JP2012072482A - Method for removing calcium in nickel electrolyte solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for stabilizing operation by solving troubles such as pipe clogging caused by the precipitation of calcium sulfate due to the accumulation of calcium in the electrolytic extraction of nickel.SOLUTION: A purification method of a nickel electrolyte solution includes extracting and removing calcium contained as an impurity from a nickel sulfate solution for producing nickel metal with an alkyl phosphate ester at a pH of 1.5 or more and 5.0 or less during extraction.

Description

  In the method for producing nickel by electrolytic collection using a nickel-containing solution, the present invention allows calcium sulfate to be deposited in piping, a battery case, etc. by removing calcium continuously or intermittently from the electrolyte. It is related with manufacturing nickel stably.

  The nickel sulfate solution used in the electrolytic solution is prepared by dissolving sulfides and scraps containing nickel in sulfuric acid, removing impurities such as copper, iron, and zinc, concentrating and cooling by heating and evaporating. It is obtained by dissolving the extracted nickel sulfate. Scraps may also contain calcium, magnesium, and the like. Usually, in order to remove copper and iron in a nickel solution, a method utilizing a neutralization reaction for forming a hardly soluble hydroxide is employed. In this neutralization reaction, calcium hydroxide and sodium hydroxide are used, and calcium hydroxide is often used because of cost and filterability.

  Further, in copper smelting, electrolytic copper is produced using a sulfuric acid bath, and among various impurities contained in the raw copper ore, metal components that are lower than copper accumulate in the electrolyte. Since there is nickel which is a valuable metal in this impurity, a part of the copper electrolyte is extracted, the main component copper is crystallized, removed by electrolysis, sulfidation, etc., and the resulting nickel sulfate solution is concentrated , Cooled and recovered as nickel sulfate. This nickel sulfate contains iron, copper, cobalt, copper, and calcium as impurities. Copper, iron, zinc and cobalt are removed by the method disclosed in Japanese Patent Application Laid-Open No. 2007-270291, converted into nickel carbonate, and then dissolved again in sulfuric acid to obtain a high-purity nickel sulfate solution.

When manufacturing nickel ingots, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2007-270291), electrolytic collection using an insoluble electrode is performed using the nickel sulfate solution from which impurities are removed as described above. It is normal. In the case of electrowinning, the nickel component reduced by electrolysis is supplied in the form of nickel carbonate or nickel hydroxide.
Impurities such as copper, iron, and zinc in the electrolyte solution co-deposit with nickel and deteriorate the purity of the nickel ingot. Therefore, nickel carbonate and nickel hydroxide that are low in copper, iron, and zinc are desired. .
Therefore, it was considered to produce nickel carbonate and nickel hydroxide from nickel sulfate from which copper, iron, zinc and cobalt were removed.
In Patent Document 2 (Japanese Patent Laid-Open No. 10-30135), a high-purity nickel solution can be obtained by purifying a nickel sulfate solution obtained by dissolving scrap in sulfuric acid to 0.03 g / L or less of iron and cobalt by solvent extraction. 0.02 g / L remains.
Nickel carbonate is produced by neutralizing nickel sulfate from which impurities have been removed with sodium carbonate as described in paragraph 0014 of Patent Document 1 (Japanese Patent Laid-Open No. 2007-270291). Calcium contained in nickel sulfate is It was found that nickel carbonate remained as an impurity.
If nickel carbonate containing calcium is used and nickel is collected for a long time, calcium accumulates. As described in the chemical handbook (Non-Patent Document 1), the solubility of calcium sulfate was 0.208 wt% (about 0.61 g / L as calcium) at 25 ° C., and 0.152 wt% (about 0% at 60 ° C.). .55 g / L) and 0.1 wt% at 80 ° C. (about 0.30 g / L), so when calcium accumulates, it deposits in the form of calcium sulfate in pipes and electrolytic cells. In particular, in a heat exchanger that adjusts the temperature of the electrolytic solution, calcium sulfate is more likely to be deposited because it is in contact with a high temperature portion of 70-80 ° C. Thus, when calcium accumulates, it precipitates in the form of calcium sulfate, which clogs the piping and heat exchanger, causing a problem of nickel electrolysis.
JP 2007-270291 “Method for producing metallic nickel from crude nickel sulfate” Japanese Patent Application Laid-Open No. 10-30135 “Method for producing high-purity nickel aqueous solution”

Non-patent contribution 1

Chemical Handbook (Revised 3rd Edition) Fundamentals II, II-168

  The present invention provides a technique for preventing troubles such as clogging of piping when calcium accumulated in an electrolytic solution is precipitated as calcium sulfate in the case of producing nickel ingots by electrowinning.

Knowledge to remove the calcium contained in the electrolyte solution by solvent extraction to solve the above problems, prevent troubles such as clogging of piping due to precipitation of calcium sulfate, and efficiently produce nickel ingots Got.
Based on this knowledge, the present invention (1) From nickel sulfate solution for producing nickel ingot, the calcium containing as impurities is alkyl phosphate ester, and the pH during extraction is 1.5 to 5.0. A method for purifying the removed nickel electrolyte, characterized by extracting and removing.

(2) The method for purifying a nickel electrolyte according to (1), wherein the concentration of calcium contained in the electrolyte is 0.2 g / L or less.
(3) A method for purifying a nickel electrolyte, comprising an activated carbon treatment step after the step of removing calcium using the electrolyte solution according to any one of (1) or (2).

From the above, according to the present invention,
(1) By removing calcium in the electrolytic solution by solvent extraction, troubles such as clogging of piping due to precipitation of calcium sulfate can be prevented.
(2) A nickel ingot can be manufactured efficiently.

The schematic of nickel electrolytic refining including the calcium removal process by solvent extraction which is one mode of the present invention is shown. The schematic of the conventional nickel electrolytic purification is shown.

  In electrolytic collection for producing nickel metal, insoluble DSE and Pb are used for the anode, so that nickel decreased by electrodeposition is supplied in the form of nickel carbonate or nickel hydroxide. To replenish nickel carbonate, a part of the electrolytic solution is continuously or intermittently extracted, a predetermined amount of nickel carbonate is added to the electrolytic solution, dissolved, filtered, and transferred back to the electrolytic cell or the storage tank. Since nickel carbonate contains calcium as an impurity, if it is continuously electrolyzed for a long period of time, calcium accumulates in the electrolyte and precipitates in the form of calcium sulfate, which causes troubles such as clogging of piping.

In the present invention, the calcium phosphate is removed from the electrolytic solution extracted continuously or intermittently by using an alkyl phosphate ester as an extractant and setting the pH during extraction to 1.5-5.0.
When the electrolyte temperature is adjusted to 50-55 ° C., the temperature in the heat exchanger is 70-80 ° C. From the solubility of calcium at 80 ° C., the calcium concentration is about 0.3 g / Precipitation of calcium sulfate can be prevented at L or less, but considering safety, 0.2 g / L or less is necessary, and 0.1 g / L or less is more preferable for more stability.

  Solvent extraction is effective for removing calcium. As the extractant, dialkyl phosphate ester (commercial example: DP-8R Daihachi Chemical) is suitable. In order to reduce the calcium concentration to 0.2 g / L or less, it can be achieved at an O / A ratio 1/1 of pH 1.5 or higher, and at an O / A ratio of 1 / 2-1 / 4, pH 2.0 or higher. In order to reduce the calcium concentration to 0.1 g / L or less, it can be achieved at an O / A ratio 1/1 of pH 2.0 or higher, and at an O / A ratio of 1 / 2-1 / 4, pH 2.5 or higher. When the pH is 5.5 or more, nickel hydroxide is precipitated, so that the pH is preferably 5.0 or less, more preferably 4.5 or less.

  A trace amount of extractant or organic solvent may remain in the electrolyte from which calcium has been removed. When nickel bullion is produced using an electrolyte mixed with organic matter, pinholes due to bubbles are formed on the surface of the nickel bullion. Since nodules are produced and the appearance is poor, it is preferable to remove the extractant and the organic solvent by activated carbon treatment. For the activated carbon treatment, a known technique is sufficient. The treatment amount of the activated carbon is 0.1-10 g per liter of the electrolytic solution.

  Next, examples of the present invention will be described. In addition, a present Example is an example to the last, and is not restrict | limited to this example. That is, all aspects or modifications other than the embodiments are included within the scope of the technical idea of the present invention.

FIG. 2 shows a schematic diagram of a conventional nickel electrowinning device. The nickel electrolyzer has a total liquid volume of 1000 L, and each tank has an electrolytic tank 100 L, a cathode storage tank 900-700 L, and an anode storage tank 0-200 L, and is equipped with a pump and a filter.
In the electrolytic cell, the cathode and the anode are separated by a diaphragm. The electrolyte is supplied to the cathode side at 10-25 L / min, and returns to the cathode storage tank due to overflow. On the anode side, the liquid level of the overflow portion is made slightly lower than that of the cathode side, and the electrolytic solution that has passed through the diaphragm is returned to the anode storage tank due to the difference between the cathode side liquid level and the anode side liquid level. In the anode liquid storage tank, the electrolytic solution accumulates at approximately 10-15 L / hour. The electrolyte stored in the anode storage tank was returned to the cathode storage tank by adjusting the nickel concentration with nickel carbonate and adjusting the pH as necessary every 6 to 8 hours. The electrolysis of nickel was carried out at an anode and cathode area of 50 dm 2 and a current density of 0.5-5.0 A / dm 2. The electrolytic solution was controlled in the nickel concentration range of 80-105 g / L.

(Example 1-9, Comparative Example 1-3)
Electrolysis was continuously performed using the electrolytic device of FIG. 2 to prepare an electrolytic solution having a calcium concentration of 0.523 g / L. Using this electrolytic solution, as a result of shaking with 20 vol% alkyl phosphate ester extractant (Daihachi Chemical; DP-8R, diluent shellsol D-70) under the conditions shown in Table 1, calcium was obtained as shown in Table 1. The conditions under which the concentration was 0.2 g / L or lower were pH 1.5 or higher when the O / A ratio was 1/1, and pH 2.0 or higher when the O / A ratio was 1/2.
Further, the conditions under which the calcium concentration was 0.1 g / L or less were pH 2.0 or more when the O / A ratio 1/1 and 1/2, and pH 2.5 or more when the O / A ratio 1/4. As shown in Comparative Examples 1 to 3, when the pH is low, the calcium concentration is 0.3 g / L or more, which exceeds the solubility of calcium sulfate at 80 ° C.

(Examples 10-14, Comparative Examples 4 and 5)
It carried out on the conditions of Table 2 using the extractant which made the alkyl phosphate ester extractant (Daihachi DP-8R, diluent shellsol D-70) 10 vol%.
As shown in Table 2, the conditions for the p calcium concentration to be 0.2 g / L or less are pH 1.5 or more when the O / A ratio is 1/1, and pH 2.0 or more when the O / A ratio is 1/2. It was.
Furthermore, the conditions for the calcium concentration to be 0.1 g / L or less were pH 2.0 or more when the O / A ratio was 1/1, and pH 4.0 or more when the O / A ratio was 1/2.
As shown in Comparative Examples 4 and 5, when the pH is low, the calcium concentration is 0.3 g / L or more, exceeding the solubility of calcium sulfate at 80 ° C.

(Example 15)
Using an electrolytic apparatus for nickel electrolytic purification including a calcium removal step by solvent extraction shown in FIG. 1, an electrolytic solution having a nickel concentration of 90 g / L and a calcium concentration of 0.582 g / L is continuously electrolyzed, and at the same time calcium After that, activated carbon treatment was performed.
The electrolyte stored in the anode storage tank is adjusted for nickel concentration with nickel carbonate every 6 to 8 hours, and with a settler mixer under the conditions of O / A ratio 1/2 and final pH 2.5-3.0. Calcium removal was performed.
As a result, the Ca concentration in the electrolyte decreased during continuous electrolysis, 0.192 g / L after 100 hours, 0.0986 g / L after 200 hours, and 0.04-0.07 g / L after 300 hours. Stable.
The surface condition of the nickel ingot obtained by electrolysis was good with no pinholes or nodules.

Claims (3)

  Removed from nickel sulfate solution for producing nickel ingot, characterized by extracting and removing calcium contained as impurities with alkyl phosphate ester at pH of 1.5 to 5.0 A method for purifying nickel electrolytes.   The method for purifying a nickel electrolyte solution according to claim 1, wherein the calcium concentration contained in the electrolyte solution is 0.2 g / L or less.   A method for purifying a nickel electrolyte, comprising an activated carbon treatment step after the step of removing calcium using the electrolyte solution according to claim 1.

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