JPH0474435B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for removing metal plating waste liquids, metal etching waste liquids, solutions containing metal ions, metal cyanide complex ions, etc. from solutions containing metal ions, metal cyanide complex ions, etc.
The present invention relates to a method for recovering metals with high yield and low power by fluidized bed electrolysis, and an electrolytic cell used to carry out the method.

Solutions containing metals are used in various industrial and decorative fields, and valuable metals are generally recovered from the solutions. For example, gold, a type of precious metal, is widely used as a standard for monetary value, various decorative purposes, dental purposes, and fountain pen nibs.When used for decorative purposes, gold is expensive. Since then, plating has been applied to the surface of ornaments to save on the amount of gold used. Relatively high concentrations of gold remain in these gold plating waste liquids, and attempts have been made to recover and reuse the remaining gold using the following methods.

(a) Add a reducing agent to the solution and deposit gold directly in the solution.

(b) A solution containing gold ions and/or gold cyanide complex ions is introduced into an ion exchange resin tower to fix the gold ions and/or gold cyanide complex ions to the ion exchange resin.

(c) The solution is electrolyzed with a low current density electrolyte layer to deposit gold onto the cathode.

Although gold can be recovered from wastewater using these methods, each method has the following drawbacks. In other words, method (a) has the disadvantages of increased processing liquid volume, long reaction time, and increased operating costs.
Although method (b) is easy to operate, it has the disadvantage of high operating costs such as equipment construction costs and regeneration chemical costs, and method (c) is suitable for waste liquid containing high concentrations of gold. In the case of low-concentration waste liquid, economical current efficiency cannot be obtained unless the current density is further lowered, and the electrolyte layer becomes larger and construction costs increase. The disadvantage is that the condition is very good, making it difficult to remove it from the cathode, and that it is actually necessary to redissolve it using a gold remover.

In addition, similar methods are used not only to recover gold from waste liquids, but also to purify gold containing small amounts of impurities into high-purity gold, and similar drawbacks have been pointed out. These drawbacks are not limited to the recovery of precious metals such as gold, platinum, and silver, but also include heavy metals such as copper, nickel, and iron, polluting metals such as cadmium and chromium, and other metals such as zinc, gallium, bismuth, and aluminum. This problem also occurs in the case of valuable metals.

The inventors of the present invention have investigated various means for eliminating the above-mentioned drawbacks and depositing the metal in solution on the cathode with high current efficiency and low electrolytic voltage. The method of the present invention for recovering metal by passing a solution between the particles and the electrolytic cell of the present invention using a fluidized bed type electrolytic cell have been achieved.

That is, the present invention first provides a method for recovering metal from a metal-containing solution, in which a liquid containing cathode particles brought into a fluidized state by an upward flow of a metal-containing solution supplied from the bottom of a cathode chamber of an electrolytic cell is provided. In addition to supplying a metal-containing solution to the bed electrolytic tank and electrolyzing it, the flow rate of the upward flow was reduced in the upper part of the cathode chamber to separate the cathode particles accompanying the upward flow from the upward flow and prevent them from flowing out from the cathode chamber. This is a method of recovering metals precipitated on cathode particles from a metal-containing solution.Secondly, the cathode chamber of an electrolytic cell is divided into an anode chamber and a cathode chamber by a diaphragm. A fluidized particle dispersion prevention tower is installed at the top of the cathode chamber. This is an electrolytic cell for metal recovery with a solution outlet provided on the wall of the dispersion prevention tower.

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

FIG. 1 is a longitudinal cross-sectional view showing a first embodiment of an electrolytic cell for metal recovery according to the present invention, and FIG. 2 is a cross-sectional view taken along the line -- in FIG.

The electrolytic cell main body 1 consists of a cylindrical body with an open upper surface and an outward flange 2 connected to the upper end, and a solution supply port 3 is provided downward in the center of the lower surface of the main body 1. An anode supporting cylinder 4 is disposed near the lower end of the inner wall of the main body 1, and a donut-shaped anode lower frame with a lattice-shaped support piece 6 disposed on the cylinder 4 is attached via an O-ring 5. 7 is placed. A porous cylindrical anode 8 is erected on the upper edge of the anode lower frame 7 by welding or the like.

As the material of the anode, commonly used materials such as graphite, stainless steel, platinum, titanium coated with a noble metal oxide, and ferrite can be used. The lower end of a short cylindrical anode upper frame 10 with an outward bent part 9 connected to the upper end of the anode 8 is connected by welding or the like, and the outer end of the outward bent part 9 is connected to the upper end of the anode 8 by welding or the like. , a gasket 11 aligned with the outer end of the outward flange 2 and between the outward bent portion 9 and the outward flange 2.
is mediated. On the inner surfaces of the anode 8 and the anode upper frame 10 and on the lattice-like support piece 6, there are many fine particles of about 10 to 100 μm made of a non-conductive organic compound or a non-conductive inorganic compound such as nylon, polyethylene, polypropylene, etc. A bag-shaped diaphragm 12 having holes is accommodated in an inscribed state, and the diaphragm 12
The upper end is bent outward and held between a pair of gaskets 13 and 14 to form an anode upper frame 10.
It is placed on the outwardly bent portion 9 of. A recess 1 is provided in the center upper surface of the inner lower part of the bag-like diaphragm 12 at the portion that comes into contact with the anode lower frame 7 via the diaphragm 12.
5, and a solution dispersion plate 1 made of vinyl chloride resin or the like and having a large number of vertically perforated communication holes 16.
7 is placed.

A gasket 14 is placed on the upper end of the bag-shaped diaphragm 12.
An outward facing flange 19 at the lower end of the fluidized particle diffusion prevention tower 18 is mounted through the flange 19 and fastened with bolts 20 . The fluidized particle diffusion prevention tower 18 includes, in order from the bottom, the lower end outward flange 19, the small diameter part 2
1. Consists of a tapered part 22, a large diameter part 23, and an upper end outward flange 24, and the outward flange 2
A disk-shaped lid 25 is fastened onto the top of the housing 4 with bolts 26. A cathode current collector 27 is vertically disposed on the lower center surface of the lid 25, and the lower end reaches near the recess 15. Part 29
and a hollow cylindrical main body 30, the main body 30
On the outer periphery of the blade body 3 is provided to increase the surface area of the current collector.
1 are arranged radially. Inside the bag-like diaphragm 12, particles having a particle size of about 0.05 to 3.0 mm, preferably 0.1
A large number of cathode particles 32 of about 0.5 mm are accommodated. The material of this cathode particle is gold, silver,
Metals such as copper, nickel, and lead, their oxides, sulfides, or alloys thereof, and conductive nonmetals such as graphite and activated carbon can be used, as well as particles of graphite, glass, ceramic, etc. It is also possible to use materials coated with metals such as gold, silver, copper, nickel, and lead. 33
34 is an anode gas and anolyte outlet connected to the upper side of the electrolytic cell main body 1, a catholyte outlet connected to the side of the large diameter part 23 of the fluidized particle diffusion prevention tower 18, and 35 is a lid. This is a cathode gas outlet connected to the upper surface of the body 25.

A metal-containing solution such as metal-containing waste liquid is supplied from the solution supply port 3 to the electrolytic cell body 1 having the above-mentioned configuration. This solution is generally an aqueous solution, but may also be an organic solution such as alcohol used in solvent extraction. The supplied solution passes through the pores of the bag-like diaphragm 12 and the communication holes 16 of the solution distribution plate 17, and is introduced into the cathode chamber under pressure. In this case, the solution serves to maintain the cathode particles 32 in a fluid state.
Here, the term "fluid state" refers to a state in which the solution passes through the solution while the cathode particles stick together or separate from each other in the solution. The solution passed through taper part 2
2, the cathode particles and the solution are separated, and a uniform laminar flow is obtained in the cathode particles. The metal ions in the solution are electrolytically reduced on the cathode particles 32, become metal atoms, and precipitate on the cathode particles 32. At the same time, as a side reaction, water is decomposed and hydrogen is generated, and this hydrogen is passed through the cathode gas outlet. 35. A part of the solution flows into the anode chamber through the bag-like diaphragm 12, and water is decomposed on the anode 8 to generate oxygen. This oxygen is electrolyzed from the anode gas outlet 33 or the cathode gas outlet 35. It is taken out of the tank. In addition, metal-containing waste liquid usually contains cyanide ions, chloride ions, iodate ions, nitrogen oxide ions, etc., and gases such as nitrogen, ammonia, and chlorine that are generated when these compound ions are decomposed can also be extracted. be done. Further, a portion of the solution is also taken out of the system, which also serves to separate impurities generated by decomposition of organic substances contained in the solution. The electrolyzed solution whose metal ion concentration has been reduced overflows from the solution outlet 34 and is taken out of the electrolytic cell.

In this electrolytic operation, in order to efficiently impart a cathode potential to the fine particles in the fluidized bed and deposit the metal on the cathode with high current efficiency and low electrolytic voltage, it is desirable to perform electrolysis under the following electrolytic conditions. .

Cathode current density: 30A/ ^dm2 or less (preferably 10A/ ^dm2 or less) Anode current density: 20A/ ^dm2 or less (preferably
5A/dm ² or less) Current concentration in fluidized bed: 30A/l-fluidized bed or less (preferably 10A/- fluidized bed or less) Fluidized bed void ratio: 40 to 90% (preferably 60 to 75%) Here, cathode If the current collector density exceeds 30A/ ^dm2 , the voltage will become unnecessarily high and the anode current density will decrease.
When it exceeds 20A/ ^dm2 , the voltage increases and
The anodic reaction shifts from a preferred reaction such as cyanide or organic matter decomposition to an undesirable reaction, water electrolysis. Furthermore, when the current concentration in the fluidized bed exceeds 30A/l-fluidized bed, not only does the voltage increase, but also plucking occurs, and when the fluidized bed void ratio exceeds 90%, the voltage increases, and when it falls below 40%, the voltage increases. Since plugging occurs near the supply port, it is preferable to keep it within the above range.

In addition, if this electrolytic operation is continued, the diameter of the cathode particles will increase as the metal is deposited, and the fluidization conditions (fluidized bed height, fluidized bed void ratio, fluidized bed pressure loss) will change, so this electrolysis will The fluidized bed section of the tank is preferably designed as follows. That is, the height of the fluidized bed is at least 1.2 times, preferably at least 1.4 times, the height of the initial fluidized bed, and the cross-sectional area of the fluidized particle scattering prevention tower is at least 1.5 times, preferably at least twice, the cross-sectional area of the electrolytic cell body. As a result, the cathode particles can be maintained in a fluid state and the particles can be prevented from escaping. In this way, metal can be deposited to a size that is more than twice the original diameter of the cathode particles.

In addition, since cathode particles in a fluid state are used as the cathode, the surface area of the cathode becomes extremely large, lowering the current density, and the cathode particles collide with each other, making the electric double layer unstable, so the electrolytic voltage decreases. Electrolysis can be performed in a state where the current is low and the current is high and efficiency is high. In particular, it is advantageous for purification because only a specific metal can be selectively deposited by utilizing the deposition potential difference of different metals in a solution using the present electrolytic cell or this method. For example, if other impurities such as silver and copper are present in the gold-cyanide solution, only the gold can be precipitated and recovered by lowering the current density sufficiently.

Through the above electrolytic operation, the cathode particles whose surfaces are coated with metal are taken out of the electrolytic cell and the metal is recovered. If the difference in specific gravity between the precipitated metal and the cathode particles is small, subsequent recovery will be easier if the particles have the same composition. If the precipitated metal and cathode particles have different components, they must be separated. For separation, conventional separation means such as dry separation method or wet separation method may be used as is. In order to separate metal from cathode particles by a dry separation method, for example, in the case of gold or platinum, the following procedure may be performed. When cathode particles coated with gold are melted and oxygen gas, chlorine gas, etc. The glass, etc. becomes slag and floats on the molten metal and is separated. after that,
When cooled and solidified, gold or platinum containing almost no impurities can be obtained. Furthermore, when an alloy is precipitated from a dilute solution containing a noble metal and a base metal, it can be redissolved and separated using a normal wet separation method. This redissolved liquid does not contain any organic substances other than metal elements, and since a small amount of highly concentrated liquid can be obtained, it can be recovered economically. The current efficiency for metal recovery is over 10%, and the recovery rate of metals from the solution varies depending on the metal content and electrolysis time, but
In a single operation, the power is almost 100% at low power when the metal content is low, and more than 65% when the metal content is relatively high. Even in the latter case, metals can be recovered almost quantitatively by circulating the solution.

FIG. 3 is a longitudinal sectional view showing a second embodiment of the fluidized bed electrolytic cell according to the present invention. This electrolytic cell is an improvement of the electrolytic cell of the first embodiment, and the same members as those of the first embodiment are given the same reference numerals and explanations thereof will be omitted.

The electrolytic cell body 1' consists of a dish-shaped lower frame 36 in which a solution supply port 3 is connected, and a cylindrical anode 8'. Both upper and lower ends of the anode 8' are folded outward. It is curved. The porous diaphragm consists of a cylindrical upper diaphragm 12' and a planar lower diaphragm 12'', and both upper and lower ends of the upper diaphragm 12' are bent outward. Solution dispersion 17' is approximately the same as the diameter of the lower diaphragm 12'',
A communication hole 16' is provided only in the center.

The bent portion at the upper end of the upper diaphragm 12' is held between the outward flange 19 of the fluidized particle diffusion prevention tower 18 and the bent portion at the upper end of the anode 8' via gaskets 13 and 14, and is secured by bolts 20. It is fastened.
The peripheral edge of the solution distribution plate 17' is connected to the upper diaphragm 12' which is held between a pair of gaskets 37 and 38, respectively.
The lower diaphragm 12'' is held between the bent portion of the lower end and the lower diaphragm 12'', and is fastened with bolts 39.

When a metal-containing solution is supplied to this electrolytic cell from the solution supply port 3, metals are recovered in the same manner as in the first embodiment.

In the electrolytic cell of this example, although the apparent thickness of the anode chamber is zero, the diaphragm does not come into close contact with the anode, and the anode chamber substantially exists between the diaphragm and the anode. The electrolytic gas generated on the surface of the anode reaches the cathode chamber through the diaphragm and is taken out together with the cathode gas from the cathode gas outlet.

The electrolytic cell of this example has a smaller number of parts and a more compact structure than the electrolytic cell of the first example because the anode constitutes the electrolytic cell main body and the solution dispersion plate is connected to the electrolytic cell main body. Become. Also, although the anode is exposed to the atmosphere, there is no risk of electric shock because the applied voltage is small.

The present invention uses a fluidized bed electrolytic cell when recovering metals from a solution, and the surface area of the cathode is extremely large, so that metals can be efficiently deposited on cathode particles at low current density. Since the cathode is in the form of particles in a fluidized state, the electric double layer is thin and unstable, and this tendency is due to the potential difference of the deposited metal, especially when refining highly valuable gold from a gold solution. It's convenient. Further, since the metal can be thickly deposited on the particulate cathode, it is extremely easy to take out the cathode from the electrolytic cell and to separate the metal from the cathode particles.

Example 1 Gold was recovered from gold plating waste liquid using a fluidized bed electrolytic cell shown in FIG. The dimensions of each part of the electrolytic cell are: height of the electrolytic cell body: 113.5 cm, inner diameter: 14.5 cm,
The height of the mesh-shaped anode is 100 cm, the diameter is 12.5 cm, the outer diameter of the cathode current collector is 5 cm, and the height of the fluidized particle diffusion prevention tower is 35 cm.
cm, and the outer diameter of the large diameter part was 113.5 cm. The materials of each member include acrylic resin for the electrolytic cell body and fluidized particle diffusion prevention tower, platinum-coated titanium for the anode, and platinum-coated titanium for the anode.
The cathode particles used were copper particles with a particle size of 0.1 to 0.15 mm, the bag-like diaphragm was a nylon net with a pore size of about 49 μm, the solution dispersion plate was made of vinyl chloride resin, and the cathode current collector was made of copper.

The test solution had a pH value of 4.1, a total organic carbon content (TOC) of 15.0 g/, a silicon dioxide content of 56 mg/,
The total amount of phosphorus was 1.6 mg/, and the following ion concentrations were used, and the gold concentration was adjusted to 1650 ppm by diluting with water before being supplied to the electrolytic cell.

Au 2580ppm Na 51ppm CN ^- 1000ppm Cl ^- 530ppm Ni 25ppm K 13300ppm SO ₄ ^3- 43000ppm This adjusted gold waste liquid was supplied to the electrolytic cell at a flow rate of about 2.8/min, and the anode current density was 260A/dm ² and the cathode current collector Current density 1.0A/dm ² , current concentration in fluidized bed 10.7A/- fluidized bed, fluidized bed void ratio of copper particles 70
When electrolyzed under the conditions of %, the electrolytic voltage was 2.1
~2.5V, average current efficiency 38%, and gold concentration at the electrolyzer outlet was 3ppm. Note that the nickel concentration did not decrease.

Example 2 Using the same electrolytic cell and waste solution containing silver and copper as in Example 1, the waste stock solution was adjusted to have a metal concentration of 53 ppm. This waste liquid was supplied to the electrolytic cell at a flow rate of 3.0 min, with an anode current density of 1.0 A/dm ² , a cathode current density of 1.4 A/dm ² , and a current density in the fluidized bed.
When electrolyzed under the conditions of 4.1A/, fluidized bed void ratio of 75%, the electrolysis voltage was 3.2V, and the average current efficiency was 34.
%, and the metal concentration at the electrolyzer outlet is 0.02ppm
It was below.

Example 3 The same electrolytic cell and waste stock solution as in Example 1 were used, except that 0.3 mm diameter glass bulbs plated with 1μ gold were used as cathode particles, and the waste stock solution had a lower gold concentration.
Adjusted to 1200ppm. This gold waste liquid 5.0
/min flow rate to the electrolytic cell, and the anode current density
When electrolysis was carried out under the following conditions: 2.6 A/dm ² , cathode current collector density 3.6 A/dm ² , current concentration in the fluidized bed 10.7 A/, and fluidized bed void ratio 65%, the electrolytic voltage was 2.6 V,
The average current efficiency was 49%, and the gold concentration at the electrolyzer outlet was 2.4 ppm.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view showing a first embodiment of a fluidized bed electrolytic cell according to the present invention, FIG. 2 is a cross-sectional view taken along the - line in FIG. 1, and FIG. 3 is a cross-sectional view of the present invention. FIG. 2 is a partially cutaway front view showing a second embodiment of the fluidized bed electrolytic cell according to the present invention. 1, 1', ... electrolytic cell body, 3, ... solution supply port, 8, 8', ... anode, 27, ... cathode current collector,
32,... cathode particle.

Claims (1)

[Claims] 1. A method for recovering metals from a metal-containing solution, in which cathode particles in the cathode chamber are brought into a fluidized state by an upward flow of a metal-containing solution supplied from the bottom of the cathode chamber of an electrolytic cell, and electrolyzed. At the same time, the flow rate of the upward flow is reduced in the upper part of the cathode chamber to separate the cathode particles accompanying the upward flow from the upward flow, thereby preventing the cathode particles from flowing out. How to recover metals. 2 In an electrolytic cell for metal recovery, the cathode chamber is divided into a cathode chamber and an anode chamber by a diaphragm, and cathode particles with a diameter larger than the pore diameter of the diaphragm are stored in the cathode chamber, and a metal-containing solution is placed at the bottom of the cathode chamber. A metal characterized in that a supply port is provided, a fluidized particle dispersion prevention tower whose cross-sectional area gradually increases toward the upper part of the cathode chamber is provided, and a solution outlet is provided on the wall of the fluidized particle dispersion prevention tower. Electrolytic cell for recovery.