Palladium Extraction Method

Abstract

To provide a method for extracting palladium.SOLUTION: A method for extracting palladium includes: a step 1 of mixing a palladium-containing raw material, a nitric acid and a catalyst including an alkali metal to obtain a mixed liquor, then heating the mixed liquor to remove a residue, thereby obtaining a palladium-containing extract; and a step 2 of separating and extracting, the palladium-containing extract acquired in the step 1, thereby obtaining a metal palladium or palladium-containing product, then feeding surplus solution to the step 1. In the invention, by employing the catalyst including the alkali metal ion, an extraction rate of the palladium can be made higher than that when employing high concentration nitric acid. The catalyst is not volatilized, therefore recycling rate of mother liquid can be enhanced. The method can be performed easily, can reduce cost of production, can shorten a palladium extraction time, and can prevent contamination which occurs twice.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to hydrometallurgy, in particular to a method for extracting palladium by hydrometallurgy, and more particularly to a method for extracting palladium. [Background technology]

[0002] Palladium is a platinum group metal with excellent plasticity, stability and catalytic activity, and is therefore widely used in the fields of aeronautics, nuclear energy, electronics and catalysts. Palladium is considered a "strategic metal" due to its unique properties and rarity. With the development of the global economy, the demand for palladium is increasing, but the reserves of palladium minerals are very scarce, so the increasing demand for palladium cannot be met. The palladium content in natural palladium minerals is low, so the cost of extracting it is high. Compared with natural palladium minerals, palladium-containing secondary raw materials have the advantages of high palladium content, low impurity content and low extraction difficulty. Therefore, extracting palladium from palladium-containing secondary raw materials has important strategic significance and high economic value.

[0003] Palladium has the characteristic of being stable chemically, soluble in low-concentration nitric acid and hydrochloric acid, but insoluble in sulfuric acid. In industrial production, palladium is usually dissolved in hot, high-concentration nitric acid or aqua regia (the ratio of nitric acid to hydrochloric acid is 1:3). However, high-concentration nitric acid has the disadvantage of being easily volatile, and a large amount of nitrogen oxides is generated during the reaction process. Since aqua regia is highly corrosive, there is an increasing demand for corrosion resistance of equipment. In addition, when aqua regia is used, there is a risk of pollution problems due to the generation of large amounts of toxic gases. In recent years, researchers have been researching solvents that can be used instead of nitric acid or aqua regia.

[0004] A Chinese patent application with publication number CN109957659 discloses a method for recovering palladium from spent palladium-containing catalytic agent. The method includes the following steps: In step (1), the spent palladium-containing catalytic agent is put into water to perform boiling, boiling at a temperature of 90-100°C for 1-2 hours, boiling is performed 5-7 times, and the solid is taken out after boiling is completed; In step (2), the solid obtained in step (1) is put into an alkaline solution with a concentration of 1-3% to perform alkaline cooking, alkaline cooking at a temperature of 85-95°C for 1-2 hours, and alkaline cooking is performed 2-4 times. In step (3), after the alkali cooking is completed, the solution is adjusted to a pH value of 1-3 by adding sulfuric acid, and then 4-6 mol / L hydrochloric acid and a certain amount of an oxidizing agent such as sodium chlorate or chlorine are added, and extraction is carried out for 2-3 hours at a temperature of 60-80°C to obtain a palladium-containing organic precipitate. This method has the advantages of a good palladium recovery rate and low energy consumption, but has the disadvantages of a complicated palladium extraction process, the need to use a large amount of water, the need to use a large amount of hydrochloric acid in the reaction process, and the high corrosiveness and toxic chlorine gas and sodium chlorate, which are not environmentally friendly.

[0005] A Chinese patent application with publication number CN108285978 discloses a method for recovering palladium from a palladium-containing catalytic agent. In the method, first, organic matter in the palladium-containing catalytic agent is removed by low-temperature distillation (150-350°C). Next, palladium is extracted by oxidation with H2O2 in an HCl+NaCl solution, and the palladium-containing extract obtained is reduced with formic acid to obtain simple palladium. Although the method can improve the extraction rate of palladium, it has the disadvantage that it is not environmentally friendly because it requires the use of large amounts of hydrochloric acid and hydrogen peroxide, and highly volatile and toxic chlorine is formed.

[0006] To solve the problems of the prior art, there is a need to provide an environmentally friendly, economical and highly efficient method for extracting palladium. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] China Patent Publication No. 109957659 [Patent Document 2] China Patent Publication No. 108285978 Summary of the Invention [Problem to be solved by the invention]

[0008] In order to solve the problems of the prior art, the present invention provides the following palladium extraction method. The palladium extraction method of the present invention can reduce the amount of acid liquid used, simplify the components, reduce the production cost, and realize the reuse of the extraction liquid. In addition, by reducing the amount of acid liquid used, the contamination of foreign ions can be reduced, the utilization rate of atoms can be improved, the generation of waste liquid can be eliminated, and the extraction rate and extraction speed of palladium can be improved, thereby expanding the industrial applicability. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides the following palladium extraction method, which includes the steps of: (1) mixing a palladium-containing raw material, nitric acid, and a catalytic agent containing an alkali metal ion to obtain a mixed solution, heating the mixed solution to remove residues to obtain a palladium-containing extract, and (2) separating and extracting the palladium-containing extract obtained in step (1) to obtain metallic palladium or a palladium-containing product, and feeding the excess solution to step (1).

[0010] In the present invention, the catalytic agent containing alkali metal ions is used to improve the extraction rate of palladium. In addition, the catalytic agent does not volatilize, so the utilization rate of the mother liquor can be improved. In the nitric acid cycle, the catalytic agent containing alkali metal ions and the palladium-containing raw material are heated, and the extract is separated to obtain metallic palladium or a palladium-containing product, and the remaining solution after separation is sent to step (1). In the present invention, palladium is extracted using a mixture of the catalytic agent containing alkali metal ions and nitric acid, and high-concentration nitric acid and aqua regia are not used, so the amount of acid liquid used can be greatly reduced and the contamination of foreign matter can be reduced. In addition, the problem of chloride ions, chlorine gas, hydrogen peroxide, etc., which cannot be reused due to volatilization and decomposition in the prior art can be solved. As a result, the manufacturing cost and the discharge of waste liquid can be greatly reduced, and an environmentally friendly effect can be obtained. Such a configuration is an innovation of the present invention that is different from the prior art.

[0011] In a preferred embodiment of the present invention, the alkali metal ion in step (1) is Li + , Na + or K + Preferably, Li + It is.

[0012] In the present invention, Li + , Na + or K + The rate at which palladium is extracted can be greatly increased by using ions as a catalyst.

[0013] In step (1) of the present invention, the catalyst containing an alkali metal ion may be lithium nitrate, lithium sulfate, lithium chloride, sodium nitrate, sodium sulfate, sodium chloride, potassium nitrate, potassium sulfate, potassium chloride, lithium carbonate, potassium carbonate, sodium carbonate, or a compound containing an alkali metal ion thereof or a solution thereof.

[0014] In a preferred embodiment of the present invention, the concentration of the alkali metal ion in the mixture is ≧1 mol / L. For example, it may be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L or 7 mol / L, etc., but the present invention is not limited thereto, and any suitable value within a certain range may be adopted in the present invention. The preferred concentration of the present invention is ≧5 mol / L.

[0015] In a preferred embodiment of the present invention, in step (1), the palladium content in the palladium-containing raw material is ≧100 ppm, for example, 100 ppm, 120 ppm, 140 ppm, 160 ppm, 180 ppm, 200 ppm, 300 ppm, 1000 ppm, or pure metallic palladium is used, but the present invention is not limited thereto, and any suitable value within a certain range can be used in the present invention.

[0016] In the present invention, the palladium-containing raw material in step (1) can be any one or a combination of at least two of metallic palladium, palladium alloy, palladium compound, palladium-containing mineral, or palladium-containing secondary raw material. Such combinations are merely illustrative of the present invention and do not limit the present invention. For example, the palladium-containing raw material can be a combination of palladium powder and palladium-containing mineral, a combination of palladium-containing mineral and palladium-containing secondary raw material, or a combination of palladium-containing secondary raw material and palladium powder.

[0017] In a preferred embodiment of the present invention, the concentration of hydrogen ions in the mixture in step (1) is ≧1 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, or 7 mol / L, etc., but the present invention is not limited thereto, and any suitable value within a certain range can be adopted in the present invention.

[0018] In the present invention, the proportion of each raw material in step (1) is not limited, and the proportion of each raw material can be appropriately adjusted according to actual demand and circumstances.

[0019] In a preferred embodiment of the present invention, the heating temperature in step (1) is ≧40° C. For example, it can be 40° C., 50° C., 60° C., 70° C., 80° C. or 90° C., but the present invention is not limited thereto, and any suitable value within a certain range can be adopted in the present invention. The preferred heating temperature is ≧60° C.

[0020] In a preferred embodiment of the present invention, the separation and extraction method in step (2) includes an electrolytic method, an extraction method, an ion exchange method, an adsorption separation method or an evaporation crystallization method, but the present invention is not limited to such methods.

[0021] In a preferred embodiment of the present invention, the separation and extraction method in step (2) is to electrolyze the palladium-containing extract obtained in step (1), obtain metallic palladium at the cathode, and then feed the electrolytic solution to step (1).

[0022] In the extraction method of the present invention, a palladium-containing solution with high purity and an extraction liquid containing alkali metal ions are obtained by adding a certain amount of extractant to a palladium-containing raw material and then performing extraction and stripping. The extractant is any one of diisoamyl sulfide (S201), sulfoxide, and hydroxamic acid, but the present invention is not limited thereto.

[0023] In the ion exchange method and adsorption separation method of the present invention, the palladium-containing extract is injected into an apparatus filled with an ion exchange resin or an adsorbent to separate palladium from the catalyst-containing mother liquor and obtain a palladium-containing compound. The ion exchange resin is any one of isothiourea resin, chelating piperidine resin (R410) and levextrel resin, and the adsorbent is activated carbon, copper powder, etc., but the present invention is not limited thereto.

[0024] In the evaporation crystallization method of the present invention, the palladium-containing extract is injected into the heated evaporation crystallization to separate the catalytic agent and palladium, and obtain the palladium-containing compound. The evaporation crystallization method can be a rotary evaporation method or a MVR multiple evaporation method.

[0025] In a preferred embodiment of the present invention, the palladium extraction method comprises the steps of: extracting palladium from a palladium-containing raw material having a palladium content of ≧100 ppm; + , Na + or K + The method includes the steps of: (1) mixing a catalytic agent containing palladium (having a concentration of ≧1 mol / L) having a hydrogen ion concentration of ≧1 mol / L with nitric acid having a hydrogen ion concentration of ≧1 mol / L, heating them at a temperature of ≧40° C. to extract, and then removing the residue to obtain a palladium-containing extract; and (2) separating and extracting the palladium-containing extract obtained in step (1) to obtain metallic palladium or a palladium-containing product, and feeding the excess solution after separation back to step (1) to realize the reuse of the mother liquor.

[0026] In step (2) of the present invention, by feeding the solution after separation to step (1), the reuse rate of the mother liquor can be improved and the amount of waste liquid discharged can be reduced. Effect of the Invention

[0027] Compared with the prior art, the present invention can achieve the following inventive effects: (1) In the present invention, the extraction rate of palladium can be improved by using a catalytic agent containing an alkali metal ion, and since the catalytic agent does not volatilize, the utilization rate of the mother liquor can be improved. (2) The present invention does not require the use of a catalytic agent containing a chlorine compound, so that the method of the present invention can produce metallic palladium or palladium compounds that do not contain chloride ions, thereby simplifying the production, improving the quality of the finished product, and avoiding the formation of chlorine gas. (3) In the present invention, after separation and extraction, the extract can be reused by adding nitric acid to the excess mother liquor. When electrolyzing the extract, the production of waste liquid can be avoided by forming nitric acid at the anode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] In order to provide a detailed understanding of the present invention, the present invention will be described in more detail with reference to the following specific examples. It should be noted that the following examples are for illustrating the present invention, but are not intended to limit the present invention. EXAMPLES

[0029] In this embodiment, a palladium extraction method is provided, which includes the steps of: (1) obtaining a palladium-containing extract by mixing 79 g of palladium powder (containing 95% palladium) with a solution containing 1.5 mol / L lithium nitrate and 6 mol / L nitric acid, heating them at 80°C to extract, and removing the residue; and (2) obtaining a palladium nitrate product by evaporating the palladium-containing extract obtained in step (1) and separating the crystals, and feeding the excess mother liquor to step (1). EXAMPLES

[0030] In this embodiment, a palladium extraction method is provided. The palladium extraction method is to mix 3.5 g of palladium powder (palladium content 87%) with 0.16 mol / L of lithium carbonate solid, and add nitric acid to make the solution H. + The concentration of Li is 1 mol / L. + (1) adjusting the concentration of the palladium-containing extract to 1 mol / L, and then heating and extracting the palladium-containing extract at a temperature of 80° C., and removing the residue to obtain a palladium-containing extract; The palladium-containing extract obtained in step (1) is electrolyzed to obtain pure metal palladium, and the current density of the electrolysis is set to 100 A / m 2 and feeding the excess solution after electrolysis into step (1). EXAMPLES

[0031] In this embodiment, a palladium extraction method is provided, which includes the steps of: (1) obtaining a palladium-containing extract by mixing 100 g of anode mud containing 100 ppm palladium with a solution containing 7 mol / L sodium nitrate and 1.3 mol / L nitric acid, heating them at a temperature of 60°C to extract the mixture, and removing the residue; and (2) obtaining a precipitate of metallic palladium by performing substitution adsorption of copper powder on the palladium-containing extract obtained in step (1), and feeding the excess solution to step (1). EXAMPLES

[0032] In this embodiment, a palladium extraction method is provided, which includes the steps of: (1) mixing 3.8 g of palladium powder (containing 99.95% palladium) with a solution containing 5 mol / L potassium nitrate, 1 mol / L lithium nitrate, and 1 mol / L nitric acid, heating the mixture at 40°C for extraction, and removing the residue to obtain a palladium-containing extract; (2) electrolyzing the palladium-containing extract obtained in step (1) to obtain a palladium sponge, and performing electrolysis at a current density of 500 A / m 2 and (2) replenishing the excess solution after electrolysis with nitric acid and then feeding it to step (1). EXAMPLES

[0033] In this embodiment, a palladium extraction method is provided, which includes the steps of: (1) obtaining a palladium-containing extract by mixing 150 g of aluminum oxide-palladium catalyst containing 0.3% palladium with a solution containing 6 mol / L lithium nitrate and 1.5 mol / L nitric acid, heating them at a temperature of 50°C to perform extraction, and removing the residue; and (2) obtaining an extraction liquid by adding diisoamyl sulfide (S201) to the palladium-containing extract obtained in step (1) and performing extraction, and sending the extraction liquid to step (1) to perform stripping of the organic phase to obtain a palladium nitrate product. EXAMPLES

[0034] In this embodiment, a palladium extraction method is provided, which includes the steps of: (1) mixing 100 g of aluminum oxide-palladium catalyst containing 0.5% palladium with a solution containing 6 mol / L sodium nitrate and 1.8 mol / L nitric acid, heating them at a temperature of 60°C to extract, and removing the residue to obtain a palladium-containing extract; and (2) absorbing the palladium-containing extract obtained in step (1) with a chelating piperidine resin (R410) adsorption rod, washing with diluted hydrochloric acid, and separating thiourea to obtain a high-purity palladium salt, and feeding the excess solution back to step (1). EXAMPLES

[0035] The difference between Example 7 and Example 6 is that in step (2) of Example 7, palladium in the extract is adsorbed by activated carbon, and the adsorbate is washed and dried to obtain a palladium carbon composite. Other conditions in Example 7 are the same as those in Example 6. EXAMPLES

[0036] In this embodiment, a palladium extraction method is provided, which includes the steps of (1) mixing 1.04 g of palladium powder (containing 99.95% palladium) with a solution containing 6 mol / L lithium nitrate and 1 mol / L nitric acid, heating them at a temperature of 80°C to extract, and removing the residue to obtain a palladium-containing extract; and (2) electrolyzing the palladium-containing extract obtained in (1) to obtain pure metallic palladium, with a current density of 400 A / m. 2 and feeding the excess solution after electrolysis into step (1). EXAMPLES

[0037] The difference between Example 9 and Example 8 is that the concentration of lithium nitrate in the solution in step (1) of Example 9 is 0.5 mol / L. Other conditions in Example 9 are the same as those in Example 8. EXAMPLES

[0038] The difference between Example 10 and Example 8 is that the heating and extraction temperature in step (1) of Example 10 is set to 30° C. The other conditions in Example 10 are the same as those in Example 8. EXAMPLES

[0039] The difference between Example 11 and Example 8 is that the concentration of nitric acid in the solution in step (1) of Example 11 is 0.5 mol / L. The other conditions in Example 11 are the same as those in Example 8.

[0040] In Comparative Example 1, a palladium extraction method is provided. The palladium extraction method includes the step (1) of mixing 1.04 g of palladium powder (containing 99.95% palladium) with 7 mol / L nitric acid, heating them at a temperature of 80° C. to extract, and then removing the residue to obtain a palladium-containing extract. The other conditions in Comparative Example 1 are the same as those in Example 8. Comparative Example 2

[0041] In Comparative Example 2, a palladium extraction method is provided. The palladium extraction method includes step (1) of mixing 1.04 g of palladium powder (containing 99.95% palladium) with a solution containing 7 mol / L lithium nitrate, heating them at a temperature of 80° C. to extract, and then removing the residue to obtain a palladium-containing extract. Other conditions in Comparative Example 2 are the same as those in Example 8.

[0042] The concentration of palladium in the palladium-containing extract is measured using an inductively coupled plasma emission spectrometer. The heating extraction time in Examples 1 to 11 and Comparative Examples 1 and 2 is 5 hours. The extraction rates of palladium in Examples 1 to 11 and Comparative Examples 1 and 2 are as shown in Table 1.

[0043] [Table 1]

[0044] As shown in Table 1, the palladium extraction method of the present invention can improve the extraction rate of palladium, and the extraction rate of palladium nitrate in Examples 1 to 8 can be 91% or more. In the palladium extraction method of Example 9, the low concentration of alkali metal ions in the liquid in step (1) leads to poor catalytic effect. As a result, the extraction rate of palladium nitrate and the recycling rate of palladium are also reduced. In the palladium extraction method of Example 10, the low temperature of the heat extraction in step (1) leads to insufficient extraction reaction, and the extraction rate of palladium nitrate and the recycling rate of palladium are also reduced. In the palladium extraction method of Example 11, the insufficient acidity of the solution in step (1) leads to a reduced oxidation ability, and the extraction rate of palladium nitrate and the recycling rate of palladium are also reduced.

[0045] In Comparative Example 1, when palladium is extracted in an environment containing 7 mol / L HNO3 and the heating extraction is carried out for 5 hours, the extraction rate of palladium is 0.6%, the rate of palladium extraction is very slow, and a large amount of waste acid solution is generated. In Example 8, when the same volume of solution containing 6 mol / L lithium nitrate and 1 mol / L nitric acid and the same temperature are used and the heating extraction is carried out for 5 hours, the extraction rate of palladium can reach 99.6%. This shows that the added lithium ions can achieve a good catalytic effect. In Comparative Example 2, when palladium is extracted in an environment containing 7 mol / L lithium nitrate and the heating extraction is carried out for 5 hours, palladium cannot be extracted. This shows that acidity is an essential condition for extracting palladium.

[0046] Although specific embodiments of the present invention have been described above, the embodiments are merely illustrative of the present invention, and the present invention is not limited to the configurations of the embodiments. Those skilled in the art may change or improve the design without departing from the spirit of the present invention, and such changes or improvements are naturally included in the scope of the claims.

Claims

1. (1) A step of obtaining a mixed solution by mixing a palladium-containing raw material, nitric acid, and a catalyst agent containing an alkali metal ion that is not a chloride compound, and then heating the mixed solution to remove residues to obtain a palladium-containing extract; and (2) obtaining metallic palladium or a palladium-containing product by separating and extracting the palladium-containing extract obtained in step (1), and feeding the remaining solution to step (1).

2. 2. The method for extracting palladium according to claim 1, wherein in step (1), the alkali metal ion is any one of Li+, Na+ or K+, and preferably Li+.

3. 3. The method for extracting palladium according to claim 1 or 2, characterized in that in step (1), the concentration of alkali metal ions in the mixed solution is ≧1 mol / L, and the preferred concentration is ≧5 mol / L.

4. The method for extracting palladium according to any one of claims 1 to 3, characterized in that in step (1), the content of palladium in the palladium-containing raw material is ≧100 ppm.

5. The palladium extraction method according to any one of claims 1 to 4, characterized in that in step (1), the concentration of hydrogen ions in the mixed solution is ≧1 mol / L.

6. The method for extracting palladium according to any one of claims 1 to 5, characterized in that in step (1), the heating temperature is ≧40°C, and the preferred heating temperature is ≧60°C.

7. The method for extracting palladium according to any one of claims 1 to 6, characterized in that the separation and extraction method in step (2) includes, but is not limited to, an electrolytic method, an extraction method, an ion exchange method, an adsorption separation method or an evaporation crystallization method.

8. The palladium extraction method according to any one of claims 1 to 7, characterized in that the separation and extraction method of step (2) is preferably a method of electrolyzing the palladium-containing extract obtained in step (1), obtaining metallic palladium at the cathode, and then feeding the electrolytic solution to step (1).

9. (1) mixing a palladium-containing raw material having a palladium content of ≧100 ppm with a catalytic agent containing Li+, Na+ or K+ (the ion concentration contained in the catalytic agent is ≧1 mol / L) and nitric acid having a hydrogen ion concentration of ≧1 mol / L, and heating them at a temperature of ≧40° C. to extract, and then removing the residue to obtain a palladium-containing extract; The palladium extraction method according to any one of claims 1 to 8, further comprising: a step (2) of obtaining metallic palladium or a palladium-containing product by separating and extracting the palladium-containing extract obtained in the step (1), and recycling the mother liquor by sending the excess solution after separation to the step (1).

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