JP4439804B2

JP4439804B2 - Cobalt recovery method

Info

Publication number: JP4439804B2
Application number: JP2002351614A
Authority: JP
Inventors: 和幸松本; 晶永富; 和良尼崎; 浩也池田; 真一内山
Original assignee: Dowa Holdings Co Ltd; Dowa Mining Co Ltd
Current assignee: Dowa Holdings Co Ltd
Priority date: 2002-12-03
Filing date: 2002-12-03
Publication date: 2010-03-24
Anticipated expiration: 2022-12-03
Also published as: JP2004182533A

Description

【０００１】
【発明の属する技術分野】
本発明は、不純物を含有するコバルト溶液からのコバルト回収方法、特にリチウム二次電池廃材からのコバルト回収方法に関するものである。
【０００２】
【従来の技術】
リチウム二次電池は、軽量、高電気容量の電池としてよく知られており、各種携帯機器用二次電池として大量に使用されている。このリチウム二次電池の正極には、正極活物質として有価金属のコバルトを含むリチウムコバルト複合酸化物が使用されている。このリチウムコバルト複合酸化物から有価金属のコバルトを回収し再利用できる形態にすることは、資源リサイクルの観点から意義のあることである。
【０００３】
このようなリチウム二次電池からのコバルトの回収方法としては、次の方法などが提案されている。すなわち、使用済みリチウム二次電池を焙焼、破砕、篩い分けして得られた篩下を二次焙焼し、次に酸で処理し、更に処理液に酸化性ガスを吹き込みながらｐＨを４〜５．５に調整して濾過した後、濾液にアルカリを添加し濾過して沈殿物を回収する方法がある（例えば、特許文献１参照。）。
【０００４】
また、コバルト成分を含むリチウムイオン電池廃材を無機酸で浸出し、浸出した水溶液のリンとアルミニウムイオンのモル比を０．６〜１．２に調整し、酸化電位を５００ｍＶ以上で、鉄イオンを酸化し、該水溶液のｐＨを３．０〜４．５に調整し、不純物金属を沈殿除去し、精製溶液を取得し、この精製溶液に蓚酸を添加してコバルト蓚酸塩を、又は、この精製溶液のｐＨを６〜１０に調整してコバルト水酸化物又はコバルト炭酸塩を沈殿として取得する方法がある（例えば、特許文献２参照。）。
【０００５】
さらに、コバルト化合物を含む電極材料又はこのような電極材料が金属箔に塗着されている金属箔塗着廃材からなる二次電池廃材を、アルキル燐酸を含む有機溶液と過酸化水素を含む水からなるエマルジョン抽出剤と接触させ、上記二次電池廃材中のコバルトを有機溶液中に選択的に溶出せしめ、得られた有機溶液からコバルトを回収する二次電池廃材からのコバルト回収方法がある（例えば、特許文献３参照。）。
【０００６】
【特許文献１】
特開平７−２０７３４９号公報
【特許文献２】
特開平１１−６０２０号公報
【特許文献３】
特開平９−１１１３６０号公報
【０００７】
【発明が解決しようとする課題】
１．従来技術の問題点の抽出
(１)有価金属の回収を工業的に行う場合には、経済性と品質のバランスが重要になるが、例えば溶媒抽出法によるコバルトの回収は使用溶媒のコストや抽出段数による操作や設備の複雑さで経済的ではない。
(２)不純物としてアルミニウム、鉄を含有するコバルト含有溶液において、過酸化水素水を加えた後、苛性ソーダを用いてｐＨを調整し、不純物を沈殿によって除去しようとした場合、不純物を完全除去するｐＨに調整すると、コバルトも共沈しコバルトの回収率が悪くなる。一方で、コバルトの回収率を確保するｐＨに調整すると、不純物濃度が低減できない場合がある。つまりコバルト回収率と不純物濃度の低減のバランスに問題があった。
【０００８】
２．解決すべき課題
本発明は、汎用薬品等を用いた経済的な方法において、上記のようなｐＨ調整時のコバルトの回収率と不純物濃度の低減においてバランスのとれた、コバルトの回収方法を提供するものである。
【０００９】
【課題を解決するための手段】
本発明者等は、硫酸や苛性ソーダ等の汎用的で比較的廉価な薬材を用いて、不純物を含有するコバルト溶液に対して、ｐＨ調整後、液温を調整しながら溶液と沈殿物を時間をかけ撹拌する熟成という操作を加えることによって、コバルトの回収率を維持しながら、不純物の濃度を低減させることができる効率的かつ低コストのコバルト回収方法をなすに至ったものである。
【００１０】
すなわち、本発明は第１に、コバルト（Ｃｏと表すことがある。）を含有し、不純物としてアルミニウム（Ａｌと表すことがある。）と鉄（Ｆｅと表すことがある。）のうちの少なくとも一種を含有する溶液を酸化し、ｐＨを４．０〜５．５に調整後、３０〜９０℃で１２０〜４８０分間熟成を行って固液分離することによってコバルトの回収率向上と不純物濃度の低減を両立することを特徴とするコバルト回収方法を、第２に、前記溶液が硫酸酸性溶液であり、前記酸化が過酸化水素水、過硫酸ソーダ、オゾンおよび空気からなる群から選ばれる少なくとも一種の酸化剤の添加によって行われ、前記ｐＨ調整が苛性ソーダ、消石灰および水酸化カリウムからなる群から選ばれる少なくとも一種のアルカリの添加によって行われる、第１記載のコバルト回収方法を、第３に、前記酸化は銀−塩化銀電極を用いた前記溶液の電位を５００〜９００ｍＶとする、第１または２に記載のコバルト回収方法を、第４に、前記硫酸酸性溶液が硫酸を用いてリチウム二次電池廃材を浸出して得られたコバルト含有溶液である、第２または３に記載のコバルト回収方法を、第５に、前記リチウム二次電池廃材がリチウム二次電池を焙焼し、粉砕して得られた粉末である、第４記載のコバルト回収方法を提供するものである。
【００１１】
【発明の実施の形態】
本発明の実施にあたっては、まず、硫酸溶液内でリチウム二次電池廃材からコバルトを浸出させる。この時の浸出液の温度は特に制限はないが、好ましくは３０℃以上、より好ましくは４０〜９０℃である。また、上記硫酸溶液の硫酸濃度についても特に制限はないが、好ましくは５〜３０ｗｔ％（ｗｔ％を単に％と表す。）、より好ましくは１０〜２５％である。また、リチウム二次電池廃材中のコバルトはリチウム二次電池の焙焼条件により酸化状態が異なり、コバルトが金属状態のものを多く含む廃材ではコバルトの浸出率が悪くなる場合がある。そのような場合は、酸化性ガスを硫酸溶液内に混合することで、廃材中の金属状態のコバルトの溶液内酸化を促進し、硫酸溶液内にイオンとして存在しやすくなると考えられ、あらゆる廃材に対応が可能となる。この酸化性ガスとしては空気、酸素等を用いることができ、経済性を考えれば空気が好ましい。
【００１２】
次に浸出操作後の溶液を濾過し、不溶残渣（炭素成分、金属成分等）と濾液に分離する。この濾液内にはコバルトの他に、不純物としてアルミニウムと鉄のうちの少なくとも一種が含まれている。濾液に酸化剤、例えば過酸化水素水を添加した後、アルカリ、例えば苛性ソーダを添加することによってｐＨを調整する。ここで、酸化剤は過酸化水素水、過硫酸ソーダ、オゾンおよび空気等から選ばれ、アルカリは苛性ソーダ、消石灰および水酸化カリウム等から選ばれる。酸化剤は鉄イオンを２価から３価に酸化するために添加する。この溶液の電位は５００〜９００ｍＶとするのがよい。５００ｍＶ未満であると鉄イオンが十分に酸化されず鉄の除去が不十分となり、一方、９００ｍＶを超すとコバルトイオンが酸化されて中和（ｐＨ調整）時に不純物と共に沈殿する量が増え、コバルト回収率が悪くなる。３価に酸化された鉄イオンはｐＨが４．０以上で水酸化物として完全除去できる。アルミニウムについてはｐＨが４．０以上で鉄と共に沈殿し始めるので調整ｐＨは４．０〜５．５、好ましくは４．５〜５．０である。ただし、このまま濾過に移ると水酸化アルミニウム、水酸化鉄と共に、局部中和で生成された水酸化コバルトが補集され、濾液内へのコバルト回収率が悪化してしまったり、溶液中に残存するアルミニウムが多くなるので、コバルトの回収率と不純物除去のバランスが良くない。
【００１３】
このため、溶液、沈殿を共に温度調整し、撹拌を時間をかけて行う熟成操作を行う。この熟成中には、沈殿内のコバルトは分解され溶液中にイオンの形で溶出し、この時の分解によって生じる水酸イオンが溶液内のアルミニウムイオンと反応し溶液内のアルミニウムを更に低減しているものと思われる。また、水酸化アルミニウムの結晶性が良くなり、コバルトとの分離性が良くなると考えられる。この時、熟成中の温度は３０〜９０℃、好ましくは４０〜８０℃である。Ａｌの除去としては、液中のＡｌ濃度とＣｏ濃度の比（単に、Ａｌ／Ｃｏと表す。）で０．２％以下が好ましく、熟成時間としてはアルミニウムやコバルトの濃度に応じて適正化する必要があり、１２０分間以上を必要とするが、４８０分間以上ではこの効果がほぼ飽和する。熟成終了後、濾過により水酸化アルミニウムと水酸化鉄の混合沈殿とコバルト含有水溶液とを固液分離する。
【００１４】
上記熟成後の濾液は、アルカリ、例えば苛性ソーダを加え液性をアルカリ性にして水酸化コバルトを沈殿とし、液中のリチウム（Ｌｉと表すことがある。）、ナトリウム（Ｎａと表すことがある。）と分離、回収できる。この時のｐＨは７以上、より好ましくは１０以上である。濾過により水酸化コバルトと濾液とを固液分離後、得られた沈殿を水洗することで沈殿物に付着したリチウム、ナトリウム等の水溶性成分が除去でき、コバルト純度を高めることができる。
ここで得られた水酸化コバルトの沈殿は、適当な濃度の硫酸に溶解し、磁性粉等の原料の硫酸コバルトとして使用可能である。
【００１５】
【実施例】
以下に実施例によって本発明をさらに具体的に示すが、本発明の技術的範囲はこの記載によって制限されるものではない。
【００１６】
〔実施例１〕コバルトを３４．９％含有するリチウム二次電池廃材８０ｇを、２０％硫酸水溶液中に投入し、７０℃で３時間浸出した。浸出後、得られた浸出液と不溶解残渣を濾過により分離し、コバルトを含有する硫酸水溶液５００ｍｌ（ｌはリットルを表す。）を得た。この硫酸水溶液内のコバルト濃度は５５．８ｇ／ｌであった。この場合のリチウム二次電池廃材からのコバルトの浸出率は１００％であった。上記のコバルトを含有する硫酸水溶液の組成を表１に示す。
【００１７】
【表１】

【００１８】
上記の硫酸水溶液を２００ｍｌ分取し、３５％過酸化水素水を１ｇ添加した。銀−塩化銀電極を用いてこの添加後の溶液の電位を測定したところ６５０ｍＶであった。液温を５０℃にして１０％苛性ソーダでｐＨを５．０に調整後、撹拌しながら４８０分間熟成し、濾過した。この時点での熟成後の濾液量は３５６ｍｌとなり、コバルトの回収率は９２．６％となった。なお、Ａｌ／Ｃｏは０．０７％であった。上記の熟成後の濾液の組成を表２に示す。
【００１９】
【表２】

【００２０】
上記の濾液にさらに１０％苛性ソーダをｐＨが１０になるまで添加し水酸化コバルト沈殿を得た。この沈殿を１リットルの純水で水洗を行い洗浄後の沈殿を硫酸溶液に溶解させ、硫酸コバルト溶液を２９４ｍｌ得た。得られた水溶液の組成は表３のようになり、最終的なコバルトの収率は９２．６％、純度は９９．１％となり、磁性粉の原料としての硫酸コバルト溶液を得ることができた。
【００２１】
【表３】

【００２２】
〔実施例２〕実施例１で得られた表１に示す硫酸水溶液を１９６ｍｌ分取し３５％過酸化水素水を１ｇ添加した。銀−塩化銀電極を用いてこの添加後の溶液の電位を測定したところ６５０ｍＶであった。液温を５０℃にして１０％苛性ソーダでｐＨを５．０に調整後、撹拌しながら１２０分間熟成し、濾過した。この時点での溶液量は２６４ｍｌとなり、コバルトの回収率は９８．１％となった。なお、Ａｌ／Ｃｏは０．１７％であった。上記の熟成後の濾液の組成を表４に示す。
【００２３】
【表４】

【００２４】
上記以降の操作は実施例1と同様に試験をし、硫酸コバルトの水溶液を３５５ｍｌ得た。得られた水溶液の組成は表５のようになり、最終的なコバルトの収率は９８．１％、純度は９９．４％となり、磁性粉の原料としての硫酸コバルト溶液を得ることができた。
【００２５】
【表５】

【００２６】
〔比較例〕実施例１で得られた表１に示す硫酸水溶液の残り１０４ｍｌを分取し３５％過酸化水素水を１ｇ添加した。銀−塩化銀電極を用いてこの添加後の溶液の電位を測定したところ６５０ｍＶであった。液温を５０℃にして１０％苛性ソーダでｐＨを５．０に調整後、熟成を行わず濾過した。この時点での濾液量は１４１ｍｌとなり、コバルトの回収率は９０．１％となった。また、熟成を行わなかったので溶液内のアルミニウム濃度は前記の両実施例よりも濃度が高い結果となり、Ａｌ／Ｃｏは０．８４％と高いものであった。上記の濾液の組成を表６に示す。
【００２７】
【表６】

【００２８】
上記以降の操作は実施例1と同様に試験をし、硫酸コバルトの水溶液を１４０ｍｌ得た。得られた水溶液の組成は表７のようになり、最終的なコバルトの収率は９０．１％、純度は９８．１％となった。最終的なアルミニウム濃度は０．２９４ｇ／ｌとなった。
【００２９】
【表７】

【００３０】
また、実施例１と同様の硫酸水溶液を得て、熟成時間を１０〜１００分間（試験例５例）、１０００〜１００００分間（試験例１例）とした以外は実施例１と同様に行って熟成後の濾液のＡｌ／Ｃｏを求め、前記の実施例１、実施例２および比較例における熟成後の濾液のＡｌ／Ｃｏとともに図１に示した。熟成時間が１２０分間以上の場合に熟成後の濾液のＡｌ／Ｃｏが目標値の０．２％以下に達すること明らかになった。
【００３１】
【発明の効果】
本発明は、不純物とともにコバルトを含有するリチウム二次電池廃材からコバルトを回収する際に、苛性ソーダ等のアルカリでのｐＨ調整後に温度を調整しながら溶液と沈殿物を時間をかけ撹拌する熟成という操作を加えることによって、中和時のコバルトの損失をなくしコバルトの回収率を維持しながら、不純物の濃度を低減させることができるものであり、さらには、使用する薬材が硫酸、苛性ソーダ等と汎用的で比較的廉価なものであって、コバルトの回収を効率的かつ経済的に行うことができるという効果を奏する。
【図面の簡単な説明】
【図１】熟成時間（分）と熟成後の濾液のＡｌ／Ｃｏの比（％）との関係図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering cobalt from a cobalt solution containing impurities, and more particularly to a method for recovering cobalt from waste lithium secondary battery materials.
[0002]
[Prior art]
Lithium secondary batteries are well known as lightweight, high electric capacity batteries and are used in large quantities as secondary batteries for various portable devices. A lithium cobalt composite oxide containing a valuable metal cobalt as a positive electrode active material is used for the positive electrode of the lithium secondary battery. From the viewpoint of resource recycling, it is significant to recover the valuable metal cobalt from the lithium cobalt composite oxide so that it can be reused.
[0003]
As a method for recovering cobalt from such a lithium secondary battery, the following method has been proposed. That is, the used lithium secondary battery is roasted, crushed and sieved, and then the secondary sieve is subjected to secondary roasting, followed by treatment with acid, and a pH of 4 while blowing oxidizing gas into the treatment liquid. There is a method in which after adjusting to ˜5.5 and filtering, an alkali is added to the filtrate and filtered to collect a precipitate (see, for example, Patent Document 1).
[0004]
In addition, lithium ion battery waste containing cobalt components was leached with inorganic acid, the molar ratio of phosphorus and aluminum ions in the leached aqueous solution was adjusted to 0.6 to 1.2, the oxidation potential was 500 mV or more, and iron ions were Oxidize, adjust the pH of the aqueous solution to 3.0-4.5, precipitate and remove impurity metals, obtain a purified solution, add oxalic acid to this purified solution to obtain cobalt oxalate or this purified There is a method in which the pH of the solution is adjusted to 6 to 10 to obtain cobalt hydroxide or cobalt carbonate as a precipitate (for example, see Patent Document 2).
[0005]
Further, a secondary battery waste material made of an electrode material containing a cobalt compound or a metal foil coating waste material in which such an electrode material is coated on a metal foil is obtained from an organic solution containing alkylphosphoric acid and water containing hydrogen peroxide. There is a method for recovering cobalt from secondary battery waste material, for example, by contacting with an emulsion extractant to selectively elute cobalt in the secondary battery waste material into an organic solution and recovering cobalt from the resulting organic solution (for example, , See Patent Document 3).
[0006]
[Patent Document 1]
JP-A-7-207349 [Patent Document 2]
Japanese Patent Laid-Open No. 11-6020 [Patent Document 3]
Japanese Patent Laid-Open No. 9-111360
[Problems to be solved by the invention]
1. Extraction of problems in conventional technology
(1) When recovering valuable metals industrially, the balance between economy and quality is important. For example, the recovery of cobalt by the solvent extraction method involves complicated operation and equipment depending on the cost of the solvent used and the number of extraction stages. That's not economical.
(2) In a cobalt-containing solution containing aluminum and iron as impurities, after adding hydrogen peroxide water, the pH is adjusted with caustic soda, and the impurities are removed by precipitation. When adjusted to cobalt, cobalt is also co-precipitated and the recovery rate of cobalt deteriorates. On the other hand, when the pH is adjusted to ensure the cobalt recovery rate, the impurity concentration may not be reduced. That is, there was a problem in the balance between the cobalt recovery rate and the reduction in impurity concentration.
[0008]
2. Problem to be Solved The present invention provides a method for recovering cobalt, which is balanced in reducing the cobalt recovery rate and impurity concentration during pH adjustment as described above in an economical method using general-purpose chemicals and the like. Is.
[0009]
[Means for Solving the Problems]
The present inventors use a general and relatively inexpensive chemical material such as sulfuric acid and caustic soda, adjust the pH of the cobalt solution containing impurities, and adjust the solution temperature and precipitate for a while. By adding an operation of aging with stirring, an efficient and low-cost cobalt recovery method that can reduce the concentration of impurities while maintaining the cobalt recovery rate has been achieved.
[0010]
That is, the present invention first includes cobalt (sometimes referred to as Co), and contains at least one of aluminum (sometimes represented as Al) and iron (sometimes represented as Fe) as impurities. After oxidizing the solution containing one species and adjusting the pH to 4.0 to 5.5, aging at 30 to 90 ° C. for 120 to 480 minutes and solid-liquid separation to improve the recovery rate of cobalt and improve the impurity concentration Cobalt recovery method characterized by achieving both reductions, secondly, the solution is an acidic solution of sulfuric acid, and the oxidation is at least one selected from the group consisting of hydrogen peroxide, sodium persulfate, ozone and air First, wherein the pH adjustment is performed by adding at least one alkali selected from the group consisting of caustic soda, slaked lime, and potassium hydroxide. Third, the cobalt recovery method is the cobalt recovery method according to the first or second aspect, in which the potential of the solution using a silver-silver chloride electrode is 500 to 900 mV. The fourth is the sulfuric acid acidity. The cobalt recovery method according to 2 or 3, wherein the solution is a cobalt-containing solution obtained by leaching lithium secondary battery waste using sulfuric acid, and fifth, the lithium secondary battery waste is lithium secondary The cobalt recovery method according to the fourth aspect, which is a powder obtained by baking and pulverizing a battery.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In carrying out the present invention, first, cobalt is leached from the lithium secondary battery waste in a sulfuric acid solution. The temperature of the leachate at this time is not particularly limited, but is preferably 30 ° C or higher, more preferably 40 to 90 ° C. The sulfuric acid concentration of the sulfuric acid solution is not particularly limited, but is preferably 5 to 30 wt% (wt% is simply expressed as%), more preferably 10 to 25%. Moreover, the oxidation state of cobalt in the lithium secondary battery waste material varies depending on the roasting conditions of the lithium secondary battery, and the waste material containing a large amount of cobalt in the metal state may deteriorate the leaching rate of cobalt. In such a case, mixing oxidizing gas into the sulfuric acid solution promotes oxidation of cobalt in the metallic state in the waste material and is likely to exist as ions in the sulfuric acid solution. Correspondence becomes possible. As this oxidizing gas, air, oxygen, or the like can be used, and air is preferable in consideration of economy.
[0012]
Next, the solution after the leaching operation is filtered and separated into an insoluble residue (carbon component, metal component, etc.) and a filtrate. In addition to cobalt, this filtrate contains at least one of aluminum and iron as impurities. The pH is adjusted by adding an oxidant such as aqueous hydrogen peroxide to the filtrate and then adding an alkali such as caustic soda. Here, the oxidizing agent is selected from hydrogen peroxide, sodium persulfate, ozone, air, and the like, and the alkali is selected from caustic soda, slaked lime, potassium hydroxide, and the like. The oxidizing agent is added to oxidize iron ions from divalent to trivalent. The potential of this solution is preferably 500 to 900 mV. If it is less than 500 mV, the iron ions are not sufficiently oxidized and the removal of iron becomes insufficient. On the other hand, if it exceeds 900 mV, the cobalt ions are oxidized and the amount precipitated with impurities during neutralization (pH adjustment) increases, thereby recovering cobalt. The rate gets worse. Trivalent oxidized iron ions can be completely removed as hydroxides at a pH of 4.0 or higher. About aluminum, since pH begins to precipitate with iron at pH 4.0 or more, adjustment pH is 4.0-5.5, Preferably it is 4.5-5.0. However, if it moves to filtration as it is, cobalt hydroxide produced by local neutralization is collected together with aluminum hydroxide and iron hydroxide, and the cobalt recovery rate in the filtrate deteriorates or remains in the solution. Since the amount of aluminum increases, the balance between cobalt recovery and impurity removal is not good.
[0013]
For this reason, the aging operation is performed in which the temperature of both the solution and the precipitate is adjusted and stirring is performed over time. During this aging, the cobalt in the precipitate is decomposed and eluted in the form of ions in the solution, and the hydroxide ions generated by the decomposition at this time react with the aluminum ions in the solution to further reduce the aluminum in the solution. It seems that there is. Moreover, it is thought that the crystallinity of aluminum hydroxide is improved and the separability from cobalt is improved. At this time, the temperature during aging is 30 to 90 ° C, preferably 40 to 80 ° C. The removal of Al is preferably 0.2% or less in terms of the ratio of Al concentration to Co concentration (simply expressed as Al / Co) in the liquid, and the aging time is optimized according to the concentration of aluminum or cobalt. Necessary, 120 minutes or more are required, but this effect is almost saturated at 480 minutes or more. After completion of aging, the mixed precipitate of aluminum hydroxide and iron hydroxide and the cobalt-containing aqueous solution are separated into solid and liquid by filtration.
[0014]
The filtrate after the above aging is made alkaline by adding caustic soda, for example, so that the liquidity becomes alkaline and cobalt hydroxide is precipitated, and lithium (sometimes expressed as Li) and sodium (sometimes expressed as Na) in the liquid. Can be separated and recovered. The pH at this time is 7 or more, more preferably 10 or more. After the cobalt hydroxide and the filtrate are separated into solid and liquid by filtration, the resulting precipitate is washed with water, so that water-soluble components such as lithium and sodium attached to the precipitate can be removed, and the cobalt purity can be increased.
The obtained cobalt hydroxide precipitate is dissolved in sulfuric acid having an appropriate concentration, and can be used as a raw material cobalt sulfate such as magnetic powder.
[0015]
【Example】
The present invention will be described more specifically with reference to the following examples. However, the technical scope of the present invention is not limited by this description.
[0016]
[Example 1] 80 g of lithium secondary battery waste material containing 34.9% cobalt was put into a 20% sulfuric acid aqueous solution and leached at 70 ° C for 3 hours. After leaching, the obtained leachate and insoluble residue were separated by filtration to obtain 500 ml of a sulfuric acid aqueous solution containing cobalt (l represents liter). The cobalt concentration in this aqueous sulfuric acid solution was 55.8 g / l. In this case, the leaching rate of cobalt from the lithium secondary battery waste was 100%. Table 1 shows the composition of the sulfuric acid aqueous solution containing cobalt.
[0017]
[Table 1]

[0018]
200 ml of the above sulfuric acid aqueous solution was collected, and 1 g of 35% hydrogen peroxide solution was added. When the potential of the solution after this addition was measured using a silver-silver chloride electrode, it was 650 mV. After adjusting the liquid temperature to 50 ° C. and adjusting the pH to 5.0 with 10% caustic soda, the mixture was aged with stirring for 480 minutes and filtered. The amount of filtrate after aging at this time was 356 ml, and the recovery rate of cobalt was 92.6%. Al / Co was 0.07%. The composition of the filtrate after the aging is shown in Table 2.
[0019]
[Table 2]

[0020]
Further, 10% caustic soda was added to the above filtrate until the pH reached 10 to obtain a cobalt hydroxide precipitate. This precipitate was washed with 1 liter of pure water, and the washed precipitate was dissolved in a sulfuric acid solution to obtain 294 ml of a cobalt sulfate solution. The composition of the obtained aqueous solution was as shown in Table 3. The final cobalt yield was 92.6% and the purity was 99.1%, and a cobalt sulfate solution as a raw material for magnetic powder could be obtained. .
[0021]
[Table 3]

[0022]
Example 2 196 ml of the sulfuric acid aqueous solution shown in Table 1 obtained in Example 1 was collected, and 1 g of 35% hydrogen peroxide solution was added. When the potential of the solution after this addition was measured using a silver-silver chloride electrode, it was 650 mV. The liquid temperature was adjusted to 50 ° C. with 10% caustic soda, and the pH was adjusted to 5.0, followed by aging for 120 minutes with stirring and filtration. The amount of solution at this point was 264 ml, and the recovery rate of cobalt was 98.1%. Al / Co was 0.17%. The composition of the filtrate after the aging is shown in Table 4.
[0023]
[Table 4]

[0024]
The subsequent operations were tested in the same manner as in Example 1 to obtain 355 ml of an aqueous solution of cobalt sulfate. The composition of the obtained aqueous solution was as shown in Table 5. The final cobalt yield was 98.1% and the purity was 99.4%, and a cobalt sulfate solution as a raw material for magnetic powder could be obtained. .
[0025]
[Table 5]

[0026]
Comparative Example The remaining 104 ml of the sulfuric acid aqueous solution shown in Table 1 obtained in Example 1 was collected, and 1 g of 35% hydrogen peroxide solution was added. When the potential of the solution after this addition was measured using a silver-silver chloride electrode, it was 650 mV. The liquid temperature was adjusted to 50 ° C. and the pH was adjusted to 5.0 with 10% sodium hydroxide, followed by filtration without aging. At this point, the filtrate amount was 141 ml, and the cobalt recovery rate was 90.1%. Further, since aging was not performed, the aluminum concentration in the solution was higher than those in both of the above examples, and Al / Co was as high as 0.84%. The composition of the filtrate is shown in Table 6.
[0027]
[Table 6]

[0028]
The subsequent operations were tested in the same manner as in Example 1 to obtain 140 ml of an aqueous solution of cobalt sulfate. The composition of the obtained aqueous solution was as shown in Table 7. The final cobalt yield was 90.1% and the purity was 98.1%. The final aluminum concentration was 0.294 g / l.
[0029]
[Table 7]

[0030]
Moreover, it carried out similarly to Example 1 except having obtained the sulfuric acid aqueous solution similar to Example 1, and having made the ripening time into 10 to 100 minutes (Test Example 5 examples) and 1000 to 10,000 minutes (Test Example 1 examples). The Al / Co of the filtrate after aging was determined and shown in FIG. 1 together with the Al / Co of the filtrate after aging in Examples 1, 2 and Comparative Examples. It was found that when the aging time was 120 minutes or longer, the Al / Co in the filtrate after aging reached 0.2% or less of the target value.
[0031]
【The invention's effect】
In the present invention, when recovering cobalt from lithium secondary battery waste containing cobalt together with impurities, an operation of aging to stir the solution and the precipitate over time while adjusting the temperature after adjusting the pH with alkali such as caustic soda In addition, it is possible to reduce the concentration of impurities while eliminating the loss of cobalt during neutralization and maintaining the recovery rate of cobalt. Furthermore, the chemicals used are general-purpose such as sulfuric acid and caustic soda. Therefore, the cobalt can be recovered efficiently and economically.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the aging time (minutes) and the Al / Co ratio (%) of the filtrate after aging.

Claims

A sulfuric acid acidic solution containing cobalt and containing aluminum and iron as impurities is oxidized by addition of at least one oxidizing agent selected from the group consisting of hydrogen peroxide, sodium persulfate, ozone and air , caustic soda, slaked lime and After adjusting the pH to 4.0 to 5.5 by adding at least one alkali selected from the group consisting of potassium hydroxide, the mixture is aged with stirring at 30 to 90 ° C. for 120 to 480 minutes to perform solid-liquid separation. The cobalt recovery method is characterized in that the impurities are removed by the following step, alkali is added to the obtained liquid to adjust the pH to 7 or higher to precipitate cobalt hydroxide, and the precipitate obtained by solid-liquid separation is washed with water.

A sulfuric acid acidic solution containing cobalt and containing aluminum and iron as impurities is oxidized by addition of at least one oxidizing agent selected from the group consisting of hydrogen peroxide, sodium persulfate, ozone and air , caustic soda, slaked lime and After adjusting the pH to 4.0 to 5.5 by adding at least one alkali selected from the group consisting of potassium hydroxide, the mixture is aged with stirring at 30 to 90 ° C. for 120 to 480 minutes to perform solid-liquid separation. Then, alkali is added to the resulting solution to adjust the pH to 7 or more to precipitate cobalt hydroxide, the precipitate obtained by solid-liquid separation is washed with water, and the washed precipitate is further added to a sulfuric acid solution. A cobalt recovery method comprising dissolving and obtaining a cobalt sulfate solution.

The cobalt recovery method according to claim 1 or 2, wherein the oxidation is performed by setting the potential of the solution using a silver-silver chloride electrode to 500 to 900 mV.

The cobalt recovery method according to any one of claims 1 to 3, wherein the sulfuric acid acidic solution is a cobalt-containing solution obtained by leaching lithium secondary battery waste using sulfuric acid.

The cobalt recovery method according to claim 4 , wherein the lithium secondary battery waste is a powder obtained by roasting and pulverizing a lithium secondary battery.