JP2795912B2 - Iron removal method and material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for removing iron from a solution having a pH of less than 7 in which two or more metals including a rare earth element and iron are dissolved and separating the iron from the rare earth element and a removing material. About.

[Conventional technology]

One example of removing iron from a solution having a pH of less than 7 in which two or more metals including a rare earth element and iron are dissolved and separating it from the rare earth element is removal of iron as an impurity in the rare earth element.

Optical glass is added with a rare earth element to improve the refractive index and / or resolution of the lens, for example, but it is well known that if iron is contained as an impurity, these performances will be inferior. It is.

One of the conventional techniques for purifying rare earth elements is a method using an ion exchange resin. However, in general, the removal of a small amount of iron metal by an ion exchange resin has a similar distribution coefficient defined by the following equation as shown in a comparative example described below, so that the rare earth element and iron are separated. There is a problem that it is difficult to do.

Where: Kd: partition coefficient (ml / g) []: concentration of metal ions in the exchanger (mol / g) [M]: concentration of metal ions in the solution (mol / ml) Removal of iron contained in radioactive liquid waste.

A method for separating high-level radioactive waste liquid into at least one or more homologous elements by a solvent extraction method is described in, for example, 1985.
Research report JAERI-M report 85-161 issued by the Japan Atomic Energy Research Institute in October 1998.

According to this method, diisodecylphosphonic acid (DIDPA) is used as a solvent in the solvent extraction step. At this time, if trivalent iron ions are present in the waste liquid to be treated, the trivalent iron ions are extracted, and a problem caused by the iron ions is said to occur.

In the prior art, in order to solve this problem, a method of adding a solvent to lower the concentration of iron ions in the solvent, or adding a new reducing agent to convert trivalent ions to divalent ions is employed. .

However, in the former method, the trivalent iron ions are not back-extracted in the back-extraction step, so they are accumulated in the solvent, and the amount of the solvent used increases. On the other hand, in the latter method, iron as a divalent ion is not used. Since it is stable and easily subject to air oxidation, there is a problem in that the amount of the reducing agent used becomes large, and the amount of waste resulting from the use of a new reducing agent increases.

[Problems to be solved by the invention]

As in the above two examples, a method of efficiently removing iron from a solution having a pH of less than pH 7 in which at least two or more metals including a rare earth element and iron are dissolved and separating it from the rare earth element, and the realization of a removing material are awaited. .

[Means for solving the problem]

The present invention is intended to solve the above-mentioned problems of the prior art, and the present inventors have made intensive studies to overcome the above-mentioned problems and completed the present invention.

That is, the present invention provides a method for removing iron from a solution having a pH of less than pH 7 in which two or more metals including a rare earth element and iron are dissolved by removing one or two of the following removing materials in combination and separating the rare earth element from the solution. Materials.

Titanium antimonate tin antimonate The present invention is intended to efficiently remove iron from a solution having a pH of less than 7 in which two or more metals including a rare earth element and iron are dissolved.Specifically, iron and Sc, Y, La "Isotope Handbook" for rare earth elements such as (December 20, 1984, Co., Ltd.)
Iron can be removed from a solution in which an element of Group A of the periodic table dissolves as described in the back spread of Maruzen, edited by The Japan Isotope Association. Further, for example, in the case of tin antimonate, iron and other elements other than the above-mentioned Group 3 A elements, which are liable to be mixed into this type of liquid to be treated, such as Sr and Cs, are separated and removed together with iron on the iron side. In some cases, however, in the present invention, the purpose of separating iron can be achieved even if such elements are mixed with any of the iron and group III A elements to be separated from each other.

In the present invention, titanium antimonate is a hydrated oxide represented by the following formula and includes an anhydride.

TiO ₂ .XSb ₂ O ₅ .nH ₂ O (However, 0 <X ≦ 0.5, n is a positive number including 0) When X exceeds 0.5 and antimony increases from titanium, rare earth elements, Sr, Cs It is not suitable for high-level radioactive effluents because of the increased partition coefficient and the difficulty in separating from iron.

 That is, specific examples in this range include the following.

TiO ₂ · 0.15Sb ₂ O ₅ · 1.6H ₂ O… TA-1 Tin antimonate is a hydrated oxide represented by the following formula, and also includes an anhydride.

SnO ₂ · YSb ₂ O ₅ · nH ₂ O (However, 0 <Y ≤ 1.0, n is a positive number including 0) When Y exceeds 1.0, separation from iron occurs for the same reason as titanium antimonate. It will be difficult.

 That is, a specific example in this range is as follows.

SnO ₂ .0.5Sb ₂ O ₅ .5H ₂ O... TA-2 In the present invention, the solution refers to an aqueous solution, a hydrophilic solvent solution and a combination thereof.

When the pH of the solution is 7 or more, it is very slight,
The pH of the solution is preferably less than 7, since the removal material of the present invention tends to elute.

The removal material in the present invention is powdery, granular, fibrous, etc.
It can be used after being processed into an arbitrary shape as needed.

The removing material of the present invention can be usually regenerated with nitric acid or the like and reused, but it is preferable to use an acid of the same kind as the acid in the solution. The concentration of the regenerating acid is usually 3 to 10 mol /, and for example, nitric acid of 4 mol / is used in Examples described later.

The present invention can be carried out in a batch system, a semi-batch system, and a continuous system. In the examples, data of a continuous system is described as a representative.

Furthermore, the removing material of the present invention can be used alone or in combination of two as needed.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples.
The present invention is not limited to these.

Example 1 0.1 g of TA-1 was added to 10 ml of a nitric acid acid solution containing Fe, Sr, Ce as an example of a liquid to be treated and La, Eu, and Yb as representatives of rare earth elements, each at 1 × 10 ^-4 mol /. A treatment of immersion in a constant temperature water bath at a temperature of 5 ° C. for 5 days was performed.

As for the results of the rare earth elements, the partition coefficient (Kd) was 1 or less in the range of the nitric acid concentration of 0.2 to 2.0 mol /, and it was found that the rare earth elements were hardly adsorbed. The results for other metals are shown in FIG.

Comparative Example 1 FIG. 2 shows an example of the result of the sulfonic acid type strongly acidic cation exchange resin under the same conditions.

Example 2-1 The present example will be described with reference to FIG. 3, which outlines an example of the method of the present invention.

A solution in which La and Nd as representatives of iron and rare earth elements are dissolved in a 0.3 mol / nitric acid solution at the concentrations shown in Table 1 respectively from the stock solution tank 1 to the metering pump 6 with a superficial velocity of 0.5 cm / min.
The TA-1 was passed through a column 8 having an inner diameter of 6.5 mm and filled with an apparent volume of 2.5 ml.

The effluent after passing through the column was collected from line 9, and the respective concentrations were measured by atomic absorption and ICP. The results are listed in Table 1.

The exchange capacity was about 1.0 meq / g TA-1, and the following examples were almost the same.

Approximately 30 to 50 c per 1 g of TA-1 with iron adsorbed at 4 mol / nitric acid
After repeated immersion in a batch system at least three times in c or passing a nitric acid solution of 4 mol / on the column until the iron no longer flowed out, it was washed with water by a batch method or a column method, dried at 60 ° C. and regenerated.

 Regenerated TA-1 was used in the following examples.

Table -1 Metal stock solution concentration (ppm) Concentration after passage (ppm) Fe 2750 2 La 1000 1000 Nd 1000 1000 Example 2-2 Example 2-1 was replaced with TA-2 under the same conditions. did. The analysis values and exchange capacities of Fe, La, and Nd after the passage of the solution were the same as those in Example 2-1. TA-2 was also reproduced in the same manner as in Example 2-1 and used in the following Examples.

Example 3-1 Sr was added to the metals in Table 1 by the method of Example 2-1. Table 2 shows the results.

Table-2 Metal stock solution concentration (ppm) Concentration after passage (ppm) Fe 2750 2 Sr 2400 2300 La 1000 1000 Nd 1000 1000 Example 3-2 The same stock solution concentration as in Table 2 by the method of Example 2-2. Carried out. The results are shown in Table-3.

Table 3 Metal stock solution concentration (ppm) Concentration after passage (ppm) Fe 2750 2 Sr 2400 90 La 1000 1000 Nd 1000 1000 Example 4-1 Cs was added to the metals in Table 3 by the method of Example 2-1. It was carried out. The results are shown in Table-4.

Table-4 Concentration of undiluted metal (ppm) Concentration after passage (ppm) Fe 2750 2 Sr 2400 2300 Cs 4800 3000 La 1000 1000 Nd 1000 1000 Example 4-2 The same method as in Table 4 by the method of Example 2-2 Performed at stock concentration. The results are shown in Table-5.

 Table-5 Metal stock solution concentration (ppm) Concentration after passage (ppm) Fe 2750 2 Sr 2400 90 Cs 4800 5 La 1000 1000 Nd 1000 1000

[Brief description of the drawings]

FIG. 1 is a view showing the performance of the substance of the present invention, FIG. 2 is a view showing the performance of the substance of the comparative example, and FIG. 3 is a view for explaining an example of the method of the present invention. 1: Stock solution tank 2-5, 7, 9: Line 6: Metering pump 8: Column (filled with TA-1 and / or TA-2) 10, 11: Valve

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C22B 1/00-61/00 C01G 30/02

Claims (2)

(57) [Claims] 1. A method for removing iron from a solution having a pH of less than 7 in which two or more metals containing a rare earth element and iron are dissolved by removing one or a combination of the following removing materials to separate the iron from the rare earth element. Titanium antimonate Tin antimonate 2. At least one of the following substances for removing iron from a solution having a pH of less than 7 in which two or more metals including a rare earth element and iron are dissolved to separate it from the rare earth element. Titanium antimonate Tin antimonate