Method for saponification-free extraction by utilizing electrolysis

Abstract

The invention provides a method for saponification-free extraction by utilizing electrolysis, which comprises the following steps: by taking an aqueous solution containing metal ions as a cathode solution, obtaining a turbid solution containing a metal solid-phase substance through electrolysis, and then sequentially carrying out extraction and reverse extraction to obtain a reverse extraction solution containing the metal ions. According to the method, saponification of an organic phase is not needed, additional alkaline matter or weak electrolyte is not needed, salt-containing wastewater is not generated, the raffinate obtained through extraction can be returned to the electrolysis step to produce acid, the raffinate can be reused in the acid dissolution process and can be reused in production, and remarkable economic advantages and environmental protection advantages are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrometallurgy, and particularly relates to a method for electrolytic non-saponification extraction. Background Art

[0002] Rare earths, vanadium, chromium and their compounds have excellent physical and chemical properties such as electricity, magnetism, light, and catalysis, and are widely used in the fields of metallurgy, chemical industry, electronics, machinery, new energy, new materials, and aerospace. At present, the mainstream method for obtaining single rare earth compounds is the solvent extraction method using P507 as the extractant, which has many advantages such as high separation efficiency, easy automatic control, and convenient continuous amplification. During the extraction process, in order to enhance the extraction ability, the organic phase needs to be pre-saponified. The saponification process not only consumes a large amount of alkali but also generates a large amount of saline wastewater, increasing the reagent cost and environmental protection treatment cost. According to statistics, 20 million tons of saponification wastewater are generated annually, accounting for 60% - 70% of the total wastewater discharge in the extraction process, and the average salt concentration reaches 10 - 50 g / L, exceeding the discharge standard by 20 or even 100 times. Therefore, the development of clean rare earth non-saponification technology has great economic value and environmental protection value.

[0003] In order to reduce the alkali consumption or the generation amount of saline wastewater, some technical solutions have been disclosed in the prior art. For example, CN111440946B uses magnesium bicarbonate to saponify the acidic extractant organic phase, and at the same time recovers the saponification wastewater and CO 2 in the saponification process. The obtained magnesium soap organic phase is then subjected to rare earth saponification treatment with the rare earth feed liquid to achieve the extraction of rare earths. The magnesium chloride wastewater generated during the rare earth saponification process is mixed with the saponification wastewater and an amine extractant, and the recycled CO 2 is used for the extraction-carbonization reaction to convert magnesium chloride into magnesium bicarbonate, which can be recycled for the saponification process, realizing the closed-loop cycle of magnesium salts and greatly reducing the salt discharge in the rare earth extraction process. However, wastewater containing hydrochloric acid will be generated during the stripping process of the amine extractant.

[0004] CN102766766B uses a composite solvent obtained by mixing an acidic phosphine extractant and an amine extractant as a composite extractant. This composite extractant can directly extract and separate rare earths without saponification, thus solving the problem of generating a large amount of ammonia-containing wastewater in the extraction process due to the use of ammonia saponification at the source. At the same time, it also greatly reduces the use of ammonia alkali and acid, reducing the production cost. However, after extraction, the deprotonation of the amine extractant is difficult, and a large amount of water is required for stripping with pure water, making it difficult to recycle.

[0005] In CN102994750B, a P507-kerosene organic phase and a solid rare earth basic compound are simultaneously added to an aqueous solution containing free rare earth ions to carry out a multi-phase reaction of organic phase-aqueous phase-solid phase. Among them, the acidic extractant first extracts the free rare earth ions in the aqueous phase and releases hydrogen ions, and the added solid basic rare earth compound reacts with these hydrogen ions to dissolve and release rare earth ions. The net effect is that the basic rare earth compound dissolves, and the organic phase realizes the saponification of rare earth. This method can keep the concentrations of rare earth ions and hydrogen ions in the solution and the rare earth concentration in the saponified organic phase at a stable level, continuously and stably obtain a qualified organic phase, and greatly reduce the wastewater discharge. However, due to the large particle size of the solid basic rare earth compound, the reaction rate is slow. At the same time, since the raw material also contains impurities such as aluminum that are prone to generate three phases, it affects the extraction phase separation.

[0006] In summary, it is of great significance to develop a new non-saponification extraction method. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a method for electrolytic non-saponification extraction. The method uses an aqueous solution containing metal ions as the cathode solution, obtains a turbid solution containing metal solid phase substances through electrolysis, and then sequentially performs extraction and stripping to obtain a stripping solution containing metal ions. The method of the present invention does not require saponification of the organic phase, does not require addition of alkaline substances or weak electrolytes, does not produce saline wastewater, and moreover, the raffinate obtained by extraction can be returned to the electrolysis step to produce acid, which can be reused in the acid dissolution process and can be reused in production, having significant economic advantages and environmental protection advantages.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] The purpose of the present invention is to provide a method for electrolytic non-saponification extraction, and the method includes the following steps:

[0010] (1) Using an aqueous solution containing metal ions as the cathode solution and placing it in the cathode chamber, using an aqueous solution of inorganic acid as the anode solution and placing it in the anode chamber, separating the cathode chamber from the anode chamber by an ion exchange membrane, and obtaining a turbid solution containing metal solid phase substances in the cathode chamber through electrolysis;

[0011] (2) Mixing the turbid solution containing metal solid phase substances in step (1) with the empty organic phase obtained in step (3) for extraction, and obtaining a metal ion-loaded organic phase and a raffinate after phase separation;

[0012] (3) Stripping the metal ion-loaded organic phase in step (2) to obtain an empty organic phase and returning it to step (2) for the extraction, and obtaining a stripping solution containing metal ions.

[0013] In the method of the present invention, an aqueous solution containing metal ions is used as the cathode solution. Through electrolysis, a turbid solution containing solid metal substances is obtained, and then extraction and back-extraction are carried out in sequence to obtain a back-extraction solution containing metal ions. The method of the present invention does not require saponification of the organic phase, does not require addition of alkaline substances or weak electrolytes, does not produce saline wastewater, and moreover, the raffinate obtained by extraction can be returned to the electrolysis step to produce acid, can be reused in the acid dissolution process, and can be reused in production, having significant economic advantages and environmental protection advantages.

[0014] As a preferred technical solution of the present invention, the anions of the cathode solution in step (1) include chloride ions. An intermediate chamber is arranged between the cathode chamber and the anode chamber. An anion exchange membrane is used to separate the cathode chamber from the intermediate chamber, and a cation exchange membrane is used to separate the intermediate chamber from the anode chamber; the raffinate in step (2) is returned to step (1) and placed in the intermediate chamber, and an acidic solution is obtained after electrolysis.

[0015] Preferably, the hydrogen ion concentration of the acidic solution is 0.5 - 1.5 mol / L, such as 0.5 mol / L, 0.7 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.3 mol / L or 1.5 mol / L, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0016] It should be noted that if the anions of the cathode solution include chloride ions, only the cathode chamber and the anode chamber separated by the anion exchange membrane are set. During electrolysis, chloride ions will enter the anode chamber from the cathode chamber through the anion exchange membrane, and chloride ions will lose electrons on the anode to become highly toxic chlorine gas, thus causing potential safety hazards; therefore, if the anions of the cathode solution include chloride ions, an intermediate chamber is arranged between the cathode chamber and the anode chamber, and the raffinate obtained by subsequent extraction is returned to the intermediate chamber. During electrolysis, chloride ions will enter the intermediate chamber from the cathode chamber through the anion exchange membrane, and hydrogen ions will enter the intermediate chamber from the anode chamber through the cation exchange membrane, so that the hydrogen ion concentration of the raffinate increases to produce acid, which can be reused in the acid dissolution process and can be reused in production, having significant economic advantages and environmental protection advantages.

[0017] As a preferred technical solution of the present invention, the anions of the cathode solution in step (1) do not include chloride ions, such as nitrate ions and / or sulfate ions. An anion exchange membrane is used to separate the cathode chamber from the anode chamber. The raffinate in step (2) is returned to step (1) and placed in the anode chamber, and an acidic solution is obtained after electrolysis.

[0018] Preferably, the hydrogen ion concentration of the acidic solution is 0.5 to 1.5 mol / L, such as 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L or 1.5 mol / L, etc., but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0019] As a preferred technical solution of the present invention, the metal ions in the cathode liquid in step (1) include VO 2+ , Cr 3+ or RE 3+ or a combination of any one or at least two of them.

[0020] It should be noted that the method of the present invention focuses on metal ions involved in saponification extraction. In addition to the metal ions RE of rare earth elements well-known to those skilled in the art 3+ , through experimental verification by the inventor, VO 2+ , Cr 3+ are also applicable.

[0021] As a preferred technical solution of the present invention, the metal ion concentration of the cathode liquid in step (1) is 1 to 300 g / L, such as 1 g / L, 5 g / L, 10 g / L, 30 g / L, 50 g / L, 70 g / L, 100 g / L, 130 g / L, 150 g / L, 180 g / L, 200 g / L, 220 g / L, 250 g / L, 260 g / L, 280 g / L or 300 g / L, etc., but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0022] As a preferred technical solution of the present invention, the inorganic acid aqueous solution in step (1) includes dilute sulfuric acid aqueous solution or dilute nitric acid aqueous solution.

[0023] As a preferred technical solution of the present invention, a current is applied between the anode and the cathode, and the current density of the electrolysis in step (1) is 50 to 500 A / m 2 , such as 50 A / m 2 , 100 A / m 2 , 150 A / m 2 , 200 A / m 2 , 250 A / m 2 , 300 A / m 2 , 350 A / m 2 , 400 A / m 2 , 450 A / m 2 or 500 A / m 2 etc., but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0024] As a preferred technical solution of the present invention, the pH of the turbid liquid corresponding to the solid phase containing metal in step (1) is 4.5 to 6.6, such as 4.5, 4.7, 5, 5.2, 5.5, 5.7, 6, 6.3 or 6.6, etc., but not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0025] As a preferred technical solution of the present invention, the organic phase without load obtained in step (3) includes an extractant and a diluent.

[0026] As a preferred technical solution of the present invention, the extractant includes any one or a combination of at least two of P204, P507, Cyanex272, Versatic10 or naphthenic acid.

[0027] It should be noted that the diluent described in the present invention refers to diluents well-known to those skilled in the art, such as inert organic solvents like kerosene and n-heptane.

[0028] As a preferred technical solution of the present invention, the stripping agent used for stripping in step (3) includes hydrochloric acid, sulfuric acid, nitric acid, etc., which belong to the prior art well-known to those skilled in the art and will not be elaborated here.

[0029] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0030] (1) In the method of the present invention, an aqueous solution containing metal ions is used as the cathode liquid, and a turbid liquid containing solid phase of metal is obtained through electrolysis, and then extraction and stripping are carried out in sequence to obtain a stripping solution containing metal ions. The method of the present invention does not require saponification of the organic phase, does not require addition of alkaline substances or weak electrolytes, does not produce salty wastewater, and moreover, the raffinate obtained by extraction can be returned to the electrolysis step to produce acid, can be reused in the acid dissolution process, and can be reused in production, having significant economic advantages and environmental protection advantages;

[0031] (2) It is a prior art to make a slurry of rare earth oxides, carbonates or hydroxides with water and then carry out non-saponifying extraction. However, the above-mentioned alkaline compounds are not freshly prepared and have poor activity, and the reaction rate with acidic extractants is slow, resulting in poor phase separation effect. The rare earth hydroxide described in the present invention is prepared by electrochemically controlled hydrolysis, having advantages such as smaller particle size and higher activity, fast reaction rate with the extractant, and can complete extraction in a shorter time with good phase separation;

[0032] (3) Most of the other saponification-free extraction processes involve adding an alkaline extractant to the organic phase and performing extraction after compounding with an acidic extractant; or adding a weak electrolyte to the aqueous phase to construct a buffer solution system. No matter what reagent is added to the aqueous phase or the organic phase, the complexity of the extraction system is increased. The method described in the present invention does not require adding external reagents, and uses the hydroxide generated by electrolysis to maintain the low-acid environment required for extraction, so as to achieve efficient extraction of target metal ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the process flow chart of the method for electrolytic saponification-free extraction described in Example 1 of the present invention;

[0034] Figure 2 is the process flow chart of the method for electrolytic saponification-free extraction described in Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] The technical solution of the present invention will be further described below with reference to the drawings and through specific embodiments.

[0036] To better illustrate the present invention and facilitate understanding of its technical solution, the typical but non-limiting embodiments of the present invention are as follows:

[0037] Example 1

[0038] This example provides a method for electrolytic saponification-free extraction. The process flow chart is as Figure 1 shown. The method includes the following steps:

[0039] (1) Using a vanadium-containing sulfuric acid solution containing 1 g / L VO 2+ , 3 g / L Mg 2+ , 2 g / L Na + as the cathode solution and placing it in the cathode chamber, using the raffinate obtained in step (2) as the anode solution and placing it in the anode chamber, separating the cathode chamber from the anode chamber with an anion exchange membrane, applying a current between the anode and the cathode, with a current density of 50 A / m 2 , and electrolyzing until the pH of the cathode solution rises to 5 to obtain a turbid solution containing vanadium solid matter;

[0040] (2) Mixing the turbid solution containing vanadium solid matter obtained in step (1) with the empty organic phase (volume concentration of 20% Cyanex272) obtained in step (3) for extraction, separating phases to obtain a vanadium-loaded organic phase and a raffinate. The extraction rate of vanadium is 90%. Return the raffinate to step (1) and place it in the anode chamber. After electrolysis, an acidic solution with a hydrogen ion concentration of 0.5 mol / L is obtained;

[0041] (3) Back-extract the vanadium-loaded organic phase described in step (2) to obtain an organic phase without load and return it to step (2) for the extraction, and obtain a back-extract solution containing vanadium for subsequent treatment.

[0042] Example 2

[0043] This example provides a method for electrolytic non-saponification extraction, and the method includes the following steps:

[0044] (1) Use a nitric acid leaching solution of electroplating sludge containing 8 g / L Cr 3+ and 0.5 g / L Fe 2+ as the cathode solution and place it in the cathode chamber, use the raffinate obtained in step (2) as the anode solution and place it in the anode chamber, separate the cathode chamber from the anode chamber with an anion exchange membrane, apply a current between the anode and the cathode, and the current density is 300 A / m 2 , and electrolyze until the pH of the cathode solution rises to 4.5 to obtain a turbid solution containing chromium solid matter;

[0045] (2) Mix the turbid solution containing chromium solid matter described in step (1) with the organic phase without load (volume concentration of 30% P204) obtained in step (3) for extraction. After phase separation, obtain a chromium-loaded 3+ organic phase and a raffinate. The extraction rate of Cr 3+ is 94%. Return the raffinate to step (1) and place it in the anode chamber. After electrolysis, obtain an acidic solution with a hydrogen ion concentration of 1.5 mol / L;

[0046] (3) Back-extract the chromium-loaded 3+ organic phase described in step (2) to obtain an organic phase without load and return it to step (2) for the extraction, and obtain a back-extract solution containing Cr 3+ for subsequent treatment.

[0047] Example 3

[0048] This example provides a method for electrolytic non-saponification extraction. The process flow chart is as Figure 2 shown, and the method includes the following steps:

[0049] (1) Use a mixed rare earth chloride solution containing 300 g / L RE 3+ as the cathode solution and place it in the cathode chamber, use a 0.5 mol / L nitric acid aqueous solution as the anode solution and place it in the anode chamber. Set an intermediate chamber between the cathode chamber and the anode chamber, separate the cathode chamber from the intermediate chamber with an anion exchange membrane, separate the intermediate chamber from the anode chamber with a cation exchange membrane, return the raffinate described in step (2) to step (1) and place it in the intermediate chamber, apply a current between the anode and the cathode, and the current density is 500 A / m 2, after electrolysis, the pH of the cathode solution is increased to 6.5 to obtain a turbid solution containing rare earth solid phase;

[0050] (2) Mix the turbid solution containing rare earth solid phase in step (1) with the empty organic phase (volume concentration of 50% P507) obtained in step (3) for extraction. After phase separation, a loaded RE 3+ organic phase and a raffinate are obtained. The extraction rate of RE 3+ is 92%. Return the raffinate to step (1) and place it in the middle chamber. After electrolysis, an acidic solution with a hydrogen ion concentration of 0.5 mol / L is obtained;

[0051] (3) Strip the loaded RE 3+ organic phase to obtain an empty organic phase and return it to step (2) for the extraction, and obtain a strip solution containing RE 3+ for subsequent treatment.

[0052] Example 4

[0053] This example provides a method using electrolytic saponification-free extraction. The method includes the following steps:

[0054] (1) Use a chloride solution containing 45 g / L Y 3+ as the cathode solution and place it in the cathode chamber, and use a 0.3 mol / L sulfuric acid aqueous solution as the anode solution and place it in the anode chamber. Set up a middle chamber between the cathode chamber and the anode chamber. Separate the cathode chamber from the middle chamber with an anion exchange membrane, and separate the middle chamber from the anode chamber with a cation exchange membrane. Return the raffinate in step (2) to step (1) and place it in the middle chamber. Apply a current between the anode and the cathode, and the current density is 400 A / m 2 , after electrolysis, the pH of the cathode solution is increased to 6.2 to obtain a turbid solution containing yttrium solid phase;

[0055] (2) Mix the turbid solution containing yttrium solid phase in step (1) with the empty organic phase (volume concentration of 20% naphthenic acid) obtained in step (3) for extraction. After phase separation, a loaded Y 3+ organic phase and a raffinate are obtained. The extraction rate of Y 3+ is 91%, and the phase separation time is 54 seconds. Return the raffinate to step (1) and place it in the middle chamber. After electrolysis, an acidic solution with a hydrogen ion concentration of 1.5 mol / L is obtained;

[0056] (3) Strip the loaded Y 3+ organic phase to obtain an empty organic phase and return it to step (2) for the extraction, and obtain a strip solution containing Y 3+ for subsequent treatment.

[0057] Example 5

[0058] This example provides a method of electrolytic soap-free extraction, and the method comprises the following steps:

[0059] (1) Using a chloride solution containing 100 g / L La 3+ as the cathode solution and placing it in the cathode chamber, using a 0.4 mol / L sulfuric acid aqueous solution as the anode solution and placing it in the anode chamber. An intermediate chamber is provided between the cathode chamber and the anode chamber. The cathode chamber is separated from the intermediate chamber by an anion exchange membrane, and the intermediate chamber is separated from the anode chamber by a cation exchange membrane. Return the raffinate obtained in step (2) to step (1) and place it in the intermediate chamber. Apply a current between the anode and the cathode, and the current density is 200 A / m 2 . After electrolysis until the pH of the cathode solution rises to 6.6, a turbid solution containing lanthanum solid matter is obtained;

[0060] (2) Mix the turbid solution containing lanthanum solid matter obtained in step (1) with the blank organic phase (volume concentration is 40% Versatic10) obtained in step (3) for extraction. After phase separation, a loaded La 3+ organic phase and a raffinate are obtained. The extraction rate of La 3+ is 91%. Return the raffinate to step (1) and place it in the intermediate chamber. After electrolysis, an acidic solution with a hydrogen ion concentration of 1.0 mol / L is obtained;

[0061] (3) Strip the loaded La 3+ organic phase obtained in step (2) to obtain a blank organic phase and return it to step (2) for the extraction, and obtain a stripping solution containing La 3+ for subsequent treatment.

[0062] Comparative Example 1

[0063] As a comparative example of Example 4, this comparative example provides a method for extracting a yttrium hydroxide turbid solution, and the method comprises the following steps:

[0064] (1) Weigh 7.082 g of yttrium hydroxide, add 100 mL of water to make a pulp, and obtain a turbid solution containing yttrium hydroxide;

[0065] (2) Mix the turbid solution containing yttrium hydroxide obtained in step (1) with cyclohexanecarboxylic acid with a volume concentration of 20% for extraction. After phase separation, a loaded Y 3+ organic phase and a raffinate are obtained. The extraction rate of Y 3+ is 81%, and the phase separation time is 5 minutes.

[0066] Comparing Example 4 of the present invention with Comparative Example 1, by using the electrolytic soap-free extraction technology, not only can the extraction rate of Y 3+The extraction rate can reach 91%, and the phase separation time can be shortened to 54 seconds, which can improve production efficiency.

[0067] In summary, the method of the present invention uses an aqueous solution containing metal ions as the cathode solution, obtains a turbid solution containing metal solid phase substances through electrolysis, and then sequentially performs extraction and back-extraction to obtain a back-extraction solution containing metal ions for recovering metal elements. There is no need to saponify the organic phase, no need to add chemical reagents, no need to add alkaline substances or weak electrolytes, and no salt-containing wastewater is generated. Moreover, the raffinate obtained by extraction can be returned to the electrolysis step to produce acid, which can be reused in the acid dissolution process and in production, having significant economic and environmental advantages.

[0068] The present invention uses the above embodiments to illustrate the detailed structural features of the present invention. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the components selected by the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

[0069] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0070] In addition, it should be noted that in the above specific embodiments, the various specific technical features described can be combined in any suitable way without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0071] In addition, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method of electrolytic soap-free extraction, characterized in that, the method comprises the following steps: (1) Using an aqueous solution containing metal ions as the cathode solution and placing it in the cathode chamber, using an aqueous inorganic acid solution as the anode solution and placing it in the anode chamber, separating the cathode chamber from the anode chamber with an ion exchange membrane, and obtaining a turbid solution containing metal solid phase in the cathode chamber through electrolysis; (2) Mixing the turbid solution containing metal solid phase in step (1) with the empty organic phase obtained in step (3) for extraction, and obtaining a loaded metal ion organic phase and a raffinate after phase separation; (3) Stripping the loaded metal ion organic phase in step (2) to obtain an empty organic phase and returning it to step (2) for the extraction, and obtaining a stripping solution containing metal ions.

2. The method according to claim 1, characterized in that, the anion of the cathode solution in step (1) includes chloride ions, an intermediate chamber is arranged between the cathode chamber and the anode chamber, the cathode chamber is separated from the intermediate chamber with an anion exchange membrane, and the intermediate chamber is separated from the anode chamber with a cation exchange membrane; returning the raffinate in step (2) to step (1) and placing it in the intermediate chamber, and obtaining an acidic solution after electrolysis; Preferably, the hydrogen ion concentration of the acidic solution is 0.5 - 1.5 mol / L.

3. The method according to claim 1, characterized in that, the anion of the cathode solution in step (1) does not include chloride ions, the cathode chamber is separated from the anode chamber with an anion exchange membrane, returning the raffinate in step (2) to step (1) and placing it in the anode chamber, and obtaining an acidic solution after electrolysis; Preferably, the hydrogen ion concentration of the acidic solution is 0.5 - 1.5 mol / L.

4. The method according to any one of claims 1 - 3, characterized in that, The metal ions in the cathode liquid in step (1) include VO 2+ Cr 3+ or RE 3+ Any one or a combination of at least two of the following.

5. The method according to any one of claims 1 - 4, characterized in that, the metal ion concentration of the cathode solution in step (1) is 1 - 300 g / L.

6. The method according to any one of claims 1 - 5, characterized in that, the aqueous inorganic acid solution in step (1) includes dilute sulfuric acid aqueous solution or dilute nitric acid aqueous solution.

7. The method according to any one of claims 1 - 6, characterized in that, The current density of the electrolysis described in step (1) is 50 to 500 A / m 2 .

8. The method according to any one of claims 1 - 7, characterized in that, the pH of the turbid solution containing metal solid phase in step (1) is 4.5 - 6.

6.

9. The method according to any one of claims 1 - 8, characterized in that, the empty organic phase obtained in step (3) includes an extractant and a diluent.

10. The method according to claim 9, characterized in that, the extractant includes any one or a combination of at least two of P204, P507, Cyanex272, Versatic10 or naphthenic acid.

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