JP3024396B2 - In recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the recovery of In from intermediates in Zn smelting, and more particularly to a method for obtaining crude In efficiently and without generating any harmful gas.

[0002]

2. Description of the Related Art It is conventionally known that In is mainly produced together with Cd as a by-product in a smelting process of Zn. In and Cd in the Zn smelting process
First, an intermediate obtained in the smelting process of Zn is reduced and leached under the acidity of a mineral acid to obtain I
n-containing leachate is obtained, and then Zn powder or Cd-Zn powder is added to the leachate containing In at about 1 chemical equivalent relative to the amount of In in the leachate, and cement I is added.
n is replaced by precipitation, and NaO is added to the cement In.
H was added and melted by heating.
n is separated and recovered, and the crude In is further electrolytically purified to obtain high-purity In.

However, when the coexisting amount of Cd in the leachate containing In increases, the Cd occupying in the cement In increases.
Or the cement In is easily oxidized due to Te coexisting with Cd when the cement In is melted. As a result, it becomes impossible to collect the crude In at a high yield. Inconvenience such as becoming.

[0004] In particular, when As is present in the leachate in an amount of 0.5 ppm or more, harmful As is removed in the displacement precipitation step of In.
This will cause the generation of H ₃ , but once AsH ₃ is generated, this AsH ₃ detoxification process is required,
Expensive investment is inevitable for improving the working environment.

Therefore, in order to reduce this investment,
Prior to adding Zn powder or Cd-Zn powder,
After reducing the content of As in the leaching solution to less than 0.5 ppm, it was common to replace and precipitate In.

As a simple method for reducing the As content, ion exchange and solvent extraction have been proposed. However, these methods cannot sufficiently remove As, and are not satisfactory. Specifically, As must be fixed as As ₂ S ₃ by performing a sulfidation treatment and separated.

Therefore, the adoption of the ion exchange method and the solvent extraction method not only complicates the step of recovering In but also sulfides the coexisting Cd at the same time as in the conventional case.
The efficiency of simultaneous recovery of n and Cd is lowered. In addition, much attention must be paid to eliminating the odors generated during the sulfurization of these metals.

[0008]

SUMMARY OF THE INVENTION The present invention provides a method for recovering In from an intermediate generated in a smelting process of Zn, which is more efficient than the conventional method and which does not generate AsH _3. Its purpose is to disclose.

[0009]

Means for Solving the Problems The present inventors have conducted intensive research tests to solve the above-mentioned problems, and as a result, Cd, Zn, In, Te, and Cd generated in the Zn smelting process.
When recovering In from an intermediate containing As or the like,
The above-mentioned intermediate is obtained by using, as a reducing agent, two or more equivalents of metal Cd and metal In necessary for generating a Te compound or an As compound or a reducing precipitate containing such amounts of metal Cd and metal In. Leaching is performed by reducing and leaching under acidic acidic conditions with mineral acid.
Was adjusted to 1.5 to 2.5, and plate-like Cd was immersed in the filtrate obtained by separating the residue from this solution, and cement In was substituted and precipitated on the surface of the plate-like Cd to form a plate-like Cd. Cement In obtained by exfoliating from the surface of Cd
After addition of ~ 20 wt% NaOH, 200 ~ 3 Celsius
Melting at 00 degrees and layer separation of the generated soda slag to recover In. Further, an alkaline aqueous solution is added to the tail liquid after the substitution and precipitation of cement In, and the pH thereof is adjusted to 4-6. It has been found that the above-mentioned problem can be solved by adding the resulting precipitate during the reductive leaching of the intermediate under the acidic condition of mineral acid, thereby achieving the present invention.

[0010]

In the present invention, the reduction leaching of In from the Zn smelting intermediate is based on the Te contained in the intermediate.
And As are converted into a sparingly soluble Te compound and an As compound to facilitate removal from the system. In this case, metals Cd and In containing more than 2 equivalents of Te and As are used as reducing agents. The reason for this is that if this amount is less than 2 equivalents, it is insufficient to convert Te and As contained in the intermediate into a poorly soluble Te compound and an As compound.

In this treatment, the amount of the reducing agent is 2
When the amount exceeds the equivalent, there is no particular restriction on the acidity of mineral acids such as HCl and H ₂ SO ₄ . Further, the concentration of the reducing agent is 5
It is desirable to adjust so as to be 0 to 200 g / liter.

When the above intermediate does not contain metal Zn, but contains a sufficient amount of metal Cd or metal In, it is particularly necessary to add such a reducing agent in the reduction leaching step. There is no.

[0013] Soda slag produced when obtaining crude In is generally suitable as a reducing agent since granular metal In is suspended therein. Not only does this metal In substitute for the reducing agent, but the use of soda slag is also effective from the viewpoint of the recovery rate of In.

Next, the pH value of the leachate is adjusted to 1.5 to 2.5.
The reason for this is to make the substitution reaction using a metal Cd plate work effectively. When the pH value is less than 1.5, there is almost no difference between the oxidation-reduction potentials of In and Cd, so the deposition rate of In is small. Conversely, when the pH value exceeds 2.5, the generation of In (OH) ₃ is accelerated, so that the precipitation of In on the Cd plate surface is prevented. It is because it becomes.

The reason why the plate is used as the metal Cd is that, when the cement In deposited on the surface is peeled off and the process is carried out, the peeling is facilitated, and the unreacted cement In is removed. This is because metal Cd is not interposed in the process in the form of powder or shot during the process.

5 to 20 with respect to the peeled cement In
The reason why NaOH is added and melted by weight is that if the amount of NaOH is less than 5%, the cement In is easily oxidized at the time of melting, and if the amount exceeds 20% by weight, the amount of soda slag to be treated is increased. This is because the amount becomes unnecessarily large. Further, the melting temperature is set to 200 to 300 degrees Celsius.
The reason for this is that if the treatment is performed at a melting temperature of less than 200 degrees, the fluidity of the slag deteriorates and it becomes difficult to separate the soda slag and the crude In. Although there is no problem in the recoverability of the wastewater, no improvement in the working efficiency due to the high-temperature treatment is recognized, and this is not a good measure from the viewpoint of energy saving.

The pH of the tail liquor is adjusted to 4 to 6 by adding an alkali solution to the tail liquor after the substitution precipitation of In, and the remaining In in the tail liquor is measured. However, in this case, the pH value was adjusted to 4 to 6 because p
If the value of H is less than 4, In (OH) for recovering In
3 is not generated sufficiently, and conversely, if its value exceeds 6, C
This is because up to d becomes hydroxide, which not only increases the number of repeated hydroxides but also lowers the direct recovery rate of Cd from the tail liquor.

The crude In recovered as described above is 1 to 3
In producing high-purity In because it contains Cd by weight but contains little Te or As, Cd is formed as a chlorine complex, and then Cd is formed using an electrolytic refining apparatus using an anion exchange resin. , And the purified In which was the final target was easily electrorefined from the intermediate of Zn smelting and In with a purity of 99.99% could be easily obtained.

In order to replace and precipitate cement In on the surface of the plate-like Cd, the following examples will be described.
Is circulated around the liquid, but the present invention is not limited to the liquid circulation. That is, the plate-shaped Cd may be swung in the liquid, or the liquid may be simply stirred.

[0020]

Embodiments of the present invention will be described below in detail.

[0021]

Example 1 In terms of% by weight, the water content was 24.3%.
n is 48.4%, Cd is 40.6%, and Te
Is 1.7%, As is 0.02%, and the moisture content is 3%.
35 g of In-cement containing 254 kg (dry weight) was stirred for about 18 hours with 550 liters of 35% by weight HCl added thereto, and then 250 g /
A solution having a pH of 2.0 was prepared by adding 160 liters of NaOH adjusted to a concentration of 1 liter, and the solution was filtered.
40 liters were obtained.

In this case, the composition of the obtained residue has a water content of 38.1% by weight and a Cd of 20.8%,
In is 9.8%, Te is 25.4%, and As
Was 0.28%.

The composition of the obtained filtrate was 98.
0 g / liter, Cd is 88.7 g / liter, Te is 0.005 g / liter or less, and As
Was 0.0005 g / liter, and the composition of the filtrate contained almost no Te and As.

A metal Cd plate is immersed in the filtrate containing little Te and As so as to have a total surface area of 4.9 m ^2, and around the metal Cd plate at a rate of 40 liters per minute. After the above filtrate was circulated for 72 hours at a rate, the cement In deposited on the surface of the Cd plate was removed by C
d. Peel off the surface of the plate, wash thoroughly with water, dry, and further melt a mixture of 15 kg of NaOH at 250 degrees Celsius using a stainless steel crucible, and separate 28 kg of soda slag and 126 kg of coarse In separated vertically. I got The soda slag was scooped and separated from the crude In.

The composition of the soda slag obtained in this case is 19.3% by weight of In and Cd is 0.90% by weight.
%, Te is 0.022%, and As is 0.00
4%.

The composition of the crude In is as follows: in terms of% by weight, In is 98.6%, Cd is 1.22%, Te is 0.001% or less, and As is 0.001% or less. In the crude In, Te and As were hardly recognized. It can be seen that Te and As are substantially distributed to the soda slag.

After the above filtrate was circulated at a rate of 40 liters per minute for 72 hours around the metal Cd plate, the cement In deposited on the surface of the Cd plate was removed from the Cd plate.
The composition of the tail liquid obtained at the time of peeling off from the surface of the d-plate was as follows: 6.3 g of In, 208 g of Cd, 0.005 g or less of Te, and 0% of As in 1 liter of tail liquid. .0
005 g or less.
An aqueous solution containing H at a rate of 250 g / liter in 35
The pH was adjusted to 5.5 using 1 liter and allowed to settle for 16 hours to give 450 liters of the In (OH) ₃ phase and 1040 liters of the CdSO ₄ phase.

In this case, the composition of the In (OH) ₃ phase is 20.6 g of In per liter, the composition of the CdSO ₄ phase is 195 g of Cd per liter, and
Was 0.004 g, Te was 0.005 g or less, and As was 0.0005 g or less. It can be seen that the CdSO ₄ phase has very few impurities, which is advantageous for Cd recovery.

When the generation of AsH ₃ gas was examined by a detector, it was not detected at the time of leaching nor at the time of displacement precipitation.

[0030]

Embodiment 2 83.9 g of Cd in 1 liter and In
Is 10.6 g, Te is 0.42 g, and As is 0.01.
8 g and 110 g of free H ₂ SO ₄ containing I
A 1070 liter aqueous solution was prepared, and the composition was 19.3% by weight and the Cd content was 0.90% by weight%.
And Te is 0.022% and As is 0.004%.
% Of soda slag and 28 kg of the soda slag obtained in Example 1.
n (OH) ₃ phase, 450 liters, powder form, wet weight 5k
g (4.6 kg dry weight) of cement Cd as a reducing agent having a Cd grade of 98.4% by weight was stirred for about 1 hour, mixed, and then further mixed with 250 g / l.
Caustic soda aqueous solution containing NaOH at a ratio of 290
One liter was added to make an aqueous solution having a pH of 2.0, and this aqueous solution was filtered to obtain a residue having a wet weight of 9.4 kg and a filtrate of 1840 liters.

In this case, the composition of the obtained residue is 36.1% of water, Cd is 24.6%, In is 7.8%, and Te is 7.6% by weight. % And A
s is 0.31%, and the composition of the filtrate is 93.9 g of Cd per liter, 14.6 g of In, 0.005 g of Te or less, and 0.000 g of As.
7 g.

A Cd plate was immersed in the above filtrate so as to have a total surface area of 4.9 m ² , circulated around the Cd plate at a circulation rate of 40 liters per minute for 48 hours, and cemented on the surface. After precipitation of In, the cement In was peeled off from the Cd plate, and then 3 kg of NaOH was further added to the sufficiently washed cement In and melted at 250 degrees Celsius in a stainless steel crucible.
6.9 kg of vertically separated soda slag and 2 of coarse In
3.2 kg were obtained.

The composition of the soda slag obtained in this case is, by weight%, 17.4% of In and 1.1% of Cd.
And Te is 0.061% and As is 0.010%.
%Met.

On the other hand, the composition of crude In is as follows: in terms of% by weight, In is 98.04%, Cd is 1.76%, Te is 0.0015 or less, and As is 0.001% or less. there were. It can be seen that Te and As were almost distributed to the soda slag.

The tail solution after the displacement precipitation was Cd 116 g, In 0.97 g and Te 0.005 g per liter.
g, containing not more than 0.0005 g of As, and adjusting the pH to 5.0 using 55 liters of a 250 g NaOH aqueous solution per liter, and allowing it to settle for 16 hours.
100 liters of (OH) ₃ phase and 1830 liters of CdSO ₄ phase were obtained. The quality of the In (OH) ₃ phase is 19.6 g of In per liter, and In is concentrated. The quality of the CdSO ₄ phase is 111 g of Cd per liter and In0.0.
An aqueous solution of CdSO ₄ containing only 09 g, 0.005 g of Te or less and 0.0005 g of As or less and having few impurities was obtained.

The generation of AsH ₃ gas was examined by a detector, but was not detected at the time of leaching or at the time of displacement precipitation.

[0037]

Conventional Example In-containing aqueous solution 1 prepared in the same manner as in Example 2.
To 020 liters, 210 liters of an alkaline aqueous solution containing NaOH at a concentration of 250 g / liter was added to prepare an In-containing aqueous solution having a pH of 2.0, and this In-containing aqueous solution was filtered. As little as 0.2 kg, a 1240 liter filtrate was obtained.

In this case, the composition of the filtrate contained 69.0 g of Cd, 8.7 g of In, 0.34 g of Te, and 0.015 g of As per liter.

The filtrate having the above composition was added to the metal Z
gently stirring the n powder was added 9.2 kg, AsH ₃
As a result of investigating the state of occurrence, the detected amount was 2.8 ppm at the peak.

Cement I obtained after 16 hours of stirring
n was muddy as compared with the case of Example 2, and the aqueous solution was black.

After obtaining the muddy cement In in this way, the composition of the tail liquid is 68.1 g of Cd in 1 liter,
It contained 1.32 g of In, 0.02 g or less of Te, and 0.001 g of As.

Further, N is added to the muddy cement In obtained here.
When 1.2 kg of aOH was added and melted at 250 degrees Celsius using a stainless steel crucible, a part of cement In showed a combustion phenomenon.
g was added.

The weight of the soda slag thus obtained was 6.7 kg, and the weight of crude In was 8.1 kg.

The composition of the soda slag in this case is 19.8% by weight of In, Cd is 5.8%, Te is 5.1%, and As is 0.09% by weight. ,
Similarly, the composition of crude In is that In is 94.8% and Cd
Is 4.13%, Te is 0.001% or less,
As was 0.001% or less.

As described above, according to the present invention, In
It is possible to disclose the possibility of producing a product having a high content of carbon dioxide by an easy method, and to almost prevent the entrapment of harmful substances such as Te and As which must be purified and removed in the sulfidation operation. Was.

[0046]

As described above, according to the present invention,
A very simple means makes it possible to recover crude In containing a very small amount of Te, As, etc., and this makes it possible to minimize the production of sulfide, an environmental pollutant, when producing high-purity In. As disclosed, there are significant contributions to the industry that is sending In products to the market by such means.

[Brief description of the drawings]

FIG. 1 is a flowchart according to an embodiment of the method of the present invention.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C22B 58/00

Claims (2)

(57) [Claims] 1. C generated in a Zn smelting process
from intermediates containing d, Zn, In, Te, As, etc.
When recovering n, a Te compound or As
Two or more equivalents of metal Cd required to form the compound
And a metal In or a reducing precipitate containing such amounts of metal Cd and In, the above intermediate is reduced and leached under acidic mineral acid to form a leaching solution, and an aqueous solution of alkali hydroxide is added to the leaching solution. The pH was adjusted to 1.5 to 2.5, and plate-like Cd was immersed in the filtrate obtained by separating the residue from this solution,
Cement In is substituted and precipitated on the surface of the plate-shaped Cd, and NaOH is added to the cement In obtained by exfoliating from the surface of the plate-shaped Cd in an amount of 5 to 20% by weight based on the cement In. A method for recovering In, which comprises melting at 200 to 300 degrees, separating the generated soda slag into layers, and recovering crude In. 2. An aqueous alkaline solution is added to the tail solution after substitution precipitation of the cement In to adjust the pH to 4 to 6, and the resulting precipitate is subjected to reductive leaching under the acidic condition of a mineral acid of an intermediate. The method for recovering In according to claim 1, wherein the In is added occasionally.