Determination Method of Silver, Platinum and Palladium in High Silver-Ash Palladium Powder

Abstract

The invention discloses a method for determining silver, platinum and palladium in high silver-ash palladium powder, which comprises the following steps: 1) Weigh a sample, add hydrochloric acid and hydrogen peroxide for dissolution, and filter to obtain a first filtrate and a first filter residue; 2) Add hydrochloric acid and hydrogen peroxide to the first filter residue for dissolution and filtration, repeat the operation for multiple times, collect the filtrate and a second filter residue, and merge the filtered filtrate with the first filtrate to obtain a second filtrate; 3) Wash the second filter residue with water for multiple times and then filter to obtain a third filter residue, and merge the filtrate with the second filtrate to obtain a third filtrate; 4) Dropwise add a reducing agent and water to the third filter residue for dissolution at low temperature, discard the liquid and retain the residue, repeat the operation for multiple times to obtain a fourth filter residue; 5) Wash the fourth filter residue with water for multiple times and then suck out the liquid to leave a fifth filter residue; 6) Add nitric acid to the fifth filter residue for dissolution to obtain a dissolution solution; 7) After respectively making the third filtrate and the dissolution solution constant volume and sampling for dilution, use ICP-OES for determination. This method can reduce the residue of the sample, reduce the chemical analysis error and improve the detection accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of precious metal detection, and particularly relates to a method for determining silver, platinum, and palladium in palladium powder with high silver ash content. Background Art

[0002] Palladium powder with high silver ash content is obtained by recycling and enriching palladium during the smelting process. This palladium powder contains silver and partially encapsulated platinum and palladium, making separation difficult. Therefore, how to efficiently separate and detect the contents of palladium, silver, and platinum in palladium powder with high silver ash content can lay a foundation for the application of palladium powder with high silver ash content.

[0003] Currently, the detection methods for precious metals such as platinum and palladium mainly use traditional fire assay pretreatment combined with ICP-OES determination. This detection method requires equipment such as a fire assay furnace and a cupellation furnace. Not only is the operation process cumbersome, time-consuming, and energy-consuming, but also this method requires high-temperature conditions during detection. The high-temperature reaction will generate heavy metal toxic gases such as lead, which is not conducive to the health of detection personnel, and there is also a certain degree of loss of elements to be detected, making the detection results inaccurate. For example, Patent CN111337477A discloses a method for determining the contents of gold, platinum, and palladium in high-silver and high-platinum palladium chemical slag. The detection steps of this invention method are to first perform fire assay pretreatment, cupellation and granulation, and nitric acid dissolution, and then the filter residue obtained after dissolution and filtration needs to be ashed at 700 °C and then determined by ICP-OES. Although this method is applicable to the determination of gold, platinum, and palladium in high-silver chemical slag, its pretreatment not only requires fire assay pretreatment but also requires ashing the filter residue at high temperature, so that the sample needs to enter the high-temperature furnace twice during the detection process, which is energy-consuming and will generate heavy metal toxic gases, resulting in the loss of elements to be detected.

[0004] CN106841180A discloses a method for continuous determination of platinum and palladium in ore. The detection steps required by this method are to first burn the sample at 700 - 750 °C, then add hydrochloric acid and hydrogen peroxide to heat and dissolve it. The filtrate is adsorbed by activated carbon and then burned at 700 - 750 °C. Finally, the content of the acid-dissolved liquid is determined by colorimetry. Although the pretreatment of this method does not use fire assay pretreatment, it needs to be burned at 700 - 750 °C twice for about 3 - 5 hours during the detection process, which is not only time-consuming and energy-consuming but also will generate heavy metal toxic gases, resulting in the loss of elements to be detected. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for determining silver, platinum, and palladium in palladium powder with high silver ash content that has simple operation steps, low energy consumption, and accurate determination results.

[0006] The technical solution adopted by the present invention to solve its technical problems is: A method for determining silver, platinum, and palladium in palladium powder with high silver ash content, comprising the following steps:

[0007] 1) Weigh the sample to be tested. Add a small amount of concentrated hydrochloric acid and hydrogen peroxide to the sample and dissolve it under low-temperature heating. Then filter to obtain the first filtrate and the first filter residue. In this step, hydrochloric acid can not only dissolve platinum and palladium, but also precipitate silver as silver chloride. At the same time, adding hydrogen peroxide can convert elemental and free silver, palladium, and platinum into silver oxide, palladium oxide, and platinum oxide. The substances contained in the first filtrate are platinum-palladium chloride solutions, etc., and the substances contained in the first filter residue are silver chloride and a small amount of silver, platinum, and palladium that are not completely dissolved, as well as palladium oxide and platinum oxide that are insoluble in hydrochloric acid.

[0008] 2) Continue to add a small amount of concentrated hydrochloric acid and hydrogen peroxide to the first filter residue and dissolve it under low-temperature heating, then filter, and repeat this operation multiple times. Collect the filtrate obtained after each filtration and the filter residue obtained after the last filtration. This filter residue is called the second filter residue, and the substances contained in this second filter residue are: platinum, palladium, silver chloride, palladium oxide, and platinum oxide. Merge the filtrate obtained after each filtration with the first filtrate to obtain the second filtrate, which contains platinum-palladium chloride solutions. By repeating the steps of dissolution and oxidation, the remaining platinum and palladium in the filter residue can be further dissolved and effectively separated from the silver in the filter residue, improving the accuracy of detection.

[0009] 3) Wash the second filter residue with water multiple times to remove chloride ions, then filter. Collect the washing liquid and the filtrate and merge them with the second filtrate to obtain the third filtrate. The filter residue obtained after filtration is called the third filter residue and is reserved for later use. Since hydrochloric acid has oxidizing properties and will react with the reducing agent in step 4) below, reducing the reduction effect, in this step, water washing is used to remove chloride ions to improve the subsequent reduction effect.

[0010] 4) Add a small amount of reducing agent and water to the third filter residue and dissolve it under low-temperature heating, then suck out the liquid and discard the sucked-out liquid, leaving the residue. Continue to repeat this operation multiple times on the remaining residue. Collect the filter residue left after discarding the liquid for the last time. This filter residue is called the fourth filter residue, and the substances contained in it are: silver, platinum, palladium, and a small amount of silver chloride, palladium oxide, and platinum oxide that are not completely reduced. In this step, the reducing agent can reduce insoluble substances such as silver chloride, palladium oxide, and platinum oxide in the third filter residue to silver, platinum, and palladium.

[0011] 5) Wash the fourth filter residue with water multiple times to wash away the reducing agent, then suck out the liquid, leaving the filter residue. This filter residue is called the fifth filter residue. Since the nitric acid added in step 6) below has oxidizing properties and will react with the reducing agent, reducing the dissolution effect of the fifth filter residue, in this step, water washing is used to remove the reducing agent to improve the subsequent dissolution effect.

[0012] 6) Add a small amount of concentrated nitric acid to the fifth filter residue to dissolve it, obtaining a dissolution solution. Since the fifth filter residue mainly contains silver and a small amount of platinum and palladium wrapped inside, adding nitric acid can dissolve all the silver and palladium.

[0013] 7) Make volume fixes for the third filtrate obtained in step 3) and the dissolution solution obtained in step 6) respectively. After sampling respectively, dilute them by 10 - 20 times to obtain the first test solution and the second test solution. The first test solution is a hydrochloric acid system and mainly contains palladium; the second test solution is a nitric acid system containing silver. Then, use ICP - OES to measure the contents of silver, platinum, and palladium in the first test solution and the second test solution respectively, and obtain the contents of silver, platinum, and palladium in the high - silver - ash - content palladium powder.

[0014] Furthermore, between step 6) and step 7), there are also the following steps: If there is residue in the funnel used during filtration in step 1) and step 2), wash the funnel with water and filter the washed liquid. The filtrate is combined with the first filtrate or the second filtrate, and the residue is combined with the first residue or the second residue. Then, perform the operation steps from step 3) to step 7) on the same first residue or second residue. By adopting this step, the residue remaining in the funnel used during filtration can be effectively collected, avoiding the loss of silver, platinum, and palladium contained in this part of the residue, which may cause inaccurate detection results, and further improving the accuracy of the detection results.

[0015] Furthermore, the specific operation steps of step 1) are: Accurately weigh 0.1 g of the test sample, add 1 - 2 mL of hydrochloric acid and 1 - 2 mL of 30% hydrogen peroxide dropwise to the test sample, and perform low - temperature heating at 50 - 150 °C for 2 - 5 min for dissolution, then filter.

[0016] Furthermore, the number of times of repeated operation in step 2) is 2 - 3 times until the reaction is complete.

[0017] Furthermore, the specific operation steps of step 4) are: Add 1 - 2 mL of 80% hydrazine hydrate as a reducing agent and 1 - 2 mL of water dropwise to the third residue, perform low - temperature heating at 50 - 150 °C for 2 - 5 min for dissolution, then suck out the liquid and discard the sucked - out liquid, leaving the residue. Repeat this operation on the remaining residue multiple times, and collect the fourth residue left after discarding the liquid for the last time.

[0018] Furthermore, the number of times of repeated operation in step 4) is 2 - 3 times.

[0019] Furthermore, the specific operation steps of step 6) are: Add 5 - 10 mL of concentrated nitric acid to the fifth residue for dissolution to obtain a dissolution solution.

[0020] Furthermore, in step 7), the third filtrate and the dissolution solution are fixed in volume using a 100 - mL volumetric flask.

[0021] Further, during the filtration in step 1-3), a G4 glass sand core funnel is used for filtration or an ordinary funnel with filter paper is used for filtration. And when using filter paper for filtration, if there are residues, they need to be ashed at 200-500 °C for 3-5 minutes, and the ashed residues are combined with the third filter residue and the subsequent operations of step 4) to step 7) are carried out together. And what is used during filtration.

[0022] Further, in steps 1-2) and 4), the instrument for low-temperature heating is a graphite furnace.

[0023] Further, according to the principle of the present invention, the reducing agent hydrazine hydrate used in the scheme can be replaced by other hydrazine reducing substances, nitrites, etc., such as sodium nitrite, hydroxylamine, etc., which are the key points and points to be protected in the present invention.

[0024] The beneficial effects of the method for determining silver, platinum and palladium in high silver ash palladium powder of the present invention: The operation steps of this method are simple, with low energy consumption and environmental friendliness. When pretreating the sample, there is no need for fire assay high-temperature enrichment. Only hydrochloric acid and nitric acid are used in combination with hydrogen peroxide and hydrazine hydrate for dissolution and filtration multiple times, and the collected solution is then subjected to ICP-OES determination. This detection method is divided into a nitric acid system and a hydrochloric acid system, which can completely dissolve silver, platinum and palladium. The entire operation process does not require high-temperature calcination treatment, which can reduce sample residue, reduce assay error, and thus improve the accuracy of the detection result, and is suitable for rapid determination on-site in industrial and mining enterprises. Description of the Drawings

[0025] Figure 1 — is the operation flow chart of the method for determining silver, platinum and palladium in high silver ash palladium powder of the present invention. Detailed Embodiments

[0026] The following further illustrates the present invention in conjunction with the drawings and embodiments, but these specific implementation schemes do not limit the protection scope of the present invention in any way.

[0027] Example 1

[0028] A method for determining silver, platinum and palladium in high silver ash palladium powder, the operation flow chart of the determination is as Figure 1 shown, and the determination method specifically includes the following steps:

[0029] 1) Accurately weigh 0.1 g of the sample into a 100 mL first beaker, add 2 mL of concentrated hydrochloric acid and 2 mL of 30% hydrogen peroxide, and carry out low-temperature heating with a graphite furnace at 50 °C for 5 minutes for dissolution, and then filter;

[0030] 2) Filter the liquid obtained from step 1) using a G4 glass sand core funnel. Collect the first filtrate into a 100 mL volumetric flask No. 1, and leave the first residue in a beaker No. 1. After washing the funnel with water, filter the liquid obtained from the water wash, collect the filtrate into the 100 mL volumetric flask No. 1 until it is combined with the first filtrate, and collect the residue in the beaker No. 1 and combine it with the first residue.

[0031] 3) Repeat the operations in steps 1) and 2) three times for the first residue in the beaker No. 1. Collect the filtrate obtained after each filtration and the residue obtained after the last filtration. This residue is called the second residue. Collect the filtrate obtained after each filtration into the 100 mL volumetric flask No. 1 and combine it with the first filtrate to obtain the second filtrate, and store it.

[0032] 4) Wash the second residue with water multiple times to remove chloride ions, filter, and collect the washing liquid and filtrate into the 100 mL volumetric flask No. 1 and then combine it with the second filtrate to obtain the third filtrate (i.e., Figure 1 the solution 1 in

[0033] ). Leave the third residue obtained after filtration for later use.

[0034] 5) Add 2 mL of 80% hydrazine hydrate as a reducing agent and 2 mL of water to the third residue, and dissolve it by heating at a low temperature of 100 °C in a graphite furnace for 5 minutes. Then suck out the liquid and discard the sucked-out liquid, leaving the residue. Repeat this operation multiple times for the remaining residue, collect the residue left after discarding the liquid for the last time. This residue is called the fourth residue.

[0035] 7) Wash the fourth residue with water 2 - 3 times to wash away hydrazine hydrate, then suck out the liquid, leaving the residue. This residue is called the fifth residue.

[0036] 8) Add 6 mL of concentrated nitric acid to the fifth residue to dissolve it, obtaining a dissolution solution (i.e., Figure 1 the solution 2 in

[0037] ). Collect the dissolution solution into a 100 mL volumetric flask No. 2.

[0038] 9) After making the volume up to the mark with water in the 100 mL volumetric flask No. 1 and the 100 mL volumetric flask No. 2, take samples respectively and dilute them 10 - 20 times to obtain the first test solution and the second test solution. The first test solution is in a hydrochloric acid system and mainly contains palladium; the second test solution is in a nitric acid system containing silver.

[0039] Calculation of the content of each element. Suppose the sampling mass is m (unit: g), the concentration of the first 100 mL volumetric flask is C1 (unit: μg / mL), the concentration of the second 100 mL volumetric flask is C2 (unit: μg / mL), and the volumes of the first 100 mL volumetric flask and the second 100 mL volumetric flask are V1 and V2 (unit: mL) respectively. The calculation formula is as follows:

[0040] W% =

[0041] According to the determination method of Example 1, weigh the sample and conduct parallel analysis and determination. The results are shown in the following table:

[0042]

[0043] As can be seen from the above table, the relative error is less than 1%, within the controllable range, and the results are accurate and reliable.

[0044] It should be noted separately that the terms "first", "second", "third", "fourth", etc. are used in this article to describe the substances or instruments used in various steps, but these substances or instruments used should not be limited by these terms. These terms are only used to distinguish one element from another.

[0045] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the technical solution scope of the present invention, can make some changes or modifications to the above-disclosed technical content to obtain equivalent embodiments with equivalent changes. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for determining silver, platinum and palladium in high-silver-ash palladium powder, characterized in that: It includes the following steps: 1) Weigh the sample to be tested, add a small amount of concentrated hydrochloric acid and hydrogen peroxide to the sample, dissolve it under low-temperature heating, filter to obtain the first filtrate and the first filter residue; 2) Continuously add a small amount of concentrated hydrochloric acid and hydrogen peroxide to the first filter residue, dissolve it under low-temperature heating, filter, and repeat the operation multiple times. Collect the filtrate obtained after each filtration and the filter residue after the last filtration to obtain the second filter residue. Combine the filtrate obtained after each filtration with the first filtrate to obtain the second filtrate; 3) Wash the second filter residue with water multiple times and then filter. Collect the washing liquid and the filtrate, combine them with the second filtrate to obtain the third filtrate. Keep the third filter residue obtained after filtration for later use; 4) Add a small amount of reducing agent and water to the third filter residue, dissolve it under low-temperature heating, then suck out the liquid, discard the sucked-out liquid, and keep the residue. Repeat this operation multiple times on the remaining residue. Collect the filter residue left after discarding the liquid for the last time to obtain the fourth filter residue; 5) Wash the fourth filter residue with water multiple times and then suck out the liquid. The remaining filter residue is the fifth filter residue; 6) Add a small amount of concentrated nitric acid to the fifth filter residue to dissolve it to obtain a dissolved solution; 7) Make the third filtrate obtained in step 3) and the dissolved solution obtained in step 6) reach a constant volume respectively. Take samples respectively and dilute them by 10 - 20 times to obtain the first test solution and the second test solution. Then use ICP - OES to measure the contents of silver, platinum, and palladium in the first test solution and the second test solution respectively to obtain the contents of silver, platinum, and palladium in the high - silver - ash - content palladium powder.

2. The method for determining silver, platinum and palladium in high-silver-ash palladium powder according to claim 1, characterized in that: The steps included between step 6) and step 7) are: If there is filter residue left in the funnel used during filtration in step 1) and step 2), the funnel can be washed with water and the washed liquid is filtered. The filtrate is combined with the first filtrate or the second filtrate, and the filter residue is combined with the first filter residue or the second filter residue and the same first filter residue or second filter residue is used for the operation steps from step 3) to step 7).

3. The method for determining silver, platinum and palladium in high-silver-ash palladium powder according to claim 1, characterized in that: The specific operation steps of step 1) are: Accurately weigh 0.1 g of the sample to be tested, add 1 - 2 mL of concentrated hydrochloric acid and 1 - 2 mL of 30% hydrogen peroxide to the sample to be tested, carry out low - temperature heating at 50 - 150 °C for 2 - 5 min to dissolve it, and then filter.

4. The method for determining silver, platinum and palladium in high-silver-ash palladium powder according to claim 1, characterized in that: The number of times of repeating the operation in step 2) is 2 - 3 times until the reaction is complete.

5. The method for determining silver, platinum and palladium in high-silver-ash palladium powder according to claim 1, characterized in that: The specific operation steps of step 4) are: Add 1 - 2 mL of 80% hydrazine hydrate as a reducing agent and 1 - 2 mL of water to the third filter residue, dissolve it under low - temperature heating at 50 - 150 °C for 2 - 5 min, then suck out the liquid, discard the sucked - out liquid, and keep the residue. Repeat this operation multiple times on the remaining residue. Collect the fourth filter residue left after discarding the liquid for the last time.

6. The method for determining silver, platinum and palladium in high-silver-ash palladium powder according to claim 5, characterized in that: The number of times of repeating the operation in step 4) is 2 - 3 times until the reaction is complete.

7. The method for determining silver, platinum and palladium in high-silver-ash palladium powder according to claim 1, characterized in that: The specific operation steps of step 6) are: Add 5 - 10 mL of concentrated nitric acid to the fifth filter residue to dissolve it to obtain a dissolved solution.

8. The method for determining silver, platinum and palladium in high-silver-ash palladium powder according to claim 1, characterized in that: In step 7), the third filtrate and the dissolved solution are made to reach a constant volume using a volumetric flask.

9. The method for determining silver, platinum and palladium in high-silver-ash palladium powder according to claim 1, characterized in that: During filtration in steps 1) - 3), filtration is carried out using a G4 glass - sintered funnel or using an ordinary funnel with filter paper. And if there are residues when using filter paper for filtration, they need to be incinerated at 200 - 500 °C for 3 - 5 min. The incinerated residues are combined with the third filter residue and the subsequent operations from step 4) to step 7) are carried out together.

10. The method for determining silver, platinum and palladium in high-silver-ash palladium powder according to claim 1, characterized in that: The instrument for low-temperature heating in the said step 1) - step 2) and step 4) is a graphite furnace.

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