JPS6160894A - Energy saving type zinc electrolysis - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zinc electrolytic process, and more particularly to a zinc electrolytic process that saves the energy required for electrolysis.

[Conventional technology]

There are two methods for obtaining metallic zinc: a dry method and a wet method.

Among them, the most common wet method is to roast zinc-containing ore, such as zinc sulfide ore, to make lead oxide, dissolve it in dilute sulfuric acid, and sweep away the zinc sulfate solution.
Impurities such as u, Cd, Go, and N- are removed by reactions such as neutralization, coprecipitation, and reduction to produce a zinc sulfate-purified neutral solution, and this clean neutral solution is used as a cathode and aluminum is used as an anode to produce a silver-containing lead alloy. Used to replenish the electrolytic sentries and direct i7! Metal zinc is precipitated on the cathode by passing an electric current through ia in an acidic sulfuric acid solution, and the generated sulfuric acid is repeated in the melting process to peel off the precipitated dumbbell from the cathode. The electrowinning method of casting and obtaining zinc ingots is practiced in many countries including Roma.

In the electrolysis in these known acidic sulfuric acid solutions, different electrochemical reactions occur from the anode and cathode in the electrolytic cell, but the reaction formula and the 'is potential in the 5i state are as follows: , ^rgonnl NaLiona
lLaboratory ANL10EPM7-3.9
4 (According to 19791, it is as follows.

Yinffi;Zn"+2t-Zn E, =-Q, 76
V (11 anode: 2H, O-0, +4H″″
+4 a E, = 1.23 V (21 Therefore, the electrolytic voltage (E, ) in the equilibrium state is E, := 1.23 V-(
-0.76V) = 1.99V, but in reality, electrolysis cannot be carried out with just this voltage; the anode must be brought to a more positive potential, and the cathode must be brought to a more base potential.

The difference between the potential of both electrodes and the equilibrium potential in the above fil te 1 formula is taken as the overvoltage of both electrodes), and the current density is 50 mA/e for the voltage to overcome this overvoltage and liquid resistance.
The electrolysis voltage under ar conditions should be operated at 3.5 V.

The theoretical energy dissipation 'R'Ik is calculated when the electrolytic voltage is 199
In the case of V, the power consumption is 1630 KWh/l, but under the above-mentioned electrolytic voltage condition of 3.5 V, it is 2870 KWh.
/L, and if we add to this loss due to current efficiency, loss due to current transformation efficiency of converting alternating current to direct current, loss due to conductor tension between rectifier and electrolytic cell, etc., the electric power per ton of electrolytic zinc is calculated. The basic unit requires approximately 3,500 KWb of energy just for electrolysis.

The zinc electrolysis method described above is an established method for obtaining high-purity metallic zinc, but it has the disadvantage of requiring a relatively large amount of energy. There was a request for the development of a zinc electrolysis method.

[Problem that the invention seeks to solve]

The present invention provides an energy-saving zinc electrolysis method by improving the electrolysis method that consumes a large amount of energy, which is a drawback of the Dixian electrolysis method using acidic zinc sulfate solution, such as Slanting. There is a particular thing. Electrolytic zinc at even lower cost! ! The purpose of this project is to develop a zinc electrolytic method for the production of zinc. [Means for solving the problem] As a result of various studies, the present inventors added sulfurous acid gas and a small amount of iodine, which plays a catalytic role in the sulfurous acid gas oxidation reaction, to a zinc sulfate electrolytic solution and solved the problem under low electrolytic voltage. The present invention was achieved by confirming that the problems of the invention described above can be solved by electrolysis.

That is, in the present invention, when electrolyzing an acidic zinc sulfate solution, the first
As shown in the figure and FIG.
A small amount of iodine ions or iodine is added to the zinc-cleaned neutral flI solution consisting of sulfuric acid and zinc as a cathode chamber i2F solution, and a small amount of sulfur dioxide gas is added to sulfuric acid as an anode chamber solution. This is an energy-saving lead electrolysis method that uses a solution containing an oxidation catalyst.

More specifically, it is characterized by using iodine or iodine ions as an oxidation catalyst, and the electrolytic conditions are as follows: iodine ion concentration: 0001-01 mol, sulfuric acid 4°C: 05-2.0 mol, sulfite gas concentration: 01-20 mol, and temperature: 20-0.0 mol. 40°C, using a porous graphite Ts electrode as an anode, having one or two diaphragms, and producing gypsum by reacting sulfuric acid produced in the anode chamber with limestone or slaked lime, Another feature is that the iodine ions in the positive rinsing chamber solution are recovered and reused.

[Effect]

The reason why the electrolytic voltage in conventionally known zinc electrolysis is much higher than the FL theory is because the cathode reaction overvoltage o, o s v is negligible, but the cathode reaction overvoltage is 0.84 V, which is quite high. be. The weakest point in the known zinc electrolysis method is the huge amount of energy consumed in the VA electrode reaction, but in this case, the huge amount of oxygen generated from the positive electrode is of no use and is rather used in the electrolytic solution. This has the effect of evaporating the zinc into electrolytic mist, deteriorating the environment, promoting corrosion of the anode, and reducing the purity of the deposited zinc.

The present invention can reduce such anode overvoltage by oxidizing Il+-sulfuric acid gas, which is known as a passive medium. Saponification reaction of sulfite gas from acidic solution! ! Looking at the I picture electrolytic reaction, A-Jappla
by and B4'1chon, J.Electr
oanal, Cbem-, 95, 59 (1979)
According to the following:

Positive i: So, +2Hρ→H3O-, +3H”+2
e l, = Q, 1 2V [31 Yin tE[i:
Zn + 2 e-Zn E=-0,
76V fil Therefore, the zinc electrolysis voltage in a sulfurous acid gas solution is only 0.12V-(-0.76V): 0.88V, which is about 1.1V in a conventionally known zinc sulfate bath. Low oxygen overvoltage does not occur.

Instead of simply oxidizing the sulfite gas solution, the present invention
A small amount of potassium iodo or iodine is added as an iodine ion that plays a catalytic role in the oxidation of sulfite gas.
-) This is a method in which oxidation of sulfite gas is carried out at a potential.

That is, in the method of the present invention, the anode chamber solution (1 mol sulfuric acid)
+ (sulfurous acid gas) + (iodine ion), the anode 11 volume is (1 mol sulfuric acid 1 + (0.8 mol zinc)), a porous graphite electrode is used as the anode, aluminum is used as the cathode, and the current density is When electrolysis is started from 50 mA101, the electrolytic voltage is about 2.0 V, which is the conventionally known operating electrolytic voltage (compared to ζ, the voltage drop is about 1.5 V in Figure P).

Even if electrolysis is carried out without injecting iodine ions [11] as a catalyst into the anode chamber solution, the electrolysis voltage will be about 2.5 µ, which is about 1.0 µ compared to the operating voltage of the conventionally known electric folding method. You can plan your descent.

Therefore, by adding a small amount of catalyst, it is possible to achieve a voltage drop of about 0.5 μ compared to when sulfurous acid gas is simply added to the solution.

This means that the oxidation reaction of sulfite gas from a catalyst-added solution is caused by the catalytic approx. It is for the purpose of

G-5-Calabrace & M-5, Wrig
hcon-J-A-C-5・103 (2116273
According to F19811, 31--1-+2 e E
=0.536V 14121"-1+2 e
E =0.621V [5lSO3+zH
2o+t;→H2So4+2J(”+31 [6
1So2+2H,O+I;-H2so,+zH"4-z
(7) In the oxidation reaction of sulfite gas, suitable electrolytic working conditions are an iodine ion concentration of 0001 to 041 mol.

Sulfuric acid concentration 05~'2. ．． 0 mol, sulfite gas concentration 01~
2.0 mol, temperature 20-40°C.

When iodine, which is inexpensive relative to the unit weight of iodide ions, is used as a catalyst instead of potassium iodo, the iodine oxidizes sulfite gas and is reduced to iodide ions.30. , l
- state, the same effect as the method using potassium iodo can be obtained, and the catalyst cost can also be reduced.

The purpose of the diaphragm is to separate the solutions in the anode and cathode chambers, thereby preventing the reduction reaction of the sulfur N dissolved in the cathode and increasing the efficiency of the cathode. Furthermore, if a double diaphragm is provided, it is possible to completely block the inflow of sulfite solution from the anode chamber to the cathode chamber, and in some cases, by separately installing an anode in this intermediate chamber, the inflow of sulfite solution can be blocked. It can be removed.

In the method of the present invention, the voltage is 1 [voltage is 2. With OV, the electric power consumption as energy consumption is 1640 KWb/(, and even if you add the current efficiency, current transformation efficiency, power loss due to the resistance of the conductor between the rectifier and the electrolytic cell, etc., the precipitated metal zinc 1
This means that only about 2000 KWh of electricity is required for electrolysis per tonne.

This electric power unit is about 57% compared to the electric power unit of conventionally known methods, and is about 15% per ton of deposited metal zinc.
00 KWh of energy required for electrolysis will be saved.

According to the present invention, +61 (7
In formula 1, sulfur dioxide gas is oxidized, sulfuric acid is produced, and the sulfuric acid concentration increases.As shown in Fig. 2, this anode chamber solution is introduced into a reaction tank charged with lime (burnt lime).
The reaction produced gypsum. After separating the plaster, min gI
! The liquid is led to a Mead ion recovery tank to recover iodine ions, added to a sulfite gas dissolution tank, and used repeatedly as an anode chamber solution. That is, according to the method of the present invention, it is possible not only to produce gypsum, but also to continue the zinc electrolysis process in a continuous process without wasting iodine ions.

Gypsum production reaction by M-Grayson and DIE
clcrothK: RK-Other aincyc
ropedia of chemical technology
H. logic, 4443 (1978)
,So,+Caco,-”Ca So,+GO,+82
0H2So, +Ca (OHI 2-Ca5O, -28
, O... (81Also, the sulfite gas in the anode chamber solution reacts with slaked lime in the reaction tank, and gypsum is produced according to the following +91 +11 formula, so the sulfite gas in the sulfuric acid produced is not a problem. No.

So, +Ca (OHI 2→Ca5O,・1/2H2
0=1912CaSO,=1/2H20+O,-2Ca
SO,・2H20・−(+1) After electrolysis was carried out by adding a small amount of iodine ions to the cathode chamber solution, when the surface condition of the electrolytically deposited zinc was observed, it was found that no pins were observed on the deposited zinc when no additive was added. Not only were there no holes, but the current efficiency was also improved compared to when no additives were added.

In the present invention, the current density is set to 2 of the operating current density of the known method.
If the bath voltage is increased to 100 mA/cIll, which is twice as high as that of 100 mA/cIll, the bath voltage will be about 2.2 V.
If the voltage is increased to A/laj, not only will the bath voltage (to 3.8 V) significantly increase, but the high bath voltage will partially collapse the Pb-Ag anode and cause pb- ions to be electrodeposited on the cathode, resulting in damage to the product. Impairs purity.

Furthermore, since the anode potential becomes higher, more MnO2 is electrodeposited on the anode, lowering the electrical conductivity of the electrode and causing an increase in voltage. On the other hand, in the present invention, the anode overvoltage due to current density is small and the anode potential is lowered, so that the graphite anode is not dissolved and MnO□ is not electrodeposited. In this way, when the operating current density is doubled according to the present invention, the productivity is also doubled, and the equipment and other AI costs can be cut in half compared to the known electrolysis method. Be able to do it.

〔Example〕

Examples 1 to 4 of the present invention will be described below.

Example 1 As shown in FIG. 1(a), a porous black bean paste anode 2 and an aluminum cathode 3 are fixedly provided in an electrolytic cell 1 with a distance of 5 cm between the anode and cathode. A long battery diaphragm is used to partition the battery into an anode chamber 5 and a cathode chamber 6 with a diaphragm 4.

In the anode chamber 5 of the electrolytic device having this configuration, a solution consisting of 1.5 mol sulfuric acid, 1 mol sulfite gas and 0.001 mol iodine ions is used as the solution, and a solution consisting of 1.5 mol sulfuric acid and 0.8 mol zinc as the cathode chamber 6 solution. using a current density of 50 mA
Electrolysis was carried out using LCD for 20 hours.

At this time, the solution rα in the anode chamber 5 and the cathode chamber 6 was continuously circulated as shown by the arrow in order to prevent the concentration of sulfite gas and zinc in the solution from decreasing.

As a result of the above, the electrolytic voltage is 2. Zinc was deposited on the cathode 3 at a current efficiency of 89%.

Example 2 In the electrolysis apparatus shown in FIG. 1(a), a solution consisting of 15 mol sulfuric acid, 1 mol sulfite gas and 0.1 mol iodine ions was used as the solution in the anode chamber 5, and the solution composition and electrolytic conditions in the cathode chamber 6 were changed. In addition, the electrolysis method is practiced! Electrolysis was carried out in the same manner as in Example 1.

As a result, zinc was deposited on the cathode 3 at an electrolytic voltage of 1.9 V and a current efficiency of 89%.

Example 3゜Sun 8Fl room 5 m? l! As in Example 1, a solution consisting of 15 mol sulfuric acid, 1 mol sulfite gas and 0.1 mol iodine ions was prepared, and as the solution in the cathode chamber 6, 1.5 mol sulfuric acid, 0.8 mol zinc and 0.01 mol iodine ions were prepared in the same manner as in Example 1. (
Electrolysis was carried out using the electrolytic apparatus shown in a) under the same electrolytic conditions and method.

The result is that the electrolytic voltage is 2. When zinc was deposited on the cathode 3 with OV at a current efficiency of 91% and iodine ions were added, the state of the deposited zinc was good with no holes such as pinholes observed.

Example 4 As shown in Figure 1 (bl), a porous black bean paste anode 2 and an aluminum cathode 3 are fixed in an electrolytic cell 1 with a distance between the electrodes Q 6 c+n, and a diaphragm similar to that in Example 1 is installed between the cathode and anode. 4a and 4b
In the anode chamber 5. Intermediate room7. It was partitioned into 6 cathode chambers.

As a solution in the anode chamber 5 of the electrolyzer configured to refuse, 15 mol sulfuric acid and 1 mol ir [! Using a solution consisting of 1ji8 acid gas and 0.01 mol iodine ions, a solution consisting of 15 mol sulfuric acid and 0.8 mol mB3 as the solution in the cathode chamber 6, and a solution consisting of 5 mol sulfuric acid as the solution in the intermediate chamber 7, a current is applied. Electrolysis was carried out for 20 hours at a density of 50 mA/cd.

At this time, as in Example 1, the solution in the anode chamber 5 and the solution in the cathode chamber 6 were continuously circulated as shown by the arrow in order to prevent the sulfite gas and zinc from decreasing by 9 degrees.

As a result of the above, the electrolytic voltage is 2. IV, current efficiency 91%
Zinc was deposited on the cathode 3.

〔Effect of the invention〕

According to the zinc electrolysis method of the present invention, not only can the electric power required for zinc electrolysis be greatly reduced compared to conventional known electrolysis methods, but also the sulfuric acid produced at the anode can be used to remove gypsum. Make it a subsidiary, 12! As a result of being able to increase the industrial current density to twice that of the conventional method, it has the advantage of reducing investment in electrolysis equipment and doubling productivity.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the electrolyzer for the method of the present invention, Figure 2 (
It is a process diagram of the method of the present invention. 1. Electrolytic cell, 2: Porous graphite anode, 3 Nialuminum cathode, 4: FfA5, 5. Anode chamber, 6 Cathode chamber, 7.
intermediate room. Note that the symbols in the drawings indicate the same or the same functions. Agent: Patent attorney Sanro Kimura 1 time (b)

Claims (6)

[Claims] (1) An anode chamber solution made of sulfuric acid with the addition of sulfite gas and a small amount of oxidation catalyst, and a cathode chamber solution made of sulfuric acid and zinc solution with a small amount of iodine ions or iodine, separated by a membrane. An energy-saving zinc electrolysis method characterized by separate electrolysis. (2) The zinc electrolysis method according to claim 1, wherein iodine ions or iodine is used as the oxidation catalyst. (3) The solution has an iodine ion concentration of 0.001 to 0.
1 mol, sulfuric acid concentration 0.5-2.0 mol, sulfite gas concentration 0.1-2.0 mol, and the electrolyte temperature is 20-40℃.
2. The zinc electrolytic method according to claim 1, wherein the zinc electrolysis is carried out in a. (4) The zinc electrolysis method according to claim 1, characterized in that the number of said diaphragms is one or two. (5) The zinc electrolysis method according to claim 1, wherein in the electrolysis method, a porous graphite electrode is used as an anode. (6) The sulfuric acid produced in the anode chamber is reacted with limestone or burnt lime to produce gypsum, the iodine ions in the anode chamber solution are recovered, and the iodine ions are repeatedly used. Zinc electrolysis method according to scope 1.