JP2019191012A - Element analysis method of inorganic sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an elemental analysis method for an inorganic sample, which enables highly accurate analysis of the content of various trace elements including rare earth elements in an inorganic sample containing silicon. SOLUTION: A first step of mixing an inorganic sample containing silicon, nitric acid and perchloric acid, dissolving a part of the inorganic sample, and then separating into a first solution and a first residue; After heating the first residue and the alkali together, cooling the second step of obtaining a second residue that is a mixture of the first residue and the alkali, and the second residue and water A third step of separating the mixed solution obtained by mixing into a third solution and a third residue; a fourth step of dissolving the third residue in an acid to obtain a fourth solution; An elemental analysis method for an inorganic sample, comprising: a first solution; and a fifth step of analyzing an element contained in the fourth solution. [Selection diagram] None

Description

  The present invention relates to an elemental analysis method for an inorganic sample containing silicon.

2. Description of the Related Art Conventionally, in a facility that handles radioactive substances such as a nuclear power plant, a structural frame is constructed of concrete because it has sufficient strength and excellent radiation shielding properties.
Since concrete exposed to radiation for a long time is activated, it is necessary to dispose and manage it as radioactive waste when dismantling the facility, and it is required to analyze the elements contained in the concrete.

  As a method for analyzing trace elements at a ppm level contained in an inorganic sample containing silicon such as concrete, a method of performing a pretreatment for chemically dissolving the inorganic sample and measuring using ICP-MS is effective (for example, Non-patent document 1). However, when conventional pretreatment is performed, there is a problem that detection accuracy of rare earth elements such as europium that can be activated is poor.

“Rapid determination of trace elements in standard rock samples by inductively coupled plasma mass spectrometry” by Takashi Okai, Analytical Chemistry, Vol. 39 (1990) No. 4, T55-T59

  The present invention has been made in view of the above circumstances, and an elemental analysis method for an inorganic sample capable of analyzing the contents of various trace elements including rare earth elements in an inorganic sample containing silicon with high accuracy. I will provide a.

  The present inventors examined pretreatment of concrete or the like in the conventional method, and found that the detection accuracy of the rare earth element was poor because the elution of the rare earth element contained in the concrete or the like was insufficient. That is, when an inorganic sample containing silicon was dissolved using a mixed acid containing hydrofluoric acid, a part of the rare earth element was not dissolved, and the value detected by ICP-MS was found to be lower than the true value. The present inventors have solved the above problems and completed the present invention described below.

[1] A first step of mixing an inorganic sample containing silicon, nitric acid, and perchloric acid, dissolving a part of the inorganic sample, and then separating it into a first solution and a first residue; The first step and the alkali are heated together and then cooled to obtain a second residue which is a mixture of the first residue and the alkali, and the second residue and water are mixed. A third step of separating the mixed solution into a third solution and a third residue, a fourth step of dissolving the third residue in an acid to obtain a fourth solution, and the first step And a fifth step of analyzing an element contained in the fourth solution. An elemental analysis method of an inorganic sample.
[2] The elemental analysis method of an inorganic sample according to [1], wherein the inorganic sample is one or more selected from concrete, aggregate, and cement.

  According to the elemental analysis method of the present invention, the contents of various trace elements including rare earth elements in an inorganic sample containing silicon can be analyzed with high accuracy.

It is a flowchart which shows an example of the elemental analysis method concerning this invention. It is an example of the result of having analyzed using standard rock with known element content as a sample.

In the first embodiment of the elemental analysis method of an inorganic sample of the present invention, an inorganic sample containing silicon, nitric acid and perchloric acid are mixed, and after dissolving a part of the inorganic sample, the first solution and the first A first step of separating the first residue and the alkali, and heating the first residue and the alkali together, followed by cooling to obtain a second residue that is a mixture of the first residue and the alkali A step, a third step of separating the mixture obtained by mixing the second residue and water into a third solution and a third residue, and dissolving the third residue in an acid An elemental analysis method for an inorganic sample, comprising: a fourth step for obtaining a fourth solution; and a fifth step for analyzing an element contained in the first solution and the fourth solution.
Details of each step will be described below, but steps and processes other than these steps may be included.

<First step>
An inorganic sample containing silicon (hereinafter sometimes referred to simply as “inorganic sample”), nitric acid and perchloric acid are mixed to dissolve a part of the inorganic sample, and then the liquid component (first solution) and solid are mixed. Separated into components (first residue).
The inorganic sample is preferably pulverized in advance in order to facilitate subsequent processing.
Examples of the inorganic sample containing silicon include concrete, aggregate for concrete, cement, rock, sand and the like.

  The order of mixing the inorganic sample, nitric acid and perchloric acid is not particularly limited, and nitric acid and perchloric acid may be added to the inorganic sample in order, or a mixed acid in which nitric acid and perchloric acid are mixed in advance. May be added to the inorganic sample. From the viewpoint of facilitating solubilization of the rare earth elements contained in the inorganic sample, it is preferable to add a mixed acid to the inorganic sample.

  As a mixing ratio of nitric acid and perchloric acid after mixing, for example, the mass ratio of nitric acid: perchloric acid is preferably 1000: 1 to 1: 1, more preferably 200: 1 to 20: 1, and 150: 1 to 50: 1 is more preferred. When the mixing ratio is in the above range, the rare earth element contained in the inorganic sample can be solubilized more easily. Nitric acid and perchloric acid are each mixed as an aqueous solution.

The nitric acid concentration after mixing is, for example, preferably 30 to 60% by mass, more preferably 50 to 60% by mass, and still more preferably 55 to 60% by mass with respect to the total mass of the liquid component.
When the mixing ratio is in the above range, the rare earth element contained in the inorganic sample can be solubilized more easily.

The perchloric acid concentration after mixing is preferably, for example, 0.06 to 30% by mass, more preferably 0.3 to 3% by mass, and further 0.4 to 1% by mass with respect to the total mass of the liquid component. preferable.
When the mixing ratio is in the above range, the rare earth element contained in the inorganic sample can be solubilized more easily.

As a mixing ratio when mixing the inorganic sample, nitric acid and perchloric acid, for example, the mass ratio of solid component: liquid component is preferably 1: 1 to 1: 100, more preferably 1: 5 to 1:50. 1:10 to 1:40 is more preferable.
An inorganic sample can fully be decomposed | disassembled as it is said mixing ratio.

It is preferable to accelerate the decomposition of the inorganic sample by heating a mixture of the inorganic sample, nitric acid and perchloric acid in, for example, a heat-resistant and pressure-resistant container. As heating temperature, 120-180 degreeC is preferable, for example, 140-180 degreeC is more preferable, and 160-180 degreeC is further more preferable. As heating time in said suitable heating temperature, 0.5 to 10 hours are preferable, for example, 1 to 5 hours are more preferable, and 1-2 hours are further more preferable.
Within the above temperature range and heating time, the rare earth element can be easily solubilized while increasing the decomposition efficiency of the inorganic sample. From the viewpoint of easily solubilizing the rare earth element with the liquid component, it is preferable to suppress evaporation of the liquid component during the heating.

  After visually confirming that the inorganic sample has decomposed, the residue (first residue) remaining in the container and the liquid component (first solution) are separated. Examples of the separation method include centrifugation, filtration treatment, and the like. The first residue is preferably subjected to the second step after drying.

  In the 4th process of a back | latter stage, the element contained in a 1st solution is analyzed by well-known methods, such as ICP-MS. Among rare earth elements, for example, Eu is solubilized in the first solution by 1 to 70% by mass of the total content contained in the original inorganic sample.

<Second step>
The first residue and the alkali are heated together and then cooled to obtain a second residue that is a mixture of the first residue and the alkali.

Heat the first residue and alkali in the same container. The alkali may be a solid or an aqueous solution in which an alkali is dissolved. In the case of an aqueous solution, it is preferable to evaporate water during heating. It is preferable to melt the solid alkali by heating and to mix the first residue and the molten alkali. The molten alkali naturally mixes with the first residue.
The alkali to be heated together with the first residue is one or more kinds of hydroxides selected from a group 1 element (alkali metal) such as Li, Na, and K and a group 2 element (alkaline earth metal) such as Mg and Ca. It is a thing. Note that the alkali element selected here is added to the original inorganic sample.
In order to dissolve the silica and alumina components insoluble in the acid by alkali melting, solid sodium hydroxide or potassium hydroxide is preferable.
The amount of alkali added is preferably 2 to 5 times the mass of the original inorganic sample, more preferably 3 to 5 times, and even more preferably 4 to 5 times.
When the concentration is within the above range, the first residue can be sufficiently decomposed.

It is preferable to expedite the decomposition of the first residue by putting the mixture of the first residue and the alkali in a crucible and heating the mixture in an electric furnace, for example. The heating temperature is preferably higher than the melting point of the alkali from the viewpoint of melting the alkali. For example, 400-600 degreeC is preferable, 450-550 degreeC is more preferable, and 450-500 degreeC is further more preferable. As heating time in said suitable heating temperature, 0.5 to 10 hours are preferable, for example, 1 to 5 hours are more preferable, and 1-2 hours are further more preferable.
In the above temperature range and heating time, silica and alumina can be solubilized while increasing the decomposition efficiency of the first residue.
After melting the alkali, the second residue (reaction product of the first residue and the alkali) is obtained by cooling naturally.

<Third step>
A mixed solution obtained by mixing the second residue and water is separated into a third solution and a third residue.
When the second residue is stuck to the inner wall of the container used in the second step, the whole second container is released from the inner wall by immersing it in water and heated, suspended, and soluble. Dissolve the ingredients in water. The heating temperature is preferably around 100 ° C. where water boils. The heating time is preferably 2 to 8 hours, more preferably 4 to 8 hours, and even more preferably 6 to 8 hours. The mass of water in which the second residue is suspended is preferably alkali: water = 1: 10 to 1:40, more preferably 1:20 to 1:40, relative to the mass of alkali added in the second step. 1:30 to 1:40 is more preferable.
When the mixing ratio is as described above, the silica or alumina component chemically reacted with the alkali is sufficiently dissolved, the rare earth element contained in the second residue is sufficiently suspended, and the silica or alumina component and the rare earth element are sufficiently suspended. Can be separated.
After sufficiently suspending in about 30 minutes to 6 hours, the residue (third residue) remaining in the suspension and the liquid component (third solution) are separated. Examples of the separation method include centrifugation, filtration treatment, and the like.

<Fourth process>
The third residue is dissolved in acid to give a fourth solution.
When the third residue contains a rare earth element, since the silica and alkali are removed in the third step, the rare earth element is easily dissolved in the acid.
Examples of the acid added to the third residue include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid. An organic acid may be used as the acid. The acid is usually added as an aqueous solution. Note that the elements making up the acid will be added to the original inorganic sample.
When using nitric acid, the density | concentration of the aqueous solution is not specifically limited, For example, 20-40 mass% is mentioned.
When using hydrochloric acid, the density | concentration of the aqueous solution is not specifically limited, For example, 20-40 mass% is mentioned.
The mass of the acid added to the third residue is not particularly limited as long as it can dissolve the third residue, and can be, for example, 100 to 1000 times the mass of the original inorganic sample.
Within the above range, the third residue can be easily dissolved.

  Add acid to the third residue and stir well. For example, if it stirs for 2-3 hours at normal temperature (15-25 degreeC), it can fully solubilize. The fourth solution is obtained by dissolving the third residue in this way. If there is an insoluble component at this stage, it is a component that is difficult to dissolve in both acid and alkali, and is considered to be a very limited element (for example, Au, Pt, etc.).

In the subsequent fifth step, the elements contained in the fourth solution are analyzed by a known method such as ICP-MS. Among the rare earth elements, for example, Eu is 30 to 99% by mass of the total content contained in the original inorganic sample solubilized in the fourth solution.
85 to 100% of the rare earth element contained in the original inorganic sample can be extracted into the first solution and the fourth solution obtained in the above steps.

<Fifth process>
The first solution and the fourth solution dissolve various elements including rare earth elements contained in the inorganic sample. Elements in these solutions can be analyzed by a known method using ICP-MS. Moreover, you may apply well-known elemental analysis methods other than ICP-MS measurement.

<Flowchart>
A flow chart of the analysis method of this embodiment is shown in FIG. A previously ground inorganic sample is decomposed with nitric acid and perchloric acid and separated into a dissolved liquid component (first solution) and an insoluble component (first residue). Next, the first residue is mixed with an alkali and heated to melt the alkali, and then cooled to obtain a second residue. Subsequently, the second residue is suspended in water and heated, and then separated into a dissolved liquid component (third solution) and an insoluble component (third residue). The third residue is then dissolved in acid to obtain a fourth solution.
Quantify various elements including rare earth elements by adjusting the volume of the first solution and the fourth solution obtained above with distilled water, nitric acid, etc., and measuring the concentration of elements by ICP-MS, etc. Analysis.

[Example 1]
Standard rock JG-3 whose element concentration was previously known by various elemental analysis methods was used. 0.5 g of the pulverized standard rock was put into 20 ml of a mixed solution obtained by mixing each aqueous solution of concentrated nitric acid (concentration 60 mass%) and concentrated perchloric acid (concentration 60 mass%) at a volume ratio of 100: 1. The mixed solution containing the standard rock was placed in a pressure vessel and heated at 150 ° C. for 1 hour. The mixed solution after cooling was centrifuged to obtain a supernatant (first solution) and a precipitate (first residue). The first solution was diluted at a predetermined magnification, and the elements contained in the first solution were analyzed using ICP-MS.
The dried first residue and 2 g of sodium hydroxide (4 times the original standard rock 0.5 g) were put in a crucible and heated in an electric furnace at 450 ° C. for 2 hours. After cooling, the second residue dried to dryness in the crucible was suspended in 80 ml of water and collected by centrifugation. The obtained 3rd residue was melt | dissolved in hydrochloric acid, it diluted by the predetermined magnification, and the element contained in the 3rd solution was analyzed using ICP-MS.
For each element Fe, Co, Cs, and Eu contained in the first solution and the third solution, the ratio (V1 / V1) between the amount V1 of each element analyzed and the nominal value V2 of each element contained in the standard rock. V2) was calculated. The closer the nominal value (true value) of the standard rock is to the analytical value, the closer the ratio is to 1. The result is shown in FIG.

[Comparative Example 1]
0.5 g of pulverized standard rock JG-3 was added to each aqueous solution of concentrated nitric acid (concentration 60 mass%), concentrated hydrofluoric acid (concentration 48 mass%) and concentrated perchloric acid (concentration 60 mass%) at a volume ratio of 3: It poured into 10 ml of mixed solutions mixed by 3: 1. This mixed solution was put in a pressure vessel and heated at 230 ° C. for 1 hour. 20 ml of a solution in which boric acid and nitric acid were mixed at a mass ratio of 1:10 was added to the mixed solution after cooling, and the mixture was heated at 80 ° C. for 1 hour. The supernatant of the mixed solution obtained by cooling was diluted at a predetermined magnification, and the elements contained in the supernatant were analyzed using ICP-MS.
The result of calculating the ratio (V1 / V2) in the same manner as in Example 1 is shown in FIG.

From the results of FIG. 2, for Fe, Co, and Cs, both Example 1 and Comparative Example 1 were able to analyze the content in the rock with good accuracy. On the other hand, with respect to Eu, Example 1 could be analyzed with good accuracy, whereas Comparative Example 1 could not detect it.
Therefore, it is clear that the method of the present invention is excellent as a method for analyzing Fe, Co, Cs and Eu contained in rocks, concrete and the like. According to the present invention, elemental analysis can be performed with an accuracy of ± 15% of the nominal value, not limited to the above elements.

  The configurations and combinations thereof in the embodiments described above are examples, and additions, omissions, substitutions, and other modifications of known configurations can be made without departing from the spirit of the present invention.

  The present invention can be widely applied to the field of handling activated concrete.

Claims (2)

A first step of mixing an inorganic sample containing silicon, nitric acid and perchloric acid, dissolving a part of the inorganic sample, and then separating into a first solution and a first residue;
A second step of heating the first residue and the alkali together and then cooling to obtain a second residue that is a mixture of the first residue and the alkali;
A third step of separating the mixture obtained by mixing the second residue and water into a third solution and a third residue;
A fourth step of dissolving the third residue in an acid to obtain a fourth solution;
A fifth step of analyzing elements contained in the first solution and the fourth solution;
A method for elemental analysis of inorganic samples, including   The elemental analysis method of an inorganic sample according to claim 1, wherein the inorganic sample is one or more selected from concrete, aggregate, and cement.

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