JPS6293390A - Method for depositing and dissolving metal - Google Patents

Abstract

PURPOSE:To recover a clean metallic salt soln. by electrolytically reducing waste liquor contg. a water soluble metallic compound with a special anion exchange membrane contg. fluorine as a diaphragm to deposit the metal on the cathode and by dissolving the metal as the anode in a soln. CONSTITUTION:An anion exchange membrane is made of a copolymer consisting of repeating units represented by the formula (where X is F or OF3, l is 0 or an integer of 1-5, m is 0 or 1, n is an integer of 1-5, each of p and q is a positive integer, the ratio of p/q is 2-16, and Y is a quat. ammonium salt). An electrolytic cell is divided into two chambers by the anion exchange membrane as a diaphragm and waste liquor contg. a water soluble metallic compound is electrolytically reduced in the cathode chamber to deposit the metal on the cathode. The metal is then dissolved as the anode to produce a metallic salt soln.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention utilizes an ion exchange membrane electrolysis method using a special 7-wire anion exchange membrane as a barrier +1'J to remove waste liquid containing water-soluble metal compounds. , a metal is deposited on the cathode, and the metal is dissolved in a solution as an anode, resulting in a clean metal +1!
The present invention relates to a method for recovering a solution.

The amount of metal-containing waste liquid discharged from various metal factories, such as iron acid cleaning solution, nickel-containing waste liquid from copper fine needles, and metal-containing waste liquid from various plating go-places, is enormous for all nine types of companies. Disposing this waste liquid untreated into rivers, oceans, etc. is not only a waste of useful resources, but also
Related industries are struggling with how to handle these waste liquids, as they also pose environmental problems. In recent years, waste liquid from plating printed circuit boards in semiconductor factories sometimes contains precious metals such as gold, and these funds must be recovered in order to effectively utilize valuable natural resources. Additionally, radioactive metals, mercury.

If it contains hazardous metals such as cadmium, it must be completely disposed of within the factory premises. Therefore, there is a strong demand for the development of a processing system that can effectively utilize resources by recovering metals from the discharged metal-containing waste liquid in a closed system within a factory and producing a clean aqueous metal salt solution.

[Conventional technology]

In addition to electrowinning, chemical recovery methods are used to recover metals from waste fluids containing water-soluble metal compounds.

Examples include ion exchange methods. For example, as a chemical recovery method for silver recovery from developing processing solutions, by adding sulfide,
There is a method of precipitating it as silver sulfide.

However, with this method, active ingredients other than silver cannot be reused, and there are restrictions on disposal of waste liquid after recovery. In the ion exchange method, the silver concentration of the waste liquid to be handled must be kept low, resulting in large equipment and low productivity.

Therefore, the electrowinning method is increasingly being adopted in factories for recovering silver from developing processing solutions.

A method for recovering metals by electrolysis from a waste solution containing a water-soluble metal compound;
This metal can be peeled off from the cathode, or the precipitated metal may remain attached to the cathode.

The metal is immersed and dissolved in a mineral acid such as hydrochloric acid or nitric acid and recovered as an aqueous solution, or the metal deposited on the cathode is subjected to direct current electrolysis using the anode as an anode, eluted into an electrolyte solution, and recovered as a metal salt solution. There is a way. Among these conventional methods,
When dissolving the recovered metal in mineral acid, it takes a long time to dissolve, the acid concentration is high, so it is of limited use, and it is uneconomical because a large amount of acid is required. Furthermore, even if electrolysis is carried out using the precipitated metal as an anode, the eluted metal will immediately precipitate on the cathode, resulting in disadvantages such as the inability to obtain a concentrated all-metal solution.

Recently, new methods using anion exchange membranes have been proposed. (JP 52-74501) In this method, a cathode is first applied to a waste liquid containing a water-soluble metal compound.

The metal immersed in the anode, electrolyzed, and deposited on the cathode is used as the anode of an electrolytic cell with a cation exchange membrane and an anion exchange membrane as a diaphragm.T2, the metal ions are electrolytically eluted using the conventional method described above. Unlike conventional methods, the anion exchange membrane inhibits the movement of metal ions into the cathode chamber, making it possible to obtain a concentrated metal salt solution.

However, when an insoluble anode is used as an anode in the step of depositing metal onto the cathode, problems arise such as a decrease in current efficiency for metal deposition due to oxidation of metal ions due to anodic reaction. On the other hand, when a soluble anode is used as an anode, the anode gradually wears out and must be replaced with a new (new) cathode each time.Also, the distance between the electrodes changes from time to time, making it difficult to adjust the distance between the electrodes. Furthermore, in the metal elution stage of a three-chamber electrolytic cell with a cation exchange membrane and an anion exchange membrane as the diaphragms, the waste liquid is often an acid solution, and conventionally commercially available hydrocarbon thread anion exchange Durability is an issue with membranes.Especially when the waste liquid contains chlorine ions, the anion exchange membrane deteriorates due to the chlorine gas generated at the anode (7). If this method were to be implemented, the anion exchange membrane would have to be replaced many times, which would be economically disadvantageous.

As described above, no satisfactory industrial process has yet been established for recovering metals as a clean water-enriched metal solution by electrolysis from waste liquid containing water-soluble metal compounds.

[Problems to be solved by the present invention]

The first aspect of the present invention is the use of a fluorine-based anion exchange membrane that has excellent resistance to chlorine gas and acids (7).
An object of the present invention is to provide a method for realizing a process for recovering a 4A aqueous solution.

[Means for solving problems]

The present inventors have related to a method for producing a total aqueous solution from a waste liquid containing a water-soluble metal compound using an ion exchange membrane method.
As a result of intensive studies regarding the deterioration of special pressure anion exchange membranes due to chlorine gas and acids, we found that the membrane has a special structure [-1 Degraded by chlorine gas and acids].

The present inventors have discovered that by using a fluorine-based anion exchange membrane, it is possible to stably produce a concentrated aqueous solution of all metals over a long period of time, leading to the completion of the present invention.

The fluorine-based anion exchange membrane having a special structure used in the present invention has the following general formula [where X = F or OF, t = 0 or an integer of 1 to 5, m = o or 1, n = 1 to An integer of 5, p.

q is a positive number and the ratio thereof is 2-16. Y is a quaternary ammonium group] It means a fluorine-based anion exchange membrane made of a copolymer of repeating units represented by:

Furthermore, the fluorine-based anion exchange membrane used in the present invention has the following general formula as a group containing a quaternary ammonium group [However, R11
n,, n, is a lower alkyl group (however, P.

and R1 may be combined to form tetramethylene or pentamethylene. 2-Halogen anion] Or the following general formula [where R4 is a hydrogen atom or a lower alkyl group, R1゜θ R,, R,, Z are the same as above] Or the following general formula [where R4, R, = hydrogen atoms or lower alkyl groups,
θ Rj+ R*+ ”l+ z is the same as above, a = 3
It is desirable to use a fluorine-based anion exchange membrane having a group containing a quaternary ammonium group [an integer of ~7]. Furthermore, it is desirable to use an anion exchange membrane in which the exchange groups are uniformly present.

Specific examples of these fluorine-based anion exchange membranes include polymer membranes having the following structure.

(-OF', -Shima+-+Shima-OF tia 10 horses-clear OF!-?F-deception+OFt 0FtvCF2-1+or, -Yu Ikko/Shimago FSpecial structure used in the present invention The exchange chamber of the fluorine-based anion exchange membrane has 0.16 mθq/9・dry resin ~5
．． Omeq/! 7. Dry resin can be used, but preferably the range is from 0.5 meq/9.dry resin to 2.8 meq/9.dry resin.

This is because if the dry resin is less than 0.5 mθq/Gj, the electrical resistance of the membrane will be high and the electrolytic voltage will increase, leading to an increase in the cost of the tank. This may cause problems and interfere with stable electrolysis operation.

The thickness of the fluorine-based anion exchange membrane used in the present invention is usually 4
It can be used in the range of 0 to 500 μ, but preferably (, < is 10
The fluorine thread anion exchange membrane used in the present invention may contain a reinforcing agent to increase the strength of the membrane.

The heptad system anion exchange membrane having the above-mentioned special structure exhibits excellent heat resistance, acid resistance, and oxidation resistance, and in particular shows no deterioration due to the oxidizing action of chlorine gas. Furthermore, a new method has been developed to perform both metal precipitation from waste liquid containing water-soluble metal compounds and electrolytic elution of the precipitated metal in a two-chamber electrolytic cell using this fluorine-based anion exchange membrane with a special structure as a diaphragm. This makes it possible to efficiently and stably generate a concentrated metal salt aqueous solution for a long period of time.

The electrolytic system according to the present invention is divided into two parts, a metal deposition process and a metal melting process, and is shown in FIGS. 1 and 2, respectively.

The waste liquid containing water-soluble metal compounds is supplied to the cathode chamber (4) K of the diaphragm electrolytic cell (1), the anode chamber (5) is supplied with a pressure mineral acid aqueous solution, and energized from the DC power supply (7). ), metal is deposited on the anode (3), while chlorine gas and/or
Or oxygen gas is generated. When the metal deposition has reached its peak, the waste liquid is extracted from the cathode chamber (4), and an aqueous mineral acid solution is supplied instead (as shown in FIG. 2), with the polarity of the electrodes being reversed. Transition to metal melting process. A large amount of metal ions are generated in the anode chamber 0◆ from the anode Q■ by the dissolution reaction and electrolytic dissolution of the metal by mineral acid, and the movement of these metal ions to the cathode chamber (B) is prevented by the anion exchange membrane 0Q. A concentrated metal salt solution is obtained in the anode chamber 64. Cathode chamber 0
Sometimes hydrogen gas is evolved.

In addition, in dual electrolysis using such an anion exchange membrane as a diaphragm, the ease of processing of the fluorine-based anion exchange membrane, that is, the use of a cylindrical membrane, makes it possible to make the electrolytic cell more compact. Furthermore, in combination with a fluidized bed electrode, it becomes possible to perform metal precipitation and dissolution with high yield.

It is desirable that the metal concentration in the waste liquid ranges widely from 10-g to 3 mol/l, preferably from 10-2 to 104 mol/l. It is desirable that the pH of the waste liquid is in the range of 1 to 7, preferably in the range of 2 to 4. The waste liquid can be supplied by either a batch method or a flow method, but in the case of a flow method, the supply rate is 0.01 to 10 t/
dnlIIhr in a wide range, and determine the optimal flow rate depending on the temperature, concentration, and current of the waste liquid. There are no restrictions on the concentration of the mineral acid aqueous solution used in the other polar chambers.

Conventionally known electrode materials can be used as the anode and cathode of the diaphragm electrolytic cell used in the present invention, but it is difficult to meet the electrode reaction of the intended electrolytic process. The electrode material is selected appropriately. Such electrode materials17 include Ti, Ta, Zr,
On the surface of a corrosion-resistant base material such as Nb, an electrode coated with a platinum group metal such as 1pt, Rh, and/or an oxide of platinum metal, and a metal such as Fe, Oo, Nj, or an alloy thereof, A cathode whose surface is coated with a substance exhibiting low-temperature voltage (for example, Raney nickel) can be used.

The electrolysis temperature of the V8 electrolytic cell in the present invention ranges from room temperature to 10
It is possible down to 0℃, and the current density is 1A/dffll to 5
0A/a? It can be implemented within the range of F/.

[Effects of the present invention]

As mentioned above, we have completed a completely new electrolytic system that uses a fluorine-based anion exchange membrane with a special structure, and we have developed a completely new electrolytic system that uses a fluorine-based anion exchange membrane with a special structure.
jl! It becomes possible to generate an aqueous salt solution.

The method of the present invention can be used in many fields, but it has a wide range of applications in metal-related fields such as metal processing and metal refining industries, where a large number of metal ions are discharged. It is of high value.

〔Example〕

Examples will be described below, but the present invention is not limited thereto.

Example 1 A waste liquid having the composition shown below was treated in a diaphragm electrolytic cell shown in FIGS. 1 and 2 to produce a clean nickel chloride solution.

The composition of the mineral acid aqueous solution was a hydrochloric acid aqueous solution with α02 mol/l. Among the cathodes, the electrode for depositing metals used in the diaphragm electrolytic cell was plated with a noble metal such as platinum on the surface of a corrosion-resistant base material such as titanium. Either an insoluble electrode or the metal itself to be deposited is used. An insoluble electrode that does not dissolve in acid was used as the cathode in the electrolytic dissolution process shown in (Summer →) in FIG. 2. Insoluble electrodes were used as the anode for both electrodes shown in FIGS.

The area used for the anion exchange membrane is expressed as 2 dff/[7, the structural formula below (% formula %)].Furthermore, fluorine-based anion exchange membranes with uniform exchange groups and hydrocarbons, which have been commercially available for a long time, are used. A system anion exchange membrane (manufactured by Asahi Glass Co., Ltd., Selemion Membrane) was used. The volume of the liquid in both electrode chambers is 1 t, and the electrolysis temperature and current density are 60
℃, 10 A/dtr/, and the current application time for both metal deposition and metal dissolution was 2 hours. Table 1 shows the current efficiency for nickel deposition and the current efficiency for nickel chloride production.

Table 1 The above electrolysis was repeated twice a day to test the durability of both anion exchange membranes. The hydrocarbon-based anion exchange membrane deteriorates due to the chlorine gas pressure generated at the anode, and within 1 ton of months, the bath voltage increases rapidly, the current efficiency decreases, and the membrane is eventually destroyed, rendering it useless as a diaphragm. Instead, acid enters the cathode chamber from the anode chamber and dissolves the precipitated metal. On the other hand, such a deterioration phenomenon was not observed in the fluorine-based anion exchange membrane, and an aqueous metal salt solution could be stably produced for more than 3 tons of months.

Example 2 Waste liquid with the composition shown below was treated in the diaphragm electrolytic cell shown in Figures 1 and 2 to produce a clean chloroplatinic acid aqueous solution.
7.

Is the current density I A /dn? Other experimental conditions were the same as in Example 1.

The current efficiencies for platinum deposition and chloroplatinic acid production are shown in Table 2.

The results of the durability test of both anion exchange membranes by repeated electrolysis in the same manner as in Example 1 were the same as in Example 1. Hydrocarbon-based anion exchange membranes deteriorated due to chlorine gas generated at the anode, while fluorine-based anion exchange membranes deteriorated due to chlorine gas generated at the anode. No such phenomenon was observed with the anion exchange membrane.

[Brief explanation of drawings]

FIG. 1 shows an example of an electrolytic system for a metal deposition process in the present invention, and FIG. 2 shows an example of an electrolytic system for a metal melting process in the present invention. 1. Diaphragm electrolytic cell 11. Diaphragm electrolytic cell 2, cathode
12. Anode accessible pole 15 cathode 4, cathode chamber 14. Anode chamber 5 anode chamber
15. Cathode chamber 6 Anion exchange membrane 1 & Anion exchange membrane 1 DC power supply 1Z DC power supply Patent applicant Toyo Soda Kogyo Co., Ltd. Figure 1 Figure 2

Claims (5)

[Claims] (1) A waste solution containing a water-soluble metal compound is electrolytically reduced in the cathode chamber of an electrolytic cell consisting of two chambers using an anion exchange membrane as a diaphragm to deposit the contained metal on the cathode, and then the metal is used as the anode,
In the metal precipitation dissolution method for producing the metal salt solution,
General formula below ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [However, X = F or CF_3, l = 0 or 1 to 5
m is an integer of 0 or 1, n is an integer of 1 to 5, p and q are positive numbers, and the ratio thereof is 2 to 16. A method for precipitation and dissolution of metals, characterized in that an anion exchange membrane made of a copolymer consisting of repeating units represented by Y is a quaternary ammonium group is used. (2) As a group containing a quaternary ammonium group, there are the following general formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ [However, R_1, R_2, R_3 are lower alkyl groups (
However, R_1 and R_2 may be combined to form a tetramethylene chain or a pentamethylene chain. )Z^■=halogen anion] The method according to claim 1, using an anion exchange membrane represented by the following formula. (3) As a group containing a quaternary ammonium group, there are the following general formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ [However, R_1, R_2, R_3 are lower alkyl groups (
However, R_1 and R_2 may be combined to form a tetramethylene chain or a pentamethylene chain. ) R_4 is a hydrogen atom or a lower alkyl group, Z^■=halogen anion] The method according to claim 1. (4) As a group containing a quaternary ammonium group, there are the following general formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ [However, R_1, R_2, R_3 are lower alkyl groups (
However, R_1 and R_2 may be combined to form a tetramethylene chain or a pentamethylene chain. )R_4, R_
5 is a hydrogen atom or a lower alkyl group, Z^■=halogen anion] The method according to claim 1. (5) The method according to claim 1, 2, 3 or 4, characterized in that an anion exchange membrane in which exchange groups are uniformly present is used.