JPH0778262B2 - Purified nickel sulfate recovery method from copper electrolyte - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for recovering highly pure nickel sulfate from a copper electrolytic solution.

[Conventional technology and problems]

In copper electrorefining, nickel contained in the anode,
Impurities such as arsenic, antimony, bismuth, and iron elute in the electrolytic solution, reducing the purity of electrolytic copper deposited on the cathode.Therefore, remove a part of the electrolytic solution from the system to prevent the concentration of these impurities from increasing. To remove and collect impurities.

In the case of treating the copper electrolytic solution extracted to the outside of the system, conventionally, most of the copper content is first converted to copper sulfate crystals or recovered by a decoppering electrolytic method or the like, and then decopperizing electrolysis is performed to obtain most of the copper electrolytic solution. The copper content is removed and recovered, and at the same time, arsenic, bismuth, antimony, etc. are removed, and then the decoppered electrolytic solution is concentrated by evaporation and cooled to recover nickel sulfate crystals. As a result, it is returned to the electrolytic solution and is recycled.

The above-mentioned conventional method recovers nickel from a nickel sulfate solution having a low nickel content of about 10 to 15 g / l, and has a drawback that a large amount of energy is required to perform evaporation and concentration.

Furthermore, in the copper electrolytic solution, organic substances, calcium, sodium, magnesium, ammonia, etc. due to the organic additive used in the electrolytic refining step remain, and these impurities are not sufficiently removed by the conventional method. There is also a problem of being mixed in the recovered nickel sulfate crystals.

[Means for solving problems]

The present inventor has found that nickel sulfate can be effectively recovered by pre-treating a copper electrolyte and applying a solvent extraction method. The present invention is based on the above findings and enables nickel sulfate to be recovered from a copper electrolytic solution with low energy and high purity.

[Structure of Invention]

According to the present invention, there is provided a method for recovering purified nickel sulfate from a copper electrolytic solution having the following constitution.

(1) A primary neutralization step of removing free sulfuric acid after decopperizing a copper electrolyte solution and a secondary neutralization step of separating and separating metal impurities other than nickel as hydroxides from the filtrate of the primary neutralization step Then, the filtrate of the secondary neutralization step is chlorinated with an extraction solvent to adjust the pH to pH 2.5 to 4, and metallic impurities other than nickel are extracted into the solvent and separated from the nickel solution. In the method for obtaining, after the above-mentioned impurity extraction step, nickel in the solvent is further added after the nickel extraction step in which the extraction solvent is added to the nickel solution and the alkali is added to adjust the pH to 5 to 7 to extract nickel in the solvent. A method for recovering purified nickel sulfate from a copper electrolytic solution, characterized in that purified nickel is obtained through a concentration step of back-extracting with nickel to increase the nickel concentration.

(2) (a) In the primary neutralization step, after removal of copper, calcium carbonate or calcium hydroxide is added to convert free sulfuric acid to gypsum, and antimony and bismuth are precipitated and separated. Then, an alkali is added to the filtrate after the primary neutralization together with an oxidizing agent to adjust the pH to 5 to 6.5,
Part of copper and zinc and iron, lead, and arsenic are precipitated as hydroxides, and in the impurity extraction step, alkali is added to the filtrate after secondary neutralization together with the extraction solvent to adjust the pH to 2.5 to 4. The copper, zinc and calcium remaining in the filtrate in the range are separated from the nickel solution by extracting into the solvent, and (d) in the nickel extraction step, an alkali is added to the nickel solution together with the solvent to add nickel in the range of pH 5 to 7. The method for recovering purified nickel sulfate according to (1) above, wherein the method is separated from sodium, magnesium and ammonia by extraction with a solvent.

(3) The method for recovering purified nickel sulfate according to (1), wherein zinc powder is added to the filtrate of the secondary neutralization step to reduce the copper concentration in the filtrate, and then the impurity extraction step is performed.

The present invention will be described in detail below with reference to the flow sheet shown in the drawings.

The copper removal treatment of the copper electrolytic solution is performed by a known method. For example, after adding copper scraps and the like to neutralize free sulfuric acid, the neutralized solution is evaporated and concentrated and cooled to recover copper sulfate crystals. Alternatively, instead of recovering as copper sulfate crystals, a copper removal electrolytic method may be applied to recover as electrolytic copper. Cu is still 15 to
About 20g / l remains, so decopperization electrolytic treatment is performed to remove Cu 3
Remove and collect up to about 7g / l. In this copper removal electrolytic process,
Part of As, Sb, and Bi remains in the solution.

The concentration of free sulfuric acid in the solution after decopperization was about 280 g / l, and calcium carbonate or calcium hydroxide was added to adjust the pH to 0.
Primary neutralization is carried out up to pH 3, preferably about pH 2, and free sulfuric acid is precipitated and removed as gypsum. At this time, most of Sb and Bi are simultaneously removed by precipitation and separated from Ni in the liquid. Secondary neutralization is performed subsequent to the primary neutralization step. First, when an alkali is further added to the solution after the primary neutralization and hydrogen peroxide is added while maintaining the pH at 5 to 6.5, divalent iron ions are oxidized to trivalent iron ions and precipitated as hydroxides. At this point, some of the Cu and Zn remaining in the solution after primary neutralization precipitated as hydroxides, and all of As, Pb, etc. co-precipitated with ferric hydroxide and separated from Ni in the solution. To be done. The amount of hydrogen peroxide added in the secondary neutralization step is 0.2 to 0.3% (as a 35% concentration) with respect to the liquid amount.
The degree is good. Also, by supplying air instead of hydrogen peroxide,
You may oxidize ferric iron ion to ferric iron ion. The type of alkali to be added is not particularly limited, but it is preferable to use calcium hydroxide or calcium carbonate in combination with calcium hydroxide in order to enhance the filterability of the formed precipitate. As an impurity element other than Ni in the liquid after secondary neutralization. , Cu, Zn,
Ca, Mg, Na and NH ₃ remain. Cu and Z remaining there
n and Ca are extracted and separated from the filtrate (nickel solution) by the solvent extraction method and removed.

The residual concentrations of Cu, Zn, and Ca vary depending on the initial concentrations in the copper electrolytic solution, but are approximately 20 to 200 mg / l Cu and 200 to 1500 mg / l Zn. Ca is dominated by solubility and is about 600 gm / l.

A solvent represented by the following formula is preferably used as an extraction solvent used in the impurity extraction step and the nickel extraction step subsequent to the step.

In the formula, R ₁ , R ₂ , R ₃ and R ₄ are alkyl groups having 8 to 10 carbon atoms,
And R ₅ , R ₆ and R ₇ are the third with total carbon number of 9, 10 and 11
The _primary saturated fatty acids, R ₁ and R ₂ , and R ₃ and R ₄ may be the same or different.

Specifically, as the solvent, di-2-ethylhexyl phosphoric acid, di-2-indecyl phosphoric acid, di-2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester, Versatic 10 (shell scientific trade name), Versatic 911 (shell Scientific trade name), Lix63 (Henkel trade name; 5,8-diethyl-7-hydroxy-6-dodecanone oxime),
Lix64 (Henkel's trade name; 2-hydroxy-5-dodecylbenzophenone oxime), Lix64N (Henkel's trade name; Lix64 with about 1% by volume added) and the like are used.

As the solvent used in the impurity extraction step, the above Cu, Zn, Ca
When one is removed with one kind of solvent, it is preferable to use a phosphoric acid-based solvent which is contained in a large amount in quantity and has selectivity for Ca and Zn. In addition, since the phosphoric acid-based solvent has poor selectivity for Cu, Zn is extracted after the secondary neutralization step before the impurity extraction step.
It is preferable to reduce the Cu concentration to about 5 to 10 mg / l by cementation and then extract with a phosphoric acid-based solvent because the number of extraction steps can be reduced.

Without using one kind of solvent to use Ca, using the above-mentioned phosphoric acid-based solvent for Zn, Versatic acid having excellent selectivity for Cu, or it is also possible to use an oxime-based solvent such as Lix63, Lix64N It is possible.

Solvent concentration and extraction pH in the impurity extraction step is not defined as a single liquid because it depends on the type of solvent used and Cu, Zn, Ca concentration in the aqueous phase, but in the case of phosphoric acid-based solvents the solvent concentration is 10-30%, Extraction pH of about 2.5-4 is preferable, extraction pH
When it is 4.5 or more, the amount of Ni extracted becomes large, which is not preferable. Ammonia water is used as alkali for pH control.
Either ammonia gas or sodium hydroxide may be used.

After the above-mentioned impurity extraction step, Ni was further extracted by a solvent extraction method.
Is extracted and separated. As the solvent used in the Ni extraction step,
Either a phosphoric acid solvent or a versatic acid may be used, but since a large amount of Ni is extracted, versatic acid having a large extraction capacity is preferable. The extraction pH is preferably pH 5-7. pH5
When the pH is less than Ni and the pH exceeds 7.5, ammonia and alkali used for pH control such as sodium hydroxide and a solvent form a salt, or the solubility of versatic acid in the aqueous phase increases rapidly. Therefore, it is not preferable.

Also in the extraction at about pH 5 to 7, the alkali used for pH adjustment is mixed in the trace amount solvent, but it can be completely removed by contacting with water or sulfuric acid at about 0.5 g / l. By the Ni extraction, Ni is separated from Na, Mg and NH ₃ in the liquid.

Following the Ni extraction step, Ni concentration is performed. In the Ni concentration step, the Ni extracted in the solvent is concentrated while being back-extracted with sulfuric acid. The sulfuric acid concentration and the ratio of the organic phase and the aqueous phase in this step are appropriately determined depending on the Ni concentration and the concentration degree in the organic phase. The degree of concentration is better as the Ni concentration is higher in order to reduce the amount of energy used in the crystallization step, but on the other hand, it is necessary not to generate nickel sulfate crystals during the concentration step. Ni concentration in the phase is 100 g / l
A degree is preferable. Incidentally, it remains in the Ni concentration step.
Na, Mg, NH ₃ are further removed.

The crystallization process of Ni sulfate following the Ni concentration process is performed by a known method. In this case, the concentration of Ni in the back-extracted aqueous phase is as high as about 100 g / l because it has undergone the above-mentioned concentration step, and the energy is about 1/7 to 1/10 of the energy required in the crystallization step of the conventional method. It can be crystallized with.

〔Example〕

 Examples of the present invention will be shown below.

Example 1 To 10 liters of the solution after electrolytic decoppering shown in Table 1 was added 2.7 kg of calcium carbonate in a slurry form with 4 liters of water, and the mixture was neutralized to pH 2.0 and solid-liquid separated. The precipitate formed was filtered off and the precipitate was washed with water 1.
It was washed with 2 l, and the filtrate and the washing solution were combined to obtain 12.8 l of liquid.
The liquid composition is shown in Table 2.

Calcium hydroxide 69 was added to 6.3 l of the solution after primary neutralization shown in Table-2.
After adding a slurry of g to 100 ml of water, 130 ml of hydrogen peroxide solution (35% concentration) was added to neutralize to pH 6.0, and the formed precipitate was filtered off and after secondary neutralization shown in Table-3. 6.4 l of liquid was obtained.

After the secondary neutralization shown in Table-3, 1N caustic soda was added to the solution to adjust the pH in each tank to 3.3, and 2-ethylhexylphosphonic acid-mono-2-ethylhexyl ester was diluted with kerosene. The organic phase adjusted to volume% is supplied so that the organic phase / aqueous phase ratio becomes 3/2, and the counter current is set to 3
Stage extraction was performed to obtain a liquid after extraction having the composition shown in Table-4.

Next, add 2N caustic soda to the extract shown in Table-4 and adjust the pH.
While adjusting to 6.5, an organic phase obtained by diluting Versatic 10 (trade name of Shell Science) to 30% by volume with kerosene was supplied so that the ratio of the cyclic phase / water phase was 3/2, and the counter current of 2 stages was used. Extraction was performed to obtain a solution after Ni extraction having the composition shown in Table-5.

The Ni extract having the composition shown in Table 5 was washed with a 0.5 g / l sulfuric acid solution at an organic phase / aqueous phase ratio of 3/1. The composition of the Ni extract after washing is shown in Table-6.

The solution after the Ni extraction cleaning having the composition shown in Table 6 was back-extracted with a sulfuric acid aqueous solution at an organic phase / aqueous phase ratio of 12/1 at pH 2.0 and concentrated. Table 7 shows the composition of the Ni concentrate. The Ni concentrate shown in Table 7 was evaporated and then cooled to obtain nickel sulfate crystals. Table 8 shows the quality of the nickel sulfate crystals.

Example 2 While adding 6.3 g of the solution after primary neutralization shown in Table 2 of Example 1 to 68 g of calcium hydroxide in a slurry form with 100 ml of water, 130 ml of hydrogen peroxide (35% concentration) was added to pH 5.6. To 6.4 l after secondary neutralization as shown in Table-9.

3 g of zinc powder was added to the solution after secondary neutralization shown in Table 9 to partially remove Cu by cementation. The liquid composition is shown in Table-10.

While adjusting the pH in the bath to 3.7 by adding 1N caustic soda to the solution after Cu cementation shown in Table-10, di-2-ethylhexyl phosphate was diluted with kerosene to an organic phase of 30% by volume. And were supplied so that the organic phase / aqueous phase ratio was 3/2, and three-stage extraction was performed with a counter current to obtain a post-extraction liquid having the composition shown in Table-11.

Thereafter, the same operation as in Example 1 was carried out to obtain nickel sulfate crystals of the quality shown in Table-12.

[Effect of the Invention] According to the recovery method of the present invention, it is not necessary to evaporate and concentrate the decoppering electrolytic solution as in the conventional method, and nickel sulfate can be effectively recovered with low energy.

Furthermore, in the recovery method of the present invention, each impurity is sequentially removed from the decoppered electrolytic solution in each step from the primary neutralization step to the nickel extraction step, so that nickel sulfate of extremely high purity can be recovered.

[Brief description of drawings]

The figure is a flow sheet showing the outline of the recovery method of the present invention.

Claims (3)

[Claims] 1. A primary neutralization step of removing free sulfuric acid after decopperizing a copper electrolyte solution and a secondary step of precipitation and separation of metal impurities other than nickel as hydroxides from the filtrate of the primary neutralization step. After the neutralization step and the second neutralization step, an alkali is added to the filtrate together with an extraction solvent to adjust the pH to 2.5 to 4, and metallic impurities other than nickel are extracted into the solvent and separated from the nickel solution. In the method for obtaining a purified nickel solution, after the above-mentioned impurity extraction step, after the nickel extraction step of further adding an extraction solvent to the nickel solution and adding an alkali to adjust the pH to 5 to 7 and extracting nickel into the solvent,
A method for recovering purified nickel sulfate from a copper electrolyte, characterized in that purified nickel is obtained through a concentration step of back-extracting nickel in a solvent with sulfuric acid to increase the nickel concentration. 2. In the first neutralization step, calcium carbonate or calcium hydroxide is added to the solution after decoppering to convert free sulfuric acid into gypsum, and antimony and bismuth are precipitated and separated, and (b) 2 In the next step, the pH is adjusted to 5 to 6.5 by adding an alkali with an oxidizing agent to the filtrate after the primary neutralization, and a part of copper and zinc and iron, lead and arsenic are precipitated as hydroxides, (C) In the impurity extraction step, alkali is added to the filtrate after the secondary neutralization together with the extraction solvent to adjust the pH to 2.5
Copper, zinc and calcium remaining in the filtrate in the range of 4 are separated from the nickel liquid by extracting into a solvent,
(D) The method according to claim 1, wherein in the nickel extraction step, alkali is added to the nickel solution together with the solvent, and nickel is extracted from the solvent in the range of pH 5 to 7 to separate from sodium, magnesium and ammonia. 3. The method according to claim 1, wherein zinc dust is added to the filtrate in the secondary neutralization step to reduce the copper concentration in the filtrate, and then the impurity extraction step is performed.