A method for leaching rare earth from NdFeB waste iron tailings

Abstract

The present invention relates to a method for leaching rare earth in NdFeB waste iron tailings, the method comprising the following steps: (1) drying the NdFeB waste iron tailings to obtain iron tailings material; (2) dry ball milling the iron tailings material obtained in step (1), and obtaining activated iron tailings material after ball material separation; (3) mixing an acid solution having a pH value of 1-3 with the activated iron tailings material obtained in step (2), and performing solid-liquid separation to obtain a rare earth-containing leachate and leach residue. The present invention combines mechanical activation with acid leaching, utilizes mechanical activation to change the chemical stability of the iron tailings, combines the reasonable pH value of the acid solution with the preparation process parameters, ensures a high rare earth element leaching rate under dilute acid excellent dissolution conditions, and the obtained rare earth-containing leachate can directly flow into the extraction and separation process without going through an iron removal process, thereby reducing production costs.

Description

Technical Field

[0001] The invention relates to the technical field of industrial waste slag recovery, and in particular to a method for leaching rare earth from NdFeB waste iron tailings. Background Art

[0002] NdFeB permanent magnet materials are widely used in new energy, consumer electronics, wind power generation and other fields due to their high coercivity and high magnetic energy product. In the production process of NdFeB permanent magnet materials, about 30% of waste will be generated, which contains about 1% boron, 60-70% iron, 20-30% rare earth elements such as praseodymium, neodymium, dysprosium, etc., and a small amount of impurities such as silicon, aluminum, cobalt, etc., and has a very high recycling value.

[0003] At present, the industry usually adopts the hydrochloric acid dissolution method to recover rare earth elements from waste materials. The process route is: oxidative roasting-hydrochloric acid dissolution-extraction separation-precipitation roasting. Among them, the slag obtained after the hydrochloric acid dissolution process is called iron tailings, whose main component is iron oxide, and the rare earth oxide content is 0.3-2%. Although the rare earth grade is still advantageous compared with natural rare earth ores, the residual rare earth in the iron tailings is not completely oxidized and the presence of a large amount of chemically stable iron oxide causes a coating effect. It is no longer possible to effectively extract the residual rare earth from the iron tailings simply by hydrochloric acid dissolution. Therefore, developing an efficient and low-cost way to extract rare earths from iron tailings is the key to improving the recycling value of iron tailings.

[0004] CN 105039727A discloses a process for recovering rare earths from ultra-low-content NdFeB waste slag, the steps of which are: mixing iron slag, an extractant and water, stirring and filtering to obtain solid A1 and liquid B1; mixing solid A1 and water for washing, and mixing the washed liquid with liquid B1 to form liquid B2; shrinking and enriching liquid B2 and a shrinkage enrichment agent for enrichment and recovery to produce solid A2 and liquid B3; mixing solid A2, a dissolving agent, water, an oxidant and a neutralizing agent in sequence for modulation to obtain solid A3 and liquid B4; liquid B4 then enters line A and / or line B for extraction and separation; and through precipitation and calcination processes, praseodymium-neodymium oxide, dysprosium oxide, gadolinium oxide and terbium oxide are obtained. This method uses inorganic acid to extract rare earths from iron tailings. Although increasing the acid concentration can more effectively dissolve the rare earths, a large amount of impurities such as iron are also dissolved, which greatly increases the subsequent impurity removal cost and has poor economic benefits.

[0005] CN 103184343A discloses a method for recovering rare earth, thorium and iron from waste residue of rare earth acid process, which is characterized by: using waste residue produced by rare earth acid process as raw material, mixing the waste residue of rare earth acid process with one or more mixed acid solutions of HCl, H2SO4 and HNO3, stirring and leaching at a temperature of 60°C to boiling, filtering and washing the filter cake to obtain a leachate and secondary waste residue; extracting the leachate with primary amine, and stripping with nitric acid to obtain a thorium nitrate solution; adjusting the pH of the thorium extract residue to 4.5-5.5 with alkali, and precipitating Fe(OH)3 byproduct; and the filtrate is a rare earth feed liquid product. However, the invention directly uses acid leaching to recover rare earth, and its leaching rate needs to be improved.

[0006] CN 105734296A discloses a comprehensive utilization method of NdFeB waste acid leaching residue, wherein the iron tailings are sequentially subjected to sulfuric acid leaching, reduction, impurity removal and oxidation to prepare iron red, and rare earth sulfate in the acid leaching residue is dissolved by filtering and washing, and the filtrate obtained after separation is sent to a rare earth extraction process for preparing rare earth products. However, the iron oxide in the invention is relatively stable, and the conventional sulfuric acid leaching method will result in low leaching rates of iron, cobalt and rare earth, and high costs.

[0007] In view of the shortcomings of the existing technology, it is necessary to provide a method for extracting rare earth from iron tailings with high rare earth leaching rate and low cost. Summary of the invention

[0008] The purpose of the present invention is to provide a method for leaching rare earths in NdFeB waste iron tailings, which combines mechanical activation with acid leaching and controls the pH of the acid solution and preparation process parameters, thereby achieving efficient and low-cost leaching of rare earths in NdFeB waste iron tailings.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for leaching rare earth in NdFeB waste iron tailings, the method comprising the following steps:

[0011] (1) drying the NdFeB waste iron tailings to obtain iron tailings material;

[0012] (2) dry-milling the iron tailings obtained in step (1) to obtain activated iron tailings after ball milling;

[0013] (3) mixing an acid solution having a pH value of 1-3 with the activated iron tailings obtained in step (2), and performing solid-liquid separation to obtain a rare earth-containing leaching solution and leaching residue.

[0014] The method provided by the present invention first dries the NdFeB iron waste iron tailings to remove moisture, and then destroys the chemical stability of the NdFeB iron waste tailings through the physical and chemical changes produced in the mechanical activation process, so that rare earths can be effectively extracted under milder conditions in the subsequent acid leaching process, and the rare earth elements in the NdFeB iron waste tailings are dissolved by acid and enter the leaching solution in the form of ions, and the iron oxide in the NdFeB iron waste tailings is basically unreacted and remains in the slag phase. The method adopted by the present invention is efficient and low-cost, significantly improves the utilization rate of the NdFeB iron waste tailings, and avoids waste of resources.

[0015] The pH value of the acid solution in step (3) is 1-3, for example, 1, 1.5, 2, 2.5 or 3, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] In the present invention, the pH value of the added acid solution is controlled to be 1-3, which can ensure the rare earth leaching effect while avoiding the dissolution of a large amount of iron.

[0017] The rare earth-containing leaching solution obtained in step (3) can be directly fed into the extraction and separation process for further purification to produce rare earth products; the obtained leaching residue contains a large amount of valuable metals such as iron and cobalt, which can be recycled.

[0018] Preferably, the NdFeB waste iron tailings in step (1) are obtained by acid dissolving the NdFeB waste.

[0019] Preferably, the rare earth oxide content of the NdFeB waste iron tailings in step (1) is ≥0.3%, for example, it can be 0.3%, 0.5%, 0.6%, 0.8%, 1%, or 1.2%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] The iron oxide content in the NdFeB waste iron tailings is 70-75%, the moisture content is 13-15%, the rare earth elements in the rare earth oxides include lanthanum, cerium, praseodymium, neodymium, gadolinium, etc., and the impurities include aluminum, silicon, calcium, chlorine, cobalt, copper, zinc, titanium, chromium, etc.

[0021] Preferably, the drying process in step (1) is performed until the NdFeB waste iron tailings have a constant weight.

[0022] The drying process described in the present invention adopts a heating drying method, which is a conventional technical means in the field.

[0023] Preferably, the mass ratio of the balls in the dry ball milling in step (2) is 1:(2-60), for example, it can be 1:2, 1:5, 1:10, 1:20, 1:30, 1:40, 1:50 or 1:60, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] Preferably, the dry ball milling in step (2) is carried out in any one of a planetary ball mill, a drum ball mill or a stirred ball mill.

[0025] Preferably, the rotation speed of the dry ball milling in step (2) is 30-1000 rpm, for example, it can be 30 rpm, 100 rpm, 300 rpm, 500 rpm, 800 rpm or 1000 rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the dry ball milling time in step (2) is 0.5-50 h, for example, 0.5 h, 5 h, 10 h, 20 h, 30 h, 40 h or 50 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, the solid-to-liquid ratio of the activated iron tailings to the acid solution in step (3) is 1g:(1-10)mL, for example, it can be 1g:1mL, 1g:3mL, 1g:5mL, 1g:8mL or 1g:10mL, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, the acid in the acid solution in step (3) comprises an inorganic acid and / or an organic acid.

[0029] Preferably, the inorganic acid comprises hydrochloric acid and / or nitric acid.

[0030] Preferably, the organic acid comprises citric acid and / or lactic acid.

[0031] Preferably, the mixing temperature in step (3) is 20-100°C, for example, 20°C, 40°C, 60°C, 80°C or 100°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the mixing time in step (3) is 0.5-10 h, for example, 0.5 h, 3 h, 5 h, 8 h or 10 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] The mixing is continuous stirring.

[0034] Preferably, the solid-liquid separation method in step (3) includes any one of suction filtration, filter press or centrifugation, or a combination of at least two of them. Typical but non-limiting combinations include a combination of suction filtration and centrifugation, a combination of filter press and centrifugation, or a combination of suction filtration, filter press and centrifugation.

[0035] As a preferred technical solution of the method of the present invention, the method comprises the following steps:

[0036] (1) drying the NdFeB waste iron tailings to a constant weight to obtain iron tailings material;

[0037] The NdFeB waste iron tailings are obtained by acid dissolving the NdFeB waste; the content of rare earth oxides in the NdFeB waste iron tailings is ≥0.3%;

[0038] (2) dry-milling the iron tailings obtained in step (1) at a rotation speed of 30-1000 rpm for 0.5-50 h, and obtaining activated iron tailings after ball-to-ball separation; the ball-to-ball mass ratio of the dry-milling process is 1:(2-60);

[0039] (3) mixing an acid solution having a pH value of 1-3 with the activated iron tailings obtained in step (2) at 20-100° C. for 0.5-10 h, and performing solid-liquid separation to obtain a rare earth-containing leaching solution and leaching residue; the solid-liquid ratio of the activated iron tailings to the acid solution is 1 g:(1-10) mL.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The method for leaching rare earths in NdFeB waste iron tailings provided by the present invention combines mechanical activation with acid leaching, utilizes mechanical activation to change the chemical stability of the iron tailings, combines the reasonable pH value of the acid solution with the preparation process parameters, ensures that the leaching rate of rare earth elements is as high as 85% under the condition of dilute acid optimal solution, and the obtained rare earth-containing leachate can directly flow into the extraction and separation process without undergoing an iron removal process, thereby greatly reducing the production cost; the method of the present invention has simple process, conventional equipment, high economic practicality, and can be used for industrial resource recovery and utilization of iron tailings. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0043] In the embodiment provided by the present invention, the NdFeB waste iron tailings are obtained after acid dissolution treatment of NdFeB waste; the chemical composition (mass percentage) of the NdFeB waste iron tailings is 73% iron oxide content, 1% rare earth oxide content, 14% moisture, and the remainder is impurities.

[0044] Example 1

[0045] This embodiment provides a method for leaching rare earth in NdFeB waste iron tailings, the method comprising the following steps:

[0046] (1) drying the NdFeB waste iron tailings to a constant weight to obtain iron tailings material;

[0047] (2) dry-milling the iron tailings obtained in step (1) in a planetary ball mill at a rotation speed of 500 rpm for 25 h, and obtaining activated iron tailings after ball-to-ball separation; the ball-to-material mass ratio of the dry-milling process is 1:25;

[0048] (3) mixing a hydrochloric acid solution having a pH value of 1 with the activated iron tailings obtained in step (2) at 90° C. for 3 h, and obtaining a rare earth-containing leaching solution and leaching residue by suction filtration; the solid-to-liquid ratio of the activated iron tailings to the acid solution is 1 g:4 mL.

[0049] Example 2

[0050] This embodiment provides a method for leaching rare earth in NdFeB waste iron tailings, the method comprising the following steps:

[0051] (1) drying the NdFeB waste iron tailings to a constant weight to obtain iron tailings material;

[0052] (2) dry-milling the iron tailings obtained in step (1) in a planetary ball mill at a rotation speed of 200 rpm for 40 h, and obtaining activated iron tailings after ball-to-ball separation; the ball-to-material mass ratio of the dry-milling process is 1:10;

[0053] (3) mixing a hydrochloric acid solution having a pH value of 1 with the activated iron tailings obtained in step (2) at 40° C. for 8 hours, and obtaining a rare earth-containing leaching solution and leaching residue by suction filtration; the solid-to-liquid ratio of the activated iron tailings to the acid solution is 1 g:8 mL.

[0054] Example 3

[0055] This embodiment provides a method for leaching rare earth in NdFeB waste iron tailings, the method comprising the following steps:

[0056] (1) drying the NdFeB waste iron tailings to a constant weight to obtain iron tailings material;

[0057] (2) dry-milling the iron tailings obtained in step (1) in a planetary ball mill at a rotation speed of 800 rpm for 10 h, and obtaining activated iron tailings after ball-to-ball separation; the ball-to-material mass ratio of the dry-milling process is 1:40;

[0058] (3) mixing a hydrochloric acid solution having a pH value of 1 with the activated iron tailings obtained in step (2) at 70° C. for 5 hours, and obtaining a rare earth-containing leaching solution and leaching residue by suction filtration; the solid-to-liquid ratio of the activated iron tailings to the acid solution is 1 g:2 mL.

[0059] Example 4

[0060] This embodiment provides a method for leaching rare earth in NdFeB waste iron tailings, the method comprising the following steps:

[0061] (1) drying the NdFeB waste iron tailings to a constant weight to obtain iron tailings material;

[0062] (2) dry-milling the iron tailings obtained in step (1) in a drum ball mill at a rotation speed of 30 rpm for 50 h, and obtaining activated iron tailings after ball-to-ball separation; the ball-to-ball mass ratio of the dry-milling material is 1:2;

[0063] (3) mixing a hydrochloric acid solution having a pH value of 1 with the activated iron tailings obtained in step (2) at 20° C. for 10 hours, and obtaining a rare earth-containing leaching solution and leaching residue by suction filtration; the solid-to-liquid ratio of the activated iron tailings to the acid solution is 1 g:10 mL.

[0064] Example 5

[0065] This embodiment provides a method for leaching rare earth in NdFeB waste iron tailings, the method comprising the following steps:

[0066] (1) drying the NdFeB waste iron tailings to a constant weight to obtain iron tailings material;

[0067] (2) dry-milling the iron tailings obtained in step (1) in a drum ball mill at a rotation speed of 1000 rpm for 0.5 h, and obtaining activated iron tailings after ball-material separation; the mass ratio of the material and the ball in the dry-milling process is 1:60;

[0068] (3) mixing a hydrochloric acid solution having a pH value of 1 with the activated iron tailings obtained in step (2) at 100° C. for 0.5 h, and obtaining a rare earth-containing leaching solution and leaching residue by suction filtration; the solid-to-liquid ratio of the activated iron tailings to the acid solution is 1 g:1 mL.

[0069] Example 6

[0070] This embodiment provides a method for leaching rare earths from NdFeB waste iron tailings. The difference from Embodiment 1 is that, except for adjusting the pH value of the hydrochloric acid solution in step (3) to 3, the rest is the same as Embodiment 1.

[0071] Example 7

[0072] This embodiment provides a method for leaching rare earths in NdFeB waste iron tailings. The difference from Embodiment 1 is that except for replacing the pH value of the hydrochloric acid solution in step (3) with a nitric acid solution, the rest is the same as Embodiment 1.

[0073] Example 8

[0074] This embodiment provides a method for leaching rare earths from NdFeB waste iron tailings. The difference from Embodiment 1 is that except for replacing the pH value of the hydrochloric acid solution in step (3) with a citric acid solution, the rest is the same as Embodiment 1.

[0075] Example 9

[0076] This embodiment provides a method for leaching rare earths in NdFeB waste iron tailings. The difference from Embodiment 1 is that except for replacing the pH value of the hydrochloric acid solution in step (3) with a lactic acid solution, the rest is the same as Embodiment 1.

[0077] Comparative Example 1

[0078] This comparative example provides a method for leaching rare earths from NdFeB waste iron tailings. The difference from Example 1 is that the method does not include step (2), and the rest is the same as Example 1.

[0079] Comparative Example 2

[0080] This comparative example provides a method for leaching rare earths from NdFeB waste iron tailings, which is different from Example 1 in that, except for adjusting the pH of the hydrochloric acid solution in step (3) to 4, the rest is the same as Example 1.

[0081] Comparative Example 3

[0082] This comparative example provides a method for leaching rare earths in NdFeB waste iron tailings, which is different from Example 1 in that, except for adjusting the hydrogen ion concentration of the hydrochloric acid solution in step (3) to 1 mol / L, the rest is the same as Example 1.

[0083] The method for leaching rare earths from NdFeB waste iron tailings provided in Examples 1-9 and Comparative Examples 1-3 was used to obtain a rare earth-containing leaching solution and leaching residue. The samples were measured and calculated according to JY / T 0567-2020 to obtain the leaching rates of rare earth oxides and iron oxide. The results are shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] As can be seen from Table 1, the method for leaching rare earths from NdFeB waste iron tailings provided by the present invention changes the chemical stability of NdFeB waste iron tailings by mechanical activation, so that rare earth elements have a higher leaching rate under dilute acid optimal dissolution conditions, and the obtained rare earth-containing leachate can be directly flowed into the extraction and separation process without iron removal, thereby reducing production costs;

[0088] By comparing Example 1 with Example 6 and Comparative Examples 2 and 3, it can be seen that the pH value of the hydrochloric acid solution has a certain influence on the leaching effect of rare earth oxides. When the pH value of the hydrochloric acid solution is within a reasonable range, a higher leaching rate can be obtained. When the pH value of the hydrochloric acid solution is lower than 1, it will cause a large dissolution of iron in the iron tailings, increase the cost of impurity removal, and when the pH value of the hydrochloric acid solution is too high, the leaching rate of rare earth oxides will decrease significantly. By comparing Example 1 with Examples 7-9, it can be seen that using nitric acid, citric acid and lactic acid as leaching agents can still effectively ensure that the rare earth oxides have a higher leaching rate.

[0089] By comparing Example 1 with Comparative Example 1, it can be seen that if the NdFeB waste iron tailings are not treated by dry ball milling, it will be difficult to change its chemical stability, thereby increasing the difficulty of rare earth leaching and significantly reducing the leaching rate.

[0090] In summary, the method for leaching rare earths in NdFeB waste iron tailings provided by the present invention combines mechanical activation with acid leaching, utilizes mechanical activation to change the chemical stability of the iron tailings, and combines the reasonable pH value of the acid solution with the preparation process parameters to ensure that the rare earth element leaching rate is as high as 85% under the conditions of dilute acid optimal dissolution. The obtained rare earth-containing leachate can directly flow into the extraction and separation process without undergoing an iron removal process, thereby greatly reducing the production cost. The method described in the present invention has a simple process, conventional equipment, and high economic practicality, and can be used for industrial resource recovery and utilization of iron tailings.

[0091] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for leaching rare earth from NdFeB waste iron tailings, characterized in that: The method comprises the following steps: (1) drying the NdFeB waste iron tailings to obtain iron tailings material; (2) dry-milling the iron tailings obtained in step (1) to obtain activated iron tailings after ball milling; (3) mixing an acid solution having a pH value of 1-3 with the activated iron tailings obtained in step (2), and performing solid-liquid separation to obtain a rare earth-containing leaching solution and leaching residue; The iron oxide leaching rate in the NdFeB waste iron tailings is 0.091%.

2. The method according to claim 1, characterized in that: The NdFeB waste iron tailings in step (1) are obtained by acid dissolving the NdFeB waste.

3. The method according to claim 1, characterized in that The rare earth oxide content of the NdFeB waste iron tailings in step (1) is ≥0.3%.

4. The method according to claim 1, characterized in that: The drying process in step (1) is performed until the NdFeB waste iron tailings have a constant weight.

5. The method according to claim 1, characterized in that The mass ratio of the balls in the dry ball milling in step (2) is 1:(2-60).

6. The method according to claim 1, characterized in that The dry ball milling in step (2) is carried out in any one of a planetary ball mill, a drum ball mill or a stirring ball mill.

7. The method according to claim 1, characterized in that The rotation speed of the dry ball milling in step (2) is 30-1000 rpm.

8. The method according to claim 1, characterized in that: The dry ball milling time in step (2) is 0.5-50h.

9. The method according to claim 1, characterized in that: The solid-to-liquid ratio of the activated iron tailings to the acid solution in step (3) is 1 g:(1-10) mL.

10. The method according to claim 1, characterized in that The acid in the acid solution in step (3) includes an inorganic acid and / or an organic acid.

11. The method according to claim 10, characterized in that The inorganic acid includes hydrochloric acid and / or nitric acid.

12. The method according to claim 10, characterized in that The organic acid includes citric acid and / or lactic acid.

13. The method according to claim 1, characterized in that The mixing temperature in step (3) is 20-100°C.

14. The method according to claim 1, characterized in that The mixing time in step (3) is 0.5-10h.

15. The method according to claim 1, characterized in that The method comprises the following steps: (1) drying the NdFeB waste iron tailings to a constant weight to obtain iron tailings material; The NdFeB waste iron tailings are obtained by acid dissolving the NdFeB waste; the content of rare earth oxides in the NdFeB waste iron tailings is ≥0.3%; (2) dry-milling the iron tailings obtained in step (1) at a rotation speed of 30-1000 rpm for 0.5-50 h, and obtaining activated iron tailings after ball-to-ball separation; the ball-to-ball mass ratio of the dry-milling process is 1:(2-60); (3) mixing an acid solution having a pH value of 1-3 with the activated iron tailings obtained in step (2) at 20-100° C. for 0.5-10 h, and performing solid-liquid separation to obtain a rare earth-containing leaching solution and leaching residue; the solid-liquid ratio of the activated iron tailings to the acid solution is 1 g:(1-10) mL.

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