis method of W according to these conventional techniques is a quantitative analysis method of W in a compound containing both a metal compound and a non-metal compound such as a W-containing ore. I came up with something. On the other hand, it was also conceived that most of the compounds used in the fields of various catalyst materials, optical materials and the like are metal compounds containing no non-metal compounds.
The compound containing W is an oxide of a metal element, such as a metal compound used in various fields such as catalyst materials and optical materials, and one or more selected from W metal and W oxide. In the case of including, the present invention has been conceived to be able to carry out the quantitative analysis of W in the metal compound accurately and easily by using a quantitative analysis method simpler than the quantitative analysis method of W according to the conventional technique. completed.

Hereinafter, the quantitative analysis operation of W according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flow chart showing an analysis operation according to a quantitative analysis of W according to the present invention, in which (a) decomposition step, (b) white smoke treatment step, (c) dissolution step, (d) masking step, ( It has each step of e) constant volume step and (f) W quantification step. Hereinafter, each step will be described.

(A) Decomposition Step The quantitative analysis sample (1) according to the present invention is an oxide of a metal element, and is a metal compound containing at least one selected from W metal and W oxide. In addition, the oxide of the metal element may contain two or more kinds of metal elements.
In the present invention, the quantitative analysis of W contained in the quantitative analysis sample (1) is carried out accurately and easily.

First, the quantitative analysis sample (1) is placed in an appropriate container and weighed precisely. Here, considering that heating is performed in the subsequent step "(b) white smoke treatment step" and that hydrofluoric acid (6) is added in "(c) dissolution step", Teflon (registered) is used as a container. It is preferable to use a beaker made of (trademark).

Next, after adding a small amount of water, nitric acid (2), hydrogen peroxide solution (3), and perchloric acid (4) are added, and the obtained mixed solution is gently heated to obtain a quantitative analysis sample (quantitative analysis sample). 1) Disassembling (a) Perform the disassembling step.
Here, it is preferable to use nitric acid (2) having a concentration of 50 to 70% by mass.
Further, as the hydrogen peroxide solution (3), it is preferable to use one having a concentration of 25 to 35% by mass.
Further, as the perchloric acid (4), it is preferable to use one having a concentration of 50 to 70% by mass.

(B) White smoke treatment step After heating for a predetermined time, the temperature is raised until white smoke of perchloric acid is generated from the mixed solution. While maintaining that state, perform white smoke treatment and concentration by heating until the contents of the mixed solution are completely dissolved, and carry out "(b) white smoke treatment step" to obtain a liquid after white smoke treatment. ..

(C) Dissolution Step When the generation of white smoke is completed, the solution is allowed to stand to cool until the temperature of the liquid after the white smoke treatment reaches room temperature.
Since W easily forms a solid substance after allowing to cool, a small amount of pure water is added to the liquid after the white smoke treatment, and then nitric acid (5) and hydrofluoric acid (6) are added to decompose the white smoke. It is preferable that the contents in the liquid after the white smoke treatment are dissolved again to carry out the "(c) dissolution step".
Here, it is preferable to use nitric acid (5) having a concentration of 50 to 70% by mass.
Further, it is preferable to use hydrofluoric acid (6) having a concentration of 45 to 50% by mass.

(D) Masking Step Next, "(d) Masking Step" is carried out by adding boric acid (7) to the solution obtained in "(c) Dissolving Step" to mask free fluoride ions.
This is because the excess fluoride ion caused by the hydrofluoric acid (6) added in the "(c) dissolution step" is liberated in the solution, and the "(f) W quantification step" described later is performed. This is to avoid adversely affecting the analyzer.
Here, as the boric acid (7), it is preferable to use saturated boric acid (for example, a supernatant solution in which 60 g of boric acid is dissolved in 1 L of water).

From this point of view, it is preferable to add boric acid (7) equal to or more than the equivalent amount of hydrofluoric acid (6) added in "(c) dissolution step" in "(d) masking step".

(E) Volume-setting step Next, after allowing the solution that has undergone the "(d) masking step" to stand to cool, in the "(e) volume-setting step", the total volume of the solution is set to 100 mL, for example. Obtain a chemical solution.

(F) W quantification step Next, the “(f) W quantification step” in the defined solution is carried out. For the quantification, for example, an ICP emission spectroscopic analyzer is convenient.
As described above, it is easy to carry out a quantitative analysis of W contained in the quantitative analysis sample (1) from the W concentration in the volumetricized solution, and a highly accurate quantitative analysis can be carried out. This is a preferable configuration.

Hereinafter, the present invention will be specifically described with reference to Examples.
(Example 1)
As a quantitative analysis sample according to Example 1, a compound in which a metal oxide contains carbon (organic substance) and 0.9% by mass of W was prepared.

0.4 g of the quantitative analysis sample according to Example 1 was placed in a Teflon beaker, and then a small amount of water was added to the beaker, followed by a concentration of 60% by mass nitric acid (10 mL) and a concentration of 30% by mass of hydrogen peroxide solution (2 mL). 10 mL of 60% by mass perchloric acid was added. Then, the beaker was gently heated to carry out a decomposition step.
After heating the beaker for about 2 hours, the temperature was raised until white smoke due to perchloric acid was generated from the liquid, and the above-mentioned metal oxides and carbon compounds were decomposed. Then, while maintaining the heated state, the contents in the solution were completely dissolved to obtain a solution.

The obtained solution was allowed to stand to cool until the melting temperature reached room temperature. After allowing to cool, a small amount of pure water was added to the solution, and then 10 mL of 60% by mass nitric acid and 1 mL of 47% by mass hydrofluoric acid were added to decompose the solution, and the contents of the solution were dissolved again. ..

After allowing the solution in which the contents were dissolved again to stand to cool, 1 mL of saturated boric acid (using a supernatant solution in which 60 g of boric acid was dissolved in 1 L of water) was added. Then, the whole amount of the solution was transferred to a flask and the volume was adjusted to 100 mL.

The solution contained in 100 mL was analyzed using an ICP emission spectrophotometer. Then, the W concentration, which is the element to be analyzed, of the sample to be analyzed according to Example 1 was quantitatively analyzed using the calibration curve sequence prepared separately.

In Example 1, the above-mentioned operations from weighing the quantitative analysis sample to ICP emission spectroscopic analysis were repeated four times (n1 to n4), and the quantitative analysis results of the W concentration of the element to be analyzed obtained by each operation were obtained. It is shown in Table 1.
Table 1 shows the average value of the quantitative analysis results of the W concentration related to n1 to n4 and the value of the relative standard deviation (RSD).

From the results of the quantitative analysis of the W concentration shown in Table 1, it was found that according to the present invention, the quantitative analysis of W in the metal compound can be carried out accurately and easily. In Example 1, the time required to obtain the W concentration quantitative analysis result shown in Table 1 was 300 minutes.

The W standard solution used for the calibration curve series was prepared as follows.
Three containers were prepared, and 0 mL, 10 mL, and 20 mL of W standard solution having a concentration of 1 g / L were taken using a whole pipette and placed in each container. Acids similar to the acids added in Example 1 (nitric acid, perchloric acid, hydrofluoric acid, boric acid, but hydrogen peroxide is an acid that volatilizes in the pretreatment, so it is added to the three containers. Was not added) in the same amount as in Example 1. These were each transferred to a 500 mL flask and the volume was adjusted using pure water to prepare W standard solutions having W concentrations of 0 mg / L, 20 mg / L, and 40 mg / L used in the calibration curve series.

(Comparative Example 1)
0.5 g of the same quantitative analysis sample used in Example 1 was placed in a beaker, and a mixed acid of 10 mL of 10% by volume phosphoric acid, 25 mL of 37% by volume hydrochloric acid and 3 mL of 60% by mass nitric acid was added and heated. Dissolved. After heating the beaker for about 3 hours, the beaker was allowed to stand to cool until the solution temperature reached room temperature. After allowing to cool, 20 mL of pure water was added to the solution to dilute the solution, and the solution was filtered with a filter paper (No. 5C).
After washing by dropping 2% ammonia water on the filter paper three times, 10 mL of warm water was dropped on the filter paper twice and washed. Both the filtrate and the washing solution were transferred to a 100 mL volumetric flask and the volume was adjusted to 100 mL. The solution contained in 100 mL was analyzed using an ICP emission spectrophotometer. The above is referred to as step A.

The filter paper was placed in a platinum crucible and heated in a dryer at 105 ° C. for 2 hours to dry. The platinum crucible containing the dried filter paper was heated in an electric furnace at 800 ° C. for 30 minutes to incinerate the filter paper. The platinum crucible was taken out from the electric furnace, allowed to cool to room temperature, 2 mL of 96% by mass sulfuric acid and 5 mL of 47% by mass hydrofluoric acid were added, and the mixture was heated at 250 ° C. for 2 hours. Then, after allowing to cool to room temperature, 2 g of sodium carbonate was added to the platinum crucible, which was heated at 1000 ° C. for 30 minutes in an electric furnace, and then the platinum crucible was taken out of the electric furnace and allowed to cool to room temperature to allow sodium carbonate molten salt. Got
A 100 mL beaker of sodium carbonate molten salt was placed together with the platinum crucible, 10 mL of 10% by volume phosphoric acid and 25 mL of 37% by mass hydrochloric acid were added, and the mixture was heated to 60 ° C. to dissolve the molten salt. The lysate was transferred to a 100 mL volumetric flask and the volume was adjusted to 100 mL. The solution contained in 100 mL was analyzed using an ICP emission spectrophotometer. The above is referred to as step B.

The W concentration in the quantitative analysis sample was determined from the above-mentioned steps A and B. The quantitative results are shown in Table 2.
The time required to obtain the quantitative analysis result of the W concentration in Table 2 by the method of the comparative example was 900 minutes.

(Summary)
As is clear from the results in Tables 1 and 2, it can be seen that the W concentration measurement results by the method of the examples have less variation as compared with the comparative examples. Further, it can be seen that the method of the example has a shorter time for obtaining the quantitative analysis result of the W concentration as compared with the comparative example.

Claims (4)

A method for quantitative analysis of tungsten in oxides of metal elements.
A decomposition step of mixing the oxide of the metal element, nitric acid, hydrogen peroxide solution, and perchloric acid to obtain a mixture.
A white smoke treatment step of heating the mixture to treat white smoke to obtain a liquid after white smoke treatment,
A dissolution step of adding nitric acid and hydrofluoric acid to the solution after white smoke treatment and decomposing it to obtain a solution.
A masking step of adding boric acid to the solution to obtain a solution in which free fluoride ions are masked.
A method for quantitative analysis of tungsten, which comprises a tungsten quantification step of quantitatively measuring the amount of tungsten in a solution in which free fluoride ions are masked. The method for quantitative analysis of tungsten according to claim 1, wherein the oxide of the metal element contains two or more kinds of metal elements, and the tungsten is one or more kinds selected from tungsten metal and tungsten oxide. .. The method for quantitative analysis of tungsten according to claim 1 or 2, wherein in the dissolution step, the liquid after the white smoke treatment is solubilized. The method for quantitative analysis of tungsten according to any one of claims 1 to 3, wherein in the masking step, boric acid equal to or more than the equivalent of hydrofluoric acid added in the dissolution step is added.

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