JP2005041711A - Iron oxide powder and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low arsenic content low cadmium content iron oxide powder produced from a solution containing iron, arsenic, and cadmium, such as a neutralized liquid produced from a zinc leach residue as a by-product in, e.g., a wet-process zinc refining and to provide a method for producing the same. <P>SOLUTION: The method comprises adjusting a neutralized liquid 16 containing iron, arsenic, and cadmium to 60°C or lower, adding a zinc powder 39 as a reducing agent to the liquid to adjust its oxidation reduction potential to -500 mV or lower, adding sulfuric acid 42 to the resultant liquid to adjust it to a pH of 4.0 or lower, separating a first solution from the obtained solid/liquid mixture, separating the solid/liquid mixture obtained by adding an acid to the first solution and leaving the resulting mixture in an oxidizing atmosphere into a second precipitate being an iron residue (jarosite compound) 18 and a second solution, adding water 44 to the second precipitate to subject it to washing 58 to form a washed iron residue 19, subjecting the iron residue 19 to roasting 59 to form an iron oxide powder material 20, and subjecting this to washing 60, drying 61 and pulverization 62 to obtain an iron oxide powder 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１８】
まず、表１のその組成を示す中和液１６へ、表２に示す２水準の条件で、反応温度の制御と、亜鉛粉末の添加とをおこなった。
【００１９】
【表２】

【００２０】
このときの中和液１６の挙動を、図２を参照しながら説明する。
図２は、縦軸に中和液１６中のカドミウム濃度を採り、横軸に反応時間を採ったグラフである。当該グラフにおいて、水準１は破線で、水準２は実線で示した。尚、添加した亜鉛粉末濃度が２ｇ／ｌのとき、中和液１６の酸化還元電位は−５００ｍＶ以下、ｐＨは３．０となり、添加した亜鉛粉末濃度が３ｇ／ｌのとき、酸化還元電位は−７００ｍＶ以下、ｐＨは４．０となった。
【００２１】
結果は図２に示すように、水準１では、反応時間の進行とともに、一旦は液中のカドミウム濃度は下がるが再び上昇する。これは、カドミウムが、一旦は澱物となるが再び液中に溶出してしまうためであると考えられる。これに対し、水準２では、カドミウム濃度は時間とともに減少する。これは、一旦、澱物となったカドミウムが、再び溶解するのを抑制できるためであると考えられる。
【００２２】
このことから、本発明者らは、中和液１６中の酸化還元電位を−７００ｍＶ以下となるように亜鉛粉末３９の添加量を調整し、さらには液温を制御することで、カドミウムを中和液１６から除去でき、カドミウム含有量の低い脱カドミウム液１７を得られることに想到した。そして、カドミウム除去が可能であるなら、中和液１６中にて、カドミウムと類似の挙動をとる砒素の除去も同時に可能であることに想到した。
【００２３】
２．［液温制御の検討］
表１に記載したものと同様の中和液１６を用い、反応温度条件を、２０℃、３０℃、４０℃の３水準とし、中和液１６からのカドミウムの除去を行った。尚、亜鉛粉末の添加量は３ｇ／ｌとし、酸化還元電位は−７００ｍＶ以下となった。
このときの、中和液１６の挙動を図３に示す。但し、図３は、図２と同様のグラフであり、２０℃の水準を一点鎖線で、３０℃の水準を実線で、４０℃の水準を２点鎖線で示した。
上述の結果より、各温度においてもカドミウム濃度が反応時間とともに減少することがわかり、反応時の液温は、６０℃以下が好ましく、さらには２０〜４０℃が適温であることが判明した。そして、この場合も、中和液１６中にて、カドミウムと類似の挙動をとる砒素の除去も同時に可能であることに想到した。
【００２４】
３．［酸化還元電位制御の検討］
表１に記載したものと同様の中和液１６を用い、亜鉛粉末添加濃度を制御することで酸化還元電位を−５００ｍＶおよび−８００ｍＶの２水準とし、中和液１６からのカドミウムの除去を行った。尚、液温は６０℃とした。
このときの、中和液１６の挙動を図４に示す。但し、図４は、図２と同様のグラフであり−５００ｍＶの水準を一点鎖線で、−８００ｍＶの水準を実線で示した。
【００２５】
図４から明らかなように、酸化還元電位が−５００ｍＶのとき、カドミウムの濃度は反応時間の経過と共に下がり、６０分後以降はほぼ一定値となった。一方、酸化還元電位が−８００ｍＶでは、その濃度が反応時間の経過と共に下がり、遂には、ほぼ０になることが判明した。この結果から、酸化還元電位が−８００ｍＶであれば十分に脱カドミウム効果が得られることがわかり、少なくとも酸化還元電位が−５００ｍＶ以下であることが好ましいと思われる。そして、この場合も、中和液１６中にて、カドミウムと類似の挙動をとる砒素の除去も同時に可能であることに想到した。
【００２６】
４．［ｐＨ制御の検討］
表１に記載したものと同様の中和液１６を用い、ｐＨの水準を２．０、３．０、４．０の３水準とし、中和液１６からのカドミウムの除去を行った。尚、液温は６０℃とし、酸化還元電位は−５００ｍＶ以下とした。
このときの、中和液１６の挙動を図５に示す。但し、図５は、図２と同様のグラフでありｐＨ２．０の水準を一点鎖線で、ｐＨ３．０の水準を実線で、ｐＨ４．０の水準を２点鎖線で示した。
【００２７】
図５から明らかなように、ｐＨが２．０では、カドミウムの濃度は、反応時間の経過と共に、一旦、減少するが、またすぐに濃度が上昇してしまう。ｐＨが３．０では、その濃度が反応時間の経過と共に減少し１０ｍｇ／ｌ程度までは減少するが、それ以降は、反応時間の経過と共にその濃度が上昇してしまう。一方、ｐＨ４．０では、反応時間の経過と共に、その濃度がほぼ０になることから、ｐＨは３．０以上であれば十分に脱カドミウム効果が得られることがわかり、さらにはｐＨが４．０以上であればさらに効果的である。そして、この場合も、中和液１６中にて、カドミウムと類似の挙動をとる砒素の除去も同時に可能であることに想到した。
【００２８】
ここで再び図１に戻り、上述した、１〜４の検討事項を要約する。
亜鉛粉末３９は、主に中和液１６の酸化還元電位を調整するために用いるが、その添加量は、中和液１６の酸化還元電位を−５００ｍＶ以下とする添加量が好ましく、−８００ｍＶ以下とする添加量がさらに好ましい。中和液１６の酸化還元電位を−５００ｍＶ以下とすることで、カドミウム、砒素沈澱除去及び澱物４１の中和液１６への再溶解を防ぐことができる。特に、酸化還元電位を−８００ｍＶ以下とすると、さらにカドミウム、砒素の沈澱除去に効果的である。
【００２９】
還元５６において中和液１６のｐＨは、２〜４に調整することが好ましい。これはカドミウム、砒素が、中和液１６へ再溶解するのを抑制するためであり、特に、ｐＨ３〜４であるとカドミウム、砒素の除去に効果的である。
反応時おける液温は、６０℃以下が好ましいが、特に、２０〜４０℃が好ましい。これは液温が高すぎると、一度は沈澱したカドミウム、砒素が再溶解するためであり、液温が低すぎると、反応の進行が遅いためである。
この処理後、得られた固液混合体からカドミウム、砒素を含んだ第１の澱物４１を固液分離し、脱カドミウム、脱砒素を終えた第１の溶液である脱カドミウム溶液１７を得る。ここで、本発明に係る第１の工程を完了する。
【００３０】
次に、本発明に係る第２の工程について説明する。
本発明に係る第１の溶液である脱カドミウム溶液１７は、含有する亜鉛と鉄とを分離するため脱鉄５７工程を経る。
本発明者らは、この脱鉄５７工程において、脱カドミウム溶液１７中の遊離酸の濃度を規定することで、亜鉛と鉄との溶解度差により鉄を分離することができることに想到した。ここで、遊離酸濃度の検討について説明する。
【００３１】
５．［遊離酸濃度の検討］
表１に記載したものと同様の中和液１６を用い、遊離酸の濃度の水準を１０ｇ／ｌ、３０ｇ／ｌの２水準とし、亜鉛と鉄との分離について検討した。尚、液温は１２０℃とした。尚、このとき添加する酸として硫酸を用いると、鉄と適宜な形成して澱物を形成するので好ましい。
この結果を表３に示す。遊離酸濃度が１０ｇ／ｌの場合は、鉄残渣中の亜鉛は８０００ｐｐｍ、鉄は６８ｗｔ％であり、遊離酸濃度が３０ｇ／ｌの場合は、亜鉛は１２００ｐｐｍ、鉄は７０ｗｔ％であった。すなわち、遊離酸濃度を適宜に設定することで、亜鉛と鉄とを分離できることが判明した。
【００３２】
【表３】

【００３３】
ここで、再び図１に戻り、５の検討事項を要約する。
例えばオートクレーブを用いて、硫酸４２を脱カドミウム溶液１７に添加して遊離酸濃度を１０〜３０ｇ／ｌ程度に調整し、反応温度を１２０℃程度、雰囲気を酸素分圧を０．３ＭＰａ程度の酸化性雰囲気とすることで、鉄と硫酸との化合物を形成させて、本発明に係る第２の澱物である鉄残渣１８を生成させることが好ましい。遊離酸濃度を３０ｇ／ｌ以下とするのは、遊離酸濃度が高いと亜鉛の脱カドミウム溶液１７への溶解度が上がり、亜鉛との分離性が低下するためである。鉄残渣１８は、酸化鉄や水酸化鉄等の種々のジャロサイト化合物の混合物である。ここで、得られた固液混合体から、ろ液４３を分離し、種々のジャロサイト化合物である鉄残渣１８を回収して本発明に係る第２の工程を完了する。尚、ろ液４３は、亜鉛の製錬工程へ進めることができる。
【００３４】
次に、本発明に係る第３の工程を説明する。
本発明に係る第２の澱物である鉄残渣１８は、そのままでは、酸や金属イオンが付着しているため、それらを洗い落とすため、水４４等により洗浄５８する。水４４は、塩素を含まない用水が好ましい。塩素が含まれる水では鉄残渣１８に塩素分が付着するため、酸化鉄粉の成分に影響を与えるためである。水４４の添加は、鉄残渣１８がリパルプできる程度よい。得られた固液混合体から、ろ液４５を除去するための固液分離と水４４の添加とを繰り返し、本発明に係る第３の澱物である洗浄された鉄残渣１９を得る。こうして、本発明に係る第３の工程を完了する。
【００３５】
洗浄された鉄残渣１９の成分の多くは酸化鉄であるが、酸化鉄としての酸化状態が不充分である場合は、さらに酸化処理を行うために焙焼５９を施す。焙焼５９は、焙焼炉などを用いて、温度７００℃以上にて酸素含有の酸化性ガス雰囲気中にて行えば良い。この焙焼５９により、組成としては９９．９％以上の酸化鉄粉材料２０が得られる。この酸化鉄粉材料２０が、酸化鉄粉２３の原材となる。ここで得た酸化鉄粉材料２０は、後工程での粉砕により用途に応じて粒径を変えこともでき、粒径を問わない工程への材料として用いることができる。
【００３６】
焙焼工程を経た酸化鉄粉材料２０は、前述の水洗工程と同様に、水４６により洗浄６０処理し、澱物２１とろ液４７とに分離後、澱物２１を乾燥６１して乾燥物２２とし、所望の粒径にするため粉砕機等により粉砕６２して、酸化鉄粉２３を得る。
尚、本実施の形態例の説明において、鉄、砒素およびカドミウムを含む原料溶液として、亜鉛精鉱を酸化処理した焼鉱に酸を加えて亜鉛浸出を行って得られた浸出液を用いた場合を例としたが、本発明は、これに限られるものではなく、種々の鉄、砒素および／またはカドミウムを含む溶液に適用することができる。
【００３７】
【実施例】
以下、実施例を参照しながら、本発明をより具体的説明する。
（実施例１）
硫化鉱からの亜鉛精鉱を酸化焙焼して亜鉛焼鉱とし、ついで硫酸により酸浸出し、浸出液をオートクレーブで温度１１０℃に加熱し、さらに亜硫酸ガス雰囲気下において亜鉛と鉄を溶解させ、難溶解である銅、貴金属、鉛などを残渣として浸出ろ液と分離する。
この浸出ろ液において、酸濃度及び銅イオン濃度を調整しながら亜鉛末等の還元剤で還元される砒素等の不純物を沈澱させ低砒素液と残渣に固液分離する。次にこの低砒素液に多く含まれる遊離硫酸をカルシウム塩によりｐＨを４に中和した中和液を１ｍ^３（１，０００ｌ）採取した。このときの中和液の液組成例を、表４に示す。
【００３８】
【表４】

【００３９】
組成は、砒素１ｍｇ／ｌ、カドミウム ４７６ｍｇ／ｌ、亜鉛 ８３ｍｇ／ｌ、鉄 ４６ｇ／ｌ、硫黄 ７７ｇ／ｌ、カルシウム ５５７ｍｇ／ｌｍ、マンガン４ｇ／ｌであった。なお、分析は化学分析を用い、以下同様な分析手法によった。
この中和液に、中和液に対して亜鉛粉により酸化還元電位が−８００ｍＶ以下になるように３．０ｇ／ｌの配合量で添加した。また硫酸を添加することで、ｐＨを４．０となるように液を調整しながら、液温を３０℃とし、９０分間の反応を行い、還元工程を行った。
次いで、液中に発生した澱物と脱カドミウム液との固液分離を行った。
【００４０】
これを繰り返し、液量が約１５ｍ^３となるまで実施した。このときの脱カドミウム液の組成測定例を、表５に示す。
【００４１】
【表５】

【００４２】
組成は、砒素 未検出（１ｍｇ／ｌ以下）、カドミウム 未検出（１ｍｇ／ｌ以下）、Ｚｎ ６５ｇ／ｌ、Ｆｅ ３７ｇ／ｌ、Ｓ ６２ｇ／ｌ、Ｃａ ４１５ｍｇ／ｌ、マンガン １ｍｇ／ｌであった。
【００４３】
この液に硫酸を添加し、遊離酸濃度を３０ｇ／ｌ以上とした。そして、この遊離酸濃度を維持しながらオートクレーブにて液温を１２０℃とし、雰囲気を酸素分圧ＰＯ_２０．３ＭＰａとし、２時間の反応を行った。次いで、固液分離をおこない鉄残渣を得た。
【００４４】
得られた鉄残渣に水を加えてリパルプし、固液分離することで、鉄残渣の水洗浄を行った。この水洗浄後の鉄残渣の組成測定例、及びＢＥＴ法により測定した比表面積を、表６に示す。
【００４５】
【表６】

【００４６】
鉄残渣の組成は、乾燥状態で、Ｆｅ_２Ｏ_３ ４９ｗｔ％、砒素 未検出（１ｐｐｍ以下）、カドミウム 未検出（１ｐｐｍ以下）、Ｚｎ ７３０ｐｐｍ、Ｓ １３２２００ｐｐｍ、Ｍｎ １８ｐｐｍ、Ｃｌ 未検出（１０ｐｐｍ以下）であった。また、ＢＥＴ法により測定した比表面積は０．５９ｍ^２／ｇであった。
【００４７】
水洗浄後の残渣を焙焼炉に投入し、焙焼温度を９００℃で４時間、雰囲気を大気として酸化させ、酸化鉄粉材料を得た。この酸化鉄粉材料の組成例、及びＢＥＴ法により測定した比表面積を、表７に示す。
【００４８】
【表７】

【００４９】
酸化鉄粉材料の組成例は乾燥状態で、Ｆｅ_２Ｏ_３ ９９．９６ｗｔ％、砒素 未検出（１ｐｐｍ以下）、カドミウム 未検出（１ｐｐｍ以下）、Ｚｎ １４００ｐｐｍ、Ｓ １３６ｐｐｍ、Ｍｎ ２１ｐｐｍ、Ｃｌ 未検出（１０ｐｐｍ以下）、という純度の高い酸化鉄粉材料が得られた。特に、砒素、カドミウム、Ｍｎ、Ｃｌは低濃度であった。また、ＢＥＴ法により測定した比表面積は０．６ｍ^２／ｇであった。
【００５０】
酸化鉄粉材料へ水を添加し、リパルプ後、固液分離することにより水洗浄を行った。水洗浄後の残渣を乾燥し、乾燥後に粉砕機へ投入して粉砕し、精製された酸化鉄粉が得られた。粉砕は、振動ミルで行い、ボール充填率７０％にて６０分間実施した。
得られた精製された酸化鉄粉の組成例、及びＢＥＴ法により測定した比表面積を、表８に示す。
【００５１】
【表８】

【００５２】
精製された酸化鉄粉の組成は、乾燥状態で、Ｆｅ_２Ｏ_３ ９９．９６ｗｔ％、砒素 未検出（１ｐｐｍ以下）、カドミウム 未検出（１ｐｐｍ以下）、Ｚｎ １４００ｐｐｍ、Ｓ １３６ｐｐｍ、Ｍｎ ２１ｐｐｍ、Ｃｌ 未検出（１０ｐｐｍ以下）であった。また、ＢＥＴ法により測定した比表面積は２．３６ｍ^２／ｇであった。
当該酸化鉄粉の製造方法によれば、純度を保持したまま粒度を制御でき、純度が高く、より細かい酸化鉄粉を得ることが可能となった。
【００５３】
【発明の効果】
以上詳述したように、本発明は、鉄、砒素およびカドミウムを含む溶液から酸化鉄粉を製造する方法であって、
前記溶液を６０℃以下とし、還元剤を添加し前記溶液の酸化還元電位を−５００ｍＶ以下とした後に、酸を添加してｐＨを４以下に調整して得られた固液混合体から、第１の溶液を分離する第１の工程と、
前記第１の溶液に酸を添加し、酸化性雰囲気下において加熱して得られた固液混合体から、第２の澱物を分離する第２の工程と、
前記第２の澱物に水を添加して得られた固液混合体から、第３の澱物を分離する第３の工程と、を有する酸化鉄粉の製造方法であり、当該製造方法により、鉄、砒素およびカドミウムを含む溶液から、砒素、カドミウムの含有量が少ない酸化鉄粉を製造することができた。
【図面の簡単な説明】
【図１】亜鉛精鉱の浸出液から精製された酸化鉄粉を得るまでの工程フロー図である。
【図２】反応温度条件および酸化還元電位を変化させた時の、中和液の挙動を示したグラフである。
【図３】反応温度条件を変化させた時の、中和液の挙動を示したグラフである。
【図４】酸化還元電位を変化させた時の、中和液の挙動を示したグラフである。
【図５】ｐＨを変化させた時の、中和液の挙動を示したグラフである。
【符号の説明】
１７．脱カドミウム液（第１の溶液）
１８．鉄残査（第２の澱物）
１９．洗浄された鉄残査（第３の澱物）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to iron oxide powder and a method for producing the same.
[0002]
[Prior art]
When wet zinc smelting is performed, zinc leaching residue is produced as a by-product. This zinc leaching residue is leached with an acid in a reducing atmosphere, the resulting leachate is pre-neutralized, then a neutralizing agent is further added to the pre-neutralization solution, and an oxidizing gas is blown into a solid liquid. To separate. This oxidizing gas blowing and solid-liquid separation oxidize a part of ferrous iron in the neutralized liquid, and at the same time, part of aluminum (Al), silicon (Si) and arsenic as iron and coprecipitate Separate from liquid. Then, zinc powder is added to the solution after separating the coprecipitate in the presence of copper ions, so that arsenic in the solution is precipitated in the form of copper arsenide, and at a temperature of 150 ° C. or less, an oxidizing gas and Patent Document 1 proposes a production method in which iron in a solution is made to be iron hydroxide and then oxidized to obtain iron oxide.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 62-21717
On the other hand, applications of the manufactured iron oxide powder include applications such as cement, ferrite, pigment, and catalyst. In recent years, it has been suggested that the amount of impurities contained in iron oxide is small due to environmental considerations, especially mercury (Hg), arsenic (As), cadmium (Cd), lead (Pb) and other environmentally regulated substances, and chlorine ( An iron oxide with less Cl) component is desired.
However, although the method according to the prior art can sufficiently remove mercury, lead, and chlorine, it has become difficult for cadmium and arsenic to meet recent strict requirements.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned demands, for example, from a solution containing iron, arsenic, and cadmium, such as a neutralized solution produced from a zinc leaching residue by-produced by wet zinc smelting. The present invention provides a method for producing iron oxide powder having a low content of arsenic and cadmium, and an iron oxide powder having a low content of arsenic and cadmium.
[0006]
[Means for Solving the Problems]
As a result of studies conducted by the present inventors to solve the above-mentioned problems, when producing iron oxide powder from an acidic solution of iron containing arsenic and cadmium, the temperature, oxidation-reduction potential, and pH of the solution are determined. By controlling, a method of selectively removing arsenic and cadmium and a method of preventing re-dissolution of cadmium once removed by this method are created, and further, this method is carried out, and the conventional method removes it. It was found that manganese in iron oxide powder, which was difficult to do, could be reduced. As a result, iron oxide powder with few impurities could be obtained.
That is, the present invention has the following configuration.
[0007]
(Configuration 1) A method for producing iron oxide powder from a solution containing iron, arsenic and cadmium,
From the solid-liquid mixture obtained by adjusting the solution to 60 ° C. or lower, adding a reducing agent to set the oxidation-reduction potential of the solution to −500 mV or lower, and adjusting the pH to 4 or lower by adding an acid, A first step of separating one solution;
A second step of separating a second starch from a solid-liquid mixture obtained by adding an acid to the first solution and heating in an oxidizing atmosphere;
And a third step of separating the third starch from the solid-liquid mixture obtained by adding water to the second starch. .
[0008]
(Configuration 2) The solution is a solution containing iron, arsenic and cadmium obtained by subjecting a leachate obtained by adding an acid to a sinter obtained by oxidizing zinc concentrate to a predetermined treatment. It is a manufacturing method of the iron oxide powder of the structure 1 characterized by these.
[0009]
(Configuration 3) An iron oxide powder characterized in that the content of cadmium and arsenic is 1 ppm or less and the content of manganese is 100 ppm or less.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the case of using the leachate obtained by performing zinc leaching by adding an acid to a calcined ore obtained by oxidizing zinc concentrate from sulfide ore as a raw material solution containing iron, arsenic and cadmium for the embodiment of the present invention Will be described with reference to the drawings.
FIG. 1 is a flow diagram of an example of a process from obtaining zinc concentrate concentrate leachate from sulfide ore to obtaining purified iron oxide powder.
In zinc smelting, zinc is obtained from zinc ore. For example, zinc concentrate 11 made of sulfide is roasted 51 in a roasting furnace to obtain zinc sinter 12 that is zinc oxide. The zinc sinter 12 is acid leached 52 with sulfuric acid 31 or the like to produce a leaching solution 13 containing metal and a residue 32. From this leachate 13, a liquid composition suitable for zinc electrowinning is purified in order to obtain zinc or the like as a desired metal. At this time, iron contained in the zinc concentrate 11 is also present in the leachate 13. For this reason, the process of removing the said iron is also included in the process of zinc refining, and an iron oxide powder material is obtained by utilizing this process.
[0011]
The leachate 13 removes the metal that becomes an obstacle during zinc electrowinning through a plurality of steps. For example, the leachate 13 is heated to 110 ° C. in an autoclave under a sulfurous acid gas atmosphere, zinc and iron are dissolved as a neutralizing agent 33, and the first neutralization 53 is performed. , Lead and the like are separated as a starch 34 to obtain a leachable filtrate 14.
[0012]
A reducing agent such as zinc powder 35 is added to the leached filtrate 14 while adjusting the acid concentration and the copper ion concentration, and this is reduced to dearsenide 54 to precipitate impurities such as arsenic to form a starch 36. This is solid-liquid separated to obtain a low arsenic liquid 15. Next, a neutralizing agent 37 is added to the low arsenic solution 15 to neutralize 55 a second amount of free sulfuric acid. In this second neutralization 55, calcium carbonate or the like is used as the neutralizing agent 37, and the low arsenic solution 15 is neutralized to pH 4 to 5, so that impurities such as silicon, aluminum, gallium and indium in the solution are gypsum. At the same time, it is separated as a starch 38 to obtain a neutralized solution 16.
So far, it is the same as that of the conventional zinc refining process.
[0013]
Hereinafter, the 1st process concerning the present invention is explained.
The neutralizing solution 16 contains various metals such as cadmium (Cd), arsenic (As), zinc (Zn), sulfur (S), calcium (Ca), and iron (Fe). Reduction 56 is performed in order to obtain iron oxide powder, which is a high-purity iron oxide powder material, from the neutralized solution containing these various elements. In the reduction 56, for the purpose of removing arsenic and cadmium from the neutralization solution 16, a reducing agent such as zinc powder 39 is added, the oxidation-reduction potential of the neutralization solution 16 during the reaction is set to −500 mV or less, and the acid 40 is added. Add to adjust pH to 4.0 or lower. Further, in this specification, for example, when “redox potential −500 mV or less” is described, it is used to mean “the redox potential is in the vicinity of −500 mV without exceeding −500 mV”. Yes.
[0014]
Here, the addition of the zinc powder 39 is suitable for adjusting the oxidation-reduction potential, and if the added material is zinc, this is a component contained in the neutralizing solution 16 before the addition. For this reason, it cannot be a new impurity, and the influence on the subsequent process can be minimized. In addition, the reason is not yet clear, but the addition of the zinc powder 39 can effectively remove arsenic and cadmium. The form of the zinc powder 39 is a powder containing zinc as a main component, and it is desirable that the particle diameter is finer, but it may be about 1 μm to 1000 μm. The acid 40 is preferably sulfuric acid.
[0015]
Here, the removal effect of arsenic and cadmium by the addition of the zinc powder 39 and the acid 40 to the neutralizing solution 16 will be described in detail with reference to FIGS.
[0016]
1. [Examination of removal of arsenic and cadmium by adding zinc powder 39 to neutralizing solution 16]
The present inventors can remove arsenic and cadmium in the neutralized solution 16 by adding zinc powder 39 to the neutralized solution 16 (examples of compositions are shown in Table 1) under appropriate conditions. I found it. This elucidation process will be explained.
[0017]
[Table 1]

[0018]
First, the reaction temperature was controlled and the zinc powder was added to the neutralizing solution 16 having the composition shown in Table 1 under the two levels of conditions shown in Table 2.
[0019]
[Table 2]

[0020]
The behavior of the neutralizing solution 16 at this time will be described with reference to FIG.
FIG. 2 is a graph in which the vertical axis represents the cadmium concentration in the neutralizing solution 16 and the horizontal axis represents the reaction time. In the graph, level 1 is indicated by a broken line and level 2 is indicated by a solid line. When the added zinc powder concentration is 2 g / l, the oxidation-reduction potential of the neutralizing solution 16 is −500 mV or less and the pH is 3.0. When the added zinc powder concentration is 3 g / l, the oxidation-reduction potential is -700 mV or less, pH became 4.0.
[0021]
As shown in FIG. 2, at level 1, as the reaction time progresses, the cadmium concentration in the liquid once decreases but increases again as the reaction time progresses. This is thought to be because cadmium once becomes a starch but elutes again in the liquid. In contrast, at level 2, the cadmium concentration decreases with time. This is considered to be because the cadmium once converted to starch can be prevented from dissolving again.
[0022]
From this, the present inventors adjusted the addition amount of the zinc powder 39 so that the oxidation-reduction potential in the neutralization solution 16 was −700 mV or less, and further controlled the solution temperature, so that cadmium was contained in the medium. It was conceived that a decadmium solution 17 having a low cadmium content that can be removed from the sum solution 16 can be obtained. If cadmium removal is possible, it has been conceived that arsenic that behaves similarly to cadmium in the neutralizing solution 16 can be removed at the same time.
[0023]
2. [Examination of liquid temperature control]
The neutralization solution 16 similar to that described in Table 1 was used, and the reaction temperature conditions were set to three levels of 20 ° C., 30 ° C., and 40 ° C., and cadmium was removed from the neutralization solution 16. The amount of zinc powder added was 3 g / l, and the oxidation-reduction potential was −700 mV or less.
The behavior of the neutralizing solution 16 at this time is shown in FIG. However, FIG. 3 is a graph similar to FIG. 2, and the level of 20 ° C. is indicated by a one-dot chain line, the level of 30 ° C. is indicated by a solid line, and the level of 40 ° C. is indicated by a two-dot chain line.
From the above results, it was found that the cadmium concentration decreased with the reaction time at each temperature, and it was found that the liquid temperature during the reaction is preferably 60 ° C. or less, and more preferably 20 to 40 ° C. In this case as well, it was conceived that arsenic having a behavior similar to that of cadmium can be removed in the neutralizing solution 16 at the same time.
[0024]
3. [Examination of redox potential control]
The neutralization solution 16 similar to that described in Table 1 is used, and the concentration of zinc powder added is controlled so that the oxidation-reduction potential becomes two levels of -500 mV and -800 mV, and cadmium is removed from the neutralization solution 16. It was. The liquid temperature was 60 ° C.
The behavior of the neutralizing solution 16 at this time is shown in FIG. However, FIG. 4 is a graph similar to FIG. 2, and the level of −500 mV is indicated by a one-dot chain line, and the level of −800 mV is indicated by a solid line.
[0025]
As is apparent from FIG. 4, when the oxidation-reduction potential was −500 mV, the cadmium concentration decreased with the lapse of the reaction time, and became substantially constant after 60 minutes. On the other hand, when the oxidation-reduction potential was −800 mV, the concentration decreased with the lapse of the reaction time, and finally became almost zero. From this result, it can be seen that if the oxidation-reduction potential is −800 mV, a sufficient cadmium effect can be obtained, and it is preferable that at least the oxidation-reduction potential is −500 mV or less. In this case as well, it was conceived that arsenic having a behavior similar to that of cadmium can be removed in the neutralizing solution 16 at the same time.
[0026]
4). [Examination of pH control]
The neutralization solution 16 similar to that described in Table 1 was used, the pH level was set to three levels of 2.0, 3.0, and 4.0, and cadmium was removed from the neutralization solution 16. The liquid temperature was 60 ° C., and the oxidation-reduction potential was −500 mV or less.
The behavior of the neutralizing solution 16 at this time is shown in FIG. However, FIG. 5 is a graph similar to FIG. 2, in which the level of pH 2.0 is indicated by a one-dot chain line, the level of pH 3.0 is indicated by a solid line, and the level of pH 4.0 is indicated by a two-dot chain line.
[0027]
As is apparent from FIG. 5, when the pH is 2.0, the concentration of cadmium once decreases with the lapse of the reaction time, but immediately increases. At pH 3.0, the concentration decreases with the lapse of the reaction time and decreases to about 10 mg / l, but thereafter, the concentration increases with the lapse of the reaction time. On the other hand, at pH 4.0, the concentration becomes almost zero with the lapse of the reaction time, so that it can be seen that a sufficient cadmium removal effect can be obtained if the pH is 3.0 or more. If it is 0 or more, it is more effective. In this case as well, it was conceived that arsenic having a behavior similar to that of cadmium can be removed in the neutralizing solution 16 at the same time.
[0028]
Here, returning to FIG. 1 again, the considerations 1 to 4 described above are summarized.
The zinc powder 39 is mainly used for adjusting the oxidation-reduction potential of the neutralization solution 16, and the addition amount is preferably an addition amount that makes the oxidation-reduction potential of the neutralization solution 16 −500 mV or less, and −800 mV or less. The addition amount is more preferable. By setting the oxidation-reduction potential of the neutralization solution 16 to −500 mV or less, it is possible to prevent cadmium and arsenic precipitation and re-dissolution of the starch 41 in the neutralization solution 16. In particular, when the oxidation-reduction potential is −800 mV or less, it is more effective for removing cadmium and arsenic precipitates.
[0029]
In the reduction 56, the pH of the neutralizing solution 16 is preferably adjusted to 2-4. This is to prevent cadmium and arsenic from redissolving in the neutralizing solution 16, and is particularly effective for removing cadmium and arsenic at pH 3-4.
The liquid temperature during the reaction is preferably 60 ° C. or less, and particularly preferably 20 to 40 ° C. This is because, if the liquid temperature is too high, cadmium and arsenic precipitated once are redissolved. If the liquid temperature is too low, the reaction proceeds slowly.
After this treatment, the first starch 41 containing cadmium and arsenic is solid-liquid separated from the obtained solid-liquid mixture to obtain a decadmium solution 17 which is the first solution after the removal of cadmium and arsenic. . Here, the first step according to the present invention is completed.
[0030]
Next, the second step according to the present invention will be described.
The decadmium solution 17, which is the first solution according to the present invention, undergoes a deironing 57 step in order to separate the contained zinc and iron.
The present inventors have conceived that in this deironation 57 step, iron can be separated by the solubility difference between zinc and iron by defining the concentration of the free acid in the decadmium solution 17. Here, the examination of the free acid concentration will be described.
[0031]
5. [Examination of free acid concentration]
The neutralization solution 16 similar to that described in Table 1 was used, and the concentration of free acid was set to two levels of 10 g / l and 30 g / l, and the separation of zinc and iron was examined. The liquid temperature was 120 ° C. In this case, it is preferable to use sulfuric acid as the acid to be added, because it forms a starch by appropriately forming with iron.
The results are shown in Table 3. When the free acid concentration was 10 g / l, the zinc in the iron residue was 8000 ppm and iron was 68 wt%. When the free acid concentration was 30 g / l, zinc was 1200 ppm and iron was 70 wt%. That is, it was found that zinc and iron can be separated by appropriately setting the free acid concentration.
[0032]
[Table 3]

[0033]
Here, returning to FIG. 1 again, the five considerations are summarized.
For example, using an autoclave, sulfuric acid 42 is added to the cadmium solution 17 to adjust the free acid concentration to about 10 to 30 g / l, the reaction temperature is about 120 ° C., and the atmosphere is an oxygen partial pressure of about 0.3 MPa. It is preferable to form an iron residue 18 as the second starch according to the present invention by forming a compound of iron and sulfuric acid by using a neutral atmosphere. The reason why the free acid concentration is set to 30 g / l or less is that when the free acid concentration is high, the solubility of zinc in the decadmium solution 17 increases and the separability from zinc decreases. The iron residue 18 is a mixture of various jarosite compounds such as iron oxide and iron hydroxide. Here, the filtrate 43 is separated from the obtained solid-liquid mixture, and the iron residue 18 as various jarosite compounds is recovered to complete the second step according to the present invention. In addition, the filtrate 43 can be advanced to the smelting process of zinc.
[0034]
Next, the 3rd process concerning the present invention is explained.
The iron residue 18 which is the second starch according to the present invention is washed 58 with water 44 or the like in order to wash off the acid and metal ions as they are. The water 44 is preferably water that does not contain chlorine. This is because, in the water containing chlorine, the chlorine component adheres to the iron residue 18, which affects the components of the iron oxide powder. The addition of water 44 is so good that the iron residue 18 can be repulped. From the obtained solid-liquid mixture, the solid-liquid separation for removing the filtrate 45 and the addition of water 44 are repeated to obtain the washed iron residue 19 which is the third starch according to the present invention. Thus, the third step according to the present invention is completed.
[0035]
Most of the components of the washed iron residue 19 are iron oxide. However, when the oxidation state as iron oxide is insufficient, roasting 59 is applied to perform further oxidation treatment. The roasting 59 may be performed in an oxygen-containing oxidizing gas atmosphere at a temperature of 700 ° C. or higher using a roasting furnace or the like. By this roasting 59, the iron oxide powder material 20 having a composition of 99.9% or more is obtained. This iron oxide powder material 20 becomes a raw material of the iron oxide powder 23. The iron oxide powder material 20 obtained here can be changed in particle size according to the application by pulverization in a subsequent process, and can be used as a material for a process regardless of the particle diameter.
[0036]
The iron oxide powder material 20 that has been subjected to the roasting process is washed 60 with water 46 and separated into starch 21 and filtrate 47 in the same manner as the above-described washing process, and then the starch 21 is dried 61 and dried 22 In order to obtain a desired particle size, the iron oxide powder 23 is obtained by pulverizing 62 using a pulverizer or the like.
In the description of the present embodiment, as a raw material solution containing iron, arsenic and cadmium, a case where a leachate obtained by leaching zinc by adding an acid to a sinter obtained by oxidizing zinc concentrate is used. As an example, the present invention is not limited to this, and can be applied to a solution containing various iron, arsenic and / or cadmium.
[0037]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
(Example 1)
Zinc concentrate from sulfide ore is oxidized and roasted to make zinc sinter, then acid leached with sulfuric acid, the leachate is heated to 110 ° C in an autoclave, and zinc and iron are dissolved in a sulfurous acid gas atmosphere, making it difficult Dissolve copper, noble metal, lead, etc. as a residue from the leach filtrate.
In this leaching filtrate, impurities such as arsenic reduced by a reducing agent such as zinc dust are precipitated while adjusting the acid concentration and copper ion concentration, and solid-liquid separation is performed into a low arsenic solution and a residue. Next, 1 m ³ (1,000 l) of a neutralized solution obtained by neutralizing free sulfuric acid contained in a large amount in the low arsenic solution to a pH of 4 with a calcium salt was collected. Table 4 shows examples of the liquid composition of the neutralization liquid at this time.
[0038]
[Table 4]

[0039]
The composition was 1 mg / l arsenic, 476 mg / l cadmium, 83 mg / l zinc, 46 g / l iron, 77 g / l sulfur, 557 mg / l calcium, 4 g / l manganese. The analysis used chemical analysis, and the same analysis method was used hereinafter.
To this neutralization liquid, it added with the compounding quantity of 3.0 g / l so that oxidation-reduction potential may be set to -800 mV or less with zinc powder with respect to the neutralization liquid. Further, by adding sulfuric acid, the liquid temperature was adjusted to 30 ° C. while adjusting the liquid so that the pH became 4.0, and the reaction was performed for 90 minutes to perform the reduction step.
Next, solid-liquid separation between the starch generated in the liquid and the decadmium liquid was performed.
[0040]
This was repeated until the liquid volume reached about 15 m ³ . Table 5 shows a composition measurement example of the decadmium solution at this time.
[0041]
[Table 5]

[0042]
The composition was arsenic not detected (1 mg / l or less), cadmium not detected (1 mg / l or less), Zn 65 g / l, Fe 37 g / l, S 62 g / l, Ca 415 mg / l, manganese 1 mg / l. .
[0043]
Sulfuric acid was added to this solution to make the free acid concentration 30 g / l or more. Then, while maintaining this free acid concentration, the reaction temperature was 120 ° C. in an autoclave, the atmosphere was oxygen partial pressure PO ₂ 0.3 MPa, and the reaction was performed for 2 hours. Next, solid-liquid separation was performed to obtain an iron residue.
[0044]
Water was added to the obtained iron residue for repulping and solid-liquid separation to wash the iron residue with water. Table 6 shows composition measurement examples of the iron residue after washing with water and specific surface areas measured by the BET method.
[0045]
[Table 6]

[0046]
The composition of the iron residue was 49 wt% Fe ₂ O ₃ in a dry state, arsenic not detected (1 ppm or less), cadmium not detected (1 ppm or less), Zn 730 ppm, S 132200 ppm, Mn 18 ppm, Cl not detected (10 ppm or less) there were. The specific surface area measured by the BET method was 0.59 m ² / g.
[0047]
The residue after washing with water was put into a roasting furnace, and the roasting temperature was 900 ° C. for 4 hours to oxidize the atmosphere as air to obtain an iron oxide powder material. Table 7 shows composition examples of this iron oxide powder material and specific surface areas measured by the BET method.
[0048]
[Table 7]

[0049]
The composition example of the iron oxide powder material is dry, Fe ₂ O ₃ 99.96 wt%, arsenic not detected (1 ppm or less), cadmium not detected (1 ppm or less), Zn 1400 ppm, S 136 ppm, Mn 21 ppm, Cl not detected ( An iron oxide powder material having a high purity of 10 ppm or less) was obtained. In particular, arsenic, cadmium, Mn, and Cl were low in concentration. The specific surface area measured by the BET method was 0.6 m ² / g.
[0050]
Water washing was performed by adding water to the iron oxide powder material, repulping, and solid-liquid separation. The residue after washing with water was dried, and after drying, it was put into a pulverizer and pulverized to obtain a purified iron oxide powder. The pulverization was performed with a vibration mill, and was performed for 60 minutes at a ball filling rate of 70%.
Table 8 shows composition examples of the obtained purified iron oxide powder and specific surface areas measured by the BET method.
[0051]
[Table 8]

[0052]
The composition of the refined iron oxide powder was as follows: Fe ₂ O ₃ 99.96 wt%, arsenic not detected (1 ppm or less), cadmium not detected (1 ppm or less), Zn 1400 ppm, S 136 ppm, Mn 21 ppm, Cl not Detection (10 ppm or less). The specific surface area measured by the BET method was 2.36 m ² / g.
According to the method for producing iron oxide powder, the particle size can be controlled while maintaining the purity, and it is possible to obtain a finer and finer iron oxide powder with high purity.
[0053]
【The invention's effect】
As described above in detail, the present invention is a method for producing iron oxide powder from a solution containing iron, arsenic and cadmium,
From the solid-liquid mixture obtained by adjusting the solution to 60 ° C. or lower, adding a reducing agent to set the oxidation-reduction potential of the solution to −500 mV or lower, and adjusting the pH to 4 or lower by adding an acid, A first step of separating one solution;
A second step of separating a second starch from a solid-liquid mixture obtained by adding an acid to the first solution and heating in an oxidizing atmosphere;
A third step of separating the third starch from the solid-liquid mixture obtained by adding water to the second starch, and a method for producing the iron oxide powder. From the solution containing iron, arsenic and cadmium, iron oxide powders with low contents of arsenic and cadmium could be produced.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a process flow diagram for obtaining purified iron oxide powder from a zinc concentrate leachate.
FIG. 2 is a graph showing the behavior of the neutralizing solution when the reaction temperature condition and the oxidation-reduction potential are changed.
FIG. 3 is a graph showing the behavior of the neutralizing solution when the reaction temperature conditions are changed.
FIG. 4 is a graph showing the behavior of the neutralizing solution when the oxidation-reduction potential is changed.
FIG. 5 is a graph showing the behavior of the neutralizing solution when the pH is changed.
[Explanation of symbols]
17. Decadmium solution (first solution)
18. Iron residue (second starch)
19. Washed iron residue (third starch)

Claims (3)

A method for producing iron oxide powder from a solution containing iron, arsenic, and cadmium, wherein the solution is adjusted to 60 ° C. or less, a reducing agent is added, and the oxidation-reduction potential of the solution is set to −500 mV or less, and then an acid is added. A first step of separating the first solution from the solid-liquid mixture obtained by adjusting the pH to 4 or less;
A second step of separating a second starch from a solid-liquid mixture obtained by adding an acid to the first solution and heating in an oxidizing atmosphere;
And a third step of separating the third starch from the solid-liquid mixture obtained by adding water to the second starch. A method for producing iron oxide powder, comprising: The solution is a solution containing iron, arsenic, and cadmium obtained by subjecting a leachate obtained by adding an acid to a sinter obtained by oxidizing zinc concentrate to a predetermined treatment. The manufacturing method of the iron oxide powder of Claim 1. An iron oxide powder characterized in that the content of cadmium and arsenic is 1 ppm or less and the content of manganese is 100 ppm or less.

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