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

Abstract

The present application belongs to the technical field of solid waste resource utilization, and particularly relates to a method for cooperatively recovering valuable components from rare earth molten salt slag and neodymium iron boron waste, which comprises: crushing and wet grinding the rare earth molten salt slag, acid leaching the treated rare earth molten salt slag, solid-liquid separation of the acid leached slag to obtain an acid leaching solution and an acid leaching residue, adding a precipitant to the acid leaching solution for precipitation, filtering to obtain a rare earth salt precipitate, returning the filtrate to the acid leaching process for recycling, mixing the dried acid leaching residue with the neodymium iron boron waste, and then roasting to obtain a roasting product, and then subjecting the roasting product to a process of optimal dissolution, extraction, precipitation and calcination to obtain a single rare earth oxide. The method provided by the present application adds the neodymium iron boron waste to the rare earth molten salt slag by introducing the idea of "waste treatment with waste", removes the fluorine in the rare earth molten salt slag through cooperative roasting, achieves the separation of rare earth and fluorine, realizes the resource recovery of rare earth, lithium and fluorine, and has a simple process flow and is easy to be industrialized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste resource utilization, and particularly relates to a method for cooperatively recovering valuable components from rare earth molten salt slag and neodymium iron boron waste. BACKGROUND

[0002] Rare earths, as an important strategic resource that is not renewable, 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, etc., and play an indispensable role in improving product performance, promoting energy saving and emission reduction, and promoting the development of new energy technology. With the rapid development of rare earth material processing and application industry, the amount of rare earth solid waste (hereinafter referred to as "rare earth solid waste") is also growing. Among them, neodymium iron boron 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 next to neodymium iron boron waste, with a rare earth content of about 1-60%, and also contains 0.1-5% lithium element and 5-50% fluorine element. Neodymium iron boron waste and rare earth molten salt slag together account for more than 90% of the total amount of rare earth solid waste. Under the strategic demand of carbon peak and carbon neutralization, the resource utilization of rare earths is particularly important. The recycling of rare earth solid waste not only changes the traditional supply mode of rare earth resources, but also significantly reduces the dependence on original rare earth ores, alleviates the resource and environmental pressure of mine exploitation, and reduces 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 has important significance for the sustainable development of the rare earth industry.

[0003] Currently, the industry typically uses a process called oxidative roasting-hydrochloric acid dissolution-extraction-precipitation-incineration to recover rare earths from NdFeB waste. Treatment of rare earth molten salt slag typically involves roasting with sodium hydroxide or calcium oxide, followed by hydrochloric acid leaching, extraction, and incineration. While the processes for treating these two rare earth solid wastes are highly similar, the presence of approximately 5-40% fluorine in molten salt slag prevents their combined treatment. Fluorine is a harmful component in rare earth solutions. Fluoride ions readily combine with rare earth and other metal ions to form fluoride colloids or precipitates. This can trigger the formation of a third phase during extraction, significantly reducing rare earth recovery. Therefore, when treating molten salt slag, a fluorine-fixing agent must be added during roasting to solidify the fluorine. However, effective treatment methods for fluorine-fixed slag have yet to be developed, and the treatment of fluorine-fixed slag still presents the potential for secondary pollution. Consequently, the current industrial treatment of NdFeB waste and rare earth molten salt slag is completely independent, and synergistic treatment of the two rare earth solid wastes has not yet 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 technological gap and room for innovation in this field. Summary of the Invention

[0004] To this end, the present invention provides a method for the synergistic recovery of valuable components from rare earth molten salt slag and NdFeB waste. The rare earth molten salt slag is first crushed and wet-milled. The treated rare earth molten salt slag is then acid-leached. After acid leaching, the slag is filtered for solid-liquid separation to obtain an acid leaching solution and an acid leaching residue. A precipitant is added to the acid leaching solution to precipitate the precipitate, which is filtered to obtain a rare earth salt precipitate. The filtrate is then recycled back to the acid leaching process to further enrich lithium and ultimately recover the lithium component. The dried rare earth salt precipitate and the acid leaching residue are then mixed with NdFeB waste, and the mixed system is co-calcined. The resulting product is then subjected to dissolution, extraction, precipitation, and calcination to obtain a single rare earth oxide. The present invention proposes an innovative process concept of "treating waste with waste" to synergistically treat rare earth molten salt slag and NdFeB waste. The calcination process effectively removes fluorine from the rare earth molten salt slag, allowing for efficient separation and resource recovery of rare earth, lithium, and fluorine. This process has the characteristics of a simple process flow, 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 proposes a method for collaboratively recovering valuable components from rare earth molten salt slag and NdFeB waste, comprising:

[0006] Step one: the rare earth molten salt slag is crushed into powder, the obtained powder is mixed with pure water, and then ball milling is carried out 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 to continue crushing, and the undersize is filtered to obtain filtrate and water leaching residue after standing. The water leaching residue is dried for standby, and the filtrate is returned to the ball milling for recycling.

[0007] Step two: the water leaching residue obtained in step one 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. Filtration is carried out to obtain rare earth salt precipitate and filtrate. The rare earth salt precipitate is dried for standby, and the filtrate is returned to the acid leaching process. After multiple cycles, a circulating liquid is obtained. In step three, the rare earth salt precipitate is calcined with the rare earth molten salt slag and neodymium iron boron waste, or in step five, the rare earth salt precipitate is subjected to leaching, extraction, precipitation and calcination treatment together with the calcination product.

[0008] Step three: the rare earth molten salt slag and the neodymium iron boron waste obtained in step two are mixed and placed in a crucible, which is put into a tube furnace. Air is introduced into one end of the tube furnace, and water solution is introduced into the other end. The calcination product obtained after calcination does not contain fluorine, and the water solution contains fluorine.

[0009] Step four: the circulating liquid obtained in step two is a lithium-rich liquid, which is further treated and recycled.

[0010] Step five: after leaching, extraction, precipitation and calcination, the calcination product obtained in step three is a single rare earth oxide.

[0011] Step six: the water solution containing fluorine obtained in step three 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 one includes F: 5% to 50%, Li: 0.1% to 5%, and RE: 1% to 60%.

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

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

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

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

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

[0019] Preferably, in step three, the neodymium-iron-boron waste is the neodymium-iron-boron production and processing recycling material indicated in the national standard (GB / T 23588-2020), and the iron content is 15-99%.

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

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

[0022] Preferably, in step five, the ratio of the roasting 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 obtained by the present application are as follows:

[0024] (1) The present application proposes the innovative idea of "waste treatment with waste", realizes the recycling of the rare earth molten salt slag and the neodymium-iron-boron waste through the synergistic treatment of the rare earth molten salt slag and the neodymium-iron-boron waste. The method effectively removes the fluorine element in the rare earth molten salt slag through the roasting process, thereby realizing the efficient separation and recovery of the rare earth and fluorine. This process not only organically combines the treatment processes of the neodymium-iron-boron waste and the rare earth molten salt slag, but also expands the raw material sources of the neodymium-iron-boron waste treatment enterprises, to a certain extent, alleviates the problem of raw material shortage, and reduces the raw material cost.

[0025] (2) The process of the present application can efficiently recover the rare earth, lithium and fluorine resources in the rare earth molten salt slag and the neodymium-iron-boron waste, the recovery rate of the rare earth is more than 96%, and the resource recovery rates of lithium and fluorine can reach more than 96% and 99% respectively. The technical route is simple, does not produce fluorine-containing wastewater, embodies the green and efficient recovery concept, and provides a novel and feasible method for the recovery of rare earth, lithium and fluorine in rare earth molten salt slag and neodymium-iron-boron waste. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1A process flow chart of a method for cooperatively recovering valuable components from rare earth molten salt slag and neodymium iron boron waste. DETAILED DESCRIPTION

[0027] The application provides a method for cooperatively recovering valuable components from rare earth molten salt slag and neodymium iron boron waste, comprising the following steps:

[0028] Step one: the rare earth molten salt slag is crushed into powder, the obtained powder is mixed with pure water, and then ball milling is performed 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 to continue crushing, and the undersize is filtered to obtain filtrate and water leaching residue after standing; the water leaching residue is dried for standby, and the filtrate is returned to the ball mill for recycling;

[0029] Step two: the water leaching residue obtained in step one 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; filtration is performed to obtain rare earth salt precipitate and filtrate; the rare earth salt precipitate is dried for standby, and the filtrate is returned to the acid leaching process to obtain circulating liquid after multiple cycles; wherein, the rare earth salt precipitate is calcined with the rare earth molten salt slag and the neodymium iron boron waste in step three, or is subjected to solubilization, extraction, precipitation and calcination treatment together with the calcination product in step five;

[0030] Step three: the rare earth molten salt slag and the neodymium iron boron waste obtained in step two are mixed and placed in a crucible, which is put into a tube furnace; air is introduced into one end of the tube furnace, and water solution is introduced into the other end; after calcination under high temperature, fluorine-free calcination product and fluorine-containing water solution are obtained;

[0031] Step four: the circulating liquid obtained in step two is lithium-enriched liquid, which is further treated and recycled;

[0032] Step five: after solubilization, extraction, precipitation and calcination, the calcination product obtained in step three is single rare earth oxide;

[0033] Step six: the fluorine-containing water solution obtained in step three is further treated and recycled.

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

[0035] In the application, the crushing of the rare earth molten salt slag adopts an eccentric crusher, and the ball milling adopts a wet rolling type ball mill.

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

[0037] After ball milling, a rare earth molten salt slag aqueous solution is obtained, the present application carries out screening and filtration on the rare earth molten salt slag aqueous solution, to obtain oversize and undersize, the oversize is returned to continue crushing, the undersize is placed and then filtered to obtain filtrate and water leaching residue, the water leaching residue is dried for standby, and the filtrate is returned to continue to be used, to realize the recycling of water. After obtaining the water leaching residue, the present application drops hydrochloric acid solution into the water leaching residue, and the molar concentration of the hydrochloric acid solution is preferably 1-4 mol / L. In the present application, the temperature of acid leaching is preferably 10-40℃, the acid leaching time is preferably 60-240 min, and the stirring speed is preferably 100-400 r / min. After acid leaching, solid-liquid separation is carried out by filtration to obtain acid leaching residue and acid leaching liquid, the acid leaching residue is dried for standby, a precipitant is added into the acid leaching liquid for precipitation, filtration is carried out to obtain rare earth salt precipitate and filtrate, the rare earth salt precipitate is dried for standby, and the filtrate is returned to the acid leaching process, to obtain lithium-rich liquid after multiple cycles.

[0038] In the present application, the drying temperature is preferably 100-105℃, and the drying time is preferably 240-420 min.

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

[0040] The above dried rare earth molten salt slag, rare earth salt precipitate and neodymium-iron-boron waste material treated by ball milling are uniformly mixed, then are put into a crucible and placed into a tube furnace, and are calcined under high temperature, one end of the tube furnace is connected with air, and the other end is connected with an aqueous solution, to obtain calcination product without fluorine and fluorine-containing aqueous solution (i.e. hydrofluoric acid aqueous solution) after calcination, and to obtain single rare earth oxide after elution, extraction, precipitation and ignition of the obtained calcination product.

[0041] In the present application, the mass ratio of the rare earth molten salt slag and the neodymium-iron-boron waste material in step three is preferably 1:0.05-90.

[0042] In the present application, the calcination temperature is preferably 900-1000℃, and the calcination reaction time is preferably 60-180 min.

[0043] In the present application, the ratio of the calcination product and the elution solution is preferably 1 g:1.5-18.5 mL, the concentration of the elution solution is preferably 6-12 mol / L, and the elution solution is hydrochloric acid solution.

[0044] In the present application, the temperature for the calcination product to be optimally dissolved is 80-160℃, 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 application, the technical solutions provided by the present application are described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0046] Example 1

[0047] A method for synergistically recovering valuable components from rare earth molten salt slag and neodymium-iron-boron waste, comprising the following steps:

[0048] S1, 100g of a certain rare earth molten salt slag is crushed by an e-type crusher, and then placed in a ball mill tank after crushing, then 100mL of water is added, the ball milling speed is set to 200r / min, and the ball milling time is 6h, after ball milling, the sieve is passed, the sieve is crushed and then ball milled, the sieve is filtered after standing, the filtrate and water leaching residue are obtained, the water leaching residue is dried at 105℃ for 240min, the water leaching residue after drying is 98.6g, and the filtrate is returned to the next ball milling for continuous use.

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

[0050] S3, 36g of the dried acid leaching residue of S2 is weighed, which contains 42.51% of rare earth oxides and 11.31% of fluorine, 4g of neodymium-iron-boron waste after ball milling is weighed, which contains 26.32% of rare earth oxides and 45.72% of iron, the acid leaching residue and the neodymium-iron-boron waste are uniformly mixed and then placed in a tube furnace for calcination at 1000℃ for 3h, the mass of the calcination product after the reaction is 22.4g, the fluorine content is 0.12%, and the removal rate of fluorine is 99.12%.

[0051] S4, 0.3 g of the rare earth oxalate obtained in S2 and 10 g of the calcined product obtained in S3 are weighed, and 12 mol / L hydrochloric acid solution is added for leaching treatment. The solid-liquid ratio of the calcined product and the rare earth oxalate 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, leaching solution and leaching residue are obtained by filtration. The leaching residue is 1.9 g, and the rare earth leaching rate is 98.06%.

[0052] Comparative Example 1

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

[0054] S1, 100 g of a certain rare earth molten salt slag is crushed by an e-type crusher, and then placed in a ball mill tank. Then 100 mL of water is added, the ball mill speed is set to 200 r / min, and the ball milling time is 6 h. After ball milling, the material is sieved, and the sieve residue is crushed and continuously ball milled until sieving. The sieve residue is filtered after standing, to obtain a filtrate and a water leaching residue. The water leaching residue is dried at 105°C for 240 min, and the dried water leaching residue is 98.6 g. The filtrate is returned to the next ball milling process for continuous use.

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

[0056] S3, 36 g of the dried acid leaching residue obtained in S2 is weighed, which contains 42.51% of rare earth oxides and 11.31% of fluorine. The acid leaching residue is calcined in a tube furnace at 1000°C for 3 h without adding neodymium iron boron waste. The mass of the calcined product after the reaction is 18 g, and the fluorine content is 2.44%. The fluorine removal rate is 87.86%.

[0057] S4, 0.3 g of the oxalate rare earth obtained in S2 and 10 g of the calcined product obtained in S3 were weighed, and 12 mol / L hydrochloric acid solution was added for leaching treatment. The solid-liquid ratio of the calcined product to the hydrochloric acid solution was 1 g:2.5 mL. The reaction temperature was 120°C, the reaction time was 3 h, and the stirring speed was 300 r / min. After the reaction, leaching solution and leaching residue were obtained by filtration. The leaching residue was 1.6 g, and the rare earth leaching rate was 92.59%.

[0058] Example 2

[0059] A method for synergistically recovering valuable components from rare earth molten salt slag and neodymium iron boron waste. The process flow is shown in Figure 1 , which includes the following steps:

[0060] S1, 100 g of a certain rare earth molten salt slag was crushed with a jaw crusher, then placed in a ball mill jar, and then 100 mL of water was added. The ball milling speed was set to 200 r / min, and the ball milling time was 6 h. After ball milling, the sieve was sieved, and the sieve was crushed and then ball milled again. The undersize was filtered after standing, and the filtrate and water leaching residue were obtained. The water leaching residue was dried at 105°C for 240 min. The water leaching residue was 98.6 g, and the filtrate was returned to the next ball milling for continuous use.

[0061] S2, 50 g of the dried water leaching residue obtained in S1 was weighed, which contained 38.18% of rare earth oxides and 1.21% of lithium. 2 mol / L hydrochloric acid solution was added for acid leaching treatment. The solid-liquid ratio of the rare earth molten salt slag to the hydrochloric acid solution was 1 g:2.5 mL. The reaction temperature was 30°C, the reaction time was 3 h, and the stirring speed was 300 r / min. After the reaction, acid leaching solution and acid leaching residue were obtained by filtration. The lithium content in the acid leaching residue was 0.051%, and the lithium leaching rate was 96.31%. The acid leaching residue was dried at 105°C for 240 min for standby use. Oxalic acid was added to the acid leaching solution for precipitation. The precipitation temperature was maintained at 60°C, and the oxalate rare earth was obtained by filtration. The oxalate rare earth was dried for standby use, and the filtrate was returned to the acid leaching process. After multiple cycles, lithium-rich liquid was obtained.

[0062] S3, 32 g of the dried acid leaching residue obtained in S2 was weighed, which contained 42.51% of rare earth oxides and 11.31% of fluorine. 0.3 g of the dried oxalate rare earth obtained in S2 was weighed. 8 g of neodymium iron boron waste after ball milling was weighed, which contained 26.32% of rare earth oxides and 45.72% of iron. The acid leaching residue and the neodymium iron boron waste were mixed and then placed in a tube furnace for calcination at 1000°C for 3 h. The mass of the calcined product after the reaction was 24.59 g, and the fluorine content was 0.046%. The removal rate of fluorine was 99.58%.

[0063] S4, 10 g of the calcined product obtained in S3 was weighed, and 12 mol / L hydrochloric acid solution was added for leaching treatment. The solid-liquid ratio of the calcined product to the hydrochloric acid solution was 1 g:2.5 mL. The reaction temperature was 120°C, the reaction time was 3 h, and the stirring speed was 300 r / min. After the reaction was completed, leaching solution and leaching residue were obtained by filtration. The leaching residue was 1.4 g, and the leaching rate of rare earth was 99.45%.

[0064] Example 3

[0065] A method for synergistically recovering valuable components from rare earth molten salt slag and neodymium iron boron waste, comprising the following steps:

[0066] S1, 100 g of a certain rare earth molten salt slag was crushed with a jaw crusher, and then placed in a ball mill tank. Then 100 mL of water was added, the ball mill speed was set to 200 r / min, and the ball milling time was 6 h. After ball milling, the material was sieved, and the sieve residue was crushed and continuously ball milled until sieving. The sieve residue was filtered after standing, to obtain a filtrate and a water leaching residue. The water leaching residue was dried at 105°C for 240 min. The dried water leaching residue was 98.6 g, and the filtrate was returned to the next ball milling process for reuse.

[0067] S2, 50 g of the dried water leaching residue obtained in S1 was weighed. The composition of the water leaching residue contained 38.18% of rare earth oxides and 1.21% of lithium. 2 mol / L hydrochloric acid solution was added for acid leaching treatment. The solid-liquid ratio of the rare earth molten salt slag to the hydrochloric acid solution was 1 g:2.5 mL. The reaction temperature was 30°C, the reaction time was 3 h, and the stirring speed was 300 r / min. After the reaction was completed, acid leaching solution and acid leaching residue were obtained by filtration. The lithium content in the acid leaching residue was 0.051%, and the lithium leaching rate was 96.31%. The acid leaching residue was dried at 105°C for 240 min for standby use. Oxalic acid was added to the acid leaching solution for precipitation. The precipitation temperature was maintained at 60°C, and oxalic acid rare earth was obtained by filtration. The oxalic acid rare earth was dried for standby use. The filtrate was returned to the acid leaching process, and lithium-enriched liquid was obtained after multiple cycles.

[0068] S3, 24 g of the dried acid leaching residue obtained in S2 was weighed. The composition of the acid leaching residue contained 42.51% of rare earth oxides and 11.31% of fluorine. 16 g of neodymium iron boron waste after ball milling was weighed. The composition of the neodymium iron boron waste contained 26.32% of rare earth oxides and 45.72% of iron. The acid leaching residue and the neodymium iron boron waste were mixed uniformly and placed in a tube furnace for calcination at 1000°C for 3 h. The mass of the calcined product after the reaction was 28.4 g, and the fluorine content was 0.054%. The removal rate of fluorine was 99.24%.

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

[0070] Example 4

[0071] A method for cooperatively recovering valuable components from a rare earth molten salt slag and a neodymium iron boron waste material, comprising the following steps:

[0072] S1, 100 g of a certain rare earth molten salt slag is crushed by an e-type crusher, and then is placed in a ball mill tank, 100 mL of water is added, the ball mill rotation speed is set to 200 r / min, and the ball milling time is 6 h, after the ball milling, the material is sieved, the sieve residue is crushed and continuously ball milled until sieving, the sieve residue is filtered after standing, a filtrate and a water leaching residue are obtained, the water leaching residue is dried at 105°C for 240 min, the dried water leaching residue is 98.6 g, and the filtrate is returned to the next ball milling for continuous use.

[0073] S2, 50 g of the dried water leaching residue obtained in S1 is weighed, the water leaching residue contains 38.18% of rare earth oxides and 1.21% of lithium, 1 mol / L hydrochloric acid solution is added for acid leaching treatment, the solid-liquid ratio of the rare earth molten salt slag to the hydrochloric acid solution is 1 g:5 mL, the reaction temperature is 30°C, the reaction time is 3 h, and the stirring speed is 300 r / min, after the reaction, a filtration is performed to obtain an acid leaching solution and an acid leaching residue, the lithium content in the acid leaching residue is 0.041%, the lithium leaching rate is 97.25%, the acid leaching residue is dried at 105°C for 240 min for standby use, oxalic acid is added to the acid leaching solution for precipitation, the precipitation temperature is maintained at 60°C, a rare earth oxalate is obtained by filtration, the rare earth oxalate is dried for standby use, and the filtrate is returned to the acid leaching process, and after multiple cycles, a lithium-enriched solution is obtained, and the lithium concentration can reach more than 10 g / L;

[0074] S3, 28 g of the dried acid leaching residue obtained in S2 is weighed, the acid leaching residue contains 42.51% of rare earth oxides and 11.31% of fluorine, 12 g of the ball milled neodymium iron boron waste material is weighed, the neodymium iron boron waste material contains 26.32% of rare earth oxides and 45.72% of iron, the acid leaching residue and the neodymium iron boron waste material are uniformly mixed, and then are placed in a tube furnace and calcined at 1000°C for 3 h, after the reaction, the mass of the calcined product is 26.4 g, the fluorine content is 0.064%, and the fluorine removal rate is 99.28%.

[0075] S4, 0.3 g of the oxalate rare earth obtained in S2 and 10 g of the calcined product obtained in S3 are weighed, and 12 mol / L hydrochloric acid solution is added for leaching 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, leaching solution and leaching residue are obtained by filtration. The leaching residue is 1.8 g, and the leaching rate of rare earth is 98.97%.

[0076] As can be seen from the above examples and comparative examples, by accurately controlling the process conditions, the enrichment of lithium-containing solution can be effectively realized, and the concentration of lithium solution can reach more than 10 g / L. In addition, by adjusting the addition amount of neodymium iron boron waste to cooperate with the calcination treatment of rare earth molten salt residue, the removal efficiency of fluorine element can be significantly improved, and the removal rate of fluorine is more than 99%. Under the condition of hydrochloric acid leaching, the leaching rate of rare earth is also improved, reaching more than 98%. These results show that by optimizing the process parameters, efficient separation and recovery of lithium, fluorine and rare earth in rare earth molten salt residue can be realized.

Claims

1. A method for collaboratively 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, 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 an oversize and undersize. The oversize is returned for further crushing. The undersize is allowed to stand and filtered to obtain a filtrate and a water-leached residue. The water-leached residue is dried for later use, and the filtrate is returned to the ball mill for recycling. The composition of the rare earth molten salt slag includes F: 5% to 50%, Li: 0.1% to 5%, and RE: 1% to 60%. 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 tube furnace. They are calcined under high temperature conditions. Air is introduced into one end of the tube furnace and an aqueous solution is connected to the other end. After calcination, a fluorine-free calcined product and a fluorine-containing aqueous solution are obtained. The NdFeB waste is a recycled material from the production and processing of NdFeB referred to in the national standard GB / T 23588-2020, and the iron content is 15-99%; the mass ratio of the rare earth molten salt slag to the NdFeB waste in step 3 is 1:0.05-100; the calcination reaction temperature is 800-1100°C; 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 subjected to dissolution, extraction, precipitation, and calcination to obtain a single rare earth oxide, wherein the solution used for the dissolution is one or more of hydrochloric acid, sulfuric acid, and nitric acid; 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.

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 water leaching residue to the acid used for acid leaching is 1g:1-10 mL, the concentration of the acid used for acid leaching is 1-6 mol / 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: In step 3, the calcination reaction time is 60 to 240 minutes.

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 5, the ratio of the calcined product to the optimal solution is 1 g: 1-20 mL, and the concentration of the optimal solution is 6-12 mol / L.

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