Method for producing palladium from ag slime

Abstract

Disclosed in an embodiment of the present invention is a method for producing palladium from an Ag slime, the method comprising: a gold separation step of preparing a separated filtrate in which palladium is leached by adding the Ag slime to an acid solution; a neutralization step of preparing a neutralized precipitate including palladium oxide by adding a neutralizing agent to the separated filtrate; a hydrochloric acid leaching step of preparing a hydrochloric acid leachate in which the palladium and platinum are leached, by adding hydrochloric acid to a filtrate including the neutralized precipitate; a chloride precipitation step of preparing a chloride precipitate containing the palladium by adding a precipitating agent to the hydrochloric acid leachate; and a purification step of recovering the palladium from the chloride precipitate.

Description

How to produce palladium from silver slime

[0001] The present invention relates to a method for producing palladium (Pd) from silver slime. More specifically, the present invention relates to a method for producing high-grade palladium by recovering palladium from silver slime generated during a silver electrolysis process.

[0002] In the process of recovering palladium (Pd) from silver slime (Ag Slime) generated during the electrolytic process, a palladium leaching process using hydrochloric acid (HCl) is performed. During this leaching process, most of the platinum (Pt) is also leached, and the leached platinum (Pt) remains until the subsequent purification process. Accordingly, in order to produce high-grade palladium (Pd) of 99.9% or higher from conventional silver slime, three or more purification processes were generally required.

[0003] In this regard, as the number of purification processes increases, the loss of palladium (Pd) increases, which reduces the recovery rate of palladium and increases the amount of raw materials required for the purification process.

[0004] The present invention aims to provide a method for producing palladium from silver slime, which can reduce the number of purification processes by lowering the leaching rate of platinum while maintaining a high leaching rate of palladium in the hydrochloric acid leaching step.

[0005] According to one embodiment of the present invention, a method for producing palladium from silver slime can be provided, including: a gold separation process for introducing silver slime into an acid solution to produce a separated filtrate from which palladium is leached; a neutralization process for introducing a neutralizing agent into the separated filtrate to produce a neutralized precipitate containing palladium oxide; a hydrochloric acid leaching process for introducing hydrochloric acid into the filtrate containing the neutralized precipitate to produce a hydrochloric acid leaching process from which palladium and platinum are leached; a chloride precipitation process for introducing a precipitant into the hydrochloric acid leaching process to produce a chloride precipitate containing palladium; and a purification process for recovering the palladium from the chloride precipitate.

[0006] According to one embodiment of the present invention, a method for producing palladium from silver slime can be provided, wherein in the hydrochloric acid leaching process, the amount of hydrochloric acid added is 9 equivalents or more and 11 equivalents or less relative to the palladium content of the neutralized precipitate.

[0007] According to one embodiment of the present invention, a method for producing palladium from silver slime can be provided, wherein the amount of hydrochloric acid added is 10 equivalents relative to the palladium content of the neutralized precipitate.

[0008] According to one embodiment of the present invention, a method for producing palladium from silver slime can be provided, wherein the concentration of the hydrochloric acid is 30 to 40%.

[0009] According to one embodiment of the present invention, a method for producing palladium from silver slime can be provided, wherein in the hydrochloric acid leaching process, the reaction temperature is 50°C or more and 70°C or less.

[0010] According to one embodiment of the present invention, a method for producing palladium from silver slime can be provided, wherein the neutralization process further includes a process of evaporating a portion of the separated filtrate before introducing the neutralizing agent.

[0011] According to one embodiment of the present invention, a method for producing palladium from silver slime can be provided, wherein the purification process is performed repeatedly by leaching the palladium from the chloride precipitate and then precipitating the palladium.

[0012] According to the present invention, the leaching rate of platinum, which acts as a major impurity, can be reduced while maintaining a high leaching rate of palladium.

[0013] Therefore, according to the present invention, the number of repetitions of the purification process for ultimately obtaining palladium can be reduced, thereby minimizing the loss of palladium and reducing the amount of raw materials used in the purification process.

[0014] FIG. 1 is a flow chart illustrating a method for producing palladium from silver slime according to one embodiment of the present invention.

[0015] The embodiments of the present invention are provided for the purpose of illustrating the technical concept of the present invention. The scope of the rights of the present invention is not limited to the embodiments presented below or the specific descriptions of these embodiments.

[0016] FIG. 1 is a flow chart illustrating a method for producing palladium from silver slime according to one embodiment of the present invention.

[0017] Referring to FIG. 1, a method (S1) for producing palladium from silver slime may include a gold separation process (S100) in which a leaching agent is added to silver slime to separate gold in the form of a cake and palladium is leached into a separated filtrate, a neutralization process (S200) in which a neutralizing agent is added to the separated filtrate to produce a neutralized precipitate containing palladium oxide, a hydrochloric acid leaching process (S300) in which hydrochloric acid is added to the neutralized precipitate to produce a hydrochloric acid leaching solution from which palladium and platinum are leached, a chloride precipitation process (S400) in which a precipitant is added to the hydrochloric acid leaching solution to produce a chloride precipitate containing palladium, and a purification process (S500) in which the palladium is recovered from the chloride precipitate.

[0018] A method for producing palladium from silver slime according to one embodiment of the present invention relates to a method for producing high-quality palladium from silver slime (Ag Slime) containing impurities. The silver slime may be, for example, generated from a silver electrolysis process, and in this case, the silver slime may contain various metal components such as palladium (Pd), platinum (Pt), gold (Au), bitumen (Bi), tellurium (Te), copper (Cu), and lead (Pb) in addition to silver (Ag). A method for producing palladium from silver slime according to one embodiment of the present invention relates to a manufacturing method capable of reducing the number of purification processes by lowering the leaching rate of platinum while maintaining a high leaching rate of palladium among the various metal components.

[0019] Gold separation process (S100)

[0020] In the gold separation process (S100), gold (Au) can be separated from silver slime (Ag Slime). Specifically, in the gold separation process (S100), silver slime is put into nitric acid (HNO3) to leach metal components including palladium into the liquid, and gold (Au) that is not leached into the liquid can be separated in the form of a cake. In addition to palladium, metals such as silver (Ag), bitumen (Bi), platinum, tellurium, copper, and lead can be leached together in the leachate. Hereinafter, the liquid obtained by separating the leachate from the gold-containing cake, in which palladium, etc. are leached, is referred to as a 'separation filtrate'. The leaching reaction in the gold separation process can be represented by the following [Reaction Scheme 1].

[0021] [Reaction Formula 1]

[0022] M + 2HNO3→ M(NO3)2+ H2(g), (M: Pd, Ag, Pt, Bi, Te, Cu, etc.)

[0023] Preferably, the gold separation process (S100) can be carried out under a reaction temperature of 60 to 80°C with a reaction time of 3 to 5 hours.

[0024] Neutralization process (S200)

[0025] In the neutralization process (S200), the separated filtrate is neutralized to produce a precipitate containing palladium oxide (PdO) from the separated filtrate. At this time, silver does not precipitate but remains in the liquid and can be separated.

[0026] In one embodiment, in the neutralization process (S200), an evaporation process may be performed to evaporate a portion of the separation filtrate produced in the gold separation process (S100) prior to the process of neutralizing the separation filtrate. This is to evaporate the acid (e.g., nitric acid) contained in the separation filtrate, thereby reducing the amount of neutralizing agent input for the neutralization reaction in the neutralization process (S200).

[0027] In addition, in the neutralization process (S200), the separated filtrate can be diluted with pure water and a neutralizing agent can be added. At this time, Na2CO3, NaOH, etc. can be used as a neutralizing agent. Through this, in the neutralization process (S200), a precipitate in which palladium is precipitated in the form of palladium oxide (PdO) is generated, while silver (Ag) does not precipitate, so that most of the silver can be separated into a liquid. Hereinafter, the precipitate containing palladium oxide is referred to as a "neutralized precipitate." The chemical reaction in the neutralization process can be represented by the following [Reaction Scheme 2].

[0028] [Reaction Formula 2]

[0029] Pd(NO3)2+ Na2CO3→ PdO + 2NaNO3+ CO2

[0030] Preferably, the neutralization reaction in the neutralization process (S200) can be carried out at a reaction temperature of 60 to 80°C for a reaction time of 1 to 3 hours.

[0031] Hydrochloric acid leaching process (S300)

[0032] In the hydrochloric acid leaching process (S300), a leaching process is performed on the neutralized precipitate using hydrochloric acid. In this hydrochloric acid leaching process (S300), palladium and platinum are leached into the leaching liquid, and silver (Ag) that is not removed in the neutralization process (S200) can be precipitated in the form of silver chloride (AgCl). Through this, silver can be further separated following the neutralization process (S200). Hereinafter, the leaching liquid from which palladium, platinum, etc. are leached in the hydrochloric acid leaching process (S300) is referred to as the "hydrochloric acid leaching liquid." The leaching reaction in the hydrochloric acid leaching process (S300) can be represented by the following [Reaction Scheme 3], and the precipitation reaction can be represented by [Reaction Scheme 4].

[0033] [Reaction Formula 3]

[0034] PdO + 2HCl → PdCl2+ H2O

[0035] [Reaction Formula 4]

[0036] AgNO3+ HCl → AgCl + HNO3

[0037] Preferably, the hydrochloric acid leaching process (S300) is carried out at a reaction temperature of 60 to 80°C for 2 to 4 hours, and the concentration of hydrochloric acid can be 30 to 40%.

[0038] Meanwhile, the inventors of the present invention have discovered that by controlling the amount of hydrochloric acid input or the reaction temperature in the hydrochloric acid leaching process, the leaching rate of palladium, which is the final target, can be maintained at a high level while reducing the leaching rate of platinum, which acts as a major impurity. If the leaching rate of platinum is reduced in the hydrochloric acid leaching process (S300), the number of repetitions of the purification process can be reduced in the purification process (S500) described below, and as a result, the yield of palladium can be increased. For example, if the purification process of the purification process (S500) is performed once, a loss of approximately 10% of palladium can occur, and therefore, it is important to reduce the leaching rate of platinum in the hydrochloric acid leaching process (S300) before the purification process (S500). In addition, reducing the leaching rate of platinum can also reduce the amount of auxiliary materials used in repeated purification processes, thereby improving the economic feasibility of palladium production.

[0039] In one embodiment, the amount of hydrochloric acid is determined in consideration of the palladium content of the neutralization precipitate (palladium oxide slime), but may be limited to a predetermined equivalent or less relative to the palladium content of the neutralization precipitate. Preferably, the amount of hydrochloric acid added may be 11 equivalents (eq) or less relative to the palladium content contained in the neutralization precipitate formed in the neutralization process (S200). This is because, when the amount of hydrochloric acid added exceeds 11 equivalents relative to the palladium content contained in the neutralization precipitate, the leaching rate of platinum, which is the target of removal, may increase. In addition, preferably, the amount of hydrochloric acid added may be 9 equivalents (eq) or more relative to the palladium content contained in the neutralization precipitate formed in the neutralization process (S200). This is because, when the amount of hydrochloric acid added is less than 9 equivalents relative to the palladium content contained in the neutralization precipitate, the leaching rate of palladium, which is the final target of acquisition, may decrease. Therefore, if the amount of hydrochloric acid input is limited to 9 equivalents or more and 11 equivalents or less compared to the palladium content contained in the neutralized precipitate, the palladium leaching rate can be maintained high while at the same time the platinum leaching rate can be lowered, thereby achieving an optimal effect.

[0040] In one embodiment, the reaction temperature in the hydrochloric acid leaching process (S300) may be limited to a predetermined temperature or lower. This is because, if the reaction temperature exceeds the predetermined temperature, the palladium leaching rate remains high, but the platinum leaching rate may increase. In this regard, the reaction temperature in the hydrochloric acid leaching process (S300) may preferably be 70°C or lower. In addition, the reaction temperature may preferably be a predetermined temperature (e.g., 50°C) or higher. This is because, if the reaction temperature is lower than the predetermined temperature, the platinum leaching rate decreases, and at the same time, the palladium leaching rate also decreases, which may lower the palladium recovery rate.

[0041] In this way, the method for producing palladium from silver slime according to one embodiment of the present invention has the effect of reducing the leaching rate of platinum while maintaining a high leaching rate of palladium by limiting the amount of hydrochloric acid added or the reaction temperature within an appropriate range.

[0042] Chloride precipitation process (S400)

[0043] In the chloride precipitation process (S400), palladium can be recovered by precipitating it in the form of palladium chloride (PdCl2) by adding a chloride precipitant to the hydrochloric acid leachate (palladium and platinum are leached out) from which silver chloride precipitate has been removed. At this time, as the precipitant, for example, ammonium chloride (NH4Cl) and sodium hypochlorite (NaOCl) can be added together, and in this case, the precipitation reaction in the chloride precipitation process (S400) can be expressed by the following [Reaction Formula 5]. Preferably, the amount of ammonium chloride added in the chloride precipitation process (S400) is 2.0 to 3.0 equivalents relative to the palladium content contained in the hydrochloric acid leachate, and the amount of sodium hypochlorite can be 0.5 to 1.5 equivalents relative to the palladium content contained in the hydrochloric acid leachate. In Reaction Scheme 5, both ammonium chloride and sodium hypochlorite directly participate in the reaction, and sodium hypochlorite plays a role in enabling the reaction by raising the ORP (oxidation-reduction potential) value of the solution. Hereinafter, the precipitate containing palladium is referred to as a "chloride precipitate," and the chloride precipitate may contain impurities such as platinum in addition to palladium.

[0044] [Reaction Formula 5]

[0045] 2PdCl2+ 4NH4Cl + 4NaOCl + 2H2O = 2(NH4)2PdCl6+ 4NaOH + O2(g)

[0046] Preferably, the neutralization reaction in the chloride precipitation process (S400) can be carried out at a reaction temperature of room temperature for a reaction time of 2 to 4 hours.

[0047] Refining process (S500)

[0048] In the purification process (S500), impurities such as platinum can be removed by repeatedly performing leaching and precipitation processes on the chloride precipitate produced in the chloride precipitation process (S400), thereby ultimately recovering high-purity palladium. Specifically, an ammonium reaction process (S510) in which the chloride precipitate is first introduced into ammonium hydroxide (NH4OH) to selectively leach palladium, followed by a hydrochloric acid reaction process (S520) in which a precipitant such as hydrochloric acid (HCl) is introduced to precipitate palladium, can be repeatedly performed. The ammonium reaction process (S510) in the purification process (S500) can be represented by [Reaction Formula 6], and the hydrochloric acid reaction process (S520) can be represented by [Reaction Formula 7].

[0049] [Reaction Formula 6]

[0050] (NH4)2PdCl6+ 2NH4OH = Pd(NH3)4Cl2+ H2(g) + 2Cl2+ 2H2O

[0051] [Reaction Formula 7]

[0052] Pd(NH3)4Cl2+ 2HCl = 2Pd(NH3)2Cl2+ H2(g)

[0053] Preferably, the ammonium reaction process (S510) in the purification process (S500) can be performed at room temperature for 2 to 4 hours under conditions of pH 10 to 11. At this time, the solid density can be 80 to 120 g / L.

[0054] The hydrochloric acid reaction process (S520) can be performed at room temperature for 2 to 4 hours under conditions of pH 1 to 2.

[0055] In one embodiment, the purification process (S500) may be repeatedly performed as needed to produce high-purity palladium. In this regard, the method for producing palladium from silver slime according to one embodiment of the present invention can significantly reduce the leaching rate of platinum by limiting the amount of hydrochloric acid input and the reaction temperature to a predetermined range in the hydrochloric acid leaching process (S300) described above, thereby drastically reducing the number of times the purification process is performed in the purification process (S500). For example, while the prior art requires three or more purification processes (S500), when the method for producing palladium from silver slime according to one embodiment of the present invention is applied, high-purity palladium can be produced with only one purification process. Accordingly, the loss of palladium can be minimized, while the amount of auxiliary materials such as leaching agents and precipitants can be minimized.

[0056] Hereinafter, an embodiment of a method for producing palladium from silver slime of the present invention will be described.

[0057] The following examples and comparative examples were performed using silver slime having the following composition.

[0058] PdAgAuBiPtTeCuPbContent(%)0.3466.630.00.490.040.130.770.18

[0059] Gold separation process (S100)

[0060] In the gold separation process (S100), multiple silver slime samples with identical compositions were leached in nitric acid (HNO3) in the same manner. The reaction time was 4 hours, the reaction temperature was 70°C, and the solid density was maintained at 250 g / L. The concentrations of the prepared separation filtrate were as follows.

[0061] PdAgAuBiPtTeCuPbConcentration (g / L)2.63144.00.0012.990.190.623.180.81

[0062] Neutralization process (S200)

[0063] In the neutralization process (S200), the separated filtrate was evaporated and concentrated, and then sodium carbonate (Na2CO3) was added as a neutralizing agent to the filtrate diluted with pure water to carry out the neutralization reaction. The reaction time was 2 hours, the reaction temperature was maintained at 70°C, and sodium carbonate was added until the final pH reached 4. After the neutralization reaction, silver (Ag) did not precipitate, so most of the silver could be separated as a liquid, and the composition of the neutralized precipitate (palladium oxide slime) containing palladium oxide is as follows.

[0064] PdAgAuBiPtTeCuPbContent(%)12.913.70.00311.41.302.565.680.48

[0065] Hydrochloric acid leaching process (S300)

[0066] In the hydrochloric acid leaching process (S300), hydrochloric acid was added to the neutralized precipitate to produce a hydrochloric acid leaching solution from which palladium and platinum were leached. At this time, in the hydrochloric acid leaching process (S300), in order to compare the leaching rates of palladium and platinum according to the hydrochloric acid input amount and reaction temperature, the hydrochloric acid input amount and reaction temperature were varied for multiple neutralized precipitates including examples and comparative examples as follows. However, for the examples and comparative examples, the reaction time was the same as 3 hours, the solid density was 150 g / L, and the hydrochloric acid (HCl) concentration was 35%, and all reaction conditions except for the hydrochloric acid input amount and reaction temperature were the same. The results of measuring the contents of palladium and platinum in the hydrochloric acid leaching solution from which palladium and platinum were leached are as follows.

[0067] 1. Palladium and platinum contents of the leached filtrate at different reaction temperatures, with 16 equivalents of hydrochloric acid added relative to the palladium content of the neutralized precipitate.

[0068] Comparative Example 1 (50℃) Comparative Example 2 (60℃) Comparative Example 3 (70℃) Comparative Example 4 (80℃) Pd Leaching Rate (%) 99.3 99.5 99.8 99.9 Pd Concentration (g / L) 16.9 17.1 17.3 17.4 Pt Leaching Rate (%) 96.5 97.1 98.6 99.4 Pt Concentration (g / L) 1.66 1.68 1.72 1.74

[0069] 2. Palladium and platinum contents of the leached filtrate at different reaction temperatures, with 13 equivalents of hydrochloric acid added relative to the palladium content of the neutralized precipitate.

[0070] Comparative Example 5 (50℃) Comparative Example 6 (60℃) Comparative Example 7 (70℃) Comparative Example 8 (80℃) Pd Leaching Rate (%) 99.199.399.599.6 Pd Concentration (g / L) 16.716.917.117.2 Pt Leaching Rate (%) 88.589.696.898.0 Pt Concentration (g / L) 1.501.541.681.70

[0071] 3. Palladium and platinum contents of the leached filtrate at different reaction temperatures, with 11 equivalents of hydrochloric acid added relative to the palladium content of the neutralized precipitate.

[0072] Example 1 (50°C) Example 2 (60°C) Example 3 (70°C) Comparative Example 9 (80°C) Pd leaching rate (%) 99.199.199.599.6 Pd concentration (g / L) 16.7 16.9 17.1 17.2 Pt leaching rate (%) 21.2 22.0 22.8 90.3 Pt concentration (g / L) 0.4 10.4 30.4 8 1.57

[0073] 4. Palladium and platinum contents of the leached filtrate at different reaction temperatures, with 10 equivalents of hydrochloric acid added relative to the palladium content of the neutralized precipitate.

[0074] Example 4 (50°C) Example 5 (60°C) Example 6 (70°C) Comparative Example 10 (80°C) Pd leaching rate (%) 99.099.099.499.6 Pd concentration (g / L) 16.816.817.017.2 Pt leaching rate (%) 11.812.012.888.3 Pt concentration (g / L) 0.200.210.231.53

[0075] 5. Palladium and platinum contents of the leached filtrate at different reaction temperatures, with 9 equivalents of hydrochloric acid added relative to the palladium content of the neutralized precipitate.

[0076] Example 7 (50°C) Example 8 (60°C) Example 9 (70°C) Comparative Example 11 (80°C) Pd leaching rate (%) 96.4 96.5 96.5 96.9 Pd concentration (g / L) 15.8 15.8 15.8 16.1 Pt leaching rate (%) 11.4 11.5 12.7 3.9 Pt concentration (g / L) 0.18 0.19 0.24 0.59

[0077] 6. Palladium and platinum contents of the leached filtrate at different reaction temperatures, with 7 equivalents of hydrochloric acid added relative to the palladium content of the neutralized precipitate.

[0078] Comparative Example 11 (50℃) Comparative Example 12 (60℃) Comparative Example 13 (70℃) Comparative Example 14 (80℃) Pd Leaching Rate (%) 90.49 1.29 2.49 2.8 Pd Concentration (g / L) 15.0 15.2 15.6 15.8 Pt Leaching Rate (%) 11.3 11.6 12.4 30.4 Pt Concentration (g / L) 0.18 0.19 0.22 0.54

[0079] Looking at Examples 1, 2, 3 and Comparative Examples 5, 6, and 7, it can be seen that when the amount of hydrochloric acid input exceeds 11 equivalents relative to the palladium content of the neutralized precipitate, the palladium leaching rate is not much different at over 99%, but the platinum leaching rate shows a significant difference of over 60%. On the other hand, looking at Examples 7, 8, and 9 and Comparative Examples 11, 12, and 13, it can be seen that when the amount of hydrochloric acid input is less than 9 equivalents relative to the palladium content of the neutralized precipitate, the platinum leaching rate is excellent, but the palladium leaching rate decreases rapidly, resulting in increased palladium loss. That is, in order to secure both excellent palladium leaching rates and platinum leaching rates, it is preferable to maintain the amount of hydrochloric acid input within a range of 9 equivalents or more and 11 equivalents or less relative to the palladium content. Among these, when the amount of hydrochloric acid input is 10 equivalents relative to the palladium content, the optimal palladium leaching rates and platinum leaching rates can be secured.

[0080] Next, looking at Examples 3, 6, and 9 and Comparative Examples 9, 10, and 11, it can be seen that when the reaction temperature of the hydrochloric acid leaching process (S300) exceeds 70°C, the leaching rate of palladium does not change significantly, but the leaching rate of platinum increases rapidly. That is, when the reaction temperature of the hydrochloric acid leaching process (S300) is maintained at 70°C or lower, the leaching rate of palladium can be maintained excellently while the leaching rate of platinum, which is an impurity, can be significantly reduced. In particular, even when the reaction temperature is lowered to 50°C, the leaching rate of palladium does not change significantly, but the leaching rate of platinum can be confirmed to decrease significantly more than that of palladium. Therefore, when the reaction temperature is set to 50°C, the leaching rate of palladium can be maintained while the leaching rate of platinum is minimized, thereby obtaining optimal process efficiency.

[0081] Chloride precipitation process (S400)

[0082] In the chloride precipitation process (S400), only for Comparative Example 1 and Example 4, where the difference in the leaching rate of platinum was sharply contrasted, ammonium chloride (NH4Cl) and sodium hypochlorite (NaOCl) were added to carry out the precipitation process, and the reaction time was 5 hours and the reaction temperature was maintained at 25℃. In this case, 2.5 equivalents of ammonium chloride were added based on the palladium content after completing the previous step (hydrochloric acid leaching process), and 1.0 equivalents of sodium hypochlorite were added based on the palladium content. The composition of the chloride precipitate (Cl2 precipitation cake) generated after the reaction is as follows.

[0083] Comparative Example 1 Example 4 Pd precipitation rate (%) 99.2 99.2 Pd content (%) 29.5 3 0.1 Pt precipitation rate (%) 28.8 2 4.7 Pt content (%) 0.6 8 0.08

[0084] Refining process (S500)

[0085] In the purification process (S500), palladium was selectively leached by adding ammonium hydroxide (NH4OH) to the chloride precipitates of Comparative Example 1 and Example 4 generated in the chloride precipitation process (S400). The reaction time was 3 hours, the reaction temperature was 25°C, and the solid density was maintained at 150 g / L. The amount of ammonium hydroxide added was 9.0 equivalents based on the palladium content after the completion of the chloride precipitation process (S400). The contents of palladium and platinum in the leached solution after the reaction are as follows.

[0086] Comparative Example 1 Example 4 Pd precipitation rate (%) 99.999.9 Pd content (%) 29.129.9 Pt precipitation rate (%) 87.685.8 Pt content (%) 0.590.07

[0087] Next, hydrochloric acid was added to the leached solution to selectively precipitate palladium. The reaction time was 5 hours, and the reaction temperature was maintained at 25°C. The amount of hydrochloric acid added was 17 equivalents based on the palladium content. The grades of palladium and platinum in the chloride precipitate after the reaction were as follows.

[0088] Comparative Example 1 Example 4 Pd precipitation rate (%) 90.4 90.7 Pd content (%) 55.1 56.2 Pt precipitation rate (%) 20.1 18.5 Pt content (%) 0.2 7 0.02

[0089] As confirmed in the table above, the method for producing palladium from silver slime according to the embodiment of the present invention can effectively suppress platinum from being leached in the hydrochloric acid leaching process (S300) by setting the input equivalent amount of hydrochloric acid or the reaction temperature to a predetermined value or lower, and as a result, the content of impurities (platinum) can be minimized with only one purification process.

[0090] While the technical concept of the present invention has been described above with reference to certain embodiments and examples illustrated in the accompanying drawings, it should be understood that various substitutions, modifications, and variations may be made without departing from the technical concept and scope of the invention, which would be understood by those skilled in the art. Furthermore, such substitutions, modifications, and variations should be considered to fall within the scope of the appended claims.

Claims

1. A gold separation process that produces a separated filtrate from which palladium is leached by adding silver slime to an acid solution; A neutralization process for producing a neutralized precipitate containing palladium oxide by adding a neutralizing agent to the above separated filtrate; A hydrochloric acid leaching process for producing a hydrochloric acid leaching solution from which palladium and platinum are leached by adding hydrochloric acid to a filtrate containing the neutralized precipitate; A chloride precipitation process for producing a chloride precipitate containing palladium by adding a precipitant to the hydrochloric acid leachate; and A method for producing palladium from silver slime, comprising a purification process for recovering palladium from the chloride precipitate.

2. In paragraph 1, A method for producing palladium from silver slime, wherein in the hydrochloric acid leaching process, the amount of hydrochloric acid added is 9 equivalents or more and 11 equivalents or less relative to the palladium content of the neutralized precipitate.

3. In paragraph 2, A method for producing palladium from silver slime, wherein the amount of hydrochloric acid added is 10 equivalents relative to the palladium content of the neutralized precipitate.

4. In any one of paragraphs 1 to 3, A method for producing palladium from silver slime, wherein the concentration of the hydrochloric acid is 30 to 40%.

5. In paragraph 1, A method for producing palladium from silver slime, wherein in the hydrochloric acid leaching process, the reaction temperature is 50°C or higher and 70°C or lower.

6. In paragraph 1, A method for producing palladium from silver slime, wherein the neutralization process further includes a process of evaporating a portion of the separated filtrate before introducing the neutralizing agent.

7. In paragraph 1, A method for producing palladium from silver slime, wherein the above purification process is performed by repeatedly performing the process of leaching the palladium from the chloride precipitate and then precipitating the palladium.

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