A method for separating neodymium, iron and gallium from gallium-containing NdFeB production waste

Abstract

The present invention discloses a method for separating neodymium, iron and gallium from gallium-containing NdFeB production waste. The present invention uses gallium-containing NdFeB production waste as raw material for oxidation roasting, and then obtains NdFeB roasted material powder through crushing and screening processes. After the NdFeB oxidized roasted powder is leached with acid, an oxidant is added to it to ensure that the Fe in the solution is 2+ Oxidized to Fe 3+ Subsequently, the pH was adjusted with an alkaline solution, causing Nd to enter the solution and Fe and Ga to enter the slag. pH-adjusted slag was obtained by centrifugal separation. The pH-adjusted slag was then back-leached to separate Fe and Ga. Analysis of the results showed that Nd had a good separation effect from Fe and Ga, with a separation rate of over 90%, indicating good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of rare metal separation, and more particularly to a method for separating neodymium, iron and gallium from gallium-containing NdFeB production waste. Background Art

[0002] Gallium is an indispensable material with a wide range of applications in high-tech fields such as infrared optics, fiber optic systems, detectors, and semiconductor devices (including transistors, diodes, and rectifiers). With the rapid development of these fields in the coming years, the demand for gallium is expected to increase significantly, and therefore, the utilization of gallium resources has attracted considerable attention. Currently, gallium is mainly recovered through extraction from various by-products of bauxite hydrometallurgy, and improvements to existing processes are unlikely to increase production on a large scale. Therefore, to meet the growing demand for gallium, new methods need to be developed to recover gallium from gallium-containing resources. When recovering gallium from secondary resources, the separation of gallium from other elements has attracted widespread attention.

[0003] Neodymium iron boron (NdFeB) permanent magnets are widely used in modern industry and electronics due to their extremely high magnetic energy product, coercivity, and energy density. To enhance NdFeB's magnetic properties and corrosion resistance, a certain amount of gallium is often added to it. However, the cutting, grinding, and polishing processes generate a large amount of NdFeB waste, accounting for approximately 30% of the raw material. Element separation is one of the major challenges in recycling this NdFeB production waste.

[0004] At present, the recycling industry of gallium-containing NdFeB waste mainly involves oxidizing and roasting gallium-containing NdFeB waste to obtain its oxidation product, and then using acid leaching to dissolve the gallium-containing NdFeB oxidation roasting product. The leaching solution contains Fe 2 + 、Fe 3+ 、Nd 3+ 、Ga 3+ Plasma, this part of the ions usually needs to be separated by adding oxalic acid, calcium hydroxide, etc. to form a precipitate or use extraction method to separate, resulting in high cost, low separation degree, and large drug consumption, which to a certain extent limits the comprehensive recycling and utilization of NdFeG. Summary of the Invention

[0005] The present invention solves the above-mentioned problems existing in the prior art. The purpose of the present invention is to provide a method for separating neodymium, iron and gallium from gallium-containing NdFeB oxidized roasted material, realizing a method for separating neodymium, iron and gallium from NdFeB hydrochloric acid leachate by adjusting the pH only without adding oxalic acid or calcium hydroxide.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for separating neodymium, iron and gallium from gallium-containing NdFeB production waste comprises the following steps:

[0008] 1) Oxidative roasting of gallium-containing NdFeB production waste;

[0009] 2) crushing the waste after oxidation roasting and leaching it with acid, and filtering the leached residue;

[0010] 3) The filtered solution is oxidized with an oxidant, and the pH is adjusted with an alkaline solution to separate the solid and liquid. Nd enters the solution, and Fe and Ga enter the pH adjustment slag. The pH adjustment slag is then back-leached to separate Fe and Ga.

[0011] Step 1) The gallium-containing NdFeB production waste is subjected to oxidation roasting in an air atmosphere, the oxidation roasting temperature is 450-700° C., preferably 700° C., and the oxidation roasting time is 1-3 hours, preferably 2 hours.

[0012] Step 2) crushing the particles to a size of 200 to 300 mesh.

[0013] Preferably, the crushing ball mill uses a planetary ball mill, the rotation speed of the planetary ball mill is 200-300 r / min, and the ball milling time is 4-6 hours.

[0014] The acid used in step 2) includes hydrochloric acid and sulfuric acid, preferably hydrochloric acid, with an acid concentration of 3 to 10 mol / L. The solid-liquid ratio of hydrochloric acid to gallium-containing NdFeB oxidized calcined powder (unit: g / ml) is 1:1 to 1:7, preferably 1:2 to 1:5.

[0015] In step 2) the acid leaching process, the leaching temperature is 50-90° C., preferably 60-80° C.; the leaching time is 3-24 hours, preferably 6-18 hours.

[0016] Preferably, after acid leaching, a water filter membrane is used for suction filtration, the pore size of the filter membrane is 0.22 to 0.88 μm, and the pressure of the suction filter is 1 MPa.

[0017] The oxidant used in step 3) includes NaOH, Na2CO3, NaHCO3, preferably NaClO3.

[0018] The purpose of using oxidants is to oxidize Fe 2+ Oxidized to Fe 3+ The oxidant only needs to be not easily decomposed by heat during the leaching process and have a high 2+ It has a good oxidation effect and does not introduce new impurity elements.

[0019] During the oxidation roasting process, it is not possible to ensure that all elements in gallium-containing NdFeB waste are oxidized to the highest valence. If only air is introduced, the oxidation rate will be slow. According to the E-pH diagram, the pH of precipitation of elements in different valence states is different. 2+ The precipitation of Fe 3+ The pH at which precipitation begins to occur is approximately 1.5, so oxidation of the ferrous ions is necessary.

[0020] Oxidant dosage and Fe 2+ Theoretically, Fe 2+ The mass ratio of sodium chlorate to sodium chloride is 3.18:1. Generally, the amount of sodium chlorate used is 0.5 to 2 times the theoretical mass. The oxidation temperature is 50 to 90°C, preferably 60 to 80°C; the oxidation time is 1 to 10 minutes, preferably 3 to 7 minutes.

[0021] Preferably, during the oxidation acid leaching process, the solution in the container is in a stirring state, and the stirring rotor speed is 100 to 600 r / min, more preferably 200 to 400 r / min.

[0022] The alkaline solution used in step 3) includes NaOH, Na2CO3, and NaHCO3; preferably, it is a NaOH solution with a concentration of 1 to 10 mol / L.

[0023] Use an alkaline solution to adjust the pH to 2-5, preferably to 3-4.

[0024] Preferably, when adjusting the pH, the solution is stirred at room temperature, the stirring rotor speed is 100-600 r / min, and the initial pH value should be negative; the NaOH solution is slowly added dropwise into the container.

[0025] After the pH of the alkaline solution is adjusted, the centrifugal separation process is as follows: 2 to 6 50 ml centrifuge tubes are used, the liquid in the container is poured into the tubes, and separation is performed using a centrifuge. The centrifuge speed is maintained at 7000 r / min, and the centrifugation time is 1 to 10 minutes, more preferably 2 to 8 minutes.

[0026] Preferably, the pH adjustment residue is dried at 40-80° C. for 2-4 days.

[0027] Step 3) The pH adjusted slag after drying is subjected to back leaching, and the back leaching agent used is preferably HCl or NaOH, the leaching temperature is 10-90° C., preferably 30-80° C.; and the leaching time is 3-24 hours, preferably 6-18 hours.

[0028] The solid-liquid ratio (g / ml) of HCl or NaOH to the pH-adjusted slag is 1:1 to 1:7, and more preferably 1:2 to 1:5.

[0029] Preferably, the back-leaching product is centrifuged using 2 to 6 50 ml centrifuge tubes, the liquid in the container is poured into the tubes, and a centrifuge is used for separation, the centrifuge speed is maintained at 7000 r / min, and the centrifugation time is 1 to 10 min, more preferably 2 to 8 min.

[0030] Preferably, the leaching residue is dried at 40-80° C. for 2-4 days.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1) The present invention provides a method for separating neodymium, iron, and gallium from gallium-containing NdFeB production waste. This method utilizes the principle that Nd, Fe, and Ga in gallium-containing NdFeB have different solubility products in an aqueous solution system. Substances with larger solubility product constants are more likely to form precipitates. Gallium-containing NdFeB oxidized and roasted powder is dissolved in acid, and the pH is adjusted to allow Nd to enter the solution and Fe and Ga to enter the pH-adjusted slag. The pH-adjusted slag is then back-leached to achieve the separation of Fe and Ga. The entire process achieves the separation and recycling of Nd, Fe, and Ga in gallium-containing NdFeB, and is characterized by ease of operation, simple principle, and low cost.

[0033] The reaction formula of the leaching process is as follows:

[0034] Nd2O3+6H + =2Nd 3+ +3H2O

[0035] Fe2O3+6H + =2Fe 3+ +3H2O

[0036] FeNdO3+6H + =Fe 3+ +Nd 3+ +3H2O

[0037] Ga2O3+6H + =2Ga 3+ +3H2O

[0038] FeO+2H + =Fe 2+ +H2O

[0039] The oxidation process reacts as follows:

[0040] 6Fe 2+ +6H ++ClO3 - =6Fe 3+ +3H2O+Cl -

[0041] The pH adjustment process reacts as follows:

[0042] Nd 3+ +3OH - =Nd(OH)3

[0043] Fe 3+ +3OH - =Fe(OH)3

[0044] Ga 3+ +3OH - =Ga(OH)3

[0045] The reaction during the back immersion process is as follows:

[0046] Ga(OH)3+3H + =Ga 3+ +3H2O

[0047] Ga(OH)3+OH - =Ga(OH)4 -

[0048] (The main purpose of the back leaching process is to enrich gallium)

[0049] The solubility product constants of common hydroxides are shown in the table below:

[0050]

[0051] According to the advantage range shown in the E-pH diagram, although Nd 3+ Precipitation begins at pH 0.6, but due to the solubility product, Fe 3+ In fact, Fe will precipitate before Nd. When the pH of the solution is low, the system will be in a colloidal state and no precipitation can be formed. When the pH is further increased, Fe 3+ Start to precipitate in large quantities. Usually, Fe 3+ 、Al 3+ 、Ga 3+ will preferentially form a precipitate, while Nd will remain in solution.

[0052] 2) The present invention provides a method for separating neodymium, iron, and gallium from gallium-containing NdFeB oxidized roasted material. This method does not introduce new impurity ions into the system during the process, and does not require significant energy consumption for the treatment of leached and adjusted slag, making it environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a flow chart of the present invention.

[0054] Figure 2 This is the XRD distribution diagram of the gallium-containing NdFeB oxidized calcined powder of the present invention.

[0055] Figure 3 This is the distribution diagram of acid leaching residue after hydrochloric acid leaching of gallium-containing NdFeB oxidized roasted powder.

[0056] Figure 4 This is the E-pH diagram of the Nd-Fe-Ga-H2O system. DETAILED DESCRIPTION

[0057] The present invention will be further described below with reference to the accompanying drawings and specific examples, but the examples do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0058] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0059] Example 1

[0060] A method for separating neodymium, iron and gallium from gallium-containing NdFeB oxidized roasted material comprises the following steps:

[0061] Step 1: The gallium-containing NdFeB oxidized calcined powder is oxidized and calcined in an air atmosphere at a temperature of 700° C. for 2 hours. The gallium-containing NdFeB oxidized calcined material is placed in a ball mill, ball milled at a speed of 250 r / min for 6 hours using a planetary ball mill, and passed through a 200-mesh sieve to obtain the gallium-containing NdFeB oxidized calcined powder.

[0062] The composition of the gallium-containing NdFeB oxidized calcined powder is shown in Table 1;

[0063] Table 1

[0064]

[0065] Step 2: Add gallium-containing NdFeB oxidized calcined powder into a conical flask, and add 10 mol / L hydrochloric acid at a liquid-solid ratio of HCl: gallium-containing NdFeB oxidized calcined powder of 3:1;

[0066] Step 3: Place the conical flask in an oil bath stirring pot and perform hydrochloric acid leaching for 6 hours at a leaching temperature of 80°C;

[0067] Step 4: After the reaction process is completed, the solution is centrifuged, washed with water and ethanol three times respectively, and dried at 65°C for 24 hours to obtain hydrochloric acid leaching solution and hydrochloric acid leaching residue;

[0068] The compositions of the hydrochloric acid leaching solution and the hydrochloric acid leaching residue are shown in Table 2 and Table 3, respectively;

[0069] Table 2

[0070]

[0071] Table 3

[0072]

[0073] Step 5: When adding 4 g of NaClO3 to 300 mL of hydrochloric acid leachate, ensure that the stirring rotor rotates at 200 r / min, the oil bath temperature is stable at 60 ° C, and the oxidation time is 5 minutes;

[0074] Step 6: Take a certain amount of NaOH and dissolve it in 100 mL of deionized water to prepare a 10 mol / L NaOH solution;

[0075] Step 7: Place the calibrated glass electrode of the pH meter into a conical flask, stir at room temperature with a rotor speed of 200 r / min, and then slowly add 10 mol / L NaOH solution to the conical flask through a dropper. After the addition is completed, the pH meter shows that the pH value is adjusted back to 3.5, and the pH meter reading does not change after 15 minutes, that is, the pH adjustment step is completed;

[0076] Step 8: Centrifuge the pH adjustment product using 6 50ml centrifuge tubes. Pour the liquid in the container into the tubes. Maintain the centrifuge speed at 7000r / min for 2min. Separate the pH adjustment residue and pH adjustment liquid using a centrifuge. The pH adjustment liquid is 300ml. Dry the pH adjustment residue at 65°C.

[0077] The compositions of pH adjustment liquid and pH adjustment slag are shown in Table 4 and Table 5, respectively;

[0078] Table 4

[0079]

[0080] Table 5

[0081]

[0082] Step 9: Take 5g of pH adjustment residue and add it to a conical flask. Add 10mL of 1mol / L hydrochloric acid at a liquid-solid ratio of HCl: pH adjustment residue of 2:1. Place the conical flask in an oil bath stirring pot and perform hydrochloric acid leaching for 5min at a leaching temperature of 70℃.

[0083] Step 10: Centrifuge the back-leaching product using two 50ml centrifuge tubes, pour the liquid in the container into the tubes, maintain the centrifuge speed at 7000r / min, centrifuge for 2min, and separate using a centrifuge to obtain acid back-leaching liquid and acid back-leaching residue;

[0084] The results of acid backleaching liquid and acid backleaching residue are shown in Table 6 and Table 7:

[0085] Table 6

[0086]

[0087] Table 7

[0088]

[0089] After the entire process is completed, the Nd extraction rate is about 80%, Fe is recovered in the form of Fe2O3 with an extraction rate of about 75.6%, and 97% of Ga enters the callback slag.

[0090] Example 2

[0091] A method for separating neodymium, iron and gallium from gallium-containing NdFeB oxidized roasted material comprises the following steps:

[0092] Step 1: The gallium-containing NdFeB oxidized calcined powder is oxidized and calcined in an air atmosphere at a temperature of 700° C. for 2 hours. The gallium-containing NdFeB oxidized calcined material is placed in a ball mill, ball milled at a speed of 250 r / min for 6 hours using a planetary ball mill, and passed through a 200-mesh sieve to obtain the gallium-containing NdFeB oxidized calcined powder.

[0093] The composition of the gallium-containing NdFeB oxidized calcined powder is shown in Table 1;

[0094] Step 2: Take a certain amount of gallium-containing NdFeB oxidized calcined powder and add it to a conical flask, and add 10 mol / L hydrochloric acid at a liquid-solid ratio of HCl: gallium-containing NdFeB oxidized calcined powder of 7:1;

[0095] Step 3: Place the conical flask in an oil bath stirring pot and perform hydrochloric acid leaching for 6 hours at a leaching temperature of 80°C;

[0096] Step 4: After the reaction process is completed, the solution is centrifuged, washed with water and ethanol three times respectively, and dried at 65°C for 24 hours to obtain hydrochloric acid leaching solution and hydrochloric acid leaching residue;

[0097] Step 5: Add 4g of NaClO3 to 300mL of hydrochloric acid leachate. During the process, ensure that the stirring rotor rotates at 200r / min, the oil bath temperature is stable at 60℃, and the oxidation time is 5min.

[0098] The solution loss coefficient is 0.8, which means that the raw material calculation process needs to be corrected to 0.8 times the original value;

[0099] Step 6: Take a certain amount of NaOH and dissolve it in deionized water to prepare a 10 mol / L NaOH solution;

[0100] Step 7: Place the calibrated glass electrode of the pH meter into a conical flask, stir at room temperature with a rotor speed of 200 r / min, and then slowly add 10 mol / L NaOH solution to the conical flask through a dropper. After the addition is completed, the pH meter displays a pH value of 4, and the pH meter reading does not change after 15 minutes, indicating that the pH value adjustment step is completed.

[0101] Step 8: Centrifuge the pH adjustment product using 6 50ml centrifuge tubes. Pour the liquid in the container into the tubes. Maintain the centrifuge speed at 7000r / min for 2min. Separate the pH adjustment residue and pH adjustment liquid using a centrifuge. The pH adjustment liquid is 300ml. Dry the pH adjustment residue at 65°C.

[0102] The compositions of pH adjustment liquid and pH adjustment slag are shown in Table 8 and Table 9, respectively;

[0103] Table 8

[0104]

[0105] Table 9

[0106]

[0107] Step 9: Take 5g of pH adjusted slag and put it into a beaker. Leach it with 1mol / L NaOH solution at room temperature and pressure. The leaching conditions used for alkaline leaching are liquid-solid ratio of 3:1, leaching temperature of 30℃, and leaching time of 6h.

[0108] The pH adjustment slag composition is shown in Table 9;

[0109] Step 10: Centrifuge the back-leaching product using two 50ml centrifuge tubes, pour the liquid in the container into the tubes, maintain the centrifuge speed at 7000r / min, centrifuge for 2min, and separate using a centrifuge to obtain alkali back-leaching liquid and alkali back-leaching residue;

[0110] The compositions of the alkali leaching solution and alkali leaching residue are shown in Tables 10 and 11;

[0111] Table 10

[0112]

[0113] Table 11

[0114]

[0115] After the entire process is completed, the Nd extraction rate is about 77.7%, Fe is recovered in the form of Fe2O3 with an extraction rate of about 74.6%, and 98.1% of Ga enters the callback slag.

Claims

1. A method for separating neodymium, iron and gallium from gallium-containing NdFeB production waste, characterized in that: The following steps are involved: 1) Oxidative roasting of gallium-containing NdFeB production waste; 2) Crushing the oxidatively roasted waste material and leaching it with acid, filtering the leached residue; 3) Using an oxidant to oxidize the filtered solution, adjusting the pH with an alkaline solution, separating the solid and liquid, allowing Nd to enter the solution and Fe and Ga to enter the pH-adjusted residue. The pH-adjusted residue is then back-leached to separate Fe and Ga; The leaching agent used is HCl; the solid-liquid ratio of HCl to pH adjustment slag is 1:1 to 1:7 g / mL.

2. The method according to claim 1, characterized in that Step 2) crushing the particles to a size of 200 to 300 mesh.

3. The method according to claim 1, characterized in that The acid used in step 2) is hydrochloric acid with a concentration of 3 to 10 mol / L, and a solid-liquid ratio of the acid to the gallium-containing NdFeB oxidized calcined powder of 1:1 to 1:7 g / mL.

4. The method according to claim 1, 2 or 3, characterized in that: In step 2) the acid leaching process, the leaching temperature is 50 to 90° C. and the leaching time is 3 to 24 hours.

5. The method according to claim 1, wherein The oxidants used in step 3) include H2O2, NaClO, and NaClO3.

6. The method according to claim 1 or 5, characterized in that The oxidation temperature is 50-90°C; the oxidation time is 1-10 minutes.

7. The method according to claim 1, characterized in that: The alkaline solution used in step 3) includes NaOH, Na2CO3, and NaHCO3, and the concentration of the NaOH solution is 1-10 mol / L.

8. The method according to claim 1 or 7, characterized in that Use alkaline solution to adjust the pH to 3-4.

9. The method according to claim 1, characterized in that Step 3) The pH adjusted residue after drying is subjected to back leaching at a leaching temperature of 10 to 90° C. and a leaching time of 3 to 24 hours.

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