JPH0210232B2 - - 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 separately 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, especially samarium (Sm), have been used as high-performance magnet alloys or hydrogen storage alloys.
Lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), etc. and Co, Ni, Fe, Cu,
Alloys with Zr etc. are often used. for example
SmCo ₅ , MMCo ₅ (MM means Mitsushimetal, which is a mixture of the above rare earth elements), CeCo ₅ ,
Sm ₂ (Co, Fe, Cu, Zr) ₁₇ and the like are typical alloys for permanent magnets, and LaNi ₅ is a typical alloy for hydrogen storage, and the demand for these is increasing year by year.

Because these rare earth elements have high performance, they are often used in small sizes, and the process of cutting, polishing, etc. from a relatively large shape into a smaller shape generally results in processing waste and abrasive powder (scrap). ) occurs in large quantities. Since these component metals are expensive, it is important to recover these valuable metals, and various methods have been proposed so far. For example, (1) SmCo ₅ alloy is heated and dissolved in aqua regia, and then triethanolamine and potassium cyanide are added to hide Co.
A method of recovering Sm as hydroxide by neutralizing it with ammonia (see JP-A-49-36526), (2) adding a slag-forming agent to rare earth-containing scrap, high-frequency melting, arc melting, Method of recovering rare earth alloys by melting them at high temperatures using plasma melting, etc., (3)
A method of adding calcium to the scrap and heating it in an argon stream to remove carbon and oxygen from the scrap and regenerating it as a rare earth alloy (Japanese Unexamined Patent Application Publication No. 1989-1999)
(Refer to Publication No. 38438).

However, method (1) above requires special equipment because it uses aqua regia, and also uses potassium cyanide, which is undesirable from a sanitary standpoint, resulting in high costs. In the case of methods (2) and (3) above, there is a drawback that valuable materials such as rare earths and Co cannot be separated, especially when impurities such as abrasives and glass are mixed in the scrap. There were problems such as making the processing difficult.

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 present inventors have developed materials containing rare earth elements, such as cobalt, nickel, iron, copper,
After extracting an alloy containing at least one type of zirconium with an aqueous sulfuric acid solution and dissolving and extracting most of the rare earth elements and other valuables, we researched a method to separate and recover each element, and copper and zirconium were extracted as undissolved residues. , cobalt, nickel, and iron as alloys by an insoluble electrolytic method, and rare earth elements as oxides, which were disclosed in a separate patent application.

The present invention is a further improvement of the above invention, and is intended to simplify the operation by combining the acid extraction step and the electrolysis step of the above invention into a single step.

According to the alloy, the alloy is electrolytically dissolved to remove Zr and Cu using the so-called direct electrolysis method using the rare earth element-containing alloy as an anode and an aqueous solution containing a rare earth element and a predetermined concentration of Co, Fe, etc. as an electrolyte. Co+Ni+Fe is deposited on the cathode at the same time as the dissolved residue is precipitated.
The first step is to precipitate the alloy in an amount commensurate with the amount electrolytically dissolved, and the oxalic acid is added in an amount equal to or less than the equivalent amount of the rare earth element contained in the electrolytic solution, and the resulting rare earth oxalate precipitate is dissolved in an aqueous solution. separated from
This method consists of a second step of firing this in the atmosphere, and the separated aqueous solution is recycled and used as an electrolyte to efficiently separate and recover rare earth elements and valuables such as Co and Fe. An important structural distinction between the present invention and the separate inventions by the present inventors lies in the use of a direct electrolytic method in which a rare earth element-containing alloy powder is directly used as an anode in the present invention.

That is, in the first step of the present invention, a powdery or lumpy alloy containing a rare earth element and one or more of Co, Ni, Fe, Cu, and Zr is placed in a titanium basket (for example, in a net shape or with small holes). If necessary, cover the titanium basket with an acid-resistant cloth such as Tetron, and use this as the anode, and use a metal plate such as stainless steel as the cathode. , preferably 5 to 15 g/, Co + Ni + Fe concentration 50 g / or less, preferably 20 to 50 g /, PH 1.5 to 4.0, preferably PH 2.0 to 3.0 as an electrolyte, DK
= 2A/dm ² or less, and the electrolytic operation is performed at a cell voltage of 5V or less.

The electrolytic solution is usually continuously supplied to the electrolytic cell,
The overflow liquid from the electrolytic cell is sent to the second R removal step, where an aqueous oxalic acid solution or solid oxalic acid is added in an amount equivalent to or less than the amount of R contained, and the formed precipitate is separated in an appropriate filter, and then reduced to atmospheric pressure. The rare earths are recovered as oxides by roasting. On the other hand, the aqueous solution is recycled as it is or after adding an appropriate amount of sulfuric acid aqueous solution to the electrolytic tank, and Zr and Cu that settle as insoluble residues in the electrolytic tank are allowed to overflow or are allowed to settle in the tank as appropriate. Separate and collect.

The electrolytic solution used in the method of the present invention is an alloy containing a rare earth element and Co, Fe, etc., for example, 50 to 100%
It is obtained by extraction at room temperature with dilute sulfuric acid at a concentration of about 1.5 oz./g/g, and the concentration of each metal and PH value are adjusted to be within the specified range. The pH of this electrolytic solution can be adjusted by adjusting the amount of alloy in the raw materials. Since this alloy is very active, the above electrolyte can be easily obtained by adding it to a dilute sulfuric acid solution and stirring it. The reason why the R concentration in the electrolyte is set to 15 g/or less, preferably in the range of 5 to 15 g/ is that after the rare earth element is electrolytically dissolved to the limit of its solubility, it is sent to the next R removal step. This is because the reaction with oxalic acid added in the R-removal step is preferably carried out efficiently.

If the oxalic acid added here has poor reactivity with rare earth elements, sufficient precipitation of R ₂ (C ₂ O ₄ ) ₃ will not be generated in the de-R step, and the mother liquor after precipitation separation will be used as an electrolyte to supply the solution. When the Co
Any of these causes undesirable results, such as interfering with electrodeposit such as +Fe and interfering with normal electrolysis.

Next, the reason why the concentration of Co + Ni + Fe is set to 50g/or less, preferably in the range of 20 to 50g/ is because if the concentration is less than this, hydrogen gas will be generated during electrolysis and efficient electrolysis will not take place. This is because even if the rare earth element concentration is sufficiently high in the electrolyte solution de-R step, the reactivity with oxalic acid will be impaired. Also, regulating the pH of the electrolyte between 1.5 and 4.0 is because
This is because when the PH is 1.5 or less, hydrogen generation increases during electrolysis and the current efficiency decreases, and when the PH is 4.0 or more, rare earth elements precipitate as oxides.

The present invention will be explained in more detail below.

The method of the present invention applies a so-called direct electrolysis method to combine alloys of rare earth elements with Co, Fe, etc.
While electrolytically dissolving a specified electrolytic solution as an electrolytic starting solution, only metals such as Co, Ni, and Fe are deposited on the cathode either singly or as an alloy.In this electrolytic process, rare earth elements are Also without electrodeposition
Zr is an oxide, and even if Cu is once dissolved, it is thought to become a metal through a substitution reaction with rare earth elements, etc., but it is essentially precipitated and separated as a metal.

This Zr and Cu can be reused as raw materials for permanent magnets, etc.

The anode installed in the electrolytic cell is made of an insoluble material such as titanium or stainless steel, and a basket with small holes around it is filled with an alloy containing rare earth elements, which is the raw material of the present invention. It is composed of As the electrolysis progresses, raw materials are replenished into the basket as appropriate. On the other hand, the cathode is preferably a stainless steel plate, and this stainless steel plate is used by placing it in a box made by gluing a cloth such as Tetron to a vinyl chloride plate. The aforementioned electrolyte is supplied into this box. Using a diaphragm type as described above not only prevents insoluble matters and precipitates from being mixed into the cathode precipitates, but also provides advantages such as facilitating the pH adjustment of the electrolytic solution.

Co, Ni, which are only dissolved in this electrolysis,
Substantially the entire amount of Fe is deposited on the cathode, and the electrolytic starting solution and the electrolytic final solution overflowing this electrolytic cell are
It is preferable to adjust the concentration of Co, Fe, etc. and pH to be approximately constant.

The final electrolysis solution is sent to the second step, a de-R step, where oxalic acid, preferably a 10% oxalic acid aqueous solution, is added so as to precipitate all the rare earth elements that were only dissolved in the electrolytic cell. is preferred. The reason why oxalic acid is added in an amount equivalent to or less than the total amount of rare earths contained in the aqueous solution is to efficiently obtain rare earth precipitates as described above, separate this using a vacuum filter, etc., and then This is to prevent contamination of electrolytic deposits and loss of rare earth oxalate when returned to the electrolytic cell in the first step.
The purpose of completely preventing the formation of precipitates such as (C ₂ O ₄ ) ₂ can also be achieved.

Preferably, the precipitate produced here is separated from the mother liquor after aging for about 1 hour or more.
After drying, the precipitate thus obtained is dried at an atmospheric pressure of approx.
A rare earth oxide is obtained by firing at a temperature of 900℃.
The metal deposited on the cathode in the electrolytic cell is pulled up and stripped at an appropriate time, and the Zr and Cu that have settled in the electrolytic cell are recovered at an appropriate period.

The metals such as Co and rare earth elements obtained by the method of the present invention are of high quality as seen in the examples, and can be used as raw materials for permanent magnets, hydrogen storage alloys, etc. as they are.

According to the method of the present invention, the final liquid of the second step is recycled into the electrolyte of the first step, so each metal in the alloy is
Zr, Cu groups, Co, Ni, Fe groups, and rare earth elements can be separated and recovered with nearly 100% yield.

Another advantage is that the known direct electrolysis method and precipitation separation method of rare earth oxalate can be performed continuously, which simplifies the operation and prevents unnecessary losses between steps.

Examples will be described below.

Example 1 The first step of the present invention is carried out using an electrolytic cell as shown in the attached drawings. The size of the electrolytic cell used was 350 mm in width, depth and height, and 300 mm in width, depth and height, respectively.
mm and 400mm. The width, length and thickness (inner dimensions) of the anode are 218mm, 270mm and 20mm, respectively.
A titanium basket 1 having a size of 5 mm and a 5 mm square mesh is used, wrapped in a Tetron bag 2 as shown in the attached drawing. A stainless steel plate 3 with a width, length, and thickness of 200 mm, 300 mm, and 3 mm, respectively, was used as the cathode, and the width, length, and thickness (inner dimensions) of this stainless steel plate were made from a vinyl chloride plate and Tetoron cloth, respectively. 260mm,
Use in 380mm and 20mm box 4.

The three anode bags and two cathode boxes are arranged alternately as shown. Approximately 10 mm made of an alloy containing 34% Sm and 65% Co by weight in the anode bag.
Charge 1 kg each of block magnet scraps with different diameters.

Co 40g/, Sm is added to this electrolytic cell as an electrolyte.
After filling with sulfuric acid acid aqueous solution of 7g/pH2.2, the liquid is supplied to each cathode box 4 at a rate of 35ml/min, and the overflow from the electrolytic cell outlet 5 is transferred to 10 beakers (not shown) equipped with a stirring device. Use this beaker as a Sm removal tank. This de-Sm
Add 10% oxalic acid aqueous solution to the tank at a rate of 2.3ml/min.
The overflow of the Sm removal tank is handled by a filter (Nutsuchie).
The second step and circulation step are carried out by adding a dilute sulfuric acid aqueous solution to the solution, adjusting the pH of the aqueous solution to 2.2, and circulating it again to the cathode box in the electrolytic cell. Electrolysis conditions are DK1.5A/d
m ² , cell voltage 4V, and electrolyte temperature 50°C for 24 hours. In addition, the Sm in the final electrolytic solution entering the Sm removal tank is 10g/
I tried to maintain the above.

The metal deposited on the cathode by this electrolysis is
The amount of Co99.0% and Sm 0.1% or less was 630g, the amount of scrap electrolysis during this period was 1Kg, and the actual yield of Co from the charged raw materials was 96.0%. In addition, the precipitate [Sm ₂ (C ₂ O ₄ ) ₃ ] that had been over-separated through the Sm removal tank was dried and fired for 1.5 hours in a Matsufuru furnace kept at 900°C, resulting in 85.2% Sm and 0.06% Co. Sm ₂ O ₃ 390g
was obtained, and the actual samarium yield from raw materials was 97.7%.
It was hot.

Example 2 Sm43.7%, Co32.9 obtained when producing Sm ₂ (Co, Fe, Cu, Zr) ₁₇ by high frequency melting method
%, Fe9.15%, Cu5.13%, Zr0.97%. After crushing 3.6 kg of slag into 2 meshes or less,
The titanium basket used in Example 1 was divided into equal parts and charged, and used as an anode.
PH2.0 containing Sm8.0, Co30.0, Fe10.0 each g/
An aqueous solution of was used as the electrolyte, and electrolysis was carried out for 24 hours in the same manner as in Example 1 except that the DK was 1.0 A/dm ² . As a result, the amount of dissolved raw material was 1.5Kg, Co78.4%,
600 g of electrodeposited material containing less than 21.0% Fe and 0.1% Sm was obtained, and the actual yield of Co+Fe from the raw materials was 94.6%.
On the other hand, after drying, the Sm compound precipitate was calcined for 2 hours in a Matsufuru furnace maintained at 900°C, resulting in a Sm of 84.5%.
753 g of Sm ₂ O ₃ containing 0.1% or less of Co+Fe was obtained, and the actual yield of Sm from the raw material was 97.1%.

Cu and Zr were hardly dissolved and their respective concentrations in the electrolyte were below 0.005 g/.

Example 3 A lump of approximately 10 mm in diameter consisting of 31.5% La and the balance Ni
When 3 kg of LaNi alloy was electrolyzed in the same manner as in Example 1, Ni and La were recovered.
The amount of raw material dissolved in 24-hour operation is 1.2Kg, and the purity of Ni is
The actual yield of 99.2% is 97.2%, and La is 85.1% La.
of La ₂ O ₃ was obtained with an actual yield of 94.6%, both values calculated from the raw materials.

In all of the above examples, the process of electrolyte solution and recovered rare earth elements has been explained using a circulation method, but only the electrolysis process or only the rare earth recovery process is circulated, respectively, after sufficiently dissolving the raw material or recovering the rare earth element. A method of proceeding to the next step may be adopted.

Further, the electrolysis conditions, the amount of oxalic acid added for recovering rare earths, the aging time of precipitation, etc. are preferably adjusted as appropriate depending on the intended use of the recovered metal.

[Brief explanation of drawings]

The accompanying drawings are longitudinal cross-sectional views of exemplary electrolytic cells used in the practice of the present invention. 1... Titanium basket; 2... Tetron anode bag; 3... Cathode plate; 4... Cathode box; 5... Overflow port; 6... Electrolytic cell.

Claims (1)

[Claims] 1 An alloy containing rare earth elements and at least one of nickel, cobalt, copper, iron, and zirconium is used as an anode, and an electrolyte with a rare earth element concentration of 15 g/or less, Co + Ni + Fe 50 g/ or less, and a pH of 1.5 to 4.0. The first step is to precipitate Co, Ni, and Fe on the cathode and separate the final electrolytic solution from the undissolved residue. It consists of a second step in which the rare earth oxalate precipitate produced by addition is separated from the aqueous solution and calcined in the atmosphere, and the aqueous solution obtained in the second step is recycled and used as the electrolyte in the first step. A method for recovering valuable metals from alloys containing rare earth elements.