JPS6134486B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention contains rare earth elements, and includes Co, Ni,
The present invention relates to a method for separating and recovering rare earth elements, Co, Ni, Fe, Cu, and Zr from an alloy containing at least one of Fe, Cu, and Zr. In recent years, rare earth elements have been used as high-performance magnet alloys or hydrogen storage alloys, etc.
Especially samarium (Sm), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd)
alloys with Co, Ni, Fe, Cu, Zr, etc. are often used. For example, SmCo ₅ , MMCo ₅
(MM means Mitsushi metal, which is a mixture of the above rare earth elements), CeCo ₅ , Sm ₂ (Co, Fe,
Cu, Zr) ₁₇ , etc. are used as alloys for permanent magnets and
LaNi ₅ is a typical hydrogen storage alloy, and its demand is increasing year by year. Due to the high performance of these rare earth elements, they are often used in small sizes, and generally the process involves cutting, polishing, etc. from a relatively large shape into a smaller shape. A large amount of is generated. Since these alloy components are expensive, it is important to recover these valuable metals, and various methods have been proposed so far. For example, (1) a method of heating and dissolving SmCo ₅ alloy in aqua regia, then adding triethanolamine and potassium cyanide to hide Co, and recovering Sm as hydroxide by neutralizing with ammonia ( (Refer to Japanese Patent Application Laid-Open No. 49-36526), (2) a method of adding a slag-forming agent to rare earth element scrap and melting it at high temperature by high frequency melting, arc melting, plasma melting, etc., and recovering it as a rare earth alloy; A method of adding calcium to scrap and heating it in an argon stream to remove carbon and oxygen from the scrap and regenerate it as a rare earth alloy.
56-38438). However, method (1) above requires special equipment because it uses aqua regia, uses potassium cyanide which is not sanitary, and has problems such as high cost. In the case of methods (2) and (3) above,
It has the fatal disadvantage of not being able to separate valuable materials such as rare earths and Co, and it also poses problems such as making processing difficult, especially when impurities such as abrasives and glass are mixed into the scrap. Ta. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for separating and recovering rare earth elements and other valuable substances as oxides or metals by a relatively simple operation that solves the above-mentioned problems. In order to achieve this objective, the inventors of the present invention first dissolved most of the rare earth elements and other valuable substances with acid, and as a result of intensive research into a method of separating each element, they found that when Cu and Zr are present, is recovered as an insoluble residue, Co, Ni, and Fe are partially separated as alloys by electrolytic method, and then the rare earth elements are separated and recovered, and the obtained mother liquor is repeatedly used as an extract of raw materials. The method of the present invention was developed by experimentally discovering a method for recovering almost 100% of the metal. That is, it contains rare earth elements and contains Co, Ni,
An alloy containing one or more of Fe, Cu, and Zr is extracted with a dilute aqueous sulfuric acid solution, and the concentration of rare earth elements is 15 g/or less, preferably 10 to 15 g/, and the total concentration of cobalt, nickel, and/or iron is 50 g/or less. Preferably, the extract having a pH of 1.5 to 4.0 is separated from the insoluble residue, and the extracted liquid is electrolyzed using an insoluble anode such as stainless steel or lead as an electrolyte to remove the Co present. , part of Ni and/or Fe is precipitated. The resulting electrolyzed final solution is stirred and added with an aqueous solution of oxalic acid in an amount equal to or less than the amount of rare earth elements contained, the oxalate precipitate formed is separated from the aqueous solution, and roasted in the atmosphere to convert the rare earths into oxides. Collect with. The aqueous solution obtained in the final step is used as it is, or after adding an appropriate amount of dilute sulfuric acid, it is recycled as an extract for the first step. In the method of the present invention, the sulfuric acid aqueous solution used in the first step is preferably relatively dilute, for example, about 50 to 100 g. The reason why it is preferable to use dilute sulfuric acid is that rare earth element-containing alloys are very active metals, so if you put the alloy into dilute sulfuric acid with a pH of 1.0 and stir it, it will dissolve in 1 to 2 hours at room temperature and the pH will increase. increases to 4-5.0. For example, if the alloy is
Even if it is a lump of 10 to 20 mm square, heating it to about 50°C will accelerate its dissolution and produce similar results. Utilizing this property, it is easy to adjust the concentration of rare earth elements, the total concentration of Co, Ni and/or Fe, and the pH value in the extract to the above-mentioned predetermined range. For example, no other agents such as alkaline agents are required to adjust the pH. In this extraction process, the concentration of rare earths should be 15g/ or less, preferably
The range of 10 to 15 g/l means that the rare earth element is dissolved to the limit of solubility, and the reaction with oxalic acid added to this extract is to be carried out efficiently. If the reaction between the added oxalic acid and the rare earth metal (hereinafter abbreviated as R) is not sufficient, the reaction will occur in the R removal process.
When the precipitate of R ₂ (C ₂ O ₄ ) ₃ is not sufficiently formed and the liquid is circulated as the extract in the first step, this precipitate is formed and exits the system as an insoluble residue, resulting in loss. Or, alternatively, in the second electrolytic step, R ₂
(C ₂ O ₄ ) ₃ is generated, which accompanies electrodeposit such as Co and becomes a cause of interfering with normal electrolysis, all of which lead to unfavorable results. Then the total concentration of Co, Ni and/or Fe is 50
The reason why the amount is set to be less than 20 g/g/, preferably in the range of 20 to 50 g/e, is that if it is less than this, hydrogen gas will be generated in large quantities during electrolysis, and efficient electrolysis will not be carried out. On the other hand, if the concentration exceeds this level, the next third step is de-R.
This is because, even if the rare earth element concentration is sufficiently high in the process, the reactivity with oxalic acid will be impaired. The pH of the extract is regulated at 1.5 to 4.0 because if the pH is lower than this, hydrogen generation will increase during electrolysis and the current efficiency will decrease, and if the pH is higher than this, the rare earth elements will become oxides. This is because it precipitates. The present invention will be explained in more detail below. The extract extracted according to the above procedure is separated from the undissolved residue, but this undissolved material contains almost all of it.
It contains Cu and Zr, and Zr is separated as ZrO ₂ , and Cu, once dissolved, is thought to become a single metal through a substitution reaction with rare earth elements, etc., but they are separated as metals. This Zr and Cu can be reused as raw materials for permanent magnets. The aqueous solution from which the insoluble residue was separated in the first step is used as an electrolyte to undergo insoluble electrolysis in the second step, at a temperature of 50 to 60°C and a DK of 2 A/dm ²
Hereinafter, the cell voltage is preferably 5V or less. As mentioned earlier, the anode uses an insoluble electrode such as lead, titanium, or stainless steel, but the cathode is made of stainless steel, for example, and is housed in a box made by gluing a cloth such as Tetron to a vinyl chloride plate if necessary. Not only can the pH of the electrolyte be easily adjusted, but even if there is precipitate of rare earth oxalate sent to the electrolytic process without sufficient ripening, the electrodeposit will not be contaminated by this precipitate. Never. In this insoluble electrolyte, the concentration of Co etc. in the electrolyte is
To the extent that it does not significantly reduce 20g/, for example, 15g/
It is preferable to stop the process at this point from the viewpoint of electrolytic efficiency. The final electrolytic solution undergoes the final step of recovering rare earths, but here an approximately 10% aqueous oxalic acid solution, equivalent to or less than the total amount of rare earths present, is added in batches or continuously at room temperature while stirring the final electrolytic solution. The formed precipitate is preferably separated from the liquid using a vacuum filter or the like after aging for about 1 hour. The obtained rare earth oxalate is fired at a temperature of approximately 900°C in a Matsufuru furnace and recovered as rare earth oxide. The oxalic acid added in the final step is preferably used in the form of an aqueous solution and is in an amount below the equivalent, preferably in an amount sufficient to reduce the dissolved R from, for example, 15 g/ to 5-10 g/. As mentioned above, it is necessary to increase the R concentration of the extract as much as possible to increase the reaction efficiency with oxalic acid, and the suppression of the amount of oxalic acid added is also for the same reason. If the amount of oxalic acid added exceeds the equivalent amount, oxalate ions will be introduced into the liquid circulated to the first step, resulting in loss of rare earths and further causing contamination of electrolyte deposits in the second step. The alloys of Co, Fe, etc. and rare earth oxides obtained through the above processes are of very high quality, as seen in the examples below, and can be used as raw materials for permanent magnets, hydrogen storage alloys, etc. can be used. According to the method of the present invention, since the aqueous solution in the final step is recycled as the extract in the first step, it has the advantage that almost 100% separation and recovery can be achieved, excluding the extraction loss of rare earths that may occur in the first step. be.
Other advantages include that operations are not complicated, such as using dilute acids in both the first and third steps and applying known electrolytic methods. In addition, in the method of the present invention, even when the raw material contains an organic solvent or the like, it can be treated in the same manner by adding a well-known activated carbon treatment step. Examples will be described below. Example 1 4 kg of magnetic alloy scrap of 1 mm or less containing 34% by weight of Sm and 5% by weight of Co (hereinafter simply referred to as %) was put into a 62.0g/100% aqueous sulfuric acid solution, stirred at room temperature for 2 hours, and then When undissolved residue was removed using a vacuum filter, the pH was 3.0,
100.2 of an extract containing Sm13.0g/, Co25.5g/ was obtained. This extract liquid is 280mm long, 360mm wide, 350mm
30 mm vertically in a vinyl chloride electrolytic cell (capacity approx. 35 mm)
mm, width 200mm, thickness 2mm three lead plate anodes,
Two stainless steel cathodes measuring 300 mm long, 200 mm wide, and 2 mm thick were filled in an electrolytic cell in which the anodes and cathodes were arranged alternately with a distance of 50 mm between the electrodes. Next, the temperature of the electrolytic solution was maintained at 50° C., and the feeding rate of the extract solution was adjusted to 60 ml/min, and electrolysis was carried out at DK=1.5 A/dm ² and cell voltage of 4 V for 18 hours. During this time, the aqueous solution that overflowed the electrolytic cell was stored in a polyethylene container as the final electrolytic solution. The amount of electrolyte obtained was 700.2 g, and its composition was 99.5% Co and 0.1% or less Sm. The final electrolytic solution was 95.0, Sm13.7g/,
It contained 19.56 g/Co. Add 10.5% oxalic acid solution (0.9 equivalent to Sm) to the above aqueous solution 95 while stirring at room temperature,
After allowing it to stand for 60 minutes, it was separated using Nutsuchie to precipitate samarium oxalate [Sm ₂ (C ₂ O ₄ ) ₃ ]2200
An aqueous solution containing 105.5 g and pH 0.5, Sm 1.4 g/, and Co 17.6 g/ was obtained. After drying the above samarium oxalate, it was fired for 2 hours in a Matsufuru furnace kept at 900℃, and the result was 85.0% Sm and 0.1% Co.
The following 1360g of samarium oxide (Sm ₂ O ₃ ) was obtained, and the actual yield from each raw material was Sm85.0%.
Co26.8%. The final liquid from which Sm has been recovered can be used again to extract valuables from raw materials. Example 2 In the same manner as in Example 1, an alloy containing rare earth metals was extracted with dilute sulfuric acid, and 100% of Sm34%,
Co65% _SmCo5 alloy and 100 with a small amount of glass pieces
1 kg of scraps smaller than a mesh was added and stirred for 2 hours, adjusting the pH of the extract to 2.0 by adding dilute sulfuric acid if necessary. After vacuum filtration, the result was Sm13.3g/Co41. 3g/
100.15 g of extract and 20.0 g of undissolved residue were obtained. The extracted aqueous solution is supplied to the electrolytic cell at a rate of 70° using two cathodes and three anodes sandwiching them.
ml/min, the liquid temperature was 55°C, the DK was 1.0A/dm ² , and the electrolytic treatment was carried out in the same manner as in Example 1 except that the electrolysis time was 24 hours, and the current efficiency was almost 100%.
633 g of 99.0% electrolytic cobalt was obtained. The actual Co yield from the raw material was 96.4%. The final electrolytic solution is
It contained Sm13.3g/, Co34.9g/ and was 100.0. In the same manner as in Example 1, 10% oxalic acid solution 3 was added in an amount sufficient to reduce the Sm concentration in this aqueous solution to 10.0 g/L, and reacted to obtain 602 g of separate samarium oxalate. The amount of samarium oxide obtained by firing was 371g, and the quality of this material was
The Sm was 85.5% and the Co was 0.1% or less, and the actual samarium yield from the raw materials was 93.3%. Note that the pH of the aqueous solution from which samarium was recovered is 0.8, and it can be used repeatedly in the first extraction step as is. Example 3 When 4 kg of fine powder (100 mesh or less) of LaNi alloy consisting of 31.5% La and the remainder Ni was treated in the same manner as in Example 1, the Ni electrodeposit was 705.5%.
g, its grade was less than 99.7% Ni and 0.1% La, and the actual yield of Ni from the raw materials was 25.7%. On the other hand, 1317 g of lanthanum oxide (La ₂ O ₃ ) containing 85.2% La and 0.05% Ni was obtained, and the actual yield of La from the raw material was 89.1%. Example 4 Sm25.5%, Co50.0%, Fe15.0%, Cu8.0%,
Magnet alloy scrap consisting of Zr1.5% [Sm ₂
(Co, Fe, Cu, Zr) ₁₇ ], 1 kg of 10 to 20 mm square pieces was added to a sulfuric acid acidic aqueous solution containing Sm, Co, Fe, etc. separately obtained in the same manner as in Example 2.
The mixture was dissolved at a temperature of 50°C for 2 hours while adjusting the pH to 2.0. The obtained extract was Sm10g/,
Fe + Co 40.0 g/, pH 2.0 aqueous solution 100.5, and undissolved residue was 120 g (dry). By analyzing this undissolved residue, the extraction rate of the first step can be calculated. The quality of each metal in the undissolved residue according to the analysis is as shown in the table below.
Cu and Zr were hardly dissolved, but more than 98% of each of the other valuable metals was dissolved. This undissolved residue is directed to a separate Cu and Zr recovery process.

[Table] The above extract was electrolyzed in the same manner as in Example 2, except that the equipment used in Example 1 was used and the electrolysis starting solution was used as it was, and the overflow of the electrolytic cell was circulated back to the electrolytic cell. Electroplated alloy 630g
was gotten. This composition is Co76.3%, Fe23.2%,
Sm was 0.06%. Oxalic acid in an amount equivalent to the amount of samarium extracted from the raw material scrap was added to the final electrolytic solution and treated in the same manner as in Example 1. As a result, Sm85.2%,
285 g of samarium oxide containing less than 0.1% Co+Fe was obtained. Actual yield from scrap is Fe+Co96.4
%, Sm95.0%. In the above examples, each process was explained using the batch method, but in actual operation, it can be performed in one process like the electrolytic operation performed in Example 4, or in continuous circulation by pooling from the first process to the third process. method can also be adopted.

Claims (1)

[Claims] 1. An alloy containing rare earth elements and at least one of cobalt, nickel, iron, copper, and zirconium is extracted with an aqueous sulfuric acid solution to obtain a rare earth element concentration of 15 g/or less and a total concentration of cobalt, nickel, and/or iron. 50g/or less, the first step of separating the extract with a pH of 1.5 to 4.0 from the insoluble residue, and the precipitation of a part of cobalt, nickel and/or iron using the insoluble electrolysis method of the extract of the first step. a second step in which oxalic acid is added in an amount equivalent to or less than the rare earth element contained in the final solution of the second step, and a third step in which the resulting oxalate precipitate is separated from the aqueous solution and roasted in the atmosphere. A method for recovering valuable metals from rare earth element-containing alloys, characterized in that the aqueous solution in the third step is recycled as the extract in the first step.