JPH08295512A - Separation and purification method of metal element - Google Patents

Abstract

PURPOSE: To remove impurities in a metal element, particularly a rare earth element by solubilizing the metal element with an inorganic aq. solution, extracting the specific metal element by mixing with an organic solvent, stripping the resultant organic layer with an inorganic acid aq. solution, removing the impurities except the specific metal element with a specific activated carbon and adding a salt of an alkali (alkaline earth) metal. CONSTITUTION: The metal element is an rare earth element of lanthanides having atomic number of 57 to 71, Y having atomic number of 39, a base metal such as Cu, Co, Ni, Zn, a noble metal such as Au, Pt, Pd, Rh. The activated carbon >=1000m<2> g inn specific surface area, 20-60Å in average diameter of narrow pore having <=100Å narrow pore diameter is used. As the organic solvent, an extracting agent (organic solvent) exhibiting selectively between rare earth metals, an anionic extracting agent, a cationic extracting agent, a solvation affinitive extracting agent or the like is used. For example, tributyl phosphate is exemplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating and refining a metal element, and more specifically, the present invention relates to a method for separating and refining a metal element suitable for removing impurities particularly when separating and refining a rare earth element.

[0002]

2. Description of the Related Art As a method for selectively separating and purifying a specific metal element from a system in which a plurality of metal elements are mixed, such as ore and soil, the specific metal is solvent-extracted and then back-extracted with an acidic aqueous solution. A method for obtaining a metal as an appropriate salt and regenerating an extraction solvent is well known, and is widely practiced in separation and purification of various metals.

Well-known examples include silicon, iron, copper,
When separating and purifying a nioph or nioph compound from a system containing aluminum, tantalum, calcium, nioph, etc., after dissolving these mixtures, an organic solvent consisting of an aliphatic ketone such as methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, A method in which niobium and tantalum are extracted in an organic solvent and then contacted with dilute sulfuric acid to separate niobium into an acidic aqueous solution, in a system in which at least one base metal of copper, nickel, cobalt and zinc and silver are present. After solubilizing these mixtures, a base metal is extracted by an organic layer containing human oxy-hydroxy oximes and human oxy-quinones as an extractant, and then contacted with a sulfuric acid acidic aqueous solution or the like to separate and purify the base metal, moributene, Mixing these in a system containing tank dust , And then contacting the aqueous solution containing them with di-2-ethylhexylphosphoric acid to extract both molybutene and tank dusten into the organic layer, and then oxidizing agents such as hydrogen peroxide and permanganate. A method of contacting an aqueous solution of sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, etc. containing slag to transfer only molybutene to the aqueous solution side to recover high-purity molybutene, and a method of separating and purifying noble metal from a noble metal-containing alloy include nitric acid and hydrochloric acid. After dissolving the alloy with the mixed acid of, the gold is selectively extracted from the solution with an organic solvent such as dibutyl carbitol and methyl isobutyl ketone, and then back-extracted with dilute hydrochloric acid.

Further, as a preferable example of the above-mentioned separation / purification method, there is a separation / purification method for rare earth elements, which is widely practiced and will be described in detail in the present specification by taking this as an example.
The rare earth element means a rare earth element having an atomic number of 57 to 71, which is called a lanthanum series, and yttrium having an atomic number of 39.

The separation and purification of rare earth elements from rare earth element-containing ores such as monazite, bastnasite, xenotime, etc. are carried out by eroding these ores with an aqueous solution of sulfuric acid, an aqueous solution of nitric acid or an aqueous solution of hydrochloric acid to solubilize the rare earth element, and then insoluble. The residue is removed by a normal solid-liquid separation technique such as filtration and centrifugation, and the obtained solution is used. This step is hereinafter referred to as a rare earth element solubilization step.

Mutual separation of rare earth elements is performed by liquid-liquid extraction between an aqueous layer containing a rare earth element obtained in the solubilization step and an organic layer containing a water-insoluble extractant (hereinafter referred to as a solvent extraction step). ), And a step of back-extracting the rare earth element from the organic layer (hereinafter referred to as a back-extraction step). An extractant that exhibits selectivity between rare earth elements is used, and an anionic extractant, a cationic extractant, or a solvate extractant is used.
Examples of these are tolyl-butyl phosphate (TB
P), triisobutyl phosphate (TIBP), butylphosphonate dibutyl (DBBP), 2-ethylhexyl phosphonate di (2-ethylhexyl) (DEHEHP), tri-n-butylphosphine oxide (TOPO) and the like. The organic layer at the time of solvent extraction may optionally contain an organic diluent other than the extractant. Examples of the diluent include petroleum fractions such as kerosene, paraffin hydrocarbons such as hexane and decan, ethers such as isopropyl ether, and benzene. , Xylene, ethylbenzene, and other aromatic hydrocarbons.

Separation of multiple rare earth elements in this solvent extraction process is operated by performing in multiple extraction steps, each step comprising a mixing-decantation operation. The aqueous layer obtained in the solvent extraction step contains most of iron, aluminum, calcium, phosphate, fluoride, etc. that were not extracted in the organic layer, and the organic layer contains rare earth elements, nitric acid, hydrochloric acid, phosphorus. Acids etc. are included.

In order to improve the purity of the rare earth element-containing solution, it is possible to provide a washing step before performing back extraction. This step is performed by mixing and separating the organic layer with a basic solution. The back-extraction step is provided to isolate the rare earth element contained in the organic layer from which the rare earth element has been extracted, as a suitable salt, and reuse the extraction solvent. Done.

By adding a basic solution containing a metal cation hydroxide or carbonate to the rare earth element-containing acidic solution obtained from the back extraction step, the rare earth element hydroxide or carbonate is added. (Hereinafter, this step is referred to as a rare earth element salt recovery step).

Of the above-mentioned steps, the solubilization step,
In a conventional metal element separation and purification method including a solvent extraction step, a back-extraction step, and a metal recovery step, a specific metal element is treated with hydrochloric acid or nitric acid from an organic layer containing the specific metal element. , One or more components such as an extractant, a part of the diluent contained in the organic layer or a decomposed product thereof or impurities contained in the extract, when back-extracted with an aqueous solution of sulfuric acid, etc. As a solution, the solution is colored yellow or yellowish brown, and thus this color remains in a salt of a metal element obtained by adding a carbonate of a metal cation, a hydroxide or the like to the solution. There is a drawback that the commercial value of the metal element salt is significantly impaired.

It has been conventionally known that these colorings can be avoided by adding a drug such as a reducing agent. However, the addition of these causes a new problem that the substance and the decomposed product of the substance remain. Therefore, as a method for removing the color-causing substance from the metal element-containing solution obtained in the back-extraction step, a satisfactory method has not yet been proposed.

[0012]

DISCLOSURE OF THE INVENTION As a result of earnest studies by the present inventors, a specific metal element is selected from a system in which a plurality of metal elements are mixed, including the steps described in (a) to (d) below. In the method of selectively separating and purifying, the metal element-containing acidic aqueous solution obtained in step (c) before the step (d) has a specific surface area of 1000 (m ² / g)
With the above, the volume of pores with a diameter of 100 Å or less is 0.30 to 1.0 (cc /
g), and the average pore diameter of pores with a pore diameter of 100Å or less is 20 to
A method for separating and purifying a metal element, which comprises a step of removing impurities other than a specific metal in an aqueous solution by contacting with activated carbon in the range of 60Å, and completed the present invention. It is an object of the invention to provide a method for removing a coloring-causing substance in a back-extracted metal element-containing solution.

(A) A step of solubilizing a metal element with an aqueous nitric acid solution, an aqueous hydrochloric acid solution or an aqueous sulfuric acid solution. (b) A step of mixing the solution obtained in step (a) with an organic solvent and selectively extracting a specific metal element into the organic solvent. (c) A step of mixing the organic layer obtained from step (b) with an aqueous hydrochloric acid solution, an aqueous nitric acid solution or an aqueous sulfuric acid solution, and back-extracting a specific metal element into the acidic aqueous solution. (d) A step of adding a salt of an alkali metal or an alkaline earth metal to the acidic solution containing a specific metal element obtained in step (c) to obtain a salt of the specific metal element.

[0014]

[Means for Solving the Problems] The above-mentioned purpose is as follows (a)
In a method for selectively separating and purifying a specific metal element from a system in which a plurality of metal elements are mixed, including the step described in (d), the step (c) is performed before step (d). Metallic element-containing acidic aqueous solution with a specific surface area of 1000 (m ² / g) or more and a pore diameter of 100
Pore volume of Å or less is 0.30 to 1.0 (cc / g), and pore diameter is 100
Achieved by a method for separating and purifying metal elements, which comprises a step of removing impurities other than a specific metal in an aqueous solution by contacting with activated carbon having an average pore diameter of Å or less of 20 to 60Å To be done.

(A) A step of solubilizing the metal element with an aqueous nitric acid solution, an aqueous hydrochloric acid solution or an aqueous sulfuric acid solution. (b) A step of mixing the solution obtained in step (a) with an organic solvent and selectively extracting a specific metal element into the organic solvent. (c) A step of mixing the organic layer obtained from step (b) with an aqueous hydrochloric acid solution, an aqueous nitric acid solution or an aqueous sulfuric acid solution, and back-extracting a specific metal element into the acidic aqueous solution. (d) A step of adding a salt of an alkali metal or an alkaline earth metal to the acidic solution containing a specific metal element obtained in step (c) to obtain a salt of the specific metal element.

The present invention will be described in detail below. The metal element of interest in the method of the present invention has an atomic number of 57.
To 71, rare earth elements called lanthanum series, yttrium with atomic number 39, base metals such as copper, cobalt, nickel and zinc, and precious metals such as gold, platinum, palladium and rhodium.

In the present invention, the impurities that are mixed as a coloring-causing substance in the back-extracted metal element-containing solution include:
Extractants, parts of diluents or their decomposition products, or impurities contained in them, which are substances that have been conventionally used to efficiently extract metal elements from mineral acid solutions in which ores containing metal elements have been eroded. One or more of these are contemplated. The degree of coloring of the back-extracted solution can be measured quantitatively from the amount of absorption by irradiating the solution with light in the visible region, and specifically, can be measured at a wavelength near 380 nm. .

The activated carbon used in the present invention includes coal-based, coconut shell-based,
BET using nitrogen can be used, including polymer resins
In the surface area measurement by the method, with a specific surface area of 1000 (m ² / g) or more, a pore volume of 100 Å or less and a pore volume of 0.30 to 1.0 (cc / g), and an average of pores of 100 Å or less Pore diameter 20 to 60Å
Activated carbon having a methylene blue adsorption performance of 150 to 400 (ml / g) and an iodine adsorption performance of 800 to 1800 (mg / g) in the above range is preferable from the viewpoints of adsorption removal rate and removal capacity of the coloring substance.

The shape of the activated carbon used in the present invention may be any of granular, crushed, powdery and shaped bodies, but in order to increase the contact area with the solution to be treated and enhance the efficiency of removing the coloring matter, it is in the form of fine particles. It is preferably powdery or crushed. However, in consideration of the complexity of the operation of separating and recovering the activated carbon from the solution by the operation of filtering and centrifuging after removing the coloring matter, and the increase of the water resistance in the continuous flow system (described later), etc. If it is too small, it causes inconvenience, so that the one that remains on the sieve with a mesh of 0.05 mm is practically suitable.

The method of contacting the activated carbon with the solution to be treated in the present invention is a batch system in which activated carbon is put into a container containing the solution to be treated and stirred and mixed for a certain period of time, or fine activated carbon or molded activated carbon. Etc. may be used in any of continuous flow systems in which the solution to be treated is continuously passed through the column. The temperature at the time of contact is not particularly limited, but the viscosity of the solution to be treated,
Practically preferable is 10 to 60 ° C in view of the adsorption rate and the like.

In the present invention, the time for contacting the solution to be treated with the activated carbon is influenced by the concentration of the coloring substance in the solution to be treated, the concentration of the activated carbon added, the treatment temperature, the specific surface area of the activated carbon, the shape, etc. It is practically preferable to examine and set the decolorization state with an absorptiometer using a part of the aqueous solution to be treated with time.

In the present invention, the activated carbon can be removed from the solution which has been treated with activated carbon and treated to be transparent by a general method such as filtration or centrifugation. Furthermore, the salt of the metal element can be separated and recovered from the decolorized metal-containing aqueous solution without any change from the conventionally known method.

(Measurement and evaluation method) (1) Method for measuring degree of coloring of metal element-containing aqueous solution 3 ml of a solution to be measured was sampled and put in a quartz cell having a bottom area of 10 mm × 10 mm and a height of 40 mm, and a Hitachi spectrophotometer ( U2000) at 380 nm and measured using distilled water as a control.

[0024] (2) After accurately weighing measurement measured activated carbon 0.1g about the specific surface area of the activated carbon, placed in a dedicated cell of a high-precision fully automatic gas adsorption apparatus BELSORP28 (manufactured by Nippon Bell Co.), the device It was used to adsorb nitrogen and determined by the BET method.

(3) Method for measuring pore volume and average pore diameter The pore diameter in the range of 0.01 to 10 μm is measured by a mercury porosimetry method (manufactured by Shimadzu Corp., Phoaisizer 9310) using a porosimeter, and the pore diameter is 100 liters or less. The pore volume was measured by measuring nitrogen adsorption with a highly accurate fully automatic gas adsorption device (BELSORP28 manufactured by Nippon Bell Co., Ltd.). Specifically, the pore diameter is 20 to 100Å
The pore volume and average pore diameter in the range of are obtained by DH analysis of the adsorption isotherm of nitrogen gas at 77K.
The pore volume below Å was determined by analyzing the adsorption isotherm of nitrogen gas at 77K from t-plot using MP method.

(4) Methylene blue adsorption performance Measurement is carried out according to the activated carbon test method (JIS K1474). That is, a methylene blue solution was added to the sample, and after adsorbing, filtration was performed, and the absorbance of the filtrate was measured to determine the amount of methylene blue adsorption from the residual concentration, an adsorption isotherm was created, and the residual concentration of methylene blue from the adsorption isotherm of 0.24 (mg / l) to determine the amount of adsorption and use it as the methylene blue adsorption performance.

(5) Iodine adsorption performance Measurement is performed according to the activated carbon test method (JIS K1474). That is, an iodine solution was added to the sample, and after adsorbing, the supernatant was separated, a starch solution was added as an indicator, titration was performed with a sodium thiosulfate solution, the iodine adsorption amount was determined from the remaining iodine solution, and the adsorption isotherm was determined. The iodine adsorption performance is obtained by calculating the adsorption amount at a residual iodine concentration of 2.5 (g / l) from the adsorption isotherm.

Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the examples.

[0029]

【Example】

Example 1 The composition shown in Table 1 was kneaded at a revolution of 15 RPM and a rotation of 30 RPM for 10 min (Shinagawa universal stirrer manufactured by Dalton Co., Ltd.), and then the bore diameter was 3 ¢ and the number of holes was 30.
Extrude at 80 kg / hr with an extrusion granulator (Perletter Double Fuji Paudal Co., Ltd.) equipped with 0 dice.
20 kg of precursor, which was cut into 5 mm each to form a cylindrical pellet,
Of the carbonized pellets obtained by carbonizing at 600 ° C for 3 hours in a nitrogen atmosphere
Activated carbon A obtained by further activating ₂ Kg with nitrogen gas (activation gas composition molar ratio: N ₂ / H ₂ O = 1/1 flow rate 1.5 Nl / min) containing steam at 950 ° C. for 8 hours, and steam activation Activated carbon B for 6 hours only and activated carbons C and A for 4 hours only for steam activation time
Grind each of the BCs in a mortar, pass through a mesh with an opening of 2mm, and leave the activated carbon DEF on the mesh with an opening of 0.5mm.
Was produced.

[0030]

[Table 1] Furthermore, a total of eight types of activated carbon, including FM150 (manufactured by Cataler Industry Co., Ltd.) as a coconut shell-based activated carbon and Kuraray Coal KW (manufactured by Kuraray Chemical Co., Ltd.) as a coal-based activated carbon, were used to color yellow brown. The coloring substances were removed from the lanthanum nitrate aqueous solution, the cerium nitrate aqueous solution, and the yttrium hydrochloride aqueous solution.

500 ml of the aqueous solution to be treated was put in a 1 l beaker, and 105
0.5 g of each activated carbon dried for 3 hr at ℃ was added, and the mixture was stirred at 20 ℃ and adsorbed and removed. Table 2 shows the raw material, specific surface area, pore volume, etc. of each activated carbon used as a sample.

[Table 2]

After the lapse of 30 minutes, 60 minutes, 120 minutes and 180 minutes after the activated carbon was charged, 3 ml of the solution to be treated was sampled and the degree of decolorization was measured by a spectrophotometer. The results are shown in FIGS. 1, 2 and 3.

Decolorization of the solution to be treated progresses with time, and although the time required for complete decolorization varies depending on each condition,
With a specific surface area of 1000 (m ² / g) or more, a pore volume of 100 Å or less and a pore volume of 0.30 to 1.0 (cc / g), and an average pore diameter of pores of 100 Å or less of 20 to 60 Å It has been shown that decolorization can be carried out quickly and practically sufficiently in the case of using the activated carbon in the range and within the range specified in the present invention. In addition, when calcium hydroxide was added to each solution treated with each activated carbon for 240 minutes to precipitate and separate a rare earth element salt, a precipitate obtained from a solution treated with other than C and F activated carbon was obtained. Were found to be completely white.

Example 2 Activated carbons A, B and C similar to those used in Example 1 were used to obtain a bottom area of 5
∘, packed in a column having a length of 30 cm, and subjected to decolorization treatment by a continuous flow system. Table 3 shows the results of examining the decolorization state by passing an aqueous solution of lanthanum nitrate colored yellow-brown through a column with a variable flow rate pump and measuring the absorbance of the solution flowing out from the column outlet.

[Table 3]

As can be seen from Table 3, specific surface area 1000 (m ² / g)
With the above, the volume of pores with a diameter of 100 Å or less is 0.30 to 1.0 (cc /
g), and the average pore diameter of pores with a pore diameter of 100Å or less is 20 to
It has been shown that the lanthanum nitrate aqueous solution can be decolorized to a practically sufficient degree by properly selecting the SV (space velocity) when using activated carbon in the range of 60Å.

Example 3 Activated carbons A, B and C similar to those used in Example 1 were used to obtain a bottom area of 5
∘, packed in a column having a length of 30 cm, and subjected to decolorization treatment by a continuous flow system. Table 4 shows the results of examining the decolorization state by passing a yellow-brown colored molybutene sulfate aqueous solution through the column with a variable flow rate pump and measuring the absorbance of the solution flowing out from the column outlet.

[0037]

[Table 3] As can be seen from Table 4, pores with a specific surface area of 1000 (m ² / g) or more and a pore diameter of 100 Å or less are 0.30 to 1.0 (cc / g) and a pore diameter of 100 Å or less. The average pore diameter of the pores is 20-60Å
SV (space velocity) when using activated carbon in the range
It was shown that the molybdenum sulfate aqueous solution can be decolorized to a practically sufficient degree by properly selecting.

[Brief description of drawings]

FIG. 1 is a graph showing the absorbance of each solution measured with time when using a lanthanum nitrate aqueous solution colored yellow-brown to remove colored substances from each of the eight activated carbons listed in Table 2. It is a figure which shows the result of having investigated the decolorization state of the to-be-processed liquid.

[Fig. 2] Fig. 2 is a graph showing the absorbance of each solution measured with time when a coloring substance removal treatment of a yellow-brown cerium nitrate aqueous solution was performed using each of the activated carbons listed in Table 2. It is a figure which shows the result of having investigated the decolorization state of the to-be-processed solution.

[Fig. 3] Fig. 3 is a graph showing the absorbance of each solution measured with time when a coloring substance removal treatment of a yellow-brown yttrium hydrochloride aqueous solution was performed using each of the activated carbons listed in Table 2. It is a figure which shows the result of having investigated the decolorization state of the to-be-processed solution.

[Table 4]

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Claims (1)

[Claims] 1. A method for selectively separating and purifying a specific metal element from a system in which a plurality of metal elements are mixed, including the steps described in (a) to (d) below. Process before doing
The metal element-containing acidic aqueous solution obtained in (c) has a specific surface area of 1000
(m ² / g) or more and the pore volume of 100 Å or less is 0.30 to 1.
0 (cc / g), and having a pore diameter of 100 Å or less, the average pore diameter of the pores is brought into contact with activated carbon in the range of 20 to 60 Å, and a step of removing impurities other than the specific metal in the aqueous solution is included. A method for separating and refining a characteristic metal element. (a) A step of solubilizing a metal element with an aqueous nitric acid solution, an aqueous hydrochloric acid solution, or an aqueous sulfuric acid solution. (b) A step of mixing the solution obtained in step (a) with an organic solvent and selectively extracting a specific metal element into the organic solvent. (c) A step of mixing the organic layer obtained from step (b) with an aqueous hydrochloric acid solution, an aqueous nitric acid solution or an aqueous sulfuric acid solution, and back-extracting a specific metal element into the acidic aqueous solution. (d) A step of adding a salt of an alkali metal or an alkaline earth metal to the acidic solution containing a specific metal element obtained in step (c) to obtain a salt of the specific metal element.