Method for recovering platinum group metal from high-silicon precious iron by using CO2 and realizing material circulation

Abstract

The invention relates to a method for recovering platinum group metals from high-silicon precious iron by using CO2 and realizing material circulation, and belongs to the technical field of secondary resource recovery of the platinum group metals. The method comprises the following steps: after melting a high-silicon precious iron alloy, blowing CO2 gas in the presence of a slag former to carry out selective desilicication smelting to obtain an active low-silicon precious iron alloy, CO-containing tail gas and silicon-containing slag; the method comprises the following steps: combusting CO-containing tail gas to obtain CO2 gas, dissolving the active low-silicon precious iron alloy to prepare liquid to obtain a platinum group solution containing iron ions, and adding oxalic acid into the platinum group solution containing iron ions to selectively precipitate iron ions to generate ferric oxalate and a platinum group metal enriched solution; the ferric oxalate is calcined to obtain iron oxide and CO2 gas, the iron oxide is used for smelting and collecting platinum group metal to generate high-silicon precious iron alloy, and platinum, palladium and rhodium are refined and separated from a platinum group enriched solution; and the CO2 gas is returned to desilicication smelting or electrocatalytic reduction to prepare oxalic acid. According to the method, through the synergistic effect of CO2 gradient impurity removal and oxalic acid iron precipitation, iron and carbon closed-loop circulation is achieved.

Description

Technical Field

[0001] This invention relates to a method for recovering platinum group metals from high-silicon noble iron using CO2 and achieving material recycling, belonging to the field of platinum group metal secondary resource recovery technology. Background Technology

[0002] Among existing secondary resource recovery processes for platinum group metals (PGMs), iron capture has the advantages of not involving heavy metals and low cost. The basic principle is to add slag-forming agents, iron or iron oxides, and reducing agents to smelt and enrich PGMs at high temperatures of 1550-1650℃. However, because the core temperature during the heating process in electric arc furnaces and plasma furnaces is much higher than the required temperature, reaching up to 2000℃, some SiO2 in the material is reduced into the molten iron in the presence of reducing agents. Therefore, the final iron-platinum group metal alloy usually contains a high silicon content. The solid solution of FeSi or FeSi3 results in the alloy having extremely strong chemical inertness in acidic solutions. Especially when the Si content is >1%, a dense, stable, and continuous silica (SiO2) glassy passivation film is formed on the surface of the alloy particles during conventional dissolution. This film acts as a highly efficient physical and chemical barrier, preventing further contact between the corrosive medium and the metal matrix, thus almost halting the dissolution process. This greatly hinders the separation of Fe and PGMs for the dissolution solution preparation in the refining stage.

[0003] The wet process for dissolving silicon-containing precious iron is ineffective. Wu Xilong used alloys obtained from plasma furnace smelting as raw materials for hydrochloric acid iron removal, and the leaching rates of platinum, palladium, and rhodium in the insoluble residue were only 57.29%, 62.12%, and 25.35%, respectively.

[0004] To address the issue of significant Si reduction during the smelting stage, numerous low-temperature capture methods have been developed. Patent application CN117721303A discloses a method that optimizes the slag-forming agent to lower the capture temperature, using CaO, MgO, and anhydrous borax to form slag at 1400℃, and then capturing it with iron oxide to produce low-silicon precious iron with a silicon content of approximately 3%. Patent application CN114774696A provides a method for capturing silicon by injecting H2 at 1350-1400℃, lowering the smelting temperature by changing the reducing agent. However, these methods still carry operational risks and are difficult to industrialize; they only provide the platinum group metal recovery rate and do not mention the Si content in the alloy.

[0005] In summary, none of the existing technologies can provide an efficient and clean method for directly, efficiently, and environmentally friendly separation of silicon, iron, and platinum group metals after a high-temperature iron capture process. Summary of the Invention

[0006] To address the problem in existing platinum group metal (PGM) secondary resource recovery processes that cannot directly, efficiently, and environmentally separate silicon, iron, and PGM after high-temperature iron capture, this invention proposes a method for recovering PGM from high-silicon precious iron and achieving material recycling. Specifically, CO2 is used to selectively oxidize and desiliconize the high-silicon iron alloy; then, the desiliconized alloy is dissolved, and oxalic acid is used to selectively precipitate iron ions, enriching the PGM; finally, the precipitated iron oxalate is calcined, achieving the recycling of iron oxide and CO2. This invention uses CO2 as the key medium to achieve a short-process technology for gradient separation of silicon, iron, and PGM and closed-loop material recycling, fundamentally solving the problems of high difficulty and high cost in processing high-silicon precious iron alloys.

[0007] A method for recovering platinum group metals from high-silicon noble iron using CO2 and achieving material recycling, the specific steps of which are as follows: (1) The high-silicon precious iron alloy is heated and melted to form a high-silicon precious iron alloy melt. A slag-forming agent is added to the high-silicon precious iron alloy melt, and CO2 gas is injected for desiliconization smelting to obtain an active low-silicon precious iron alloy, CO-containing tail gas and silicon-containing slag. The CO-containing tail gas is burned to obtain CO2 gas, and the CO2 gas is returned to the desiliconization smelting or electrocatalytically reduced to prepare oxalic acid. (2) The active low-silicon noble iron alloy is added to the hydrochloric acid solution, and the oxidant is slowly added at a temperature of 65~95℃ for 4~8h to carry out the oxidation reaction, and a platinum group solution containing iron ions is obtained. (3) Oxalic acid is added to a platinum group solution containing iron ions to carry out an iron precipitation reaction. Solid-liquid separation is performed to obtain iron oxalate precipitate and platinum group enrichment solution. Iron oxalate is calcined to obtain iron oxide (Fe recovery rate >97%) and CO2 gas. The iron oxide is used to smelt and capture platinum group metals in waste platinum group catalysts to generate high-silicon noble iron alloys. The CO2 gas is returned to step (1) for desilication smelting or electrocatalytic reduction to prepare oxalic acid. (4) Refining and separating platinum, palladium, and rhodium from a platinum group enrichment solution; the refining and separation method specifically includes: adding ammonium chloride to the platinum group enrichment solution, precipitating platinum at a temperature of 20-60℃ and a potential of 300-800mV, and separating the solid and liquid to obtain ammonium chloroplatinate and filtrate A; adding sodium chlorate solution to filtrate A to adjust the potential to 800-1100mV, adding ammonium chloride and precipitating palladium at a temperature of 20-80℃, and separating the solid and liquid to obtain ammonium chloropalladate and filtrate B; adjusting the pH of filtrate B to 10-12 with NaOH powder, and reacting the precipitate at a temperature of 20-80℃, and separating the solid and liquid to obtain rhodium hydroxide and wastewater. The recovery rates of platinum, palladium, and rhodium can reach platinum >98.5%, palladium >99%, and rhodium >98%, respectively.

[0008] The high-silicon noble iron alloy in step (1) is obtained by smelting and capturing waste platinum group catalysts with a mixture of Fe-FeO-Fe2O3 as a collector. The silicon content in the high-silicon noble iron alloy is 1wt.%≤Si≤20wt.%, the platinum group metal content is 0.5wt.%≤PGMs≤30wt.%, and the balance is iron-based and unavoidable impurities.

[0009] Preferably, the heating and melting temperature in step (1) is 1500~1650℃, and the slag-forming agent is one or more of CaO, MgO, CaCO3, MgCO3, and Na2CO3; the selective desilication reaction is as follows: 2CO2(g)+[Si]+2CaO / MgO / Na2O(s)=CO(g)+2CaO·SiO2 / MgO·SiO2 / Na2O·SiO2(s) Preferably, the CO2 gas injection rate in step (1) is 0.2~5.0 Nm, calculated per ton of high-silicon precious iron alloy melt. 3 The blowing speed is 1 / min, and the blowing time is 10~120min. The blowing method is one or more of top blowing, bottom blowing, and side blowing.

[0010] In step (1), the silicon content in the active low-silicon noble iron alloy is less than 0.5 wt.%.

[0011] Preferably, in step (2), the hydrochloric acid concentration is 6~10 mol / L, and the solid-liquid ratio (g:mL) of the active low-silicon precious iron alloy to the hydrochloric acid solution is 1:5~10.

[0012] Preferably, in step (2), the oxidant is an H2O2 solution or a NaClO3 solution, the concentration of the H2O2 solution is 6~10 mol / L, the concentration of the NaClO3 solution is 5~8 mol / L, and the solid-liquid ratio of the active low-silicon precious iron alloy to the oxidant is 1:2~5 g:mL.

[0013] Preferably, in step (3), the molar ratio of oxalic acid to iron ions is 1.05~1.2:1, the temperature of the iron precipitation reaction is 40~80℃, the pH value is 2~3, and the potential is not greater than 400mV.

[0014] The reaction formula for iron deposition is as follows: C2O4 2- +2Fe 3+ =2CO2(g)+2Fe 2+ Fe 2+ +C2O4 2- =FeC2O4(s) Preferably, the method for preparing oxalic acid by electrocatalytic reduction specifically includes: using a macrocyclic nickel complex containing a CMe group or a platinum group metal catalyst as the electrocatalytic reduction catalyst, a saturated sodium carbonate solution as the electrolyte, and electrocatalyzing CO2 to obtain oxalic acid at a temperature of 20~60℃, a voltage of 3~15V, a current of 30~100A, and a CO2 introduction rate of 10~500mL / L·min.

[0015] Preferably, in step (4), the amount of ammonium chloride added during the platinum precipitation process is 1.2 to 1.5 times the molar amount of platinum in the platinum group enrichment solution; and in the palladium precipitation process, the amount of ammonium chloride added is 1.2 to 1.5 times the molar amount of palladium in filtrate A.

[0016] The beneficial effects of this invention are: (1) This invention innovatively utilizes CO2 to pretreat high-silicon precious iron for desiliconization. In the presence of a specific slag-forming agent, Si in the alloy can be removed to <0.5%, achieving directional and efficient removal of silicon, and creating key conditions for subsequent oxidation and dissolution of active low-silicon precious iron alloys. (2) The present invention uses oxalic acid to separate Fe ions in the solution, which efficiently and selectively removes iron, thereby achieving deep separation of iron and platinum group metals, so that platinum group metals are highly enriched in the solution, avoiding the adverse effects of high concentration of Fe on the refining stage, and improving the yield of platinum, palladium and rhodium. (3) The present invention constructs a complete iron and carbon cycle path, and the iron trapping agent and CO2 gas are recycled within the system, which greatly reduces the consumption of raw materials and the cost of waste treatment. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0019] Example 1: A method for recovering platinum group metals from high-silicon noble iron using CO2 and achieving material recycling (see Example 2) Figure 1 The specific steps are as follows: (1) High-silicon precious iron alloy (by mass percentage, the main components are Si 5.53%, Pt 0.63%, Pd 3.97%, Rh 0.35%, Fe 84.31%, with the remainder being impurities such as Ni, Cu, and C) is obtained by conventional smelting of waste platinum group catalysts with a Fe-FeO-Fe2O3 mixture. The high-silicon precious iron alloy is heated to 1550℃ and melted to form a high-silicon precious iron alloy melt. A slagging agent (CaO) is added to the high-silicon precious iron alloy melt, and CO2 gas is injected from the top (the CO2 gas injection rate is 1.5 Nm per ton of high-silicon precious iron alloy melt). 3 The process involves desiliconization smelting (with a blowing rate of 10 mL / min and a blowing time of 30 min) to obtain an active low-silicon precious iron alloy, CO-containing tail gas, and silicon-containing slag. The CO-containing tail gas is then combusted in a CO combustion furnace at a temperature of 250-300℃ to obtain CO2 gas, which is then returned to the desiliconization smelting process or electrocatalytically reduced to prepare oxalic acid. The electrocatalytic reduction method for preparing oxalic acid specifically includes: using a platinum metal mesh as the electrocatalytic reduction catalyst and a saturated sodium carbonate solution as the electrolyte, electrocatalytically reducing CO2 to obtain oxalic acid at a temperature of 30℃, a voltage of 5V, a current of 30A, and a CO2 introduction rate of 20 mL / L·min. The active low-silicon precious iron alloy was crushed into powder with a particle size of <75μm. Testing revealed a silicon content of 0.37 wt.%. (2) An active low-silicon precious iron alloy was added to an 8 mol / L hydrochloric acid solution, and an oxidant (5 mol / L NaClO3 solution) was slowly added at 80°C for 5 hours to carry out the oxidation reaction, resulting in a platinum group solution containing iron ions and an insoluble residue; the solid-liquid ratio (g:mL) of the active low-silicon precious iron alloy to the hydrochloric acid solution was 1:8, and the solid-liquid ratio (g:mL) of the active low-silicon precious iron alloy to the oxidant was 1:2; the iron ion (Fe 2+ +Fe 3+ The TFe content in the platinum group solution was 86.3 g / L, and the Pt content in the insoluble residue was 22.3 ppm, Pd 16.3 ppm, and Rh 13.5 ppm. (3) The pH of the iron-containing platinum group solution was adjusted to 2.5 with NaOH. Oxalic acid was added to the iron-containing platinum group solution to carry out the iron precipitation reaction. The solid and liquid were separated to obtain iron oxalate precipitate and platinum group enrichment solution. The iron oxalate was calcined at 900℃ for 2h to obtain iron oxide (calculated as FeO, the iron recovery rate is 96.93%) and CO2 gas. The iron oxide was used to smelt and capture platinum group metals in the waste platinum group catalyst to generate high silicon noble iron alloy. The CO2 gas was returned to step (1) desilication smelting or electrocatalytic reduction to prepare oxalic acid. The molar ratio of oxalic acid to iron ions was 1.1:1, the temperature of the iron precipitation reaction was 60℃, and the endpoint potential of the iron precipitation reaction was 350mV. (4) Refining and separating platinum, palladium, and rhodium from a platinum group enrichment solution; the refining and separation method specifically includes: adding ammonium chloride (the amount of ammonium chloride added is 1.3 times the molar amount of platinum in the platinum group enrichment solution) to the platinum group enrichment solution, precipitating platinum at a temperature of 45°C and a potential of 400mV, and separating the solid and liquid to obtain ammonium chloroplatinate and filtrate A; adding sodium chlorate solution to filtrate A to adjust the potential to 1100mV, adding ammonium chloride (the amount of ammonium chloride added is 1.3 times the molar amount of palladium in filtrate A) and precipitating palladium at a temperature of 60°C, and separating the solid and liquid to obtain ammonium chloropalladate and filtrate B; adjusting the pH of filtrate B to 11 with NaOH powder, and reacting the precipitation reaction at a temperature of 70°C, and separating the solid and liquid to obtain rhodium hydroxide and wastewater; In this embodiment, the platinum recovery rate was 99.1%, the palladium recovery rate was 99.3%, and the rhodium recovery rate was 98.7%.

[0020] Example 2: A method for recovering platinum group metals from high-silicon noble iron using CO2 and achieving material recycling (see Example 2) Figure 1 The specific steps are as follows: (1) High-silicon precious iron alloy (by mass percentage, the main components are Si 5.53%, Pt 0.63%, Pd 3.97%, Rh 0.35%, Fe 84.31%, with the remainder being impurities such as Ni, Cu, and C) is obtained by conventional smelting and capturing of waste platinum group catalysts with a Fe-FeO-Fe2O3 mixture. The high-silicon precious iron alloy is heated to 1600℃ and melted to form a high-silicon precious iron alloy melt. A slagging agent (MgO) is added to the high-silicon precious iron alloy melt, and CO2 gas is injected from the bottom (the CO2 gas injection rate is 1.0 Nm per ton of high-silicon precious iron alloy melt). 3 The process involves desiliconization smelting (with a blowing rate of 10 mL / min and a blowing time of 40 min) to obtain an active low-silicon precious iron alloy, CO-containing tail gas, and silicon-containing slag. The CO-containing tail gas is then combusted in a CO combustion furnace at a temperature of 250-300℃ to obtain CO2 gas, which is then returned to the desiliconization smelting process or electrocatalytically reduced to prepare oxalic acid. The electrocatalytic reduction method for preparing oxalic acid specifically includes: using Raney nickel catalyst as the electrocatalytic reduction catalyst and saturated sodium carbonate solution as the electrolyte, electrocatalytically reducing CO2 to obtain oxalic acid at a temperature of 60℃, a voltage of 10V, a current of 100A, and a CO2 introduction rate of 300 mL / L·min. The active low-silicon precious iron alloy was crushed into powder with a particle size of <75μm. Testing revealed a silicon content of 0.29 wt.%. (2) An active low-silicon precious iron alloy was added to an 8 mol / L hydrochloric acid solution, and an oxidant (5 mol / L NaClO3 solution) was slowly added at 75°C for 6 hours to carry out the oxidation reaction, resulting in a platinum group solution containing iron ions and an insoluble residue; the solid-liquid ratio of the active low-silicon precious iron alloy to the hydrochloric acid solution (g:mL) was 1:7, and the solid-liquid ratio of the active low-silicon precious iron alloy to the oxidant (g:mL) was 1:3; the iron ion (Fe 2+ +Fe 3+ The TFe content in the platinum group solution was 92.3 g / L, and the Pt content in the insoluble residue was 19.3 ppm, Pd content was 22.1 ppm, and Rh content was 11.2 ppm. (3) The pH of the iron-containing platinum group solution was adjusted to 2.3 with NaOH. Oxalic acid was added to the iron-containing platinum group solution to carry out the iron precipitation reaction. The solid and liquid were separated to obtain iron oxalate precipitate and platinum group enrichment solution. The iron oxalate was calcined at 950℃ for 3h to obtain iron oxide (calculated as FeO, the iron recovery rate is 98.1%) and CO2 gas. The iron oxide was used to smelt and capture platinum group metals in the waste platinum group catalyst to generate high silicon noble iron alloy. The CO2 gas was returned to step (1) desilication smelting or electrocatalytic reduction to prepare oxalic acid. The molar ratio of oxalic acid to iron ions was 1.05:1, the temperature of the iron precipitation reaction was 50℃, and the endpoint potential of the iron precipitation reaction was 300mV. (4) Refining and separating platinum, palladium, and rhodium from a platinum group enrichment solution; the refining and separation method specifically includes: adding ammonium chloride (the amount of ammonium chloride added is 1.4 times the molar amount of platinum in the platinum group enrichment solution) to the platinum group enrichment solution, precipitating platinum at a temperature of 40°C and a potential of 400mV, and separating the solid and liquid to obtain ammonium chloroplatinate and filtrate A; adding sodium chlorate solution to filtrate A to adjust the potential to 1000mV, adding ammonium chloride (the amount of ammonium chloride added is 1.4 times the molar amount of palladium in filtrate A) and precipitating palladium at a temperature of 70°C, and separating the solid and liquid to obtain ammonium chloropalladate and filtrate B; adjusting the pH of filtrate B to 10.5 with NaOH powder, and reacting the precipitation at a temperature of 80°C, and separating the solid and liquid to obtain rhodium hydroxide and wastewater; In this embodiment, the platinum recovery rate was 99.2%, the palladium recovery rate was 99.3%, and the rhodium recovery rate was 98.4%.

[0021] Example 3: A method for recovering platinum group metals from high-silicon noble iron using CO2 and achieving material recycling (see Example 3). Figure 1 The specific steps are as follows: (1) High-silicon precious iron alloy (by mass percentage, the main components are Si 9.43%, Pt 0.33%, Pd 1.97%, Rh 0.25%, Fe 83.57%, with the remainder being impurities such as Ni, Cu, and C) is obtained by conventional smelting and capturing of waste platinum group catalysts using a Fe-FeO-Fe2O3 mixture. The high-silicon precious iron alloy is heated to 1650℃ and melted to form a high-silicon precious iron alloy melt. A slagging agent (CaCO3) is added to the high-silicon precious iron alloy melt, and CO2 gas is injected from the side (the CO2 gas injection rate is 2.0 Nm per ton of high-silicon precious iron alloy melt). 3 The process involves desiliconization smelting (with a blowing time of 60 min) to obtain an active low-silicon precious iron alloy, CO-containing tail gas, and silicon-containing slag. The CO-containing tail gas is then combusted in a CO combustion furnace at a temperature of 250-300℃ to obtain CO2 gas. The CO2 gas is then returned to the desiliconization smelting process or electrocatalytically reduced to prepare oxalic acid. The method for preparing oxalic acid by electrocatalytic reduction specifically includes: using [Ni(14)4,11-diene-N4]I2 catalyst as the electrocatalytic reduction catalyst and saturated sodium carbonate solution as the electrolyte, electrocatalytically reducing CO2 to obtain oxalic acid at a temperature of 45℃, a voltage of 10V, a current of 50A, and a CO2 introduction rate of 100mL / L·min. The active low-silicon precious iron alloy was crushed into powder with a particle size of <190μm. Testing revealed a silicon content of 0.18 wt.%. (2) An active low-silicon precious iron alloy was added to an 8 mol / L hydrochloric acid solution, and an oxidant (5 mol / L NaClO3 solution) was slowly added at 90°C for 5 hours to carry out the oxidation reaction, resulting in a platinum group solution containing iron ions and an insoluble residue; the solid-liquid ratio of the active low-silicon precious iron alloy to the hydrochloric acid solution was 1:10 g:mL, and the solid-liquid ratio of the active low-silicon precious iron alloy to the oxidant was 1:5 g:mL; the iron ions (Fe 2+ +Fe 3+ The TFe content in the platinum group solution was 57.4 g / L, and the Pt content in the insoluble residue was 15.7 ppm, Pd content was 18.6 ppm, and Rh content was 8.77 ppm. (3) The pH of the iron-containing platinum group solution was adjusted to 2.0 with NaOH. Oxalic acid was added to the iron-containing platinum group solution to carry out the iron precipitation reaction. The solid and liquid were separated to obtain iron oxalate precipitate and platinum group enrichment solution. The iron oxalate was calcined at 900℃ for 3.5h to obtain iron oxide (calculated as FeO, the iron recovery rate is 95.1%) and CO2 gas. The iron oxide was used to smelt and capture platinum group metals in the waste platinum group catalyst to generate high silicon noble iron alloy. The CO2 gas was returned to step (1) desilication smelting or electrocatalytic reduction to prepare oxalic acid. The molar ratio of oxalic acid to iron ions was 1.1:1, the temperature of the iron precipitation reaction was 60℃, and the endpoint potential of the iron precipitation reaction was 330mV. (4) Refining and separating platinum, palladium, and rhodium from a platinum group enrichment solution; the refining and separation method specifically includes: adding ammonium chloride (the amount of ammonium chloride added is 1.35 times the molar amount of platinum in the platinum group enrichment solution) to the platinum group enrichment solution, precipitating platinum at a temperature of 50°C and a potential of 300mV, and separating the solid and liquid to obtain ammonium chloroplatinate and filtrate A; adding sodium chlorate solution to filtrate A to adjust the potential to 1200mV, adding ammonium chloride (the amount of ammonium chloride added is 1.35 times the molar amount of palladium in filtrate A) and precipitating palladium at a temperature of 75°C, and separating the solid and liquid to obtain ammonium chloropalladate and filtrate B; adjusting the pH of filtrate B to 10 with NaOH powder, and reacting the precipitation at a temperature of 75°C, and separating the solid and liquid to obtain rhodium hydroxide and wastewater; In this embodiment, the platinum recovery rate was 99%, the palladium recovery rate was 99.1%, and the rhodium recovery rate was 98.6%.

[0022] Example 4: A method for recovering platinum group metals from high-silicon noble iron using CO2 and achieving material recycling (see Example 4) Figure 1 The specific steps are as follows: (1) High-silicon noble iron alloy (by mass percentage, the main components are Si 16.8%, Pt 1.38%, Pd 6.72%, Rh 1.66%, Fe 67.65%, with the remainder being impurities such as Ni, Cu, and C) is obtained by conventional smelting of waste platinum group catalysts with a Fe-FeO-Fe2O3 mixture. The high-silicon noble iron alloy is heated to 1500℃ and melted to form a high-silicon noble iron alloy melt. Slagging agents (CaCO3 and MgCO3) are added to the high-silicon noble iron alloy melt, and CO2 gas is injected from the top (the CO2 gas injection rate is 1.50 Nm per ton of high-silicon noble iron alloy melt). 3 The process involves desilication smelting (with a blowing rate of 80 min and a blowing time of 80 min) to obtain an active low-silicon precious iron alloy, CO-containing tail gas, and silicon-containing slag. The CO-containing tail gas is then combusted in a CO combustion furnace at a temperature of 250-300℃ to obtain CO2 gas, which is then returned to the desilication smelting process or electrocatalytically reduced to prepare oxalic acid. The electrocatalytic reduction method for preparing oxalic acid specifically includes: using a macrocyclic nickel complex containing a CMe group as the electrocatalytic reduction catalyst, a saturated sodium carbonate solution as the electrolyte, and electrocatalytically reducing CO2 to obtain oxalic acid at a temperature of 25℃, a voltage of 8V, a current of 20A, and a CO2 injection rate of 50 mL / L·min, with a CO2 utilization rate of 55%. The active low-silicon precious iron alloy was crushed into powder with a particle size of <190μm. Testing revealed a silicon content of 0.22 wt.%. (2) An active low-silicon precious iron alloy was added to an 8 mol / L hydrochloric acid solution, and an oxidant (5 mol / L NaClO3 solution) was slowly added at 80°C for 6 hours to carry out the oxidation reaction, resulting in a platinum group solution containing iron ions and an insoluble residue; the solid-liquid ratio of the active low-silicon precious iron alloy to the hydrochloric acid solution (g:mL) was 1:8, and the solid-liquid ratio of the active low-silicon precious iron alloy to the oxidant (g:mL) was 1:4; the iron ions (Fe 2+ +Fe 3+ The TFe content in the platinum group solution was 51.4 g / L, and the Pt content in the insoluble residue was 20.88 ppm, Pd content was 29.32 ppm, and Rh content was 12.26 ppm. (3) The pH of the iron-containing platinum group solution was adjusted to 2.0 with NaOH. Oxalic acid was added to the iron-containing platinum group solution to carry out the iron precipitation reaction. The solid and liquid were separated to obtain iron oxalate precipitate and platinum group enrichment solution. The iron oxalate was calcined at 920℃ for 2h to obtain iron oxide (calculated as FeO, the iron recovery rate is 97.6%) and CO2 gas. The iron oxide was used to smelt and capture platinum group metals in the waste platinum group catalyst to generate high silicon noble iron alloy. The CO2 gas was returned to step (1) desilication smelting or electrocatalytic reduction to prepare oxalic acid. The molar ratio of oxalic acid to iron ions was 1.2:1, the temperature of the iron precipitation reaction was 60℃, and the endpoint potential of the iron precipitation reaction was 320mV. (4) Refining and separating platinum, palladium, and rhodium from a platinum group enrichment solution; the refining and separation method specifically includes: adding ammonium chloride (the amount of ammonium chloride added is 1.3 times the molar amount of platinum in the platinum group enrichment solution) to the platinum group enrichment solution, precipitating platinum at a temperature of 40℃ and a potential of 320mV, and separating the solid and liquid to obtain ammonium chloroplatinate and filtrate A; adding sodium chlorate solution to filtrate A to adjust the potential to 1000mV, adding ammonium chloride (the amount of ammonium chloride added is 1.3 times the molar amount of palladium in filtrate A) and precipitating palladium at a temperature of 60℃, and separating the solid and liquid to obtain ammonium chloropalladate and filtrate B; adjusting the pH of filtrate B to 12 with NaOH powder, and reacting the precipitation at a temperature of 60℃, and separating the solid and liquid to obtain rhodium hydroxide and wastewater; In this embodiment, the platinum recovery rate was 99.2%, the palladium recovery rate was 99.1%, and the rhodium recovery rate was 98.4%.

[0023] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for recovering platinum group metals from high-silicon noble iron with CO2 and realizing material circulation, characterized in that, The specific steps are as follows: (1) high-silicon noble iron alloy is heated and melted to form a high-silicon noble iron alloy melt, a slag former is added to the high-silicon noble iron alloy melt, CO2 gas is sprayed and blown for desiliconizing smelting, and an active low-silicon noble iron alloy, CO-containing tail gas and a silicon-containing slag are obtained; the CO-containing tail gas is combusted to obtain CO2 gas, which is returned to the desiliconizing smelting or is prepared into oxalic acid through electrocatalytic reduction; (2) the active low-silicon noble iron alloy is added to a hydrochloric acid solution, an oxidizing agent is slowly added at a temperature of 65-95 DEG C for 4-8 h to obtain a platinum group solution containing iron ions; (3) oxalic acid is added to the platinum group solution containing iron ions for iron precipitation, solid-liquid separation is performed to obtain an iron oxalate precipitate and a platinum group enrichment solution; the iron oxalate is calcined to obtain an iron oxide and CO2 gas, the iron oxide is used for smelting and capturing platinum group metals in waste platinum group-containing catalysts to generate high-silicon noble iron alloy, and the CO2 gas is returned to the desiliconizing smelting in step (1) or is prepared into oxalic acid through electrocatalytic reduction; (4) the platinum group enrichment solution is refined and separated into platinum, palladium and rhodium; The refining and separation method specifically comprises: ammonium chloride is added to the platinum group enrichment solution, platinum is precipitated at a temperature of 20-60 DEG C and a potential of 300-800 mV, solid-liquid separation is performed to obtain ammonium chloroplatinate and filtrate A; sodium chlorate solution is added to the filtrate A to adjust the potential to 800-1100 mV, ammonium chloride is added and palladium is precipitated at a temperature of 20-80 DEG C, solid-liquid separation is performed to obtain ammonium chloropalladate and filtrate B; the filtrate B is adjusted to a pH value of 10-12 by NaOH powder, precipitates at a temperature of 20-80 DEG C, and solid-liquid separation is performed to obtain rhodium hydroxide and waste water.

2. The method for recovering platinum group metals from high-silicon noble iron and realizing material circulation by using CO2 according to claim 1, characterized in that: Step (1) the high-silicon noble iron alloy is obtained by smelting and capturing of waste platinum group-containing catalysts with a mixed material of a capturing agent Fe-FeO-Fe2O3, the high-silicon noble iron alloy contains 1 wt.%≤Si≤20 wt.% of silicon, 0.5 wt.%≤PGMs≤30 wt.% of platinum group metals, and the balance is iron-based and unavoidable impurities.

3. The method for recovering platinum group metals from high-silicon noble iron and realizing material circulation by using CO2 according to claim 1, characterized in that: Step (1) the heating and melting temperature is 1500-1650 DEG C, and the slag former is one or more of CaO, MgO, CaCO3, MgCO3 and Na2CO3.

4. The method for recovering platinum group metals from high-silicon noble iron and realizing material circulation by using CO2 according to claim 1, characterized in that: The CO2 gas blowing rate in step (1) is 0.2-5.0 Nm 3 / min per ton of high-silicon noble iron alloy melt, and the blowing time is 10-120 min.

5. The method for recovering platinum group metals from high-silicon noble iron and realizing material circulation by using CO2 according to claim 1, characterized in that: Step (1) the active low-silicon noble iron alloy contains less than 0.5 wt.% of silicon.

6. The method for recovering platinum group metals from high-silicon noble iron and realizing material circulation by using CO2 according to claim 1, characterized in that: Step (2) the concentration of the hydrochloric acid is 6-10 mol / L, and the solid-liquid ratio g:mL of the active low-silicon noble iron alloy to the hydrochloric acid solution is 1:5-10.

7. The method for recovering platinum group metals from high-silicon noble iron and realizing material circulation by using CO2 according to claim 1, characterized in that: Step (2) the oxidizing agent is H2O2 solution or NaClO3 solution, the concentration of the H2O2 solution is 6-10 mol / L, the concentration of the NaClO3 solution is 5-8 mol / L, and the solid-liquid ratio g:mL of the active low-silicon noble iron alloy to the oxidizing agent is 1:2-5.

8. The method for recovering platinum group metals from high-silicon noble iron and realizing material circulation by using CO2 according to claim 1, characterized in that: Step (3) the molar ratio of oxalic acid to iron ions is 1.05-1.2:1, the temperature of the iron precipitation reaction is 40-80 DEG C, the pH value is 2-3, and the potential is not more than 400 mV.

9. The method for recovering platinum group metals from high-silicon noble iron and realizing material circulation by using CO2 according to claim 1, characterized in that: The method for electrocatalytically reducing to prepare oxalic acid specifically comprises: using a macrocyclic nickel complex containing a COMe group or a platinum group metal-containing catalyst as an electrocatalytic reduction catalyst, saturated sodium carbonate solution as an electrolyte, and electrocatalytically reducing CO2 at a temperature of 20-60 DEG C, a voltage of 3-15 V, a current of 30-100 A, and a CO2 input speed of 10-500 mL / L min to obtain oxalic acid.

10. The method for recovering platinum group metals from high-silicon noble iron and realizing material circulation by using CO2 according to claim 1, characterized in that: The adding amount of ammonium chloride in the step (4) of precipitating platinum is 1.2-1.5 times of the molar amount of platinum in the platinum group enrichment solution; and the adding amount of ammonium chloride in the step (4) of precipitating palladium is 1.2-1.5 times of the molar amount of palladium in the filtrate A.

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