Method for synergistically recovering valuable components from rare earth molten salt slag and neodymium iron boron waste

Abstract

The invention belongs to the technical field of solid waste resource utilization, and particularly relates to a method for synergistically recovering valuable components from rare earth molten salt slag and neodymium iron boron waste, which comprises the following steps: carrying out crushing and wet grinding treatment on the rare earth molten salt slag, carrying out acid leaching on the treated rare earth molten salt slag, carrying out solid-liquid separation after acid leaching to obtain an acid leaching solution and acid leaching slag, adding a precipitator into the acid leaching solution for precipitation, and carrying out solid-liquid separation on the precipitation solution; filtering to obtain a rare earth salt precipitate, returning the filtrate to the acid leaching process for continuous recycling, drying the acid leaching residue, adding neodymium iron boron waste, uniformly mixing, roasting to obtain a roasted product, and carrying out optimal dissolution, extraction, precipitation and firing on the roasted product to obtain a single rare earth oxide. According to the method, the thought of'treating waste with waste 'is introduced, the neodymium iron boron waste is added into the rare earth molten salt slag, fluorine in the rare earth molten salt slag is removed through collaborative roasting, the purpose of separating rare earth from fluorine is achieved, resource recycling of rare earth, lithium and fluorine is achieved, the technological process is simple, and industrial production is easy.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, and specifically relates to a method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste. Background Art

[0002] As an important non-renewable strategic resource, rare earths have shown great application potential in the field of modern high technology. They are widely used in clean energy technology, magnetic materials, electronic devices, catalysts and optical devices, and have played an indispensable role in improving product performance, promoting energy conservation and emission reduction, and promoting the development of new energy technologies. With the rapid development of rare earth material processing and application industries, the amount of rare earth solid waste (hereinafter referred to as "rare earth solid waste") generated has also continued to grow. Among them, NdFeB waste is one of the most important rare earth solid wastes, with a rare earth content of about 20-30% and an iron content of about 15-99%; rare earth molten salt slag is an important rare earth solid waste second only to NdFeB waste, with a rare earth content of about 1-60%, and contains 0.1-5% lithium and 5-50% fluorine. NdFeB waste and rare earth molten salt slag together account for more than 90% of the total rare earth solid waste. Under the strategic needs of carbon peak and carbon neutrality goals, the resource utilization of rare earths is particularly important. The recycling of rare earth solid waste has not only changed the traditional supply model of rare earth resources, but also significantly reduced the dependence on original rare earth ores, alleviated the resource and environmental pressure of mining, and reduced the environmental pollution caused by rare earth mining and processing. Therefore, the recovery of rare earth resources from rare earth solid waste has become an important part of the rare earth supply chain and is of great significance to the sustainable development of the rare earth industry.

[0003] At present, the industry usually uses the oxidation roasting-hydrochloric acid dissolution-extraction-precipitation-burning process to recover rare earths from NdFeB waste; while the treatment of rare earth molten salt slag adopts the sodium hydroxide or calcium oxide roasting-hydrochloric acid acid leaching-extraction-burning process. Although the treatment processes of the two rare earth solid wastes have a high similarity in process, the rare earth molten salt slag contains about 5-40% fluorine, which makes it impossible to achieve joint treatment of the two. Fluorine is a harmful component in rare earth solution. Fluoride ions are easily combined with rare earth and other metal ions to form fluoride colloids or precipitations, which will cause the formation of a third phase during the extraction process, thereby significantly reducing the recovery rate of rare earths. Therefore, when treating rare earth molten salt slag, a fluorine-fixing agent needs to be added for roasting to achieve fluorine solidification. However, an effective treatment method for solid fluorine slag has not yet been proposed, and the treatment of solid fluorine slag still has potential secondary pollution risks. For this reason, the current industrial treatment of NdFeB waste and rare earth molten salt slag is completely independent, and the coordinated treatment of the two rare earth solid wastes has not been achieved. In addition, there are no reports in existing literature and patent technologies on the combined treatment of NdFeB waste and rare earth molten salt slag, which indicates that there is still a huge technical gap and room for innovation in this field. Summary of the invention

[0004] To this end, the present invention provides a method for synergistically recovering valuable components from rare earth molten salt slag and NdFeB waste. The rare earth molten salt slag is first crushed and wet-milled, and the treated rare earth molten salt slag is acid-leached. After acid leaching, the solid-liquid separation is obtained by filtering and obtaining an acid leaching solution and an acid leaching residue. A precipitant is added to the acid leaching solution for precipitation, and rare earth salt precipitation is obtained by filtering. The filtrate is circulated back to the acid leaching process to further enrich lithium, and finally the lithium component is recovered therefrom. Then, NdFeB waste is added to the dried rare earth salt precipitation and the acid leaching residue to mix evenly, and the mixed system is synergistically roasted. The product obtained by roasting is then subjected to the steps of optimal dissolution, extraction, precipitation and calcination to obtain a single rare earth oxide. The present invention proposes to adopt the innovative process concept of "waste treatment with waste", synergistically treat rare earth molten salt slag and NdFeB waste, effectively remove the fluorine element in the rare earth molten salt slag through the roasting process, and realize efficient separation and resource recovery of rare earth, lithium and fluorine. The process has the characteristics of simple process flow and high comprehensive resource utilization efficiency, and is easy to promote and apply industrially. The method of the present invention can not only reduce the potential environmental pollution risk during the treatment process, but also realize the recovery of rare earth, lithium and fluorine resources from rare earth solid waste while separating rare earth and fluorine, showing significant technical and economic value and environmental benefits, and has broad promotion prospects.

[0005] The present invention provides a method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste, comprising:

[0006] Step 1: The rare earth molten salt slag is crushed into powder, the powder is mixed with pure water, and then ball-milled in a ball mill. After ball milling, the rare earth molten salt slag is screened and filtered to obtain oversize and undersize. The oversize is returned for further crushing, and the undersize is filtered after standing to obtain filtrate and water-leached residue. The water-leached residue is dried for standby use, and the filtrate is returned to the ball mill for recycling;

[0007] Step 2: The water leaching residue obtained in step 1 is subjected to acid leaching to obtain acid leaching residue and acid leaching liquid, the acid leaching residue is dried to obtain treated rare earth molten salt slag, a precipitant is added to the acid leaching liquid for precipitation, and rare earth salt precipitate and filtrate are obtained by filtration. The rare earth salt precipitate is dried for standby use, and the filtrate is returned to the acid leaching process to obtain a circulating liquid after multiple cycles; wherein the rare earth salt precipitate is roasted together with the rare earth molten salt slag and NdFeB waste in step 3, or, in step 5, is dissolved, extracted, precipitated, and calcined together with the roasting product;

[0008] Step 3: The rare earth molten salt slag obtained in step 2 and the NdFeB waste are mixed and placed in a crucible and placed in a tubular furnace, and roasted under high temperature conditions, with air introduced into one end of the tubular furnace and an aqueous solution connected to the other end, and a fluorine-free roasted product and a fluorine-containing aqueous solution are obtained after roasting;

[0009] Step 4: The circulating liquid obtained in step 2 is a lithium-enriched liquid, which is further treated and recycled;

[0010] Step 5: The roasted product obtained in step 3 is dissolved, extracted, precipitated and calcined to obtain a single rare earth oxide;

[0011] Step 6: The fluorine-containing aqueous solution obtained in step 3 is further treated and recycled.

[0012] Preferably, the rare earth molten salt slag in step one includes one or more of praseodymium-neodymium molten salt slag, gadolinium-iron slag, holmium-iron slag, terbium-calcium slag and dysprosium-calcium slag.

[0013] Preferably, the composition of the rare earth molten salt slag in step 1 includes F: 5% to 50%, Li: 0.1% to 5%, and RE: 1% to 60%.

[0014] Preferably, in step one, the mass ratio of rare earth molten salt slag powder to pure water is 1:1-10, the ball milling speed is 100-500 r / min; the drying temperature is 100-120° C.; and the drying time is 180-480 min.

[0015] Preferably, in step 2, the ratio of water leaching residue to the acid used for acid leaching is 1g:1-10mL, the concentration of the acid used for acid leaching is 1-6mol / L, and the acid used for acid leaching is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0016] Preferably, in step 2, the acid leaching temperature is 10-90° C., the acid leaching time is 60-360 min, and the stirring speed is 100-400 r / min.

[0017] Preferably, in step 2, the drying temperature is 100-120° C., and the drying time is 180-480 min.

[0018] Preferably, in step 2, the mass ratio of rare earth to precipitant in the acid leaching solution is 1:1-3; the precipitant is one or more of oxalic acid solution, sodium carbonate solution and ammonium carbonate solution.

[0019] Preferably, in step three, the NdFeB waste is NdFeB production and processing recycled material referred to in the national standard (GB / T 23588-2020), with an iron content of 15 to 99%.

[0020] Preferably, in step three, the mass ratio of rare earth molten salt slag to NdFeB waste is 1:0.05-100.

[0021] Preferably, in step three, the calcination reaction temperature is 800-1100° C., and the calcination reaction time is 60-240 min.

[0022] Preferably, in step five, the ratio of the calcined product to the optimal solution is 1 g: 1-20 mL, the concentration of the optimal solution is 6-12 mol / L, and the optimal solution is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0023] The beneficial effects achieved by the present invention are as follows:

[0024] (1) The present invention proposes to adopt the innovative idea of ​​"treating waste with waste" and realizes the resource recovery of rare earth molten salt slag and NdFeB waste by co-processing them. The method effectively removes the fluorine element in the rare earth molten salt slag through a roasting process, thereby realizing the efficient separation and recovery of rare earth and fluorine. This process not only organically combines the treatment process of NdFeB waste and rare earth molten salt slag, but also expands the raw material source of NdFeB waste treatment enterprises, alleviates the problem of raw material shortage to a certain extent, and reduces the cost of raw materials;

[0025] (2) The process of the present invention can efficiently recover rare earth, lithium and fluorine resources from rare earth molten salt slag and NdFeB waste, with a rare earth recovery rate exceeding 96%, and lithium and fluorine resource recovery rates reaching 96% and 99% respectively. The technical route is simple and does not produce fluorine-containing wastewater, embodying the concept of green and efficient recycling, and providing a novel and feasible method for the recovery of rare earth, lithium and fluorine from rare earth molten salt slag and NdFeB waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1The present invention provides a process flow chart for a method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste. DETAILED DESCRIPTION

[0027] The present invention provides a method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste, comprising the following steps:

[0028] Step 1: The rare earth molten salt slag is crushed into powder, the powder is mixed with pure water, and then ball-milled in a ball mill. After ball milling, the rare earth molten salt slag is screened and filtered to obtain oversize and undersize. The oversize is returned for further crushing, and the undersize is filtered after standing to obtain filtrate and water-leached residue. The water-leached residue is dried for standby use, and the filtrate is returned to the ball mill for recycling;

[0029] Step 2: The water leaching residue obtained in step 1 is subjected to acid leaching to obtain acid leaching residue and acid leaching liquid, the acid leaching residue is dried to obtain treated rare earth molten salt slag, a precipitant is added to the acid leaching liquid for precipitation, and rare earth salt precipitate and filtrate are obtained by filtration. The rare earth salt precipitate is dried for standby use, and the filtrate is returned to the acid leaching process to obtain a circulating liquid after multiple cycles; wherein the rare earth salt precipitate is roasted together with the rare earth molten salt slag and NdFeB waste in step 3, or, in step 5, is dissolved, extracted, precipitated, and calcined together with the roasting product;

[0030] Step 3: The rare earth molten salt slag obtained in step 2 and the NdFeB waste are mixed and placed in a crucible and placed in a tubular furnace, and roasted under high temperature conditions, with air introduced into one end of the tubular furnace and an aqueous solution connected to the other end, and a fluorine-free roasted product and a fluorine-containing aqueous solution are obtained after roasting;

[0031] Step 4: The circulating liquid obtained in step 2 is a lithium-enriched liquid, which is further treated and recycled;

[0032] Step 5: The roasted product obtained in step 3 is dissolved, extracted, precipitated and calcined to obtain a single rare earth oxide;

[0033] Step 6: The fluorine-containing aqueous solution obtained in step 3 is further treated and recycled.

[0034] In the present invention, the mass percentage of fluorine element in the rare earth molten salt slag in step one is preferably 5-45%; the mass percentage of lithium element in the rare earth molten salt slag in step one is preferably 0.5-5%; the mass percentage of rare earth in the rare earth molten salt slag in step one is preferably 1-50%.

[0035] In the present invention, the rare earth molten salt slag is crushed by a jaw crusher and ball milled by a wet rolling ball mill.

[0036] In the present invention, the mass ratio of the rare earth molten salt slag to pure water is preferably 1:1 to 5. In the present invention, the mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 200 to 400 r / min.

[0037] After ball milling, a rare earth molten salt slag aqueous solution is obtained. The present invention screens and filters the rare earth molten salt slag aqueous solution to obtain an oversize and an undersize. The oversize is returned for further crushing. After the undersize is left to stand, a filtrate and a water-leaching residue are obtained by filtering. The water-leaching residue is dried for standby use, and the filtrate is returned to the ball mill for further use, thereby realizing the recycling of water. After obtaining the water-leaching residue, the present invention drips a hydrochloric acid solution into the water-leaching residue, and the molar concentration of the hydrochloric acid solution is preferably 1 to 4 mol / L. In the present invention, the acid leaching temperature is preferably 10 to 40°C, the acid leaching time is preferably 60 to 240 min, and the stirring speed is preferably 100 to 400 r / min. After acid leaching, solid-liquid separation is performed by filtering to obtain acid leaching residue and acid leaching liquid, the acid leaching residue is dried for standby use, a precipitant is added to the acid leaching liquid for precipitation, and rare earth salt precipitate and filtrate are obtained by filtering. The rare earth salt precipitate is dried for standby use, and the filtrate is returned to the acid leaching process, and lithium-enriched liquid is obtained after multiple cycles.

[0038] In the present invention, the drying temperature is preferably 100 to 105° C., and the drying time is preferably 240 to 420 min.

[0039] In the present invention, the mass ratio of rare earth to precipitant in the acid leaching solution is 1:1-2; the precipitant is oxalic acid.

[0040] The dried rare earth molten salt slag, rare earth salt precipitate and the ball-milled NdFeB waste are mixed evenly, then placed in a crucible and put into a tubular furnace for roasting at high temperature. Air is introduced into one end of the tubular furnace and an aqueous solution is connected to the other end. After roasting, a fluorine-free roasting product and a fluorine-containing aqueous solution (i.e., a hydrofluoric acid aqueous solution) are obtained. The obtained roasting product is subjected to dissolution, extraction, precipitation and calcination to obtain a single rare earth oxide.

[0041] In the present invention, the mass ratio of rare earth molten salt slag to NdFeB waste in step three is preferably 1:0.05-90.

[0042] In the present invention, the calcination temperature is preferably 900 to 1000° C., and the calcination reaction time is preferably 60 to 180 min.

[0043] In the present invention, the ratio of the calcined product to the optimal solution is preferably 1 g:1.5-18.5 mL, the concentration of the optimal solution is preferably 6-12 mol / L, and the optimal solution is a hydrochloric acid solution.

[0044] In the present invention, the optimal dissolution temperature of the calcined product is 80-160° C., the optimal dissolution time is preferably 60-180 min, and the stirring speed is preferably 100-400 r / min.

[0045] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0046] Example 1

[0047] A method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste, comprising the following steps:

[0048] S1. Take 100g of a rare earth molten salt slag and crush it with a jaw crusher. After crushing, put it in the ball mill of a ball mill, then add 100mL of water, set the ball mill speed to 200r / min, and the ball milling time to 6h. After ball milling, sieve it, crush the sieve material and continue to ball mill it until it passes the sieve. Let the sieve material stand and filter it to obtain filtrate and water-leached residue. Dry the water-leached residue at 105℃ for 240min. After drying, the water-leached residue is 98.6g, and the filtrate is returned to the next ball milling for continued use.

[0049] S2, weighing 50g of the water leaching residue dried by S1, which contains 38.18% rare earth oxide and 1.21% lithium, adding 2mol / L hydrochloric acid solution for acid leaching, the solid-liquid ratio of rare earth molten salt slag to hydrochloric acid solution is 1g:2.5mL, the reaction temperature is 30°C, the reaction time is 3h, and the stirring speed is 300r / min. After the reaction is completed, the acid leaching solution and acid leaching residue are obtained by filtering, the lithium content in the acid leaching residue is 0.051%, and the lithium leaching rate is 96.31%. The acid leaching residue is dried at 105°C for 240min for standby use, oxalic acid is added to the acid leaching solution for precipitation, the precipitation temperature is maintained at 60°C, and rare earth oxalate is obtained by filtering. The rare earth oxalate is dried for standby use, and the filtrate is returned to the acid leaching process. After multiple cycles, a lithium-enriched solution containing lithium is obtained;

[0050] S3. Weigh 36 g of the acid leaching residue dried by S2, which contains 42.51% rare earth oxides and 11.31% fluorine. Weigh 4 g of ball-milled NdFeB waste, which contains 26.32% rare earth oxides and 45.72% iron. Mix the acid leaching residue and the NdFeB waste and place them in a tubular furnace and calcine them at 1000°C for 3 hours. The mass of the calcined product after the reaction is 22.4 g, the fluorine content is 0.12%, and the fluorine removal rate is 99.12%.

[0051] S4. Weigh 0.3g of rare earth oxalate obtained in S2 and 10g of the calcined product obtained in S3, add 12mol / L hydrochloric acid solution for dissolution treatment, the solid-liquid ratio of the calcined product and rare earth oxalate to the hydrochloric acid solution is 1g:2.5mL, the reaction temperature is 120℃, the reaction time is 3h, the stirring speed is 300r / min, after the reaction is completed, filter to obtain the optimal solution and optimal slag, the optimal slag is 1.9g, and the rare earth leaching rate is 98.06%.

[0052] Comparative Example 1

[0053] A method for recovering valuable components from rare earth molten salt slag comprises the following steps:

[0054] S1. Take 100g of a rare earth molten salt slag and crush it with a jaw crusher. After crushing, put it in the ball mill of a ball mill, then add 100mL of water, set the ball mill speed to 200r / min, and the ball milling time to 6h. After ball milling, sieve it, crush the sieve material and continue to ball mill it until it passes the sieve. Let the sieve material stand and filter it to obtain filtrate and water-leached residue. Dry the water-leached residue at 105℃ for 240min. After drying, the water-leached residue is 98.6g, and the filtrate is returned to the next ball milling for continued use.

[0055] S2, weighing 50g of the water leaching residue dried by S1, which contains 38.18% rare earth oxide and 1.21% lithium, adding 2mol / L hydrochloric acid solution for acid leaching, the solid-liquid ratio of rare earth molten salt slag to hydrochloric acid solution is 1g:2.5mL, the reaction temperature is 30°C, the reaction time is 3h, and the stirring speed is 300r / min. After the reaction is completed, the acid leaching solution and acid leaching residue are obtained by filtering, the lithium content in the acid leaching residue is 0.051%, and the lithium leaching rate is 96.31%. The acid leaching residue is dried at 105°C for 240min for standby use, oxalic acid is added to the acid leaching solution for precipitation, the precipitation temperature is maintained at 60°C, and rare earth oxalate is obtained by filtering. The rare earth oxalate is dried for standby use, and the filtrate is returned to the acid leaching process. After multiple cycles, a lithium-enriched solution containing lithium is obtained;

[0056] S3. Weigh 36 g of the acid leaching residue dried by S2, which contains 42.51% rare earth oxides and 11.31% fluorine. Place the acid leaching residue in a tubular furnace and roast it at 1000°C for 3 hours without adding NdFeB waste. The mass of the roasted product after the reaction is 18 g, the fluorine content is 2.44%, and the fluorine removal rate is 87.86%.

[0057] S4. Weigh 0.3 g of rare earth oxalate obtained in S2 and 10 g of the calcined product obtained in S3, add 12 mol / L hydrochloric acid solution for dissolution treatment, the solid-liquid ratio of the calcined product to the hydrochloric acid solution is 1 g:2.5 mL, the reaction temperature is 120°C, the reaction time is 3 h, and the stirring speed is 300 r / min. After the reaction is completed, filter to obtain a solution and slag, 1.6 g of slag, and a rare earth leaching rate of 92.59%.

[0058] Example 2

[0059] A method for synergistically recovering valuable components from rare earth molten salt slag and NdFeB waste. Figure 1 As shown, the following steps are included:

[0060] S1. Take 100g of a rare earth molten salt slag and crush it with a jaw crusher. After crushing, put it in the ball mill of a ball mill, then add 100mL of water, set the ball mill speed to 200r / min, and the ball milling time to 6h. After ball milling, sieve it, crush the sieve material and continue to ball mill it until it passes the sieve. Let the sieve material stand and filter it to obtain filtrate and water-leached residue. Dry the water-leached residue at 105℃ for 240min. After drying, the water-leached residue is 98.6g, and the filtrate is returned to the next ball milling for continued use.

[0061] S2, weighing 50g of the water leaching residue dried by S1, which contains 38.18% rare earth oxide and 1.21% lithium, adding 2mol / L hydrochloric acid solution for acid leaching, the solid-liquid ratio of rare earth molten salt slag to hydrochloric acid solution is 1g:2.5mL, the reaction temperature is 30°C, the reaction time is 3h, and the stirring speed is 300r / min. After the reaction is completed, the acid leaching solution and acid leaching residue are obtained by filtering, the lithium content in the acid leaching residue is 0.051%, and the lithium leaching rate is 96.31%. The acid leaching residue is dried at 105°C for 240min for standby use, oxalic acid is added to the acid leaching solution for precipitation, the precipitation temperature is maintained at 60°C, and rare earth oxalate is obtained by filtering. The rare earth oxalate is dried for standby use, and the filtrate is returned to the acid leaching process. After multiple cycles, a lithium-enriched solution containing lithium is obtained;

[0062] S3. Weigh 32g of the acid leaching residue dried by S2, which contains 42.51% rare earth oxides and 11.31% fluorine. Weigh 0.3g of rare earth oxalate dried by S2. Weigh 8g of ball-milled NdFeB waste, which contains 26.32% rare earth oxides and 45.72% iron. Mix the above acid leaching residue and NdFeB waste and place them in a tubular furnace and calcine them at 1000°C for 3h. The mass of the calcined product after the reaction is 24.59g, the fluorine content is 0.046%, and the fluorine removal rate is 99.58%.

[0063] S4. Weigh 10 g of the calcined product obtained in S3, add 12 mol / L hydrochloric acid solution for dissolution treatment, the solid-liquid ratio of the calcined product to the hydrochloric acid solution is 1 g:2.5 mL, the reaction temperature is 120°C, the reaction time is 3 h, and the stirring speed is 300 r / min. After the reaction is completed, filter to obtain a solution and slag, 1.4 g of slag, and a rare earth leaching rate of 99.45%.

[0064] Example 3

[0065] A method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste, comprising the following steps:

[0066] S1. Take 100g of a rare earth molten salt slag and crush it with a jaw crusher. After crushing, put it in the ball mill of a ball mill, then add 100mL of water, set the ball mill speed to 200r / min, and the ball milling time to 6h. After ball milling, sieve it, crush the sieve material and continue to ball mill it until it passes the sieve. Let the sieve material stand and filter it to obtain filtrate and water-leached residue. Dry the water-leached residue at 105℃ for 240min. After drying, the water-leached residue is 98.6g, and the filtrate is returned to the next ball milling for continued use.

[0067] S2, weighing 50g of the water leaching residue dried by S1, which contains 38.18% rare earth oxide and 1.21% lithium, adding 2mol / L hydrochloric acid solution for acid leaching, the solid-liquid ratio of rare earth molten salt slag to hydrochloric acid solution is 1g:2.5mL, the reaction temperature is 30°C, the reaction time is 3h, and the stirring speed is 300r / min. After the reaction is completed, the acid leaching solution and acid leaching residue are obtained by filtering, the lithium content in the acid leaching residue is 0.051%, and the lithium leaching rate is 96.31%. The acid leaching residue is dried at 105°C for 240min for standby use, oxalic acid is added to the acid leaching solution for precipitation, the precipitation temperature is maintained at 60°C, and rare earth oxalate is obtained by filtering. The rare earth oxalate is dried for standby use, and the filtrate is returned to the acid leaching process. After multiple cycles, a lithium-enriched solution containing lithium is obtained;

[0068] S3. Weigh 24 g of the acid leaching residue dried by S2, which contains 42.51% rare earth oxides and 11.31% fluorine. Weigh 16 g of ball-milled NdFeB waste, which contains 26.32% rare earth oxides and 45.72% iron. Mix the acid leaching residue and the NdFeB waste and place them in a tubular furnace and calcine them at 1000°C for 3 hours. The mass of the calcined product after the reaction is 28.4 g, the fluorine content is 0.054%, and the fluorine removal rate is 99.24%.

[0069] S4. Weigh 0.3 g of rare earth oxalate obtained in S2 and 10 g of the calcined product obtained in S3, add 12 mol / L hydrochloric acid solution for dissolution treatment, the solid-liquid ratio of the calcined product to the hydrochloric acid solution is 1 g:2.5 mL, the reaction temperature is 120°C, the reaction time is 3 h, and the stirring speed is 300 r / min. After the reaction is completed, filter to obtain a solution and slag, 1.8 g of slag, and a rare earth leaching rate of 99%.

[0070] Example 4

[0071] A method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste, comprising the following steps:

[0072] S1. Take 100g of a rare earth molten salt slag and crush it with a jaw crusher. After crushing, put it in the ball mill of a ball mill, then add 100mL of water, set the ball mill speed to 200r / min, and the ball milling time to 6h. After ball milling, sieve it, crush the sieve material and continue to ball mill it until it passes the sieve. Let the sieve material stand and filter it to obtain filtrate and water-leached residue. Dry the water-leached residue at 105℃ for 240min. After drying, the water-leached residue is 98.6g, and the filtrate is returned to the next ball milling for continued use.

[0073] S2, weigh 50g of the water leaching residue dried by S1, which contains 38.18% rare earth oxide and 1.21% lithium, add 1mol / L hydrochloric acid solution for acid leaching, the solid-liquid ratio of rare earth molten salt slag to hydrochloric acid solution is 1g:5mL, the reaction temperature is 30°C, the reaction time is 3h, and the stirring speed is 300r / min. After the reaction is completed, filter to obtain acid leaching solution and acid leaching residue, the lithium content in the acid leaching residue is 0.041%, and the lithium leaching rate is 97.25%. Dry the acid leaching residue at 105°C for 240min for use, add oxalic acid to the acid leaching solution for precipitation, keep the precipitation temperature at 60°C, filter to obtain rare earth oxalate, dry the rare earth oxalate for use, and return the filtrate to the acid leaching process. After multiple cycles, a lithium-enriched solution is obtained, and the lithium concentration can reach more than 10g / L;

[0074] S3. Weigh 28g of the acid leaching residue dried by S2, which contains 42.51% rare earth oxides and 11.31% fluorine. Weigh 12g of ball-milled NdFeB waste, which contains 26.32% rare earth oxides and 45.72% iron. Mix the acid leaching residue and the NdFeB waste and place them in a tubular furnace and calcine them at 1000°C for 3h. The mass of the calcined product after the reaction is 26.4g, the fluorine content is 0.064%, and the fluorine removal rate is 99.28%.

[0075] S4. Weigh 0.3 g of rare earth oxalate obtained in S2 and 10 g of the calcined product obtained in S3, add 12 mol / L hydrochloric acid solution for dissolution treatment, the solid-liquid ratio of the calcined product to the hydrochloric acid solution is 1 g:2.5 mL, the reaction temperature is 120°C, the reaction time is 3 h, and the stirring speed is 300 r / min. After the reaction is completed, filter to obtain a solution and slag, 1.8 g of slag, and a rare earth leaching rate of 98.97%.

[0076] It can be seen from the above embodiments and comparative examples that by accurately controlling the process conditions, the enrichment of lithium-containing solutions can be effectively achieved, so that the concentration of lithium solutions reaches more than 10g / L. In addition, by adjusting the amount of NdFeB waste added to coordinate the roasting of rare earth molten salt slag, the removal efficiency of fluorine elements can be significantly improved, and the removal rate of fluorine exceeds 99%. Under the conditions of hydrochloric acid optimal solution, the leaching rate of rare earths is also improved to more than 98%. These results show that by optimizing the process parameters, efficient separation and recovery of lithium, fluorine and rare earths in rare earth molten salt slag can be achieved.

Claims

1. A method for synergistically recovering valuable components from rare earth molten salt slag and NdFeB waste, characterized in that: include: Step 1: The rare earth molten salt slag is crushed into powder, the powder is mixed with pure water, and then ball-milled in a ball mill. After ball milling, the rare earth molten salt slag is screened and filtered to obtain oversize and undersize. The oversize is returned for further crushing, and the undersize is filtered after standing to obtain filtrate and water-leached residue. The water-leached residue is dried for standby use, and the filtrate is returned to the ball mill for recycling; Step 2: acid leaching the water leaching residue obtained in step 1 to obtain acid leaching residue and acid leaching liquid, drying the acid leaching residue to obtain treated rare earth molten salt slag, adding a precipitant to the acid leaching liquid for precipitation, filtering to obtain rare earth salt precipitate and filtrate, drying the rare earth salt precipitate for standby use, and returning the filtrate to the acid leaching process to obtain a circulating liquid after multiple cycles; wherein the rare earth salt precipitate is roasted together with the rare earth molten salt slag and NdFeB waste in step 3, or the rare earth salt precipitate is dissolved, extracted, precipitated, and calcined together with the roasting product in step 5; Step 3: The rare earth molten salt slag obtained in step 2 and a certain amount of NdFeB waste are mixed and placed in a crucible and placed in a tubular furnace for roasting at high temperature. Air is introduced into one end of the tubular furnace and an aqueous solution is connected to the other end. After roasting, a fluorine-free roasting product and a fluorine-containing aqueous solution are obtained; Step 4: The circulating liquid obtained in step 2 is a lithium-enriched liquid, which is further treated and recycled; Step 5: The roasted product obtained in step 3 is dissolved, extracted, precipitated and calcined to obtain a single rare earth oxide; Step 6: The fluorine-containing aqueous solution obtained in step 3 is further treated and recycled.

2. The method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste according to claim 1, characterized in that: The rare earth molten salt slag in step 1 includes one or more of praseodymium-neodymium molten salt slag, gadolinium-iron slag, holmium-iron slag, terbium-calcium slag, and dysprosium-calcium slag; the components of the rare earth molten salt slag include F: 5% to 50%, Li: 0.1% to 5%, and RE: 1% to 60%.

3. The method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste according to claim 1, characterized in that: In step 1, the mass ratio of rare earth molten salt slag powder to pure water is 1:1-5, and the ball milling speed is 100-400 r / min.

4. The method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste according to claim 1, characterized in that: In step 1, the drying temperature is 100-120° C. and the drying time is 180-480 min.

5. The method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste according to claim 1, characterized in that: In step 2, the ratio of the water leaching residue to the acid used for acid leaching is 1g:1-10mL, the concentration of the acid used for acid leaching is 1-6mol / L, the acid used for acid leaching is one or more of hydrochloric acid, sulfuric acid, and nitric acid, the acid leaching temperature is 10-90°C, the acid leaching time is 60-360min, and the stirring speed is 100-400r / min.

6. The method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste according to claim 1, characterized in that: In step 2, the drying temperature is 100-120° C. and the drying time is 180-480 min.

7. The method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste according to claim 1, characterized in that: In step 2, the mass ratio of rare earth to precipitant in the acid leaching solution is 1:1-3; the precipitant is one or more of oxalic acid solution, sodium carbonate solution, and ammonium carbonate solution.

8. The method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste according to claim 1, characterized in that: The NdFeB waste in the step three is the NdFeB production and processing recycled material referred to in the national standard GB / T23588-2020, and the iron content is 15-99%; the mass ratio of rare earth molten salt slag to NdFeB waste in the step three is 1:0.05-100.

9. The method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste according to claim 1, characterized in that: In step 3, the calcination reaction temperature is 800-1100° C., and the calcination reaction time is 60-240 min.

10. The method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste according to claim 1, characterized in that: In step 5, the ratio of the calcined product to the optimal solution is 1g:1-20mL, the concentration of the optimal solution is 6-12mol / L, and the optimal solution is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

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