JP6325358B2 - Method for separating and analyzing trace noble metals - Google Patents

Description

  The present invention relates to a method for separating a trace noble metal for analyzing a noble metal contained in a trace amount and an analysis method therefor.

  Until now, iridium, ruthenium and rhodium have been quantified from other elements in the sample after alkali melting by collecting rhodium with tellurium or selenium, and iridium and ruthenium with ethanol reduction to obtain a precipitate. The precipitate was dissolved in aqua regia, and the target metal concentration in the obtained solution was determined by ICP emission spectroscopy (ICPOES). However, as described above, rhodium, iridium, and ruthenium are separated from each other and cannot be quantified at the same time.

  In the technique described in Patent Document 1, a sample containing iridium, ruthenium and rhodium is added with a predetermined amount of metallic copper powder or metallic copper particles as a collector for these elements and mixed to obtain a mixture. In a crucible, an alkali mixture (sodium peroxide 1: sodium carbonate 1 weight mixture) is added, the mixture is heated and melted (alkaline melting), and the melt obtained by cooling is leached with warm water to obtain a solution. A method for separating iridium, ruthenium, and rhodium is described, wherein ethanol is added to the solution to collect the precipitate, and solid-liquid separation is performed to obtain a precipitate containing iridium, ruthenium, and rhodium. . According to this technique, the above-mentioned three components can be quantified at once, and the method is rapidly applied, and is applied to the analysis of a sample containing the entire element in the order of several tens of ppm.

JP 2002-030357 A

  There is a demand for commercializing noble metals such as iridium, ruthenium, and rhodium from samples containing these noble metals, such as samples obtained from a copper smelting process. The abundance of iridium, ruthenium and rhodium contained in the sample from the actual copper smelting process is often less than the ppm order. For this reason, an analysis technique of ppm order or less is required together with the separation method described in Patent Document 1, and in order to grasp the balance of quantity and distribution behavior to slag with respect to iridium, ruthenium and rhodium, 0.01 ppm order Analyzes in are essential.

  Under such circumstances, an analysis technique based on ICP mass spectrometry (ICPMS) that does not require separation for the element to be analyzed is expected. However, when measuring in a state containing coexisting substances with respect to ICPMS, spectral interference due to molecular ions and a decrease in sensitivity due to the matrix effect cannot be avoided. Therefore, the lower the concentration, the greater the effect.

  That is, the presence of coexisting substances at the time of analysis may affect the analysis result, and it is difficult to ensure accuracy. For this reason, establishment of a reference method as an analysis method for trace elements has been demanded.

  The present invention provides a method for analyzing a noble metal capable of quantification on the order of 0.01 ppm with respect to a sample containing a noble metal such as iridium, ruthenium, and rhodium in a trace amount such as a sample from a copper smelting process. The purpose is to do.

That is, the present invention is as follows.
(1) Cool a melt obtained by heating and melting a sample containing at least one kind of iridium, ruthenium and rhodium at a total amount of less than 10 ppm and containing an iron or copper compound together with an alkali flux. The first step of adding ethanol to the solution obtained by leaching with warm water to form a precipitate, followed by solid-liquid separation;
The precipitate obtained in the first step is leached in water and ethanol, and hydrochloric acid is added to the obtained solution to dissolve it by heating. Then, if necessary, a sodium chloride solution is added and the mixture is heated to dryness. Two processes,
Separation of a trace amount of noble metal including a third step in which hydrochloric acid is added to the precipitate obtained in the second step and heated to dissolve, and then the solution obtained by cooling is passed through a cation exchange resin. Method.
(2) The method according to (1), wherein a sodium chloride solution is added in the second step when the sample contains ruthenium.
(3) Cool a melt obtained by heating and melting a sample containing at least one of iridium, ruthenium and rhodium in a total amount of less than 10 ppm and containing an iron or copper compound together with an alkali flux. The first step of adding ethanol to the solution obtained by leaching with warm water to form a precipitate, followed by solid-liquid separation;
The precipitate obtained in the first step is leached in water and ethanol, and hydrochloric acid is added to the obtained solution to dissolve it by heating. Then, if necessary, a sodium chloride solution is added and the mixture is heated to dryness. Two processes,
A third step in which hydrochloric acid is added to the precipitate obtained in the second step and dissolved by heating, and then the solution obtained by cooling is passed through a cation exchange resin;
A fourth method for analyzing a trace amount of noble metal, wherein the eluate obtained in the third step is quantified by ICPMS.
(4) The method according to (3), wherein when the sample contains ruthenium, a sodium chloride solution is added in the second step.

  According to the present invention, it becomes possible to quantify a noble metal with respect to a sample containing a noble metal such as iridium, ruthenium, and rhodium in an extremely small amount.

It is a flowchart which shows an example of this embodiment. It is a graph which shows the calibration curve of rhodium in the measuring method of the present invention. It is a graph which shows the calibration curve of ruthenium in the measuring method of this invention. It is a graph which shows the calibration curve of iridium in the measuring method of this invention.

From one aspect, the present invention provides a method for analyzing trace noble metals.
That is, as shown in FIG. 1, the trace noble metal analysis method of the present invention comprises a sample containing at least one of iridium, ruthenium and rhodium in a total amount of less than 10 ppm and containing an iron or copper compound. The melt obtained by heating together with the agents (S12, S14) (S18) is cooled, leached with warm water (S22), and ethanol is added to the resulting solution (S24) to form a precipitate. Solid-liquid separation (S28) The first step and the precipitate (S30) obtained in the first step are leached in water and ethanol (S32, S34), and hydrochloric acid is added to the obtained solution (S36). ) After heating and dissolving (S38), if necessary, a sodium chloride solution is added (S40) and heated to dryness (S42). The precipitate obtained in the second step and the second step is added with hydrochloric acid. (S4 ) Heat and dissolve, then cool (S46) and pass the solution obtained through the cation exchange resin (S48). The eluate obtained in the third step and the third step is treated with ICPMS. (S50) and a fourth step.

In the first step, iridium, ruthenium and rhodium contained in the sample are precipitated and separated as hydroxides.
In the present invention, the sample to be processed in step (S10) contains a trace amount of noble metals such as iridium, ruthenium and rhodium, and the total amount of the noble metals is 10 ppm. Less, typically less than 1 ppm, and even less than 0.5 ppm. Such a sample is typically discharged from a copper smelting process, or may be obtained by leaching electronic component waste, home appliance waste, waste catalyst, or the like. In addition, such a sample contains iron and copper in the order of 0.1 to several tens% mass fraction, and such iron and copper are iron or copper compounds, that is, oxides and sulfides. Included in the form of things. The iron content and copper content need only be about 0.1% by mass and need not be added again.

In steps S12 and S14, the sample is mixed with an alkali flux (S16) and heated and melted (S18).
At this time, examples of the alkali flux added include sodium peroxide and sodium carbonate. Moreover, it is preferable to cover the surface of the mixture of the sample and the alkaline flux with sodium peroxide.

  Thereafter, the mixture is melted in a burner or an electric furnace. This heat melting is preferably performed in an alumina crucible.

Next, the melt is cooled (S20) and leached with warm water (S22), and ethanol is added to the resulting solution to form a precipitate (S24). By this operation, the noble metal having a high oxidation number can be reduced and concentrated and collected as a hydroxide.
The precipitate is separated into solid and liquid by suction filtration (S28), and the precipitate is recovered (S30).

In the second step, the precipitate obtained in the first step is heated to dryness in order to obtain an acidic solution so as to be applied to the cation exchange resin used in the subsequent third step.
That is, the precipitate obtained by the above solid-liquid separation is leached in warm water (S32), subsequently leached in ethanol (S34), hydrochloric acid is added (S36), and heated to dissolve (S38). Heat to dryness (S42). This heating and drying is performed at a relatively low hot plate temperature, for example, about 90 to 140 ° C.
At this time, if ruthenium is contained in the analysis target, it is oxidized by hydrochloric acid, for example, octavalent ruthenium may be volatilized, and ruthenium loss may occur. From such a viewpoint, it is preferable to add a sodium chloride solution as a fixing agent for fixing oxidized ruthenium after the precipitate is dissolved and prior to heating to dryness (S40).

In the third step, the solid obtained in the second step is added to hydrochloric acid (S44) to make an acidic solution, then heated and dissolved, allowed to cool (S46), and passed through a cation exchange resin. (S48).
Examples of the cation exchange resin preferably used here include fine mesh strongly acidic cation exchange resin, for example, DOWEX50WX8 manufactured by Dow Chemical.
The acidic solution can be passed through the cation exchange resin under the conditions of 0.5 M hydrochloric acid acidic solution.
By this operation, it is possible to effectively remove coexisting substances such as iron, copper, aluminum, and sodium that may be mixed in the middle. In addition, iridium, ruthenium, rhodium and the like exist as chlorine complex anions and are eluted without being adsorbed on the resin. However, since their distribution coefficients are different, they can be separated according to the elution timing.

  As described above, the separation technique for obtaining a solution suitable for the analysis of iridium, ruthenium, and rhodium is constituted up to the third step. From such a viewpoint, the present invention provides a trace amount of noble metal. A separation method is provided.

  Subsequently, in the fourth step, each fraction is subjected to cation exchange treatment in the third step, and each is analyzed by ICPMS (S50).

Examples of the present invention will be described below, but the present invention is not limited to the examples.
(Reference Example 1) Preparation of calibration curve Using a rhodium standard solution, a ruthenium standard solution, and an iridium standard solution, measurement was performed by the ICPMS method under the following conditions to prepare rhodium, iridium, and ruthenium calibration curves. FIG. 2 shows a calibration curve for rhodium, FIG. 3 shows a calibration curve for ruthenium, and FIG. 4 shows a calibration curve for iridium. In the examples, the analysis values are evaluated based on these calibration curves.

・ Rhodium standard solution (for atomic absorption analysis, 1000 mg / L): Kanto Chemical Co., Ltd. ・ Ruthenium standard solution (for atomic absorption analysis, 1000 ppm): Acros Organics
-Iridium standard solution (for atomic absorption analysis, 1000 ppm): Acros Organics
ICP mass spectrometer: Hitachi High-Tech Science Corporation, SPQ9000 series

Reference Example 2 Preparation of Ion Exchange Resin Column A cation exchange resin (DOWEX50WX8 (100-200 mesh)) was activated with 3M NaOH and 3M HCl, and then made neutral with water as RH type. 15 mL of the sample was packed in a quartz column (8 mmφ × 400 mmL) so that no bubbles were introduced, and 30 mL each of 3 M HCl, water, and 0.5 M HCl were passed therethrough.

(Example 1) Analysis of platinum ore Platinum ore (SARM-7B) was used as a sample, and 0.5 g of the sample was charged into an alumina crucible. 1 g of sodium carbonate (Wako Pure Chemical Industries, Ltd., special grade) and 2 g of sodium peroxide (Kanto Chemical Co., Ltd., first grade) were added thereto. The surface of the crucible while leaving the mixture obtained by mixing the sample, sodium carbonate and sodium peroxide was covered with 2 g of sodium peroxide and heated with a burner to melt.

  The melt was transferred to a 300 mL beaker, to which 100 mL of water and 5 mL of ethanol (Wako Pure Chemical Industries, Ltd., special grade) were added and heated to conduct a leaching reaction. After the leaching, the liquid was subjected to solid-liquid separation by suction filtration using a filter having a pore diameter of 0.47 μm.

  The filtered solid was placed in a beaker, to which 50 mL of water, 5 mL of ethanol, and 20 mL of hydrochloric acid were added, heated and stirred. Thereafter, 1 mL (10 w / v%) of an aqueous solution of sodium chloride was added to the dissolved portion and stirred. The obtained mixture was heated to dryness at a hot plate temperature of 90 to 140 ° C.

  To the solid obtained after drying, 10 mL of 0.5 M HCl was added, and heated and dissolved. Thereafter, the mixture was allowed to cool and supported on the ion exchange resin column prepared in Reference Example 2.

  A 0.5 M hydrochloric acid solution was passed through the ion exchange resin column, and the eluate was collected. Thereafter, water was added to the eluate to make a total volume of 50 mL, thereby preparing a sample for ICP measurement. Each noble metal was analyzed under the conditions of the ICPMS measurement in Reference Example 1. The results are shown in the table below.

(Example 2)
In Example 1, instead of platinum ore (SARM-7B), copper concentrate (CRM No. 1701-86 (KM-1)) was used as a sample in the same procedure as in Example 1, except that ICP. A sample for measurement was prepared. Each noble metal was analyzed under the conditions of the ICPMS measurement in Reference Example 1. The results are shown in the table below.

  In the table, the guaranteed value is the solution obtained by separating and concentrating iridium, ruthenium and rhodium on lead button, tin button, nickel sulfide and iron-copper-nickel button obtained by dry assay, and dissolving them with hydrochloric acid etc. Is a value obtained by measuring ICPMS.

Claims (4)

Cool the melt obtained by heating and melting a sample containing at least one of iridium, ruthenium and rhodium at a total amount of less than 10 ppm and containing an iron or copper compound together with an alkaline flux, A first step of adding ethanol to the solution obtained by leaching to form a precipitate, followed by solid-liquid separation;
The precipitate obtained in the first step is leached in water and ethanol, and hydrochloric acid is added to the obtained solution to dissolve it by heating. Then, if necessary, a sodium chloride solution is added and the mixture is heated to dryness. Two processes,
The precipitate obtained in the second step is dissolved by adding hydrochloric acid and heated, and then cooled, and then the third step of passing the solution obtained by cooling through the cation exchange resin is separated. Method.   The method according to claim 1, wherein a sodium chloride solution is added in the second step when the sample contains ruthenium. Cool the melt obtained by heating and melting a sample containing at least one of iridium, ruthenium and rhodium at a total amount of less than 10 ppm and containing an iron or copper compound together with an alkaline flux, A first step of adding ethanol to the solution obtained by leaching to form a precipitate, followed by solid-liquid separation;
The precipitate obtained in the first step is leached in water and ethanol, and hydrochloric acid is added to the obtained solution to dissolve it by heating. Then, if necessary, a sodium chloride solution is added and the mixture is heated to dryness. Two processes,
A third step in which the precipitate obtained in the second step is dissolved by adding hydrochloric acid to be heated and then cooled, and the solution obtained by cooling is passed through a cation exchange resin;
A fourth method for analyzing a trace amount of noble metal, wherein the eluate obtained in the third step is quantified by ICPMS.   The method according to claim 3, wherein a sodium chloride solution is added in the second step when the sample contains ruthenium.

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