JPS6157900B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for efficiently separating rare earth metals. More specifically, the present invention relates to a method for separating and recovering rare earth metals at a high elution rate and in good yield using ion exchange fibers. Rare earth metals such as lanthanum, yttrium, cerium, neodymium, and samarium are widely used as ceramic additives, hydrogen absorbers, alloy components, catalyst components, etc., but since they are usually produced in a mixed state, they are in a pure state. It is necessary to separate each metal. However, since rare earth metals have similar properties, it is very difficult to separate them, and it is difficult to separate them using conventional separation methods such as fractional crystallization and fractional precipitation. , cerium, europium, and other limited metals. Later, a method using ion exchange resin was proposed, but this method was batch-type and required a long period of several 10 days for one separation operation, and the equipment was large and productivity was low. However, the methods that are currently being put into practical use are mainly solvent extraction methods. However, this solvent extraction method is not necessarily satisfactory as an industrial method because the operation is complicated and there are problems in processing the used solvent. Therefore, the development of a method for obtaining highly pure rare earth metals through simple operations and short processing times has become one of the important issues in the field of industry that utilizes rare earth metals. The inventors of the present invention have conducted extensive research to develop a method for separating rare earth metals with high yield in a short time using simple operations. The inventors have discovered that the objective can be achieved by adsorbing rare earth metals and then performing fractional elution using a chelating agent as an eluent, and based on this finding, the present invention has been accomplished. That is, the present invention provides a method for mutually separating a plurality of rare earth metals by selectively adsorbing rare earth metals on an ion exchanger and then fractionally eluting the rare earth metals with an aqueous solution of a chelating agent. The present invention provides a separation method characterized by using an ion exchange fiber having an exchange group and a weak cationic exchange group in a molar ratio of 5:1 to 1:1 and carrying out the separation at an elution rate of 5.0 or higher. Examples of rare earth metal-containing substances used as raw materials in the method of the present invention include acid extracts of monazite, yttrium phosphate, bastnasite, etc., and acid solutions of mitshumetal. These typically have rare earth metal concentrations of 10-30g/
, used after adjusting to PH0.5~3.0. On the other hand, the ion exchange fibers used in the method of the present invention include, for example, ion exchange fibers made of a polymer having a sulfonic acid group as a strong cationic exchange group and a carboxyl group as a weak cationic exchange group. The ion exchange capacity of the strong cationic exchange group and the weak cationic exchange group in this ion exchange fiber is preferably 1.0 meq/g or more, and the molar ratio of the strong cationic exchange group and the weak cationic exchange group is It needs to be 5:1 to 1:1. If this molar ratio is out of this range, mutual separation of the rare earth metals will be incomplete. Such ion exchange fibers can be manufactured, for example, as follows. That is, after spinning polyvinyl alcohol with an average degree of polymerization of 1000 to 3000, it is heat treated at 150 to 230°C for several hours in air or an inert gas atmosphere, and then placed in concentrated sulfuric acid and heated at 50 to 100°C for several hours. Upon treatment, polyenation through dehydration of polyvinyl alcohol, carboxyl group formation through oxidation of alkyl groups, and sulfonation occur, resulting in the desired ion-exchange fibers being obtained. At this time, by appropriately changing the heat treatment conditions in air or an inert gas atmosphere and the sulfuric acid treatment conditions, the ion exchange capacity of the ion exchange fiber and the strength of the strong cationic exchange group and the weak cationic exchange group can be adjusted. The molar ratio can be adjusted. The ion exchange fibers may be used as they are by being filled into a suitable column, or may be knitted and woven by a conventional method and then filled into a container for use. Next, in the method of the present invention, the chelating agents used to elute the rare earth metals adsorbed on the above ion exchange fibers include ethylenediaminetetraacetic acid,
Mention may be made of known chelating agents such as nitrile triacetic acid. These are used in the form of salts as aqueous solutions, but ammonium salts are particularly preferred for convenience when regenerating and repeatedly using ion exchange fibers. This chelating agent has a concentration of 0.5 to 3
%, pH 7-9. The method of the present invention is characterized in that elution is performed at an elution rate of 5.0 or higher, preferably 8.0 or higher.
When a normal ion exchange resin is used, in order to separate rare earths with a practical yield, that is, a yield of 80% or more, it is necessary to reduce the elution rate to 1.0 or less. It was completely unexpected that a yield of over 80% could be achieved at such a high elution rate. Here, the elution rate (SV) means the volume ratio of the eluent passed through the ion exchange fiber per hour to the ion exchange fiber capacity, and is calculated by the following formula. SV=V'/V, where V is the capacity of the ion exchange fiber, and V' is 1
(volume of eluent passed through the ion-exchange fiber per hour) To suitably carry out the method of the present invention, the specified ion-exchange fiber is filled, conditioned with a dilute hydrochloric acid solution and a dilute ammonium chloride aqueous solution, and then adjusted to a pH of 1. Inject a rare earth metal-containing aqueous solution adjusted to 5 to allow the rare earth metals to be adsorbed onto the ion exchange fibers. Next, after washing the adsorbed column with water, the concentration
A 0.1-2.0% ammonium ethylenediaminetetraacetate aqueous solution with a pH of 6-9 is passed through the sample at an elution rate of 5.0 or higher, preferably 8.0 or higher for elution. A fixed volume of the flowing liquid is collected, and the rare earth metals contained therein are traced using a fluorescent X-ray method, and each fraction of the same metal is collected. In this way, rare earth metals with a purity of 99.9% or more can be obtained with a yield of 85% or more. In this case, if necessary, one or more auxiliary columns may be connected in series to facilitate separation of each rare earth component. The method of the present invention is suitable as an industrial rare earth metal recovery method because it can obtain highly purified rare earth metals at a processing speed of five times or more than conventional methods using ion exchange resins. Next, the present invention will be explained in more detail with reference to Examples. Reference example 1 A stock solution of fully saponified polyvinyl alcohol with an average degree of polymerization of 1200 and 5% ammonium polyphosphate added to it by weight was dry spun, and the fineness
A 150d/50 polyvinyl alcohol fiber was obtained. When this fiber was treated in nitrogen gas at 220°C for 3 hours, its weight decreased by 23% and it became a blackish brown partially polyenated fiber. Next, this polyenated fiber was treated in 98% sulfuric acid at 60° C. for 3 hours, and then thoroughly washed in boiling water to obtain ion exchange fiber S-1. Reference Example 2 When polyvinyl alcohol fibers produced in the same manner as in Reference Example 1 were treated in air at 190°C for 3 hours, they became black partially polyenized fibers with a weight loss of 26%. This fiber was sulfated under the same conditions as in Reference Example 1 to obtain ion exchange fiber S-2. Reference Example 3 A partially polyenated fiber produced in the same manner as in Reference Example 2 was treated in 96% sulfuric acid at 90°C for 3 hours, and then thoroughly washed with boiling water to obtain ion exchange fiber S-3. Table 1 shows the physical properties of the ion exchange fibers obtained as described above.

[Table] Example 1 Bastnaesite was calcined at 600 to 620°C for 3 hours, extracted with 1N nitric acid, and cerium was removed according to a conventional method, resulting in a rare earth metal content of about 2% and a pH of 1.5. Samples were prepared. A glass column with a diameter of 3.54 cm and a height of 35 cm was filled with 280 ml of each ion exchange fiber obtained in the reference example, conditioned three times each with 1N hydrochloric acid and 1N ammonium chloride aqueous solution, and then adsorbed through the sample. and washed with water. Then, using a 0.5% aqueous solution of ammonium ethylenediaminetetraacetate (PH8.5), the elution rate (SV
) eluted at 5.0. Aliquot the eluent in approximately 200 ml portions,
The rare earth metal was recovered as an oxalate, and the oxide obtained after firing was analyzed by fluorescent X-ray. On the other hand, for comparison, a commercially available ion exchange resin (Diaion PX228) was used in an amount (80 ml) that provided approximately the same ion exchange capacity, and the above sample was separated under similar conditions. These results are shown in Table 2.

[Table] As is clear from this table, the method of the present invention shows a significantly higher yield than the method using a commercially available ion exchange resin. Example 2 Ion exchange fiber (S-1) obtained in Reference Example 1 4.25
, 5 volumes - adsorption column (diameter 9.9 cm, height 100 cm)
cm) and then conditioned three times each with 1N hydrochloric acid and 1N ammonium chloride aqueous solution, and prepared from bastnasite. La ₂ O ₃ 66.8%, Nd ₂ O ₃ 23.3%, Pr ₆ O ₁₁ 7.6%,
Adsorption of 4.5% of a nitric acid aqueous solution (PH1.5) containing 2% of other mixed rare earth elements at a concentration of 2.3% was performed. After washing with water, the mixture was eluted with a 0.5% aqueous solution of ethylenediaminetetraacetic acid ammonium salt (PH8.5). That is, eluent 97 was allowed to flow down from the top of the column over 4.5 hours, and gadolinium, samarium, neodymium, praseodymium, and lanthanum were separated as eluents in this order. After treating this eluent with hydrochloric acid, it was separated as an oxalate and calcined to obtain oxides of each rare earth metal. Purity at this time
The yield of 99.9% or more lanthanum oxide was 52.1 g, and the yield was 86.7%. Example 3 The 5-volume adsorption column used in Example 2 was used as the main column, and three auxiliary columns each filled with the same ion exchange fiber were connected in series, and each column was conditioned. After that, the auxiliary column was further heated with 1N zinc chloride aqueous solution (PH1.85) 18
Processed with. Then La ₂ O ₃ 46.5 prepared from monazite
_% , _{Nd2O3 32.6} %, _pr6O11 10.3%, _{Sm2O3 4.6} %,
A nitric acid aqueous solution (PH 1.5) 4.5% containing a mixed rare earth of 6.0% at a concentration of 2% was passed through the main column to be adsorbed, and then washed with water. Next, a 0.5% aqueous solution of ammonium ethylenediaminetetraacetate (PH8.5) was flowed down from the top of the main column at an elution rate of 8.0, and the elution process was stopped when the rare earth adsorption band reached the tip of the auxiliary column. After separating the main column and each auxiliary column separately, each column was again subjected to elution treatment at the same elution rate. After each of the separated eluents was treated with hydrochloric acid, the rare earth metals contained therein were converted into oxalates, which were then calcined to form oxides. In this way,
La ₂ O ₃ , Nd ₂ O ₃ , Pr ₆ O ₁₁ and more than 99.9% purity
Sm ₂ O ₃ was obtained in yields of 92%, 82%, 60% and 19%, respectively. Example 4 After applying 4.25 ion exchange fibers containing exchange groups with a strong cation exchange capacity of 2.3 meq/g and a weak cation exchange capacity of 1.3 meq/g to a column, conditioning was carried out in the same manner as in Example 2. The same mixed rare earths as used in Example 2 were adsorbed through a nitric acid aqueous solution (PH 1.5) containing a concentration of 2%. After washing with water, remove the nitrile triacetate ammonium salt.
Elution was performed using a 0.5% aqueous solution (PH8.5) as an eluent. In other words, the eluent is poured from the top of the column for 1 hour.
The eluent was collected at a rate of 25% and separated for each rare earth metal component, and was treated in the same manner as in Example 2 to obtain oxides of each rare earth metal. As a result of analysis using fluorescent X-rays, the purity is 99.9%.
It was found that the above lanthanum oxide was obtained with a yield of 87%. Additionally, praseodymium and neodymium were concentrated to 66% and 97% purity, respectively.

Claims (1)

[Scope of Claims] 1. In a method for mutually separating a plurality of rare earth metals by selectively adsorbing rare earth metals on an ion exchanger and then fractionally eluting the rare earth metals with an aqueous solution of a chelating agent, Using an ion exchange fiber having a cationic exchange group and a weak cationic exchange group in a molar ratio of 5:1 to 1:1,
A separation method characterized by being carried out at an elution rate of 5.0 or higher. 2. The method according to claim 1, wherein the aqueous chelating agent solution is an aqueous solution of an ammonium salt of ethylenediaminetetraacetic acid or nitriletriacetic acid.