JPS63312991A - Control of amount of zinc powder in removal of impurities from zinc sulfate solution - Google Patents

Abstract

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

Description

Description: TECHNICAL FIELD The present invention relates to a method for removing impurities from a zinc sulfate solution in electric N-mixing of zinc, and more particularly to adjusting the amount of zinc powder used for impurity removal.

Prior art Removal of impurities such as copper, cobalt, nickel, dalmanium, cadmium, etc. is carried out by cementing them using zinc powder, and the amount of zinc powder used is optimized by redox potential measurements.

The main raw material used in zinc electrolytic treatment is zinc concentrate.

This is first distributed by oxidation. The burned main component is dissolved in a recovered acidic solution containing sulfuric acid recovered by electrolytic separation. Insoluble inclusions are separated from the zinc sulfate solution produced during the dissolution process.

This solution is further purified to remove all elements that are more inert than zinc. Electrolysis is performed after solution purification.

The crude solution of zinc processing contains elements that are more inert than zinc, and their content varies depending on the zinc concentrate and other constituents. Particularly important are copper, cadmium, cobalt, nickel, arsenic, antimony, chelium, and thallium.

These elements are more inert than zinc, so in electrolysis,
It tends to precipitate on the cathode side. This is undesirable since it reduces the purity of the deposited zinc and some elements undergo secondary reactions (hydrogen evolution).

Since the above elements are more cineactive than zinc, they can be extracted from solution as cement by metallic zinc.

This method, apart from solution purification methods, is used almost exclusively in zinc production. In the solution purification method, elements that are more inert than zinc are removed from the zinc electrolyte solution by extraction with β-naphthol.

A common cementing agent used in solution refining is metallic zinc, but adjuvants such as arsenic or antimony are commonly used. When antimony is used, the purification is an entirely continuous reaction step, with the first step removing cadmium and copper, the second step removing cobalt and nickel, and the second step being primarily a backup of the previous step. .

In principle, there are two ways to use arsenic as a supplement to zinc. In the first method, copper, cobalt, and nickel are purified in the first stage of solution purification in a batch or continuous reaction process.
Zinc is removed from the electrolyte in steps. A second step removes the cadmium and, if necessary, a third step paraphrases these steps.

A second solution purification method using arsenic as an adjuvant for zinc is carried out in solution purification/fi3 steps, generally:
The first and third steps are continuous processes, and intermediate steps are automatic batch processes. In the first step,
Most of the copper is separated from the zinc electrolyte solution. Second step fU, Fl copper; 6: Separated together with cobalt, nickel, and dalmanium. The third step mainly involves separation of cadmium.

The second step f (batch process) in a three-step solution purification process using arsenic as an adjuvant is generally carried out as follows. That is, the supply of zinc electrolytic solution to the reaction tank is started. For example, if the reaction vessel is half filled with solution,
Start Mixing Now you can start feeding the zinc powder. Initially, the powder feed is done fairly quickly to get enough volume into the tank. Near the end of the feed to the reactor, reduce the feed rate but continue until the total calculated amount of zinc per batch has been fed. After a certain period of time, the solution is subjected to a copper analysis and if the amount of cobalt precipitated is sufficient, the batch is ready. If the analysis results show that the amount of cobalt precipitation is insufficient, powder supply is continued until sufficient cobalt precipitation is achieved. The precipitate obtained is not removed each time, but after several precipitations have been carried out in succession, that is, from time to time, the precipitate is removed.

The dosage of zinc powder was a big problem. In general, feed enough zinc powder to achieve a good final result. Even slight disturbances will usually increase the amount of powder used. Additionally, if you move to small amounts of powder addition early, becomes difficult.

i.e. a suitable indicator (
indicators) were not available.

Conventionally, it has been known that precipitation or precipitation follows the following equation.

C.

kXt = 1n, where k: precipitation rate coefficient t: precipitation time co = initial content Ct: content at a certain point According to this equation, if the conditions in the reaction tank are appropriate and the amount of zinc powder is If there is enough, precipitation will occur. However, it is known that increasing powder addition beyond the "sufficient" point does not increase the precipitation rate. On the contrary, excessive use of powder can even slow down the reaction, due to the formation of alkaline zinc sulfate.

In the solution purification process of a zinc electrolyte reservoir described in Finnish Publication No. 66027, the amount of zinc powder required for copper removal is adjusted to approximately correspond to the stoichiometric amount required to remove copper from the solution. Ru. Zinc powder addition can be adjusted by the redox potential of the electrolytic solution. The zinc powder addition is controlled by adjusting the redox potential, thereby keeping the electrolyte potential in the range of +200 mV to -600 mV. The redox criteria used here determines the extent of copper removal and limits the precipitation of other metals. The solution from which copper has been removed is further subjected to cobalt removal treatment.

“Zinc electrolytic smelting at Ijima zinc smelter J” by Sawaguchi et al.
, MMIJ/Aus IMM Joint Symp
Osjum 1983, Sendai, pp. 217-229 describes the use of potential adjustment to control the germanium content in order to sufficiently reduce the germanium level in the second step of solution purification. According to this, the germanium level can be maintained below 10 ppn+ by adjusting the potential within the range of -610 mV to -640 mV.

The above paper uses redox potential measurements to control the extent of metal removal from solution. This is of course an important factor regarding the quality of the final product. Another factor that affects zinc production costs is the amount of zinc powder used for solution purification. As is clear from Finnish Publication No. 66027, for example in copper removal, the initial amount of added zinc powder roughly corresponds to the stoichiometrically obtained amount, after which the powder is added to the required degree. Added. The above paper describes using the redox potential to regulate this addition, but on the other hand, in a given range (+200 mV to -600 mV), the interdependence between powder addition and the potential is unknown. It remains as it is.

DISCLOSURE OF THE INVENTION According to the method of the invention, the addition of zinc powder, especially in the purification of zinc electrolyte solutions, can be adjusted within an optimum range by redox potential measurements. The essential features of the present invention are clear from the description in claim 1.

In the second step of solution purification, so-called cobalt removal,
The residual steel after the removal process precipitates out of the solution along with cobalt, nickel, and germanium. The amounts of elements used in the second step of solution purification are shown in the following table. The residual content in the solution resulting from the second step is very low.

Copper 50-150m9/l <0.
i m9/1 cobalt 10-501n9/l
(0.2mg 7B Nickel 10~501KFl
<0.1 111'71! Ke9 Rumanium 0.1~
3~/l (0,02■4 As mentioned above, metal zinc powder and As2O3f are used in the precipitation treatment.The precipitation treatment follows the following reaction formula.

(1) Cu + Zn −+ Cu + Zn”C2
) 6Cu + AS20'3 +9 Zn →2
Cuμs+9Zn++(3) 2Me+As2O
3+5 Zn −+ 2MeAs +5 Zn”Me
= Co, Ni The precipitation of germanium is unknown.

As a secondary reaction, decomposition of the zinc powder occurs.

(4) Zn + H2SO4−+ ZnSO4+
H2↑(5) xZn +ZnSO4+ (x+y)
H2O→znS04・xZn(OH)2・yH20↓+
The amount of xH2↑arsenic is easily adjusted by the initial content. Therefore, if too little or too much is used, precipitation becomes difficult or the final arsenic content becomes high.

Remarkably, it was revealed that by adjusting the amount of added zinc powder according to the redox potential, the optimum precipitation conditions could be maintained without using an excessive amount of zinc powder.

At the same time, this measurement also reveals the possibility of interference due to powder addition.

Description of examples Next, the present invention will be described with reference to the accompanying drawings.

These figures graphically illustrate essential features of the invention.

As is clear from the figure, the deposition of cobalt and nickel already reaches its maximum value at a potential of -575 mV. The maximum value for germanium precipitation is obtained in the range of 600 mV to -625 mV. Redox potential was measured with a platinum electrode, and a calomel electrode was used as the reference electrode.

Through further research, we discovered that by adjusting powder addition using potential measurements, we could essentially reduce the amount of unused zinc powder without changing the degree of impurity content, to half the amount compared to conventional methods. This is a point that can be reduced. That is, the production capacity of the production plant can be essentially increased, and in this case if the M-torque of the process is electrolysis, the achieved benefits can be calculated according to the yield. Even a mere reduction in the cost of producing zinc powder is a considerable advantage.

According to this new control method, the addition of zinc powder to the reactor is regulated by measuring the redox potential during powder charging into the reactor in the second step of solution purification. The amount of powder introduced is chosen such that the cobalt arsenide or nickel arsenide already precipitated in the reactor is not dissolved by the Cu entering the reactor with the solution, allowing copper precipitation.

On the other hand, adding zinc powder prevents the zinc powder from dissolving.
In addition, although the solution contains arsenic, it must be carried out in such a way that hydrogen arsenide is not generated. The formation of hydrogen arsenide causes environmental damage and, of course,
Zinc powder consumption increases. The applicant has revealed that by carrying out the potential adjustment, the amount of hydrogen arsenide released together with the exhaust gas becomes lower than before. This means that at low enough levels that hydrogen arsenide formation is possible,
This is because the potential does not drop. In fact, by adjusting the redox potential to a range of -480 to -550 mV with respect to the calomel electrode, good results have been obtained with this steno test.

When the reactor is full, residual steel in the solution after the first step of solution purification is also removed in the above process. The zinc powder addition is then adjusted to initiate the cobalt, nickel, and germanium precipitation. In fact, this potential range is
It ranges from -570 to -650 mV relative to the calomel electrode. Each impurity has its own potential range, and the optimum range is influenced by the amount of precipitate previously present in the reaction vessel.

Therefore, using the redox potential, the zinc powder addition can be adjusted to obtain the desired potential and the metal is deposited. Moreover, at the same time, excessive use of zinc powder can be prevented.

The content of various impurities in the solution supplied to the reaction tank, and
If you know the amount of precipitate present in the reaction tank after the previous batch,
The precipitation time can be determined experimentally, after which the powder feed is stopped.

The redox potential adjustment in the second stage of solution purification in batch processing was explained.

However, the redox potential is a regulatory factor even in continuous processing. Therefore, cobalt removal can be performed in a continuous process and redox potential adjustment can be performed in other steps of solution purification.

The present invention has been described above primarily with respect to treatments using arsenic as an adjuvant. However, the present invention can also be applied to treatments using other adjuvants and is fully consistent with the spirit of the invention. Although the optimum value of the redox potential may change slightly compared to the above value, it does not essentially change.

[Brief explanation of the drawing]

Figure 1 is a graph showing co-Gult removal from an electrolytic solution at various redox potential values as a function of time; Figure 2 is a graph showing nickel removal similar to Figure 1; Figure 3 is a graph showing nickel removal from an electrolytic solution as a function of time. , is a graph similar to that of FIG. 1 illustrating kermanium removal. 1 (machine) □

Claims (1)

[Claims] 1. A method for adjusting the amount of zinc powder used for precipitating impurities from a zinc sulfate solution in zinc electrolytic scouring, the method comprising:
A method for adjusting the amount of zinc powder in removing impurities from a zinc sulfate solution, the method comprising adjusting the amount of zinc powder added by measuring redox potential. 2. The method according to claim 1, characterized in that the amount of added zinc powder is adjusted by redox potential measurement performed in the cobalt removal step of the solution purification. 3. The method according to claim 1, comprising adjusting the redox potential within the range of -480 to -550 mV with respect to a calomel electrode while supplying zinc powder for copper deposition. Features a method for adjusting the amount of zinc powder. 4. The method according to claim 1 or 2, wherein the redox potential is adjusted to between -570 and -650 mV with respect to a calomel electrode while supplying zinc powder for the precipitation of cobalt, nickel and germanium. A method for adjusting the amount of zinc powder, characterized by adjusting the amount within a range. 5. The method according to claim 1, wherein the amount of added zinc powder is adjusted by measuring redox potential in batch processing. 6. The method according to claim 1, characterized in that the amount of added zinc powder is adjusted by measuring redox potential in continuous treatment. 7. A method for adjusting the amount of zinc powder according to claim 1, characterized in that the amount of added zinc powder is adjusted by measuring redox potential in the treatment using arsenic as an auxiliary agent. 8. A method for adjusting the amount of zinc powder according to claim 1, wherein the amount of zinc powder added is adjusted by measuring redox potential in the treatment using antimony as an auxiliary agent.