JP6473102B2 - Cobalt electrowinning method - Google Patents
Cobalt electrowinning method Download PDFInfo
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- JP6473102B2 JP6473102B2 JP2016115586A JP2016115586A JP6473102B2 JP 6473102 B2 JP6473102 B2 JP 6473102B2 JP 2016115586 A JP2016115586 A JP 2016115586A JP 2016115586 A JP2016115586 A JP 2016115586A JP 6473102 B2 JP6473102 B2 JP 6473102B2
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- 229910017052 cobalt Inorganic materials 0.000 title claims description 97
- 239000010941 cobalt Substances 0.000 title claims description 97
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 title claims description 94
- 238000000034 method Methods 0.000 title claims description 87
- 238000005363 electrowinning Methods 0.000 title claims description 39
- 238000005868 electrolysis reaction Methods 0.000 claims description 119
- 239000008151 electrolyte solution Substances 0.000 claims description 66
- 239000000243 solution Substances 0.000 claims description 30
- 239000003792 electrolyte Substances 0.000 claims description 13
- 239000007788 liquid Substances 0.000 description 12
- 238000000605 extraction Methods 0.000 description 8
- -1 polypropylene Polymers 0.000 description 8
- 239000001257 hydrogen Substances 0.000 description 7
- 229910052739 hydrogen Inorganic materials 0.000 description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 238000011084 recovery Methods 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 150000001868 cobalt Chemical class 0.000 description 3
- 229940044175 cobalt sulfate Drugs 0.000 description 3
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 3
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 230000003746 surface roughness Effects 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 1
- 229910000978 Pb alloy Inorganic materials 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910001429 cobalt ion Inorganic materials 0.000 description 1
- XLJKHNWPARRRJB-UHFFFAOYSA-N cobalt(2+) Chemical compound [Co+2] XLJKHNWPARRRJB-UHFFFAOYSA-N 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004070 electrodeposition Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 239000010926 waste battery Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Electrolytic Production Of Metals (AREA)
Description
この発明は、コバルトが溶解した電解液からコバルトを電解採取する方法に関するものであり、特には、コバルトを高い効率で電解採取するための技術を提案するものである。 The present invention relates to a method for electrolytically collecting cobalt from an electrolytic solution in which cobalt is dissolved, and in particular, proposes a technique for electrolytically collecting cobalt with high efficiency.
高純度のコバルトを得るための電解採取では、コバルト及び、場合によってはその他の元素が溶解した硫酸系の電解液に、不溶性陽極（アノード）及び陰極（カソード）を浸漬させ、それらの間に所定の電圧を印加することにより、コバルトを電解還元して陰極の表面に電着させて採取する。 In electrowinning to obtain high-purity cobalt, an insoluble anode (anode) and cathode (cathode) are immersed in a sulfuric acid-based electrolyte in which cobalt and other elements are dissolved, and a predetermined amount is set between them. Is applied, and cobalt is electrolytically reduced and electrodeposited on the surface of the cathode to be collected.
この種の電解採取の技術では、主として、電解採取時の陰極表面への目的金属の密着性及び、電解採取の後に陰極表面に電着した目的金属の剥離性に着目したものが多数提案されている。
たとえば特許文献１では、電解採取により陰極母板上に電着した目的金属を、当該陰極母板から剥離させて回収する際の剥離作業能率の向上を目的として、金属の電解採取用陰極母板の研磨方法が提案されている。
In this type of electrowinning technique, many techniques have been proposed mainly focusing on the adhesion of the target metal to the cathode surface during electrowinning and the peelability of the target metal electrodeposited on the cathode surface after electrowinning. Yes.
For example, in Patent Document 1, for the purpose of improving the separation work efficiency when a target metal electrodeposited on a cathode base plate by electrowinning is peeled from the cathode base plate and recovered, the cathode base plate for electrowinning metal is used. A polishing method has been proposed.
また特許文献２では、電解採取中に陰極からの電着コバルトの剥離を防止すること等を目的として、硫酸コバルトを含む電解液から電解採取によるコバルトの製造方法で、陰極にアルミニウム板を用い、アルミニウム板に析出させて採取したコバルトを水酸化ナトリウム溶液で洗浄する方法が提案されている。 Further, in Patent Document 2, for the purpose of preventing peeling of electrodeposited cobalt from the cathode during electrowinning, a method for producing cobalt by electrowinning from an electrolytic solution containing cobalt sulfate, using an aluminum plate for the cathode, There has been proposed a method of washing cobalt collected by precipitation on an aluminum plate with a sodium hydroxide solution.
特許文献３では、カソードの表面粗さを、５点標準粗さ（Ｒｚ）で表した値で１０〜２０μｍになるように粗さ調整することにより、電解時にカソードと電着金属の密着性を保持することができるとされている。
特許文献４では、通電中での自然剥離をさせずに、コバルトが電着した陰極板からのコバルト剥離回収作業の能率を向上させるため、陰極板側の電解液のｐＨを１．５から２の間で保持することが記載されている。
In Patent Document 3, the cathode surface roughness is adjusted so that the surface roughness of the cathode is 10 to 20 μm in terms of 5-point standard roughness (Rz), thereby improving the adhesion between the cathode and the electrodeposited metal during electrolysis. It can be held.
In Patent Document 4, the pH of the electrolyte solution on the cathode plate side is set to 1.5 to 2 in order to improve the efficiency of the cobalt stripping recovery operation from the cathode plate on which cobalt is electrodeposited without spontaneous peeling during energization. It is described to hold between.
ところで、コバルトを電解採取するに当っては、電解液のｐＨが比較的低いと、陰極へのコバルトの密着性は良好になるが電流効率は低下すること、及び、電解液のｐＨが比較的高いと、電流効率は向上するが陰極へのコバルトの密着性が悪化することが解かった。
したがって、コバルトの密着性と電流効率は、ｐＨの大小について互いに背反の関係にあり、電解液のｐＨを高くしても低くしても、コバルトの密着性又は電流効率のいずれかに不都合が生じる。
By the way, when electrolytically collecting cobalt, if the pH of the electrolytic solution is relatively low, the adhesion of cobalt to the cathode is improved, but the current efficiency is lowered, and the pH of the electrolytic solution is relatively low. It was found that when the value was high, the current efficiency was improved, but the adhesion of cobalt to the cathode deteriorated.
Therefore, the adhesion and current efficiency of cobalt are in a trade-off relationship with respect to the magnitude of pH, and inconvenience occurs in either the adhesion or current efficiency of cobalt regardless of whether the pH of the electrolyte is high or low. .
この一方で、密着性を確保するため、先述した特許文献２に記載されているように陰極をアルミニウム板にすることや、特許文献３のようにカソードの表面粗さを調整することは、新たな設備の導入、別途の作業等が必要になり、手間及びコストがかかるという問題がある。
また、特許文献４に記載されているように、電解液のｐＨを１．５〜２と比較的高くすると、特に電解開始時に陰極表面にコバルトが十分に密着せず、コバルトの電解採取の効率が低下するという問題があった。
On the other hand, in order to ensure adhesion, the cathode is made of an aluminum plate as described in Patent Document 2 described above, or the surface roughness of the cathode as in Patent Document 3 is newly added. Installation, additional work, etc. are required, and there is a problem that it takes time and cost.
Further, as described in Patent Document 4, when the pH of the electrolytic solution is relatively high, 1.5-2, cobalt is not sufficiently adhered to the cathode surface particularly at the start of electrolysis, and the efficiency of electrolytic extraction of cobalt is reduced. There was a problem that decreased.
この発明は、従来技術が抱えるこのような問題を解決することを課題とするものであり、その目的は、電解採取にかかるコストを抑えつつ、コバルトを高い効率で電解採取することのできるコバルトの電解採取方法を提供することにある。 An object of the present invention is to solve such problems of the prior art, and the object of the present invention is to reduce the cost of electrolytic collection and to collect cobalt with high efficiency. It is to provide an electrolytic collection method.
発明者は、上述したような電解液のｐＨに対するコバルトの密着性と電流効率の関係を見出した上で鋭意検討した結果、電解開始時には、陰極へのコバルトの密着性を確保するため、電解液を所定の低いｐＨとし、一定時間が経過して陰極上にある程度コバルトが密着した後は、電解液のｐＨを上昇させて電解採取を継続することにより、電解採取の全体にわたって、電流効率を高めながらも、コバルトを高い効率で電解採取できるとの知見を得た。 As a result of diligent research after finding the relationship between cobalt adhesion to the pH of the electrolyte and the current efficiency as described above, the inventor has obtained the electrolyte solution in order to ensure the cobalt adhesion to the cathode at the start of electrolysis. After a certain time has elapsed and cobalt has adhered to the cathode to some extent, the current efficiency is improved throughout the electrowinning by increasing the pH of the electrolyte and continuing the electrowinning. However, the knowledge that cobalt can be electrolyzed with high efficiency was obtained.
この知見に基き、この発明のコバルトの電解採取方法は、コバルトが溶解した電解液からコバルトを電解採取するコバルト電解工程を有し、前記コバルト電解工程が、電解採取の開始時にｐＨ１．０未満の電解液を用い、当該電解液のｐＨを１．０未満に維持する電解開始過程と、電解開始過程の後、ｐＨ１．０〜２．０の電解液を供給する電解継続過程とを含むものである。 Based on this finding, the cobalt electrowinning method of the present invention includes a cobalt electrolysis step of electrowinning cobalt from an electrolytic solution in which cobalt is dissolved, and the cobalt electrolysis step has a pH of less than 1.0 at the start of electrowinning. It includes an electrolysis start process using an electrolyte solution to maintain the pH of the electrolyte solution below 1.0, and an electrolysis continuation process of supplying an electrolyte solution having a pH of 1.0 to 2.0 after the electrolysis start process.
この発明のコバルトの電解採取方法では、電解開始過程で、電解液のｐＨを１．０未満に維持する時間を、０．５時間〜２．５時間とすることが好ましい。 In the cobalt electrowinning method of the present invention, it is preferable that the time during which the pH of the electrolytic solution is maintained at less than 1.0 during the electrolysis start process is 0.5 to 2.5 hours.
また、この発明のコバルトの電解採取方法では、電解開始過程のｐＨ１．０未満の電解液として、当該コバルト電解工程に先立って実施した前回のコバルト電解工程にて電解液の供給を停止した状態で電解採取を行った後に得られる電解後液を用いることが好ましい。 Moreover, in the cobalt electrowinning method of the present invention, as an electrolytic solution having a pH of less than 1.0 in the electrolysis start process, the supply of the electrolytic solution is stopped in the previous cobalt electrolysis step performed prior to the cobalt electrolysis step. It is preferable to use a post-electrolysis solution obtained after electrolytic collection.
前記コバルト電解工程は、電解継続過程の後、電解採取の終了時に電解液の供給を停止した状態で、電解採取を行う電解終了過程をさらに含むことが好適である。
この場合、電解終了過程で得られた電解後液を、当該コバルト電解工程の後に実施する次回のコバルト電解工程で電解採取の開始時の電解液として用いることが好ましい。
It is preferable that the cobalt electrolysis step further includes an electrolysis termination process in which electrolysis is performed in a state where supply of the electrolytic solution is stopped at the end of electrolysis after the electrolysis continuation process.
In this case, it is preferable to use the post-electrolysis solution obtained in the electrolysis completion process as the electrolyte solution at the start of the electrowinning in the next cobalt electrolysis step performed after the cobalt electrolysis step.
また、上記の電解終了過程では、電解液の供給を停止した状態で電解採取を行う時間を、１．０時間〜１４．０時間とすることが好ましい。電解終了過程では、電解液のｐＨを１．０未満とすることが好ましい。
なお、電解終了過程で得られた電解後液は回収して、電解後液回収槽で貯留することができる。
In the above electrolysis termination process, it is preferable that the time for performing electrowinning in a state where supply of the electrolytic solution is stopped be 1.0 hour to 14.0 hours. In the electrolysis termination process, the pH of the electrolytic solution is preferably less than 1.0.
In addition, the post-electrolysis solution obtained in the electrolysis completion process can be recovered and stored in the post-electrolysis solution recovery tank.
この発明のコバルトの電解採取方法によれば、ｐＨを１．０未満に維持する電解開始過程と、その後、ｐＨ１．０〜２．０の電解液を供給する電解継続過程とを含むことにより、コバルト密着性および電流効率を向上させることができるので、電解採取にかかるコストを抑えつつ、コバルトを高い効率で電解採取することができる。 According to the cobalt electrowinning method of the present invention, by including an electrolysis start process for maintaining the pH below 1.0, and then an electrolysis continuation process for supplying an electrolyte solution having a pH of 1.0 to 2.0, Since cobalt adhesion and current efficiency can be improved, cobalt can be electrolytically collected with high efficiency while suppressing the cost of electrolytic collection.
以下に、この発明の実施の形態について詳細に説明する。
この発明の一の実施形態に係るコバルトの電解採取方法では、図１に例示するような電解槽を用いて、電解槽内のコバルトが溶解した電解液にアノード及びカソードを浸漬させ、それらのアノードとカソードとの間に電圧を印加することで、当該電解液からコバルトを電解採取するコバルト電解工程を実施する。そして、このコバルト電解工程では、電解採取の開始時にｐＨ１．０未満の電解液を電解槽に供給し、当該電解液のｐＨを１．０未満に維持する電解開始過程と、電解開始過程の後、ｐＨ１．０〜２．０の電解液を電解槽に供給する電解継続過程を経る。
Hereinafter, embodiments of the present invention will be described in detail.
In the cobalt electrowinning method according to one embodiment of the present invention, an anode and a cathode are immersed in an electrolytic solution in which cobalt in the electrolytic cell is dissolved using an electrolytic cell as illustrated in FIG. By applying a voltage between the cathode and the cathode, a cobalt electrolysis process is performed in which cobalt is electrolyzed from the electrolyte. In this cobalt electrolysis process, an electrolyte solution having a pH of less than 1.0 is supplied to the electrolytic cell at the start of electrowinning, and an electrolysis start process for maintaining the pH of the electrolyte solution at less than 1.0, and an electrolysis start process. The electrolytic continuation process of supplying an electrolytic solution having a pH of 1.0 to 2.0 to the electrolytic cell is performed.
＜電解液＞
電解液には、電解採取の対象とするコバルトが溶解した酸性溶液、たとえば硫酸溶液を用いることができる。電解液中のコバルト濃度は、７０ｇ／Ｌ〜１１０ｇ／Ｌとすることができ、好ましくは９０ｇ／Ｌ〜１００ｇ／Ｌとする。コバルト濃度が高すぎると、硫酸コバルトの溶解度以上になって硫酸コバルトが析出し、この一方で、コバルト濃度が低すぎると、長時間にわたる電解が実施できなくなることがある。
電解液には、コバルトだけでなく、銅等の他の金属が含まれていてもよい
<Electrolyte>
As the electrolytic solution, an acidic solution in which cobalt to be subjected to electrowinning is dissolved, for example, a sulfuric acid solution can be used. The cobalt concentration in the electrolytic solution can be 70 g / L to 110 g / L, preferably 90 g / L to 100 g / L. If the cobalt concentration is too high, the solubility of cobalt sulfate is exceeded and cobalt sulfate is precipitated. On the other hand, if the cobalt concentration is too low, electrolysis over a long period of time may not be performed.
The electrolytic solution may contain not only cobalt but also other metals such as copper.
電解液として具体的には、リチウムイオン電池の処理を行って得られる硫酸等を含むコバルト含有液、銅製錬で得られるコバルト含有液、電池リサイクルで得られるコバルト含有溶液等を挙げることができる。 Specific examples of the electrolytic solution include a cobalt-containing liquid containing sulfuric acid obtained by treating a lithium ion battery, a cobalt-containing liquid obtained by copper smelting, a cobalt-containing solution obtained by battery recycling, and the like.
＜コバルト電解工程＞
コバルト電解工程の概要は次のとおりである。
図１に例示するところでは、電解槽はアノードとカソードを備え、アノードとカソードは、ポリプロピレンやポリエチレンのろ布あるいは素焼き磁性物等からなる隔膜を介して隔てられて設けられている。アノード側とカソード側との間で電解液のｐＨに差が生じると、電解液は隔膜を介してｐＨの低いほうから高いほうへ移動する。
なお、アノードには、鉛および鉛合金や不溶性電極（ＤＳＥ）を用いることができ、また、カソードには、ステンレス、チタン、ニッケルおよびコバルトを電極として用いることができる。
<Cobalt electrolysis process>
The outline of the cobalt electrolysis process is as follows.
In the example illustrated in FIG. 1, the electrolytic cell includes an anode and a cathode, and the anode and the cathode are separated from each other through a diaphragm made of polypropylene or polyethylene filter cloth, unglazed magnetic material, or the like. When a difference in pH of the electrolytic solution occurs between the anode side and the cathode side, the electrolytic solution moves from the lower pH side to the higher side through the diaphragm.
In addition, lead, a lead alloy, or an insoluble electrode (DSE) can be used for the anode, and stainless steel, titanium, nickel, and cobalt can be used for the cathode.
電解採取を実施すると、カソード側では電解液に含まれるコバルトがカソード電極に電着するとともに、電解液中の水素イオン（Ｈ+）が消費されて水素（Ｈ2）が発生する。この一方で、アノード側では、以下の反応が生じて、水（Ｈ2Ｏ）が電気分解して酸素（Ｏ2）及び水素イオン（Ｈ+）が発生する。
Ｈ2Ｏ→１／２Ｏ2＋Ｈ+＋２ｅ-
When electrolytic collection is performed, cobalt contained in the electrolytic solution is electrodeposited on the cathode electrode on the cathode side, and hydrogen ions (H + ) in the electrolytic solution are consumed to generate hydrogen (H 2 ). On the other hand, the following reaction occurs on the anode side, and water (H 2 O) is electrolyzed to generate oxygen (O 2 ) and hydrogen ions (H + ).
H 2 O → 1 / 2O 2 + H + + 2e −
したがって、アノード側では、発生した水素イオンにより電解液の水素イオン濃度が上昇して、電解液のｐＨが低下する。それにより、カソード側にｐＨが低下した液が移動するところ、水素イオンよりもイオン化傾向の大きいコバルトが、水素イオンよりも陽イオンになりやすいので、カソード電極の表面に電着したコバルトがコバルトイオンに戻り、電解液に溶け出す。 Therefore, on the anode side, the hydrogen ion concentration of the electrolytic solution increases due to the generated hydrogen ions, and the pH of the electrolytic solution decreases. As a result, when the liquid having a lowered pH moves to the cathode side, cobalt, which has a higher ionization tendency than hydrogen ions, tends to become cations rather than hydrogen ions, so that the cobalt electrodeposited on the surface of the cathode electrode becomes cobalt ions. Return to the electrolyte.
これを防止するため、カソード側に電解液を供給する。このとき、電解液を一定量で供給することが好ましく、たとえば、この給液流量は以下の式で計算することができる。
Ｖ＝Ｄ／２０×（０．８〜１．２）
ここで、Ｖは１時間当たりの給液時間（Ｌ／Ｈｒ）であり、Ｄは１時間当たりのカソード１枚当たりの理論電着量（ｇ／Ｈｒ）である。なお、給液流量が上記の式の範囲を下回ると、カソード側の電解液のｐＨが低下し、電流効率が低下するおそれがある。
In order to prevent this, an electrolytic solution is supplied to the cathode side. At this time, it is preferable to supply the electrolyte solution at a constant amount. For example, the liquid supply flow rate can be calculated by the following equation.
V = D / 20 × (0.8 to 1.2)
Here, V is a liquid supply time per hour (L / Hr), and D is a theoretical electrodeposition amount (g / Hr) per cathode per hour. In addition, when the liquid supply flow rate is below the range of the above formula, the pH of the electrolyte solution on the cathode side is lowered, and the current efficiency may be lowered.
電解時の電解液の温度は、室温と同程度の温度でも問題なく電気分解を行うことができるが、それによりも若干高温であるほうが好ましく、特に４０〜６０℃に調整することが好ましい。高温であるほうが電解液の導電性が大きくなるからである。 Electrolysis can be carried out without any problem even when the temperature of the electrolytic solution at the time of electrolysis is about the same as room temperature. However, it is preferable that the temperature is slightly higher, and it is particularly preferable to adjust the temperature to 40 to 60 ° C. This is because the conductivity of the electrolyte is increased at a higher temperature.
この実施形態では、コバルト電解工程は、以下の電解開始過程、電解継続過程および電解終了過程を含む。 In this embodiment, the cobalt electrolysis process includes the following electrolysis start process, electrolysis continuation process, and electrolysis end process.
（電解開始過程）
電解開始当初は、カソード電極にコバルトがまだ付着しておらず、カソード電極へのコバルトの密着性を確保する必要があることから、電解槽に供給する電解液は、ｐＨが１．０未満と低いものとする。これにより、電解開始時にカソード電極にコバルトを有効に密着させることができる。この観点から、電解開始過程で電解槽に供給する電解液のｐＨは、０．７以上かつ１．０未満とすることが好ましく、特に０．８〜０．９とすることがより好ましい。初期のｐＨが低すぎると、コバルトが剥離不能になる可能性がある。
(Electrolysis start process)
At the beginning of electrolysis, cobalt has not yet adhered to the cathode electrode, and it is necessary to ensure the adhesion of cobalt to the cathode electrode. Therefore, the electrolyte supplied to the electrolytic cell has a pH of less than 1.0. It shall be low. Thereby, cobalt can be effectively adhered to the cathode electrode at the start of electrolysis. From this viewpoint, the pH of the electrolytic solution supplied to the electrolytic cell during the electrolysis start process is preferably 0.7 or more and less than 1.0, and more preferably 0.8 to 0.9. If the initial pH is too low, cobalt may not be peelable.
電解開始過程で供給する電解液は、具体的には、このコバルト電解工程に先立って行った前回の同様のコバルト電解工程で、後述するような電解終了過程として、電解液の供給を停止した状態で電解採取を行った後に得られる電解後液を用いることができる。但し、ｐＨが１．０未満と低い電解液であれば、電解開始過程で用いる電解液は特に限定されるものではない。 Specifically, the electrolytic solution supplied in the electrolysis start process is a state in which the supply of the electrolytic solution is stopped as an electrolysis end process as described later in the same cobalt electrolysis process performed prior to this cobalt electrolysis process. It is possible to use a post-electrolysis solution obtained after the electrowinning. However, the electrolyte solution used in the electrolysis initiation process is not particularly limited as long as the electrolyte solution has a pH as low as less than 1.0.
カソード電極にコバルトが十分に密着しないままで、高いｐＨの電解液を供給すれば、コバルトの密着性が悪化することから、電解開始過程では、電解液のｐＨを一定時間にわたって１．０未満に維持することが好ましい。たとえば、ｐＨ１．０未満の低ｐＨの電解液を連続的に供給するとともに電解後液を連続的に排出させること等により、ｐＨを１．０未満に維持することができる。 If a high pH electrolyte solution is supplied without sufficiently adhering cobalt to the cathode electrode, the adhesion of cobalt deteriorates. Therefore, in the electrolysis start process, the pH of the electrolyte solution is reduced to less than 1.0 over a certain period of time. It is preferable to maintain. For example, the pH can be maintained at less than 1.0 by continuously supplying an electrolyte solution having a low pH of less than 1.0 and continuously discharging the solution after electrolysis.
電解液のｐＨを１．０未満に維持する時間は、０．５時間〜２．５時間とすることが好適である。この時間にわたってｐＨを１．０未満に維持することにより、カソード電極にコバルトが十分に密着するからである。一方、ｐＨを１．０未満に維持する時間が長すぎると、低いｐＨに起因して電流効率が低下する。それ故に、電解液のｐＨを１．０未満に維持する時間は、より好ましくは０．５時間〜２．５時間、さらに好ましくは１時間〜２時間とする。 The time for maintaining the pH of the electrolyte below 1.0 is preferably 0.5 to 2.5 hours. This is because cobalt is sufficiently adhered to the cathode electrode by maintaining the pH below 1.0 over this time. On the other hand, if the time for maintaining the pH below 1.0 is too long, the current efficiency decreases due to the low pH. Therefore, the time for maintaining the pH of the electrolytic solution below 1.0 is more preferably 0.5 hours to 2.5 hours, and further preferably 1 hour to 2 hours.
（電解継続過程）
上述した電解開始過程でカソード電極にコバルトを十分に密着させた後は、カソード電極へのコバルトの密着性をそれほど考慮しなくてもよくなるので、電流効率を高めるため、電解槽に、ｐＨが１．０〜２．０と比較的高い電解液を供給する。それにより、電解槽内の電解液のｐＨを１．０〜２．０の範囲内に維持することができる。
この電解継続過程で供給する電解液のｐＨが低すぎると、電流効率が低下してコストの増大を招く。この一方で、この電解液のｐＨが高すぎると、電解採取工程を経た電解後液へコバルトを補給するため、電解後液に対して逆抽出工程を行う場合に、その逆抽出工程で溶媒中にコバルトが残留してコバルトの取りこぼし量が多くなって、直行率が低下することが懸念される。したがって、電解継続過程で供給する電解液のｐＨは、１．２〜１．８とすることが好ましく、特に１．３〜１．５とすることが好ましい。
(Continuation process of electrolysis)
After the cobalt is sufficiently adhered to the cathode electrode in the electrolysis start process described above, it is not necessary to consider so much the adhesion of cobalt to the cathode electrode. A relatively high electrolyte solution of 0.0 to 2.0 is supplied. Thereby, pH of the electrolyte solution in an electrolytic cell can be maintained in the range of 1.0-2.0.
If the pH of the electrolyte supplied during this electrolysis continuation process is too low, the current efficiency is lowered and the cost is increased. On the other hand, if the pH of the electrolytic solution is too high, cobalt is replenished to the post-electrolysis solution that has undergone the electrowinning process. There is a concern that cobalt may remain and the amount of cobalt dropped increases, resulting in a decrease in the direct rate. Therefore, the pH of the electrolyte supplied during the electrolysis process is preferably 1.2 to 1.8, and particularly preferably 1.3 to 1.5.
電解継続過程で電解槽に供給する比較的ｐＨの高い電解液は、たとえば、リチウムイオン電池、特にその正極活物質（ＬｉＣｏＯ2、ＬｉＮｉＯ2等）を溶解させた浸出後液に対して溶媒抽出および逆抽出を実施することで得られる逆抽出後液とすることができる。なお、このリチウムイオン電池は、電池製品の寿命や製造不良またはその他の理由によって廃棄された廃電池から取り出したものを用いることが好ましい。 Electrolytic solution having a relatively high pH supplied to the electrolytic cell in the course of electrolysis is, for example, extracted from a lithium ion battery, particularly a leached solution in which a positive electrode active material (LiCoO 2 , LiNiO 2, etc.) is dissolved and It can be set as the liquid after back extraction obtained by implementing back extraction. In addition, it is preferable to use this lithium ion battery taken out from the waste battery discarded due to the life of the battery product, manufacturing failure, or other reasons.
（電解終了過程）
上記の電解継続過程で、ｐＨが比較的高い電解液を供給して電解採取を実施した後は、電解終了過程として、当該電解液の供給を停止し、その状態で電解採取を行うことが好ましい。
この電解終了過程では、電解液の供給を停止した状態で好ましくは１．０時間〜１４．０時間にわたって電解採取を行うことにより、電解液のｐＨは、アノード側での水素イオンの生成により次第に低下していく。そしてここでは、電解液のｐＨを１．０未満とすることが好ましく、このようにｐＨが１．０未満に低下した電解後液を回収し、これを、このコバルト電解工程の後に行う次回の同様のコバルト電解工程の電解開始工程で電解槽に供給するため、たとえばタンク等に貯留させて保管することができる。
(End of electrolysis process)
In the above electrolysis continuation process, after supplying an electrolytic solution having a relatively high pH and performing electrolytic collection, it is preferable to stop the supply of the electrolytic solution and perform electrolytic collection in that state as an electrolysis termination process .
In this electrolysis termination process, the electrolytic solution is collected for 1.0 hour to 14.0 hours in a state where the supply of the electrolytic solution is stopped, so that the pH of the electrolytic solution gradually increases due to the generation of hydrogen ions on the anode side. It goes down. And here, it is preferable that the pH of the electrolytic solution is less than 1.0. Thus, the post-electrolysis solution whose pH is lowered to less than 1.0 is collected, and this is performed next time after this cobalt electrolysis step. Since it supplies to an electrolytic cell in the electrolysis start process of the same cobalt electrolysis process, it can be stored, for example in a tank etc. and stored.
（電解設備）
上述したコバルトの電解採取方法は、たとえば、図２に示すような設備を用いて実施することができる。
図２に示す設備は、コバルト電解工程を実施するための電解槽と、電解開始過程および電解継続過程における電解槽での電解採取により得られる電解後液を貯留する電解後液貯槽と、電解後液貯槽から電解後液が供給されて逆抽出を行う逆抽出槽と、逆抽出後の液を電解前液として貯留する電解前液貯槽と、電解前液を電解前に加温・撹拌する加温・撹拌槽とを備える。
(Electrolytic equipment)
The cobalt electrowinning method described above can be carried out, for example, using equipment as shown in FIG.
The equipment shown in FIG. 2 includes an electrolytic cell for performing a cobalt electrolysis process, a post-electrolysis solution storage tank for storing a post-electrolysis solution obtained by electrowinning in the electrolytic cell in the electrolysis start process and the electrolysis continuation process, and after electrolysis A reverse extraction tank that performs reverse extraction by supplying a post-electrolysis solution from a liquid storage tank, a pre-electrolysis liquid storage tank that stores the liquid after back extraction as a pre-electrolysis liquid, and a heater that heats and stirs the pre-electrolysis liquid before electrolysis It is equipped with a temperature and stirring tank.
さらに図２に示す設備は、電解終了過程における電解槽での電解採取により得られる電解後液を回収して貯留する電解後液回収槽と、その電解後液を電解開始過程で電解槽に供給するための電解後液供給タンクとを備えるものである。これにより、図２に破線の矢印で示すように、電解終了過程で得られる低ｐＨの電解後液を回収し、電解後液回収槽に貯留させ、これを、次回のコバルト電解工程において電解開始過程で用いるべく、電解後液供給タンクから電解槽へ供給することができる。 Furthermore, the equipment shown in FIG. 2 supplies a post-electrolysis solution recovery tank that recovers and stores a post-electrolysis solution obtained by electrowinning in the electrolysis tank in the electrolysis termination process, and supplies the post-electrolysis solution to the electrolysis tank in the electrolysis start process. And a post-electrolysis solution supply tank. As a result, as shown by the broken line arrow in FIG. 2, the low pH post-electrolysis solution obtained in the electrolysis completion process is recovered and stored in the post-electrolysis solution recovery tank, and the electrolysis is started in the next cobalt electrolysis process. In order to use in the process, it can be supplied from the post-electrolysis solution supply tank to the electrolytic cell.
次に、この発明のコバルトの電解採取方法を試験的に実施し、その効果を確認したので以下に説明する。但し、ここでの説明は単なる例示を目的とするものであって、それに限定されることを意図するものではない。 Next, the cobalt electrowinning method of the present invention was experimentally implemented and the effects thereof were confirmed, which will be described below. However, the description here is for illustrative purposes only and is not intended to be limiting.
表１及び２に示すように、電解開始過程でｐＨの低い電解初期液を用いるとともに、一定時間経過後の電解継続過程でそれよりもやや高いｐＨの電解前液を用いた試験例１〜３と、電解継続過程で試験例１〜３のものよりもさらに高いｐＨの電解前液を供給した試験例４〜６を行ったところ、試験例４〜６では、試験例１〜３と比べて約６％の平均電流効率の向上が確認された。 As shown in Tables 1 and 2, Test Examples 1 to 3 using an electrolysis initial solution having a low pH in the electrolysis start process and a pre-electrolysis solution having a slightly higher pH in the electrolysis continuation process after a predetermined time elapsed. And when the test examples 4 to 6 in which a pre-electrolysis solution having a pH higher than that of the test examples 1 to 3 was supplied in the electrolysis continuation process were performed, the test examples 4 to 6 were compared with the test examples 1 to 3. An improvement in average current efficiency of about 6% was confirmed.
以上より、電解継続過程で供給する電解前液のｐＨを高くすることによって、電流効率が高まるので、電解採取にかかるコストを低く抑えることのできる可能性があることが解かった。 From the above, it was found that the current efficiency is increased by increasing the pH of the pre-electrolysis solution supplied in the electrolysis continuation process, so that the cost for electrowinning may be reduced.
Claims (8)
前記コバルト電解工程が、電解採取の開始時にｐＨ１．０未満の電解液を用い、当該電解液のｐＨを１．０未満に維持する電解開始過程と、電解開始過程の後、ｐＨ１．０〜２．０の電解液を供給する電解継続過程とを含むコバルトの電解採取方法。 Having a cobalt electrolysis step of electrolytically collecting cobalt from an electrolytic solution in which cobalt is dissolved;
The cobalt electrolysis step uses an electrolyte solution having a pH of less than 1.0 at the start of electrowinning, and maintains an electrolyte solution having a pH of less than 1.0. And an electrolytic continuation process of supplying 0.0 electrolytic solution.
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