JPH0148340B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves mixing and contacting an organic solvent containing extracted metal ions with a fluoride-based stripping solution to precipitate metal fluoride complex crystals, and removing fluorine-based metal complexes generated by firing the crystals. The present invention relates to a method and apparatus for adjusting the concentration composition of a fluoride stripping solution in a process of recovering and reusing decomposition products.

In recent years, solvent extraction has attracted attention as a method for obtaining high-purity metals and metal oxides, and has been evaluated as a method with a simple purification process and low energy consumption. In addition, the metals that can be extracted include Mg, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn,
These include Cd, Nb, Zr, Ta, Mo, W, In, and many others.

In the solvent extraction method, the stripping (reverse extraction) method of conventionally extracted metal ions has been a problem, but fluoride-based stripping solutions (one or two of HF, NH ₄ , HF ₂ and NH ₄ F) are used.
The problem was solved by using an aqueous solution containing more than one type of
(See Japanese Patent Application Laid-open No. 57-73141 and Japanese Patent Application Laid-open No. 57-85943).
In addition, the equipment for carrying out this method is as follows:
The inverted cone-shaped "crystallizer" shown in JP-A No. 58-81402, and its improved version "Crystallizer for metal peeling" shown in Japanese Patent Application No. 59-62432 (JP-A No. 60-208429) "Device", Patent Application No. 1983-94070 (Japanese Patent Application No. 60-238427)
``Metal back extraction equipment'' shown in No.) can be used. Furthermore, regarding the stripping of extracted Fe ³⁺ ions, the control range for the concentration, composition, etc. of the fluoride-based stripping solution that is used in circulation is also presented (see "Crystallizer operating method").

However, these inventions do not disclose an adjustment method for maintaining the concentration and composition of the metal stripping solution used in circulation within a certain control range, and the equipment for carrying out the method is not necessarily required. It wasn't enough. If the type and location of the agent supplied to the circulation flow of the fluoride stripper is not appropriate, problems such as crystal precipitation and clogging may occur in the piping and pump, which is not desirable. During operation of metal stripping equipment, problems such as crystal precipitation and clogging occur in piping, pumps, etc., as shown in the comparative example, often occur, forcing the equipment to stop operating.

An object of the present invention is to provide a method for measuring and adjusting the concentration and composition that is effective for controlling the concentration and composition of a fluoride-based stripping solution for metal stripping, and also to provide a suitable device that overcomes the problems of metal stripping devices. The object of the present invention is to provide smooth operation of a metal stripping process.

That is, the present invention has a mixing zone, an organic solvent standing zone, a fluoride stripping solution standing zone, and below these a metal fluoride complex crystal separation zone, and a crystal growth zone or a stripping solution cooling zone. In the crystallizer, when extracting metal ions in the mixing zone and bringing the containing organic solvent into contact with a fluoride stripping solution to precipitate metal fluoride complex crystals, and converting the obtained crystals into metal oxides or metals, Supplying an NH ₄ HF ₂ solution to the crystal growth zone or stripping liquid cooling zone of the crystallizer, and causing the stripping liquid discharged from the stripping liquid outlet of the crystallizer to absorb the metal fluoride complex crystal decomposition gas. The fluoride stripping solution is supplied to the mixing zone of the crystallizer, and the filtrate after crystal separation is supplied to the stripping solution standing zone below the organic solvent standing zone of the crystallizer, thereby circulating the fluoride stripping solution. The present invention provides a metal stripping method characterized in that the concentration and composition of the metal stripping solution can be adjusted by using the metal stripping solution.

The present invention also has a mixing zone, an organic solvent standing zone, and a fluoride stripping solution standing zone, and below these, a metal fluoride complex crystal separation zone, and a crystal growth zone or a stripping solution cooling zone. In the analysis apparatus, when extracting metal ions in the mixing zone and bringing the containing organic solvent into contact with a fluoride stripping solution to precipitate metal fluoride complex crystals and converting the obtained crystals into metal oxides or metals, An NH ₄ HF ₂ solution was supplied to the crystal growth zone or the stripping solution cooling zone of the crystallizer, and the stripping solution discharged from the stripping solution outlet of the crystallizer absorbed the metal fluoride complex crystal decomposition gas. supplying ammonia from the crystal growth zone or stripping liquid cooling zone of the crystallizer to a receiving tank for crystals discharged from this,
The filtrate after crystal separation is supplied to the stripping solution standing zone below the organic solvent standing zone of the crystallizer, and the concentration and composition of the metal stripping solution is adjusted by circulating and using the fluoride stripping solution. The present invention provides a metal peeling method characterized by the following.

The present invention also has a mixing zone of an organic solvent containing an extracted metal ion and a fluoride stripping solution, a stripping solution standing zone below the organic solvent standing zone, and a metal fluoride complex crystal below these. A crystallizer having a separation zone and a crystal growth zone or a stripping liquid cooling zone, a receiving tank for crystals obtained in this crystallizer,
It is composed of a crystal solid-liquid separation device, a crystal drying/decomposition device, a crystal decomposition gas absorption device, a NH ₄ HF ₂ solution supply device for the crystallizer, and a stripping liquid concentration measuring device, and the crystal decomposition gas absorption device is The NH ₄ HF ₂ supply port of the NH 4 HF 2 solution supply device is connected to the stripping solution outlet of the crystallizer and the stripping solution supply port in the mixing zone by piping, and the NH 4 HF 2 supply port of the NH ₄ HF ₂ solution supply device is connected to the stripping solution outlet of the crystallizer and the stripping solution supply port in the mixing zone. The present invention provides a metal stripping device, which is provided in a liquid cooling zone, and a supply port for the filtrate after crystal separation is provided in a stripping solution standing zone of the crystallizer.

The present invention further includes a mixing zone of an organic solvent containing extracted metal ions and a fluoride stripping solution, and a stripping solution standing zone below the organic solvent standing zone,
A crystallizer having a metal fluoride complex crystal separation zone and a crystal growth zone or a stripping liquid cooling zone below these, a receiving tank for the crystals obtained in this crystallizer, a solid-liquid separation device for crystals, and a crystal drying/decomposition device ,
It is composed of a crystal decomposition gas absorption device, an ammonia supply device, an NH ₄ HF ₂ solution supply device of the crystallizer, and a stripping liquid concentration measuring device, and the crystal decomposition gas absorption device is connected to the stripping liquid outlet of the crystallization device and The NH ₄ HF ₂ supply port of the NH ₄ HF ₂ solution supply device is provided in the crystal growth zone or the stripping solution cooling zone of the crystallizer, and the ammonia The ammonia supply port of the supply device is provided between the crystal growth zone or stripping liquid cooling zone of the crystallizer and the crystal receiving tank, and the supply port of the filtrate after crystal separation is provided between the crystal growth zone or stripping liquid cooling zone of the crystallizer. The present invention provides a metal stripping device characterized in that it is installed in a storage zone.

The present invention improves the concentration composition of the fluoride stripper by changing the concentration composition to all HF.
By managing with two items: and total NH ₄ F,
The present invention provides a metal stripping method characterized by supplying an NH ₄ HF ₂ solution, a fluorine-based decomposition product, and, if necessary, ammonia to appropriate locations, and an apparatus for carrying out the method.

As an organic solvent for extracting metal ions, an alkyl phosphate-based or carboxylic acid-based extractant diluted with n-paraffin can be used.
In addition, fluoride strippers include HF, NH ₄ HF ₂ ,
An aqueous solution containing one or more types of NH ₄ F can be used.

The details of the present invention will be explained in detail based on the drawings using the case of extraction of Fe ³⁺ ions as an example, but the types of metals targeted by the present invention and the method and apparatus to be illustrated using the drawings will be described in detail. It is not limited to.

FIG. 1 is a flow sheet of metal solvent extraction equipment including a step of circulating a fluoride stripping solution, which is the subject of the present invention. When the metal ion-containing aqueous solution A and the organic solvent S are brought into contact with each other in the metal extraction step 1, A
The metal ions inside are extracted into S. The aqueous solution after metal extraction is the raffinate solution R, and when A is a metal-containing waste acid, R is the recovered acid. When the metal ion in the aqueous solution A is Fe ³⁺ and the organic solvent S contains an ion exchange extractant such as an alkyl phosphate, the chemical formula of S can be expressed as HR, so the extraction reaction formula is as follows. .

Fe ³⁺ +3HR→FeR ₃ +3H ⁺ (1) FeF ₂ ⁺ +3HR→FeR ₃ +H ⁺ +2HF (2) FeF ₂ ⁺ +HR→FeF ₂ R+H ⁺ (3) In reaction formulas (2) and (3), A is iron This is the case of a nitrofluoric acid waste solution containing nitric fluoride, and the Fe ³⁺ ions in A mainly take the form of FeF ₂ ⁺ ions.

Organic solvent S containing extracted metal ions in step 1
is mixed with the fluoride stripping solution D heated in metal stripping step 2, and the metal ions are mixed with the fluoride metal complex crystal X.
becomes. The metal ion is Fe ³⁺ and the stripping solution D is
In the case of an aqueous solution mainly composed of NH ₄ HF ₂ , the peeling reaction formula is as follows.

FeR ₃ +3NH ₄ HF ₂ →3HR+(NH _-4 ) ₃ FeF ₆
↓(4) FeF ₂ R＋3NH ₄ HF ₂ →HR＋(NH ₄ ) ₃ FeF ₆ ↓
+2HF(5) FeR ₃ +3NH ₄ HF ₂ +3NH ₄ F→3NH ₄ R+(NH ₄
) ₃ FeF ₆ ↓＋3HF(6) In this case, a part of the extractant after the iron is removed becomes ammonia type (NH ₄ R) through the reaction shown in equation (6).

The stripping solution D containing the crystals X that has come out of step 2 has X separated therefrom in solid-liquid separation step 3, returns to the stripping step 2 again, and is recycled.

The separated crystals X are fired in a drying/decomposition step 4 to become metal M or metal oxide O. The reaction in which metallic iron or iron oxide is produced from iron fluoride complex crystals (NH ₄ ) ₃ FeF ₆ is as follows.

(NH ₄ ) ₃ FeF ₆ +3/2H ₂ →3NH ₄ F+3HF+F
e(7) (NH ₄ ) ₃ FeF ₆ +3/4O ₂ →3NH ₄ F+3/2F ₂ +1
/2Fe ₂ O ₃ (8) The fluorine-based decomposition gas G consisting of NH ₄ F, HF, F ₂ and the like generated in step 4 is returned to the stripping solution D and used again.

Now, the extractant of the organic solvent S that has come out of step 2 and is in the ammonia form is converted back into the hydrogen form (HR) by contact with the aqueous hydrochloric acid solution C in the solvent conversion step 5.
Then, the process returns to step 1 and is used again.

NH ₄ R+HCl→HR+NH ₄ Cl (9) Aqueous ammonia E is recovered from the aqueous hydrochloric acid solution C containing NH ₄ Cl discharged from step 5 through neutralization and distillation in ammonia recovery step 6.

NH ₄ Cl + NaOH → NH ₄ OH + NaCl (10) The recovered ammonia water (ammonium water) E is returned to the stripping solution D and used as necessary.

Next, in relation to changes and adjustments in the concentration and composition of fluoride stripping solution D, we will examine the characteristics of the solubility curve of metal fluoride complexes in the case where the metal ion is Fe ³⁺ (NH ₄ ) ₃ FeF ₆
This will be explained using an example.

Regarding this example, in the operating method of a crystallizer already filed on March 30, 1982, a crystallizer having a mixing zone or mixing tank, a crystal separation zone, and a crystal growth zone or cooling zone in order from the top is described. When operating a device that precipitates iron complex crystals by bringing an organic solvent containing Fe ³⁺ ions into contact with a fluoride stripping solution in the mixing zone, the concentration of the stripping solution discharged from the device is NH ₄ . HF ₂ is 85-115g/and HF is 10
The concentration and composition of the stripping solution supplied to the device is adjusted so that the concentration and composition of the stripping solution are adjusted to 20 to 25 ° C., and the temperature of the organic solvent supplied to the device is adjusted to 20 to 25 ° C. When the organic solvent and the stripping solution are mixed in two phases. The temperature of the stripping liquid in the crystal growth zone or cooling zone is set to 40℃ or less.
It is disclosed that long-term continuous operation of the device is facilitated by maintaining the temperature at 15 to 20°C. Therefore,
Comparative Examples and Examples are conducted under these conditions.

Figures 2 to 5 are graphs of the solubility of (NH ₄ ) ₃ FeF ₆ in fluoride-based stripping solutions.
NH ₄ HF ₂ is 75-150g/, HF is 0-20g/
The solubility curve is given in the range of .

In stripping step 2, when Fe ³⁺ ions are stripped by the reaction of formula (4), NH ₄ HF ₂ in stripping solution D is consumed and the concentration decreases. Further, when the metal ion-containing aqueous solution A is an iron-containing nitrofluoric acid waste solution,
When Fe ³⁺ ions are stripped by the reaction of equation (5), not only does the NH ₄ HF ₂ concentration in stripping solution D decrease;
The F ^- ions transferred from the organic phase to the stripping solution become HF, increasing the HF concentration. In this case, as can be easily seen from the solubility curve above,
As the NH ₄ HF ₂ concentration decreases, the solubility of (NH ₄ ) ₃ FeF ₆ increases. Furthermore, as the HF concentration increases,
This trend will become even more pronounced.

Thus, in the special case where the metal ion stripping reaction progresses, the NH ₄ HF ₂ concentration decreases, and the metal ions are extracted as fluoride ions.
As the HF concentration increases, in order to circulate and reuse the metal stripping solution, it is necessary to maintain it within a certain control range by adjusting its concentration and composition.

The chemicals, etc. that should be supplied to adjust the concentration and composition of the fluoride stripping solution D that is used in circulation are as follows. To increase _{the NH4HF2} concentration,
Either add NH ₄ HF ₂ solution (usually 30 to 40% concentration) F, or absorb the fluorine-based decomposition gas G generated in reactions such as equations (7) and (8) into the stripping solution in an appropriate manner. There are two methods. The composition of the gas generated in the reaction of equations (7) and (8) is the composition of NH ₄ HF ₂ , i.e.
It corresponds to NH ₄ F + HF, and the absorption of cracked gas G has substantially the same effect as the addition of NH ₄ HF ₂ solution. Also, to reduce the concentration of HF, add ammonia water or _NH3 gas E.
Although it is preferable to neutralize HF, the addition of ammonia E also contributes to an increase in the NH ₄ HF ₂ concentration, as shown in the following reaction formula.

HF+1/2NH ₃ →1/2NH ₄ HF ₂ (11) In this way, when adding NH ₄ HF ₂ solution F or absorbing fluorine-based decomposition gas G, stripping solution D
_NH4HF2 concentration increases, ammonia water _or
When NH ₃ gas E is added, the HF concentration in stripping solution D decreases and the NH ₄ HF ₂ concentration increases, but the supply of these chemicals, etc., tends to decrease the solubility of the metal fluoride complex in the stripping solution. It acts on

However, when a chemical for concentration adjustment is supplied to Stripper D, in which the metal stripping reaction has progressed and the solubility of the metal fluoride complex has increased, the solubility of the metal fluoride complex rapidly decreases, and the solubility of the metal fluoride complex decreases rapidly. Complex crystals X precipitate at once. Therefore, if the location where the medicine is supplied is not appropriate, undesirable precipitation of crystals will occur, leading to troubles such as clogging of the piping as described above.

Therefore, preferable locations where chemicals and the like for concentration/composition adjustment should be provided will be explained using FIG. 6 of a comparative example and FIGS. 7 and 8 showing the basic configuration of the metal stripping apparatus of the present invention.

_NH4HF2 solution (30-40% ₎ F crystallizer 1
It is preferable to add it to the lower part of the main body of 0. This supply point 73 corresponds to a region in the main body of the crystallizer 10 where the metal fluoride complex crystal Crystal growth also occurs, and crystal growth is promoted.
At other locations, undesirable precipitation of crystals occurs, making them undesirable addition locations. for example,
In FIG. 6 of the comparative example, F is added to the absorption liquid tank 62 of the cracked gas absorption device 60, but when added to this location, crystals X precipitate in the absorption liquid tank 62, and the absorption liquid pump 63 and the cracked gas This causes X to adhere or become clogged in the absorption tower 61 or the pipes connecting these. Further, the crystal receiver tank 30 is also considered as a place where F should be added, but the crystal filtrate after leaving the crystal receiver tank 30 is supplied to the stripping solution standing zone 20 below the organic solvent standing zone 13 of the crystallizer 10. Therefore, the effect of adding F is inferior to the lower part of the main body of the crystallizer 10.

Ammonia E is added as necessary, and can be added as aqueous ammonia or NH ₃ gas, but when added as aqueous ammonia, ammonium chloride recovered from ammonia recovery step 6 shown in Figure 1 is used. can also be used. E is the lower part of the main body of the crystallizer 10 mentioned above as shown in FIG.
Alternatively, as shown in FIG. 8, it is preferable to add it to the crystal receiving tank 30 or between these. The reason why E should be added to the lower part of the main body of the crystallizer 10 is as follows.
The same is true for NH ₄ HF ₂ solution F. When F is added to the crystal receiving tank 30, HF in the stripping solution is reduced by neutralization, and NH ₄ HF ₂ increases by a corresponding amount, so that the crystals X are further precipitated. Since the crystal filtrate after solid-liquid separation has reduced HF, it is suitable as a stripping solution to be supplied to the stripping solution standing zone 20 of the crystallizer 10. If E is added to the above two locations or to a location other than those in between, undesirable crystal precipitation will also occur. for example,
In FIG. 6 of the comparative example, NH ₃ gas E is introduced into the _cracked gas absorption tower ₆₁ of the cracked gas absorption device 60, but crystals This is undesirable because it causes precipitation, adhesion, and clogging.

The fluorine-based crystal decomposition gas G is absorbed by the decomposed gas absorbing tower 61 into the discharged stripping liquid discharged from the stripping liquid outlet 28 of the crystallizer 10, and is then absorbed into the mixing zone 18 of the crystallizer 10.
It is appropriate to supply With other feeding methods, undesirable crystal precipitation still remains a problem. In _{addition ,} even in the above preferred method of supplying G, there is a concern that crystals This will resolve the issue. For example, if the metal ion is Fe ³⁺ ,
The NH ₄ HF ₂ concentration of the draining liquid discharged from the discharge port 28 is set to 85 g/ or more and 115 g/ or less, and the HF concentration is set to 10
If the amount is maintained at less than g/g, undesirable precipitation of (NH ₄ ) ₃ FeF ₆ crystals X can be suppressed.

As described above, in the metal stripping method provided by the present invention, the NH ₄ HF ₂ solution and ammonia are used in an effective manner from the bottom of the crystallizer main body to the crystal slurry receiving tank, where there is no problem even if crystal analysis occurs. The fluorine-based crystal decomposition gas is absorbed into the discharge stripping solution whose concentration and composition are controlled and then supplied to the mixing tank of the crystallizer, and as shown in the example, the metal stripping process is operated. can be continued smoothly.

Next, an apparatus for carrying out the above metal peeling method will be explained.

FIG. 7 and FIG. 8 are basic configuration diagrams showing an embodiment of the metal stripping apparatus of the present invention. This device includes a crystallizer 10, a crystal receiver 30, a solid-liquid separator 40,
Crystal drying/decomposition device 50, cracked gas absorption device 6
0, NH ₄ HF ₂ solution supply device 70, ammonia supply device 80, and stripping solution concentration/composition measurement device 90.

The crystallizer 10 may be a crystallizer for metal stripping as shown in Japanese Patent Application Laid-open No. 50-81402 or Japanese Patent Application No. 59-62432, or
The inverted conical crystallizer described in the metal stripping device shown in Japanese Patent Application No. 94070 can be used, but preferably the metal stripping crystallizer shown in Japanese Patent Application No. 59-62432 or the metal stripping crystallizer described in Japanese Patent Application No. This is an inverted conical crystallizer described in the metal reverse extraction device shown in No. 59-94070, which has a stripping liquid forced circulation zone 25 as shown in Figure 8 at the bottom of the main body, and is capable of discharging the supplied chemical. It is best to use a type that can be mixed with the stripping solution immediately. As the solid-liquid separator 40, a centrifugal separator can be used in addition to the filters shown in FIGS. 7 and 8. Further, as the crystal drying/decomposition device 50, a type in which a crystal drying kiln and a crystal decomposition kiln are separated, or various types of furnaces can be adopted.

The cracked gas absorption device 60 includes a cracked gas absorption tower 61,
It consists of an absorption liquid tank 62, an absorption liquid pump 63, a supply stripping liquid pump 64, etc., and is connected by piping to the stripping liquid outlet 28 of the crystallizer 10 and the stripping liquid supply port 16 in the mixing tank 18, and is also used for crystal drying. - Fluorine-based decomposition gas G discharged from the decomposition kiln 51 is introduced.
The NH ₄ HF ₂ solution supply device 70 includes an NH ₄ HF ₂ solution tank 71, an NH ₄ HF ₂ solution pump 72, an NH ₄ HF ₂ solution supply port 73, etc., and the supply port 73 is connected to the crystallizer 1.
It is provided at the bottom of the main body of 0. Further, the ammonia supply device 80 is provided as necessary, and includes an ammonia water tank 81, an ammonia water pump 82, an ammonia supply port 85 or an NH ₃ gas holder 83,
It consists of an NH ₃ gas valve 84, an ammonia supply port 85, etc., and the supply port 85 is provided in the lower part of the main body of the crystallizer 10 or in the crystal receiving tank 30.
Naturally, new crystals X will precipitate near the NH ₄ HF ₂ solution supply port 73 and the ammonia supply port 85, so it is desirable that the stripping solution D in this region be in a fluid state. This is realized by adopting the type having the stripping liquid forced circulation zone 25 at the lower part of the main body as described above, and by providing the crystal slurry stirrer 31 in the crystal receiving tank 30.

As described above, FIGS. 7 and 8 show the basic configuration of the metal stripping apparatus provided by the present invention, and it goes without saying that the embodiments thereof are not limited thereto.

Next, a method for controlling the concentration and composition of a fluoride stripping solution for carrying out the metal stripping method described above will be described.

As is clear from the above explanation, metal stripping step 2
The fluoride-based stripping solution D for precipitating metal fluoride complex crystals X through mixed contact with an organic solvent S containing extracted metal ions is generally NH ₄ HF ₂
It is an aqueous solution consisting of and HF. As mentioned above
Since the composition of NH ₄ HF ₂ is equivalent to NH ₄ F + HF,
It is effective to manage the concentration and composition of stripping solution D using two items: total HF (hereinafter referred to as T.HF) and total NH ₄ F (hereinafter referred to as T.NH ₄ F). Stripping liquid D
When the molar concentrations (mol/) of NH ₄ HF ₂ and HF are a and b, respectively, the following relationship holds true.

T.HF=b (12) T.NH ₄ F=a+b (13) Now, T.HF and T.NH ₄ F can be measured by neutralization titration using a potentiometric titrator, as described below. Alternatively, conductivity measurement using an electromagnetic conductivity meter and total fluorine (hereinafter referred to as TF) using the ion electrode method, etc.
This can be done by a combination method with analysis.

FIG. 9 to FIG. 11 are examples of neutralization titration curves (differential type) of stripping solution D with N/2NaOH solution obtained using a potentiometric titration device. 1 ml of stripping solution D was collected for each titration, and the concentration and
The composition in Figure 9 is NH ₄ HF ₂ concentration a = 1.75 mol/
=100g/, HF concentration b=0mol/=0g/,
Figure 10 shows a=1.75mol/=100g/, b=
0.50mol/=10g/, Figure 11 shows a=
1.75mol/=100g/, b=1.00mol/=20
It corresponds to g/. Two main peaks appear in each of these titration curves, and the one from the start of titration (0 ml) to the first peak is T.HF, and the first peak is T.HF.
Assigning the peak to the second peak to T.NH ₄ F and calculating the respective concentrations, T.HF and T.
It agrees well with the NH ₄ F concentration. Therefore, the T.HF and T.NH ₄ F values can be determined from these neutralization titration curves, and the values of a and b can be determined using the following equations.

a=T.NH ₄ F−T.HF (14) b=T.HF (15) Figure 12 shows the conductivity measured using an electromagnetic conductivity meter.
The isoconductivity curve was created based on the conductivity value C at 25°C of stripping solution D with various a and b values, and the horizontal and vertical axes represent the T.HF and T.NH ₄ F values, respectively. It is attached. The isoconductivity curve is a slightly downward sloping curve. When the conductivity C is measured with an electromagnetic conductivity meter and the total F (denoted as TF) is analyzed using the ion electrode method, for example, T.HF and T. of stripping solution D are determined as follows.
The NH ₄ F value can be determined. For example c=
If 160mS/cm and TF = 3.00mol/ are obtained, in Figure 12, from the intersection of the c = 160mS/cm = constant curve and the TF = 3.00mol/ = constant line segment XY, it is plotted on the horizontal and vertical axes. When the perpendicular lines are drawn down, the values at the points where both axes meet become the T.HF and T.NH ₄ F values of stripping solution D, respectively.

Note that a metal ammonium fluoride complex is dissolved in stripping solution D, and strictly speaking, metal ions are Fe ³⁺
For example, stripping solution D is NH ₄ HF ₂ −HF
-(NH ₄ ) ₃ FeF ₆ based solution. However, in general, metal fluoride ammonium salts have a relatively low solubility in stripping solution D, and dissolved metal fluoride ammonium salts have almost no effect on analysis or measurement, so T.HF and T.NH ₄ When determining the F value, stripping solution D can be considered to be an NH ₄ HF ₂ -HF-based solution.

As described above, the concentration and composition of the fluoride stripper can be controlled by determining the values of total HF and total NH ₄ F. Total HF and total NH ₄ F values can be determined by two methods. The neutralization titration method is convenient because it allows direct determination of total HF and total NH ₄ F values, but the measurements are intermittent.
In the combined method of conductivity measurement and total fluorine analysis,
If the total fluorine analysis is performed intermittently, the conductivity measurement can be performed continuously, so that the concentration and composition of the stripping solution can be continuously controlled.

In the metal stripping apparatus of the present invention shown in FIGS. 7 and 8, the locations where the concentration and composition of the stripping solution D should be measured are the supply stripping solution measuring section 91, the discharged stripping solution measuring section 92, and the crystal filtrate measuring section 93. There are 3 locations. Appropriate control ranges for concentration and composition can be determined at each of these measurement points, and adjustments can be made by supplying drugs, etc. while measuring the total HF and total NH ₄ F values.

As explained in detail above, the concentration and composition of the fluoride stripper provided by the present invention are different from total HF to total HF.
The supply of chemicals, etc. can be achieved by operating the metal stripping process using a metal stripping method and equipment that is characterized by supplying chemicals, etc. to appropriate locations by controlling them using two items: NH ₄ F. It is possible to prevent troubles such as piping clogging caused by this, and achieve stable operation over a long period of time.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Comparative Example 1 Using the apparatus shown in Figure 6, 30v/v% di-
(2-ethylhexyl) phosphoric acid and 70v/v%n-
extracted into an organic solvent consisting of paraffin and
Exfoliation of Fe ³⁺ ions as (NH ₄ ) ₃ FeF ₆ crystals
It was carried out on a scale of 45 tons - crystals/month. Crystallizer 1
The temperature of the liquid in the mixing zone 18 was adjusted to 30 to 40°C, and the temperature of the liquid in the stripping liquid cooling zone 22 was adjusted to 15 to 20°C. Then, the concentration and composition of the stripping solution in the discharged stripping solution measuring section 92 is 85 to 115 g/NH ₄ HF ₂ ,
In order to adjust HF to 0 to 10g/,
30% NH ₄ HF ₂ solution is absorbed into the NH ₄ HF ₂ in the liquid tank 62.
When the solution was added through the solution supply port 73, (NH ₄ ) ₃ FeF ₆ crystals precipitated in the absorption liquid tank 62 within 24 hours after addition and adhered to the absorption liquid pump 63 and the cracked gas absorption tower 61, causing clogging. This caused the equipment to be unable to continue operating. In addition, separately from the NH ₄ HF ₂ solution F, NH ₃ gas E is sent to the decomposition gas absorption tower 6.
When the ammonia was added to the ammonia supply port 85 of No. 1, the absorbent pump 63 and cracked gas absorption tower 61 were clogged with (NH ₄ ) ₃ FeF ₆ crystals.

Example 1 Using the apparatus of the present invention shown in FIG. 8, an iron stripping process was carried out under substantially the same conditions as in the comparative example. In order to maintain the concentration and composition of the stripping solution D in the discharged stripping solution measuring section 92 within the same control range as in the comparative example, a 30% NH ₄ HF ₂ solution is placed in the crystal growth zone of the crystallizer 10 or in the stripping solution forced circulation zone 25. To,
Additions were made as appropriate. Even after 30 days had passed since the start of operation, no precipitation or clogging of (NH ₄ ) ₃ FeF ₆ crystals due to the addition of chemicals was observed, and operation could be continued without any problems.

Example 2 Using the apparatus of the present invention shown in FIG. 8, an iron stripping process was carried out under substantially the same conditions as in the comparative example. In order to maintain the concentration and composition of the stripping solution D in the discharged stripping solution measuring section 92 within the same control range as in the comparative example, a 30% NH ₄ HF ₂ solution is placed in the crystal growth zone of the crystallizer 10 or in the stripping solution forced circulation zone 25. To,
NH ₃ gas was appropriately added to the crystal growth zone or cooling zone at the lower part of the main body of the crystallizer 10, or to the crystal receiving tank 30, respectively. Even after 30 days have passed since the start of operation, (NH ₄ ) ₃ FeF ₆ due to the addition of drugs, etc.
No crystal precipitation or clogging was observed, and operation could be continued without any problems.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of a metal ion separation process using a solvent extraction method, including a process of circulating a fluoride stripping solution. Figures 2 to 5 are
NH ₄ HF ₂ 75-150g/, HF 0-20g/
It is a graph of the solubility curve of ( _NH4 ) _3FeF6 with respect to the fluoride stripping solution containing in the _range of. 6th
The figure is a basic configuration diagram of a metal stripping device of a comparative example.
8 and 8 are basic configuration diagrams showing embodiments of the apparatus of the present invention. Figures 9 to 11 are examples of neutralization titration curves (differential type) for fluoride-based strippers using a potentiometric titrator, where the NH ₄ HF ₂ concentration is constant at 100 g/, and the HF concentrations are 0, 10, and 20 g, respectively. / represents the measurement results of the stripping solution. FIG. 12 is an isoconductivity curve of a fluoride stripper at 25° C., prepared by measurement using an electromagnetic conductivity meter. Explanation of symbols, A... Metal ion-containing aqueous solution, C
...Hydrochloric acid aqueous solution, D...Fluoride stripper, E...
Ammonia water or NH ₃ gas, F...NH ₄ HF ₂
Solution (30-40%), G...Fluorine decomposition gas, M...
...Metal, O...Metal oxide, R...Raffinate, S...
...Organic solvent, Process, 6...Ammonia recovery process, 10
... Crystallizer main body, 11 ... Organic solvent heat exchanger,
12... Organic solvent supply port, 13... Organic solvent standing zone, 14... Organic solvent outlet, 15... Stripping liquid heat exchanger, 16... Stripping liquid supply port, 17... Crystal filtrate supply port, 18... Mixing zone or mixing tank, 19... Downcomer, 20... Stripping liquid standing zone, 21... Crystal growth zone, 22... Stripping liquid cooling zone, 23... Cooling stripping liquid pump, 24...
Cooling stripping liquid heat exchanger, 25... Stripping liquid forced circulation zone, 26... Circulating stripping liquid pump, 27... Crystal separation zone, 28... Stripping liquid outlet, 29... Crystal discharge pipe, 30... Crystal Receiving tank, 31...Crystal slurry stirrer, 40...Solid-liquid separator, 41...Crystal slurry pump, 42...Crystal filter, 43...
...Filtrate tank, 44...Crystal filtrate pump, 50...Crystal drying/decomposition device, 51...Crystal drying/decomposition kiln, 60...Cracked gas absorption device, 61...Cracked gas absorption tower, 62...Absorption liquid Tank, 63... Absorption liquid pump, 64... Supply stripping liquid pump, 70...
NH ₄ HF ₂ solution supply device, 71... NH ₄ HF ₂ solution tank, 72... NH ₄ HF ₂ solution pump, 73...
_{NH4HF2 solution} supply port, 80...Ammonia supply device, 81...Ammonia water tank, 82...Ammonia water pump, 83... _NH3 gas holder, 8
4...NH ₃ gas valve, 85... Ammonia supply port, 90... Stripper concentration/composition measuring device, 91
...Supplied stripping liquid measuring section, 92... Discharged stripping liquid measuring section, 93... Crystal filtrate measuring section.

Claims (1)

[Claims] 1. It has a mixing zone, an organic solvent standing zone, and a fluoride stripping solution standing zone, and below these, a metal fluoride complex crystal separation zone, and a crystal growth zone or a stripping solution cooling zone. In a crystallizer having a metal ion, in the mixing zone, metal ions are extracted and an organic solvent containing the metal ions is brought into contact with a fluoride-based stripping solution to precipitate metal fluoride complex crystals, and the resulting crystals are converted into metal oxides or metals. , in the crystal growth zone or stripping liquid cooling zone of the crystallizer.
NH ₄ HF ₂ solution is supplied, and the stripping solution discharged from the stripping solution outlet of the crystallizer absorbs the metal fluoride complex crystal decomposition gas, and the resulting mixture is supplied to the mixing zone of the crystallizer, and the stripping solution discharged from the stripping solution outlet of the crystallizer is supplied to the mixing zone of the crystallizer. The filtrate after separation is supplied to the stripping solution standing zone below the organic solvent standing zone of the crystallizer, and the concentration and composition of the metal stripping solution is adjusted by circulating and using the fluoride stripping solution. A metal peeling method characterized by: 2 The concentration and composition of the fluoride stripper are total HF and total HF.
The metal stripping method according to claim 1, characterized in that the metal stripping method is controlled by two items: NH ₄ F. 3. A crystallizer having a mixing zone, an organic solvent standing zone, a fluoride stripping liquid standing zone, and below these a metal fluoride complex crystal separation zone, and a crystal growth zone or a stripping liquid cooling zone, When extracting metal ions in the mixing zone and bringing the containing organic solvent into contact with a fluoride stripping solution to precipitate metal fluoride complex crystals and converting the obtained crystals into metal oxides or metals, In the crystal growth zone or stripping liquid cooling zone
NH ₄ HF ₂ solution is supplied, and the stripping solution discharged from the stripping solution outlet of the crystallizer absorbs the metal fluoride complex crystal decomposition gas, and the mixture is supplied to the mixing zone of the crystallizer. Ammonia is supplied from the crystal growth zone or stripping liquid cooling zone of the crystallizer to the receiving tank for the crystals discharged from this zone, and the filtrate after crystal separation is stripped at the lower part of the organic solvent standing zone of the crystallizer. A metal stripping method characterized by adjusting the concentration and composition of a metal stripping solution by supplying the solution to a stationary zone and then circulating the fluoride stripping solution. 4 Change the concentration and composition of the fluoride stripper to total HF and total HF.
The metal stripping method according to claim 3, which is controlled by two items: NH ₄ F. 5 A mixing zone of an organic solvent containing an extracted metal ion and a fluoride stripping solution, a stripping solution standing zone below the organic solvent standing zone, and a fluoride metal complex crystal separation zone and a crystallization zone below these. A crystallizer having a growth zone or a stripping liquid cooling zone, a receiving tank for crystals obtained in this crystallizer, a solid-liquid separation device for crystals, a crystal drying/decomposition device, a crystal decomposition gas absorption device, an NH of the crystallizer ₄ HF ₂ solution supply device,
and a stripping solution concentration measuring device, the crystal decomposition gas absorption device is connected via piping to a stripping solution outlet of the crystallizer and a stripping solution supply port in the mixing zone, and the NH ₄ HF ₂ solution supply device of
The NH ₄ HF ₂ supply port is provided in the crystal growth zone or stripping solution cooling zone of the crystallizer, and the supply port for the filtrate after crystal separation is provided in the stripping solution standing zone of the crystallizer. Characteristic metal stripping equipment. 6 It has a mixing zone of an organic solvent containing an extracted metal ion and a fluoride stripping solution, a stripping solution standing zone below the organic solvent standing zone, and a fluoride metal complex crystal separation zone and a crystallization zone below these. A crystallizer having a growth zone or a stripping liquid cooling zone, a receiving tank for crystals obtained with this crystallizer, a solid-liquid separator for crystals, a crystal drying/decomposition device, a crystal decomposition gas absorption device, an ammonia supply device, the crystallization device analysis equipment
It is composed of an NH ₄ HF ₂ solution supply device and a stripping solution concentration measuring device, and the crystal decomposition gas absorption device is connected by piping to a stripping solution outlet of the crystallizer and a stripping solution supply port in the mixing zone, Said
The NH ₄ HF ₂ supply port of the NH ₄ HF ₂ solution supply device is provided in the crystal growth zone or stripping liquid cooling zone of the crystallizer, and the ammonia supply port of the ammonia supply device is provided in the crystal growth zone or stripping liquid cooling zone of the crystallizer. A metal stripping device, which is provided between a stripping solution cooling zone and the crystal receiving tank, and a supply port for the filtrate after crystal separation is provided in a stripping solution standing zone of the crystallizer.