JPS588306B2 - Metal salt waste liquid purification equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to an apparatus for purifying metal salt waste liquid.

In a purification device for metal salt waste liquid, there is a method in which metal ions are moved in the direction of the cathode force using an electrodialysis purification device in which an ion exchange membrane is placed at a distance between the anode and the cathode, and concentrated in a predetermined compartment. It has been implemented.

Examples of the arrangement of ion exchange membranes in conventional devices are conceptually shown in Figures 1a and b1, Figures 2a and b, and Figure 3c.

In these drawings, only the cathode 1 is shown as an electrode, and the anion exchange membrane and cation exchange membrane are respectively A.
and C.

The compartment 2 formed between the cathode 1 and the ion exchange membrane 3 closest to the cathode 1, that is, the cathode chamber, provides an appropriate conductivity to the electrolyte contained therein, and provides a suitable conductivity for the electrolyte contained therein. The metal ions M+ are moved toward the cathode.

The compartment 4 formed between the ion exchange membrane 5 adjacent to the ion exchange membrane 3 and the former 3 is used for introducing the solution to be treated (Fig. 1 a, Fig. 2 a). , Fig. 3) or to concentrate the metal ions removed from the treated solution (Fig. 1b, Fig. 2b).

In the latter case, the solution to be treated is placed in the compartment 6 between the ion exchange membranes 5 and 7.

However, the above-mentioned device has the following drawbacks.

That is, when the cation membrane 3 is placed adjacent to the cathode as shown in FIG. 1a and FIG. It precipitates on the electrode plate or becomes a hydroxide.

For this reason, it is necessary to disassemble and clean the device every month or so.

Naturally, since the metal ions M+ are concentrated in the electrolyte, the metal ions and the electrolyte are mixed, and it cannot be said that ideal purification has been performed.

On the other hand, when the anion exchange membrane 3 is placed adjacent to the cathode as shown in FIGS. 1b, 2b, and 3, permeation of cations into the cathode chamber 2 can be avoided.

However, if the catholyte contains a substance with high electrical conductivity such as sulfuric acid, the bath voltage is kept low but the anions A pass through the anion exchange membrane 3 and proceed to the compartment 4 containing the treated liquid.

As a result, anions are mixed into the treated liquid.

Furthermore, when a solution such as aqueous ammonia is used as the catholyte, only hydroxyl groups that do not impair the purification results are mixed into the adjacent compartment 4, but the bath voltage becomes extremely high.

For example, even if the current density is as low as 0.4 A/dm2, the bath voltage will be as high as 20 V, and if the process is performed under such conditions, the purification process will take a very long time.
It is inappropriate for practical use.

It is a general object to provide a metal salt waste liquid purification apparatus in which metals are not deposited on the cathode and in which there are no difficulties due to the intrusion of anions into compartments adjacent to the cathode chamber.

Furthermore, a special object of the invention is to overcome the drawbacks of the method for purifying aluminum surface treatment waste liquid using an apparatus such as that illustrated in FIG.

That is, in the arrangement of electrodes and anion A or cation C exchange membrane conceptually shown in FIG. solution is contained.

In addition, when electrodialysis is performed with a metal salt waste solution containing NH4+, SO4, and metal ions such as Ni and Sn in compartments 4 and 6, the metal ions move to the cathode chamber and are deposited on the electrode plate 1 and the ion exchange membrane 3. The NH4+ ions that not only adhere as the substance 10 but also move to the cathode chamber 1 become supersaturated and are released into the atmosphere as a gas.

For this reason, it is preferable that the pH of the compartment 4, where an ammonia odor is generated, be acidic to about pH 2 in order to selectively recover Sn.

As the treatment progresses, the sulfate ions in compartment 4 move to the anode side, while the ammonium ions move to the cathode side, leaving compartment 4.
The pH in it is kept acidic in order to leave.

In order to recover the solution in which Sn has been collected as a precipitate and use it again as a Sn salt solution, a large amount of aqueous ammonia must be used to neutralize the pH.

The general object is to provide a metal salt waste liquid purification device comprising an anode, a cathode, and an ion exchange membrane spaced apart from each other between these two electrodes; This is achieved by an apparatus characterized in that the ion exchange membrane consists of a cation exchange membrane facing the cathode on one side, and an anion exchange membrane in close contact with the other side of the cation exchange membrane. .

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 5 shows the ion exchange membrane 11 closest to the cathode 1. The part of this ion exchange membrane 11 facing the cathode 1 side is the cation exchange membrane 12, and the anion exchange membrane 13 is in close contact with the opposite side. are doing.

Therefore, the anion A- in the cathode chamber cannot pass through the cation exchange membrane 12 and remains in the cathode chamber.

On the other hand, the cation M+ in the compartment adjacent to the cathode compartment cannot pass through the anion exchange membrane 11 and remains there.

Among the ions, hydrogen ions and hydroxyl ions pass through the composite ion exchange membrane 11 according to the present invention because the ion exchange membrane has high permeability.

Because of this property, even in devices in which the composite ion exchange membrane 11 is used, charge movement occurs between the anode and the cathode, and anions and cations move toward one pole.

However, since cations do not enter the cathode chamber, precipitation of metal hydroxide in the cathode chamber and metal deposition on the cathode plate are prevented.

Also, to prevent catholyte anions from entering adjacent compartments,
Contamination of the polar liquid with the treated liquid is prevented.

The devices shown in FIGS. 1b, 2b and 3 are improved according to the invention as shown in FIGS. 6, 7 and 8, respectively.

Components in FIGS. 6 to 8 that perform the same functions as in FIGS. 1 to 3 are given the same reference numerals, and their functions will not be described here to avoid duplication.

In FIGS. 6 to 8, the function of the ion exchange membrane 11 closest to the cathode is the same as that described in connection with FIG.

According to such a function, in FIG. 6, metal ion M+ and anion A- are removed from compartment 6 and concentrated in pore compartments 4 and 8, respectively.

Also in FIG. 7, only metal ions M+ are removed from compartment 6 and concentrated in compartment 4.

Furthermore, in FIG. 8, only the anion A- is removed from compartment 4 and concentrated in compartment 6.

As mentioned above, 1 concentration or removal of metal ions and anions,
Effects such as concentration or removal of only 2 metal ions and concentration or removal of only 3 anions, which are not expected with the conventional apparatuses shown in FIGS. 1 to 3, are easily realized.

Furthermore, the apparatus illustrated in FIG.
It is improved as shown in the figure.

In the apparatus of FIG. 9, in which parts performing similar functions as in FIG. 5 are given the same reference numerals, the compartments 4, 6.8 are filled with the same type of solution as in FIG.

The device of FIG. 9 achieves the same effect as that of FIG. 8.

One of its effects is that anions move from the cathode chamber 2 to the compartment 4 and are not consumed, making it possible to use a sulfuric acid solution in the cathode chamber 2.

Since the sulfuric acid solution has good conductivity, the bath voltage is lower than when aqueous ammonia is used in the compartment 2 using the conventional method as shown in FIG.

In addition, ammonium ions are not included in the catholyte from the beginning,
Furthermore, since ammonium ions in the solution in the compartment 4 do not enter the cathode chamber, no ammonia odor is generated.

Next, ammonium ions do not move from compartment 4 to cathode compartment 2 or compartment 6, but sulfate ions pass through anion conversion membrane 5 and leave compartment 4, so the pH of the solution changes from acidic to neutral. to move to.

Therefore, there is no need to replenish ammonia water.

It goes without saying that in the apparatuses shown in FIGS. 6 to 9, the anion and cation exchange membranes according to the present invention are brought into close contact with each other, and liquid is substantially excluded from between them.

The apparatus of the present invention is capable of treating metal salt waste liquid containing one or more of cobalt, chromium, cadmium, copper, antimony, nickel, lead, selenium, tellurium, manganese, molybdenum, tungsten, vanadium, gold, and silver in addition to tin and nickel. Used for processing.

Furthermore, the arrangement of the ion exchange membranes is not limited to the arrangement of the other ion exchange membranes as illustrated in FIGS. 6 to 9, as long as the composite exchange membrane according to the present invention is used as the exchange membrane closest to the cathode. , it can be anything.

The present invention will be explained below using comparative examples and examples.

Comparative Example Ion exchange membranes 3, 5, 7 (first
An electrodialysis experiment was conducted using the electrolytic cell 15 (FIG. 10) in which the electrolytic cell 15 (FIG. 10) was placed.

As the anion exchange membrane and the cation exchange membrane, AMV and CMV manufactured by Asahi Glass Co., Ltd. were used, respectively.

The liquids in compartments 2, 4, 6.8 were circulated between the water tank 16 and the electrolytic cell 15 by four independent pipelines.

The water storage tank 16 is partitioned into four compartments corresponding to the compartments of the electrolytic cell by three liquid-impermeable partition walls 17.

Electrodialysis was performed under the following conditions.

(1) Starting solution for cathode chamber 2; 5% ammonium sulfate solution (2) Starting solution for compartment 4; Waste solution containing nickel and tin salts used for coloring aluminum (3) Starting solution for compartment 6; Waste liquid containing nickel and tin salts used for coloring treatment (4) Starting solution for anode chamber 8; 5% sulfuric acid solution (5) Current density; 3.5 A/dm2 (6) Liquid current density; 12.6 AH/ l (7) Electrodialysis time: 18 hours (8) Voltage: 8V (9) Bath temperature: room temperature, but when electrodialysis experiments were conducted at a maximum of 30°C or higher, it was found that the catholyte and the metal salt water bath in compartment 4 The metal ion concentration of the liquid changed as shown in Table 1.

The above method is performed in batch mode for one period of 18 hours.
When the test was carried out continuously for several months, the cation membrane 3 on the cathode side and the anion exchange membrane 5 in the middle were damaged.

In addition, metal on the cathode plate 11 was locally abnormally deposited.

This deposited metal is thought to be caused by metal ions in the metal salt waste liquid in the compartment 4 passing through the cation exchange membrane 3 and being reduced at the cathode plate interface.

The metal deposited on the cathode plate was locally abnormally precipitated, broke through the cation exchange membrane 3, and reached the anion exchange membrane 5.

For this reason, these exchange membranes 3 and 5 were damaged.

Assuming that the ion exchange membrane closest to the cathode is a close-contact composite membrane of an anion exchange membrane and a cation exchange membrane, in the apparatus of Examples and Comparative Examples,
Electrodialysis was performed under the following conditions with the cation membrane facing the cathode side.

(1) Starting solution in cathode chamber 2; 5% sulfuric acid solution (2) Starting solution in compartment 4; same waste solution as in comparative example (3) Compartment 6
starting solution; same waste solution as in comparative example (4) starting solution in anode chamber; 5
% sulfuric acid solution (5) Current density; 4.5/dm3; 4.5A/dm2 (
6) Liquid current density: 14.4 AH/l (7) Electrodialysis time: 8 hours (8) Voltage: 20 ■ (9) Bath temperature: Room temperature, but maximum 40°C Metals in catholyte and metal salt aqueous solution in compartment 4 The ion concentration changed as shown in Table 2.

From the results in Table 2, it can be said that there is almost no movement of ions between the catholyte and the metal salt aqueous solution.

[Brief explanation of drawings]

Figures 1 a and b, Figures 2 a and b, Figures 3 and 4 are conceptual diagrams showing the arrangement of electrodes and ion exchange membranes in a conventional electrodialysis device, and Figure 5 is a conceptual diagram showing the arrangement of electrodes and ion exchange membranes in a conventional electrodialysis device. A cross-sectional view of the ion exchange membrane disposed closest to the cathode, Figures 6 to 9 are conceptual diagrams showing the arrangement of electrodes and ion exchange membranes in the device according to the present invention, and Figure 10 is an electrodialysis membrane. FIG. 2 is a conceptual diagram of a conventional device used in an experiment. 1-Cathode, 2-Cathode chamber, 3,5.7-Ion exchange membrane, 8
- anode chamber, 9 - anode, 10 - deposited metal, 11 - ion exchange membrane, 15 - electrolytic cell, 16 - water tank.

Claims (1)

[Scope of Claims] 1. A metal salt waste liquid purification device comprising an anode, a cathode, and an ion exchange membrane separated from each other between these two electrodes, wherein the most cathode of the ion exchange membranes is provided. A metal salt waste liquid characterized in that the close ion exchange membrane consists of a cation exchange membrane facing the cathode on one side and an anion exchange membrane in close contact with the other side of the cation exchange membrane. Purification device.