Method for synergistically recovering failed lithium iron phosphate black powder and failed platinum-containing catalyst

Abstract

The invention relates to the field of recycling of solid waste resources. The invention particularly relates to a method for synergistically recovering failed lithium iron phosphate black powder and a failed platinum-containing catalyst. The invention discloses a method for synergistically recovering failed lithium iron phosphate black powder and a failed platinum-containing catalyst. The method comprises the following steps: A, vacuum reduction smelting; b, oxidizing and dissolving; c, carbon thermal reduction; and D, ammonium salt precipitation and calcination. The method for recovering the platinum group metal does not need to add a trapping agent, has the advantages of being high in resource utilization rate, good in economic benefit and short in process, and effectively reduces the influence of solid waste resources on the environment.

Description

Technical Field

[0001] The present invention relates to the field of recycling of solid waste resources, and in particular to a method for collaboratively recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst. Background Art

[0002] With the rapid development of economy and industry, the demand for coal, oil and natural gas is increasing. The consumption of fossil energy has seriously aggravated the greenhouse effect and changed the ecological environment of soil and water sources. Fossil energy still accounts for 81% of the global energy structure. In response to the above problems, the development of new energy industry is an irresistible trend in the world. As the main promoter of global energy transformation, my country has actively improved new energy technology and the development of new energy industry. Especially in the application field of lithium power batteries, my country's production and sales of new energy vehicles in 2023 will reach 9.587 million and 9.495 million respectively, ranking first in the world for 9 consecutive years.

[0003] As new energy vehicles and batteries reach the end of their service life, there will be 803,600 tons of scrapped batteries, with a total recycling market of 35.403 billion yuan. Among the positive electrode materials of lithium batteries for new energy vehicles, lithium positive electrode materials account for about 40% of the total battery cost, among which lithium iron phosphate is the main product. From January to July 2024, the installed capacity of lithium iron phosphate accounted for 69.9% of the total installed capacity. Lithium iron phosphate batteries will be scrapped in 6-8 years, and the recycling value is huge. Nowadays, the main methods for recycling lithium iron phosphate black powder include wet recovery and pyrometallurgical recovery. Among them, the wet method is the main method. The wet method mainly uses acid and alkali solutions to dissolve the metal ions in the lithium iron phosphate battery, and then uses precipitation, adsorption, ion exchange and other methods to extract the dissolved metal ions in the form of oxides, salts, etc. The whole process has problems such as large amount of wastewater, long process flow, and serious secondary pollution.

[0004] With the continuous development of the new energy vehicle industry, lithium iron phosphate has gradually increased. If this "urban mine" can be efficiently recycled, it will inevitably reduce resource waste and environmental pollution, and produce lasting economic benefits and social value. Therefore, this method proposes the coordinated recovery of spent lithium iron phosphate black powder and platinum-containing catalysts to achieve efficient recovery of valuable components in lithium iron phosphate black powder and platinum-containing catalysts. Summary of the invention

[0005] The purpose of the present invention is to provide a method for the coordinated recovery of spent lithium iron phosphate black powder and spent platinum-containing catalyst. The method comprises the following steps: adding a slag-forming agent, a flux, a reducing agent and the like to the lithium iron phosphate black powder and the platinum-containing catalyst for vacuum reduction smelting, volatilizing the phosphorus and lithium obtained by a multi-stage condensation device at 1500° C. to 1700° C., and obtaining a platinum-iron alloy and smelting slag; oxidizing and dissolving the platinum-iron alloy to obtain a platinum- and iron-containing solution, adding phosphate and an oxidant to the solution to ensure that the iron is precipitated as iron phosphate, and preparing lithium carbonate with the obtained metallic lithium by solid phase carbon thermal reduction at 700 to 900° C. by adding a reducing agent, preparing lithium iron phosphate, filtering the obtained platinum-containing solution after precipitation, and precipitating and calcining with ammonium chloride to obtain metallic platinum. The present invention adopts a collaborative recovery treatment method to achieve the collaborative recovery of spent lithium iron phosphate black powder and platinum-containing catalyst, making full use of resources. The recovery rate of metallic lithium is greater than 90%, and the recovery rate of platinum group metals is greater than 98%. 99.95% of metallic platinum and lithium iron phosphate for preparing power batteries can be obtained. This method recovers platinum group metals without adding a collector, has the advantages of high resource utilization, good economic benefits, and a short process, and effectively reduces the impact of solid waste resources on the environment.

[0006] In order to achieve the above object, the technical solution provided by the present invention is: A method for collaboratively recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst is carried out in the following steps: A. Vacuum reduction smelting: Mix spent platinum-containing catalyst, spent lithium iron phosphate black powder, slag-making agent, flux, and reducing agent in the proportion of 100 parts, 10-20 parts, 60-120 parts, 3-5 parts, and 10-20 parts to prepare pellets, and then place them in a vacuum reduction smelting furnace for smelting. The vacuum reduction smelting temperature is 1500°C to 1700°C, and the smelting time is 2 to 5 hours to obtain platinum-containing ferroalloy, smelting slag, and waste gas. A graded condensation condenser is used, and the mixed vapor is subjected to a distillation pressure of 10 to 1000 Pa to obtain metallic lithium in a condensation region below 150°C, and phosphorus in a condensation region of 300°C to 400°C; the parts are by weight; B. Oxidative dissolution: The platinum-containing iron alloy obtained in step A is oxidized and dissolved by adding acid, maintaining a liquid-solid ratio of 4:1 to 10:1 ml / g, a temperature of 30° C. to 70° C., and a time of 2 to 5 hours. An oxidant is added, and the pH is adjusted to 4.5 to precipitate iron phosphate. After filtering, the iron phosphate and platinum-containing solution are obtained; C. Carbothermal reduction: The iron phosphate obtained in step B and the lithium carbonate obtained by carbonizing the metal lithium obtained in step A are mixed in a molar ratio of 1:1, and then a reducing agent is added, wherein the amount of the reducing agent added is 10% to 50% of the total mass of the iron phosphate and the lithium carbonate, the solid phase synthesis temperature is 700° C. to 900° C., the solid phase synthesis time is 1 to 5 hours, and lithium iron phosphate is obtained after sintering by carbothermal reduction method; D. Ammonium salt precipitation and calcination: The platinum-containing solution obtained in step B is precipitated with ammonium chloride and then calcined to obtain metallic platinum powder.

[0007] In step A, the slag-forming agent is one or a mixture of aluminum oxide, calcium oxide, and silicon dioxide in any ratio, the cosolvent is one or a mixture of calcium fluoride, borax, and boron oxide in any ratio, and the reducing agent is one or a mixture of coke, ferrosilicon, graphite, and starch in any ratio.

[0008] In step B, the acid is one of hydrochloric acid, sulfuric acid or nitric acid or a mixture of any ratio of them, and the oxidant is one of sodium hypochlorite, sodium aluminate and sodium bromate or a mixture of any ratio of them.

[0009] In step C, the reducing agent is one of coke, graphite and starch or a mixture of any proportion of the two or more thereof. Beneficial effects of the present invention: 1. The present invention adopts a collaborative disposal method to achieve the collaborative recovery of valuable metals from failed lithium iron phosphate black powder and failed platinum-containing catalysts, which effectively improves resource utilization while reducing the impact of solid waste on the environment, with significant economic benefits.

[0010] 2. The present invention obtains metallic lithium and phosphorus respectively by means of graded condensation, and has high recovery efficiency.

[0011] 3. The present invention obtains lithium iron phosphate by solid phase carbon thermal reduction synthesis of the product obtained by oxidative precipitate and multi-stage condensation, which can be directly used in the production of lithium iron phosphate batteries, effectively shortening the lithium iron phosphate black powder recovery process and reducing energy consumption.

[0012] 4. The present invention adopts a collaborative recovery treatment method, with a platinum group metal recovery rate of >98%, and 99.95% of metallic platinum can be obtained. The platinum group metal capture process does not require the addition of new collectors, so that the iron in the black powder is fully utilized, and lithium iron phosphate for the preparation of power batteries is synthesized.

[0013] 5. The equipment used in the present invention is conventional equipment in metallurgy or resource recovery process, with high maturity and broad industrialization prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION Example 1

[0015] A method for collaboratively recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst is carried out in the following steps: A. Vacuum reduction smelting: 100g of spent platinum-containing catalyst, 10g of spent lithium iron phosphate black powder, 60g of aluminum oxide, 3g of calcium fluoride, 5g of coke and 5g of starch are mixed to prepare pellets, which are then placed in a vacuum reduction smelting furnace for smelting. The vacuum reduction smelting temperature is 1500°C and the smelting time is 5h to obtain platinum-containing ferroalloy, smelting slag and mixed vapor. A graded condensation condenser is used. Under the condition of a distillation pressure of 1000Pa, metallic lithium is obtained in the condensation region below 150°C, and phosphorus is obtained in the condensation region between 300°C and 400°C. B. Oxidative dissolution: The platinum-containing iron alloy obtained in step A is oxidized and dissolved by adding hydrochloric acid, maintaining a liquid-solid ratio of 4:1 ml / g, a temperature of 30° C., and a time of 5 h, and sodium hypochlorite is added to adjust the pH to 4.5 to precipitate iron phosphate, and the iron phosphate and platinum-containing solution are obtained after filtration; C. Carbothermal reduction: The iron phosphate obtained in step B and the lithium carbonate obtained by carbonizing the metal lithium obtained in step A are mixed in a molar ratio of 1:1, and then graphite accounting for 10% of the total mass of the iron phosphate and the lithium carbonate is added. The solid phase synthesis temperature is 700° C. and the solid phase synthesis time is 5 h. Lithium iron phosphate is obtained by sintering through a carbothermal reduction method, and the carbon content is 0.6%; D. Ammonium salt precipitation and calcination: The platinum-containing solution obtained in step B is precipitated with ammonium chloride and then calcined to obtain metallic platinum powder.

[0016] In this embodiment, the recovery rate of platinum group metals is 98.70%, the purity of platinum powder after four precipitations is 99.95%, and the recovery rate of lithium is 91.30%. Example 2

[0017] A method for collaboratively recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst is carried out in the following steps: A. Vacuum reduction smelting: 100g of spent platinum-containing catalyst, 10g of spent lithium iron phosphate black powder, 50g of silicon dioxide, 20g of calcium oxide, 3g of borax and 10g of coke are mixed to prepare pellets, which are then placed in a vacuum reduction smelting furnace for smelting. The vacuum reduction smelting temperature is 1500°C and the smelting time is 4h to obtain platinum-containing ferroalloy, smelting slag and mixed vapor. A graded condensation condenser is used. Under the condition of a distillation pressure of 500Pa, metallic lithium is obtained in the condensation region below 150°C, and phosphorus is obtained in the condensation region between 300°C and 400°C. B. Oxidative dissolution: The platinum-containing iron alloy obtained in step A is oxidized and dissolved by adding sulfuric acid, maintaining a liquid-solid ratio of 5:1 ml / g, a temperature of 40° C., and a time of 4 hours, and sodium aluminate is added to adjust the pH to 4.5 to precipitate iron phosphate, and the iron phosphate and platinum-containing solution are obtained after filtration; C. Carbothermal reduction: The iron phosphate obtained in step B and the lithium carbonate obtained by carbonizing the metal lithium obtained in step A are mixed in a molar ratio of 1:1, and then starch accounting for 20% of the total mass of the iron phosphate and the lithium carbonate is added. The solid phase synthesis temperature is 700° C. and the solid phase synthesis time is 4 hours. Lithium iron phosphate is obtained by sintering through a carbothermal reduction method, and the carbon content is 0.8%; D. Ammonium salt precipitation and calcination: The platinum-containing solution obtained in step B is precipitated with ammonium chloride and then calcined to obtain metallic platinum powder.

[0018] In this embodiment, the recovery rate of platinum group metals is 98.9%, the purity of platinum powder after four precipitations is 99.95%, and the recovery rate of lithium is 92.10%. Example 3

[0019] A method for collaboratively recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst is carried out in the following steps: A. Vacuum reduction smelting: 100g of spent platinum-containing catalyst, 15g of spent lithium iron phosphate black powder, 50g of silicon dioxide, 30g of calcium oxide, 4g of boron oxide, and 15g of ferrosilicon are mixed to prepare pellets, which are then placed in a vacuum reduction smelting furnace for smelting. The vacuum reduction smelting temperature is 1600°C, and the smelting time is 4h. Platinum-containing ferroalloy, smelting slag and mixed vapor are obtained. A graded condensation condenser is used. Under the condition of a distillation pressure of 300Pa, metallic lithium is obtained in the condensation region below 150°C, and phosphorus is obtained in the condensation region between 300°C and 400°C. B. Oxidative dissolution: add nitric acid to the platinum-iron alloy obtained in step A, maintain the liquid-solid ratio at 6:1 ml / g, temperature at 50° C., time for 4 hours, completely oxidize and dissolve the alloy, add sodium bromate, adjust the pH to 4.5 to precipitate iron phosphate, and filter to obtain iron phosphate and platinum-containing solution; C. Carbothermal reduction: The iron phosphate obtained in step B and the lithium carbonate obtained by carbonizing the metal lithium obtained in step A are mixed in a molar ratio of 1:1, and then coke accounting for 30% of the total mass of the iron phosphate and the lithium carbonate is added. The solid phase synthesis temperature is 800° C. and the solid phase synthesis time is 3 h. Lithium iron phosphate is obtained by sintering through a carbothermal reduction method, and the carbon content is 1.1%; D. Ammonium salt precipitation and calcination: The platinum-containing solution obtained in step B is precipitated with ammonium chloride and then calcined to obtain metallic platinum powder.

[0020] In this embodiment, the recovery rate of platinum group metals is 99.00%, the purity of platinum powder after four precipitations is 99.95%, and the recovery rate of lithium is 90.90%. Example 4

[0021] A method for collaboratively recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst is carried out in the following steps: A. Vacuum reduction smelting: 100g of spent platinum-containing catalyst, 15g of spent lithium iron phosphate black powder, 50g of silicon dioxide, 50g of calcium oxide, 2g of calcium fluoride, 2g of borax, 5g of coke, 5g of starch and 5g of graphite are mixed to prepare pellets, which are then placed in a vacuum reduction smelting furnace for smelting. The vacuum reduction smelting temperature is 1600°C and the smelting time is 3h to obtain platinum-containing ferroalloy, smelting slag and mixed vapor. A graded condensation condenser is used. Under the condition of a distillation pressure of 200Pa, metallic lithium is obtained in the condensation region below 150°C, and phosphorus is obtained in the condensation region between 300°C and 400°C. B. Oxidative dissolution: The platinum-iron alloy obtained in step A is oxidized and dissolved by adding a mixture of hydrochloric acid and sulfuric acid in a mass ratio of 1:1, maintaining a liquid-solid ratio of 8:1 ml / g, a temperature of 50° C., and a time of 3 h, and a mixture of sodium hypochlorite and sodium aluminate is added in a mass ratio of 1:1, and the pH is adjusted to 4.5 to precipitate iron phosphate, and the iron phosphate and platinum-containing solution are obtained after filtration; C. Carbothermal reduction: The iron phosphate obtained in step B and the lithium carbonate obtained by carbonizing the metal lithium obtained in step A are mixed in a molar ratio of 1:1, and then 15% of graphite and 15% of starch are added to the total mass of the iron phosphate and the lithium carbonate. The solid phase synthesis temperature is 800° C. and the solid phase synthesis time is 3 h. Lithium iron phosphate is obtained by sintering through a carbothermal reduction method, and the carbon content is 1.2%; D. Ammonium salt precipitation and calcination: The platinum-containing solution obtained in step B is precipitated with ammonium chloride and then calcined to obtain metallic platinum powder.

[0022] In this embodiment, the recovery rate of platinum group metals is 98.80%, the purity of platinum powder after four precipitations is 99.95%, and the recovery rate of lithium is 94.30%. Example 5

[0023] A method for collaboratively recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst is carried out in the following steps: A. Vacuum reduction smelting: 100g of spent platinum-containing catalyst, 20g of spent lithium iron phosphate black powder, 110g of calcium oxide, 2g of calcium fluoride, 3g of boron oxide, and 20g of starch are mixed to prepare pellets, which are then placed in a vacuum reduction smelting furnace for smelting. The vacuum reduction smelting temperature is 1700°C, and the smelting time is 2h to obtain platinum-containing ferroalloy, smelting slag and mixed vapor. A graded condensation condenser is used. Under the condition of a distillation pressure of 100Pa, metallic lithium is obtained in the condensation region below 150°C, and phosphorus is obtained in the condensation region between 300°C and 400°C. B. Oxidative dissolution: The platinum-iron alloy obtained in step A is oxidized and dissolved by adding a mixture of sulfuric acid and nitric acid in a mass ratio of 4:5, maintaining a liquid-to-solid ratio of 9:1 ml / g, a temperature of 60° C., and a time of 2 h, and a mixture of sodium hypochlorite and sodium bromate is added in a mass ratio of 1:1, and the pH is adjusted to 4.5 to precipitate iron phosphate, and the iron phosphate and platinum-containing solution are obtained after filtration; C. Carbothermal reduction: The iron phosphate obtained in step B and the lithium carbonate obtained by carbonizing the metal lithium obtained in step A are mixed in a molar ratio of 1:1, and then 20% of graphite and 20% of coke are added to the total mass of the iron phosphate and the lithium carbonate. The solid phase synthesis temperature is 900° C. and the solid phase synthesis time is 2 h. Lithium iron phosphate is obtained by sintering through a carbothermal reduction method, and the carbon content is 1.3%; D. Ammonium salt precipitation and calcination: The platinum-containing solution obtained in step B is precipitated with ammonium chloride and then calcined to obtain metallic platinum powder.

[0024] In this embodiment, the recovery rate of platinum group metals is 98.50%, the purity of platinum powder after four precipitations is 99.95%, and the recovery rate of lithium is 95.10%. Example 6

[0025] A method for collaboratively recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst is carried out in the following steps: A. Vacuum reduction smelting: 100g of spent platinum-containing catalyst, 20g of spent lithium iron phosphate black powder, 120g of silicon dioxide, 2g of borax, 3g of boron oxide, and 20g of graphite are mixed to prepare pellets, which are then placed in a vacuum reduction smelting furnace for smelting. The vacuum reduction smelting temperature is 1700°C, and the smelting time is 2h to obtain platinum-containing ferroalloy, smelting slag and mixed vapor. A graded condensation condenser is used. Under the condition of a distillation pressure of 10Pa, metallic lithium is obtained in the condensation region below 150°C, and phosphorus is obtained in the condensation region between 300°C and 400°C. B. Oxidative dissolution: The platinum-iron alloy obtained in step A is oxidized and dissolved by adding a mixture of hydrochloric acid and nitric acid in a mass ratio of 1:1, maintaining a liquid-solid ratio of 10:1 ml / g, a temperature of 70° C., and a time of 2 h, adding a mixture of sodium aluminate and sodium bromate in a mass ratio of 1:1, adjusting the pH to 4.5 to precipitate iron phosphate, and filtering to obtain an iron phosphate and platinum-containing solution; C. Carbothermal reduction: The iron phosphate obtained in step B and the lithium carbonate obtained by carbonizing the metal lithium obtained in step A are mixed in a molar ratio of 1:1, and then 25% of starch and 25% of coke are added to the total mass of the iron phosphate and lithium carbonate. The solid phase synthesis temperature is 900° C. and the solid phase synthesis time is 1 h. Lithium iron phosphate is obtained by sintering through a carbothermal reduction method, and the carbon content is 1.8%; D. Ammonium salt precipitation and calcination: The platinum-containing solution obtained in step B is precipitated with ammonium chloride and then calcined to obtain metallic platinum powder.

[0026] In this embodiment, the recovery rate of platinum group metals is 98.60%, the purity of platinum powder after four precipitations is 99.95%, and the recovery rate of lithium is 94.50%.

Claims

1. A method for the coordinated recovery of spent lithium iron phosphate black powder and spent platinum-containing catalyst, characterized by the following steps being carried out in sequence: A. Vacuum reduction smelting: Mix spent platinum-containing catalyst, spent lithium iron phosphate black powder, slag-making agent, flux, and reducing agent in the proportion of 100 parts, 10-20 parts, 60-120 parts, 3-5 parts, and 10-20 parts to prepare pellets, and then place them in a vacuum reduction smelting furnace for smelting. The vacuum reduction smelting temperature is 1500°C to 1700°C, and the smelting time is 2 to 5 hours to obtain platinum-containing ferroalloy, smelting slag, and waste gas. A graded condensation condenser is used, and the mixed vapor is subjected to a distillation pressure of 10 to 1000 Pa to obtain metallic lithium in a condensation region below 150°C, and phosphorus in a condensation region of 300°C to 400°C; the parts are by weight; B. Oxidative dissolution: The platinum-containing iron alloy obtained in step A is oxidized and dissolved by adding acid, maintaining a liquid-solid ratio of 4:1 to 10:1 ml / g, a temperature of 30° C. to 70° C., and a time of 2 to 5 hours. An oxidant is added, and the pH is adjusted to 4.5 to precipitate iron phosphate. After filtering, the iron phosphate and platinum-containing solution are obtained; C. Carbothermal reduction: The iron phosphate obtained in step B and the lithium carbonate obtained by carbonizing the metal lithium obtained in step A are mixed in a molar ratio of 1:1, and then a reducing agent is added, wherein the amount of the reducing agent added is 10% to 50% of the total mass of the iron phosphate and the lithium carbonate, the solid phase synthesis temperature is 700° C. to 900° C., the solid phase synthesis time is 1 to 5 hours, and lithium iron phosphate is obtained after sintering by carbothermal reduction method; D. Ammonium salt precipitation and calcination: The platinum-containing solution obtained in step B is precipitated with ammonium chloride and then calcined to obtain metallic platinum powder.

2. The method for synergistically recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst according to claim 1, characterized in that: In step A, the slag-forming agent is one or a mixture of aluminum oxide, calcium oxide, and silicon dioxide in any ratio, the cosolvent is one or a mixture of calcium fluoride, borax, and boron oxide in any ratio, and the reducing agent is one or a mixture of coke, ferrosilicon, graphite, and starch in any ratio.

3. The method for synergistically recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst according to claim 1 or 2, characterized in that: In step B, the acid is one of hydrochloric acid, sulfuric acid or nitric acid or a mixture of any ratio of them, and the oxidant is one of sodium hypochlorite, sodium aluminate and sodium bromate or a mixture of any ratio of them.

4. The method for synergistically recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst according to claim 1 or 2, characterized in that: The reducing agent in step C is one or a mixture of any ratio of coke, graphite and starch.

5. The method for collaboratively recovering spent lithium iron phosphate black powder and spent platinum-containing catalyst according to claim 3, characterized in that: The reducing agent in step C is one or a mixture of any ratio of coke, graphite and starch.

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