JP4126415B2 - Method for removing and fixing arsenic present in iron sulfate solution - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、硫酸鉄溶液中に存在する砒素の除去及び固定方法に関するものである。
【０００２】
【従来の技術】
従来から、硫酸鉄溶液中に存在する砒素の除去法としては、多くの技術が提案され、実施されているものもある。その主な方法としては、
（１）硫酸鉄あるいは水酸化鉄との共沈及び／又は吸着法。
（２）銅イオンを共存させ電解もしくは置換による砒化銅沈殿法。
（３）硫化水素，硫化ソーダ等の硫化剤を用いた硫化物沈殿法、などがある。
【０００３】
上記（１）の方法は、更に次の２つの方法に大別される。
（イ）砒素を含む硫酸鉄溶液に消石灰等の中和剤を添加し、大気圧下で砒素鉄化合物沈殿を生成させる方法。
【０００４】
（ロ）砒素を含む溶液または固形分と、鉄を含む溶液または固形分とをオートクレーブに投入し、２００℃程度まで昇温して結晶性の鉄砒素化合物を沈殿させると同時に、亜鉛や銅等の元素を液中に浸出させる熱力学的な沈殿方法。
【０００５】
上記（イ）の方法は極めて一般的であり、砒素を含む硫酸鉄溶液に中和剤を添加しｐＨを４以上とし、砒酸鉄あるいは水酸化鉄との共沈及び／又は吸着により除去している。このとき、砒素が五価でなく、及び／又は鉄が二価の場合は、空気，酸素及び／又は酸化剤を用いて酸化処理を行う。
【０００６】
この方法によれば、砒素は有効に除去されるが、中和剤の使用に伴い最終殿物量が膨大になっていしまうという問題がある。また、この方法で生成された殿物処理に膨大な費用がかかる。
【０００７】
次に、上記（ロ）は装置をよりコンパクトにするための方法で、砒素の固定と有価金属の回収を同時にかつ簡単なプロセスで行うことができる方法である。
【０００８】
しかしながら、実際の硫酸鉄溶液、例えば特に湿式亜鉛製錬の亜鉛浸出残渣のＳＯ２還元あるいは高温高酸浸出から得られる硫酸鉄溶液の場合は、含有される砒素に対して圧倒的に多量の鉄を含んでいるのが常で、直接該方法を用いて砒素を分離固定することはできなかった。
【０００９】
上記（２）の方法は、酸性溶液中に存在する砒素と共存する銅イオンを還元によって砒化銅として沈殿除去するものであるが、本反応で得られる最終沈殿物の砒化銅は内部に多量の銅は勿論、インジウムやガリウム等の有価金属も同時に沈殿させてしまう。
【００１０】
上記（３）の方法もまた、上記（２）と同様である。この方法の場合、最終殿物の廃棄に際して特公昭５６−６９６２７号公報記載の砒素の溶出を防止する技術が提案されているが、有価金属損失の問題は解消されていない。
【００１１】
近年、いわゆる環境問題への関心の高まりから、上記のような技術の提案がなされているが、脱砒素及び砒素の固定技術が実操業に取り入れられた例は知られていない。
上記の各プロセスにはそれぞれ各所定条件下では優れた技術であるが、それらを工業的に実施することは、初期条件の相違あるいは経済的な問題から極めて困難である。
【００１２】
【発明が解決しようとする課題】
本発明は、上記のような従来技術に鑑みてなされたものであり、硫酸鉄溶液，例えば特に湿式亜鉛製錬の亜鉛浸出残渣のＳＯ２還元あるいは高温高酸浸出から得られる硫酸鉄溶液中に存在する砒素をインジウム，ガリウム等の有価金属を損失することなく系内から除去すると共に濃縮し、更には鉄との安定な結晶性化合物として固定する方法を確立し、実際の湿式亜鉛製錬プロセスへ適応させることができる技術を提案するものである。
【００１３】
【課題を解決するための手段】
第１の発明は、硫酸鉄溶液中に存在する砒素を鉄との安定な結晶性でかつ不溶出性の鉄・砒素化合物として除去し、固定することを特徴とする硫酸鉄溶液中に存在する砒素の除去及び固定方法である。
【００１４】
第２の発明は、砒素含有硫酸鉄溶液に脱砒素剤を添加し砒素を除去する第１工程と、第１工程で得られた砒素濃縮パルプのＦｅ／Ａｓ比，温度及び酸素分圧を所定条件に調整することにより結晶性の安定な鉄・砒素化合物として砒素を固定する第２の工程と、からなることを特徴とする硫酸鉄溶液中に存在する砒素の除去及び固定方法を提供するものである。
【００１５】
上記発明において、脱砒素剤は亜鉛末，鉄粉等の金属粉、あるいは水硫化ソーダ，硫化水素等の硫化剤であり、第１工程での金属粉を添加し脱砒素反応時の液温度が４０〜１００℃で、酸化還元電位が−１５０ｍＶに調整することが好ましく、硫化剤の場合は液の酸化還元電位が１５０ｍＶ程度であることが好ましいのである。
【００１６】
上記発明において、必要に応じて使用する銅源は砒素を固定する第２工程から得られる溶液中に浸出された銅を用いることが好ましく、第２工程でのＦｅ／Ａｓ比が１〜３又は１０以上であり、使用する鉄源は湿式亜鉛製錬の亜鉛浸出残渣のＳＯ２還元浸出から得られる硫酸鉄溶液が好ましいのである。
【００１７】
上記発明における第２工程での反応温度は１５０〜２００℃、酸素分圧は酸素を加え全圧で１．８〜２．０ＭＰａ（メガパスカル）が好ましく、上記硫酸鉄溶液は湿式亜鉛製錬の亜鉛浸出残渣のＳＯ２還元浸出から得られる砒素を含む溶液であることが好ましいのである。
【００１８】
【作用】
以下、本発明を更に詳細に説明する。
本発明は次の２工程から構成され、図１は本発明に係る基本的なフローを示す概念図、図２は本発明に係る脱砒試薬として金属粉末還元剤を使用した場合の概念図、図３は本発明をＳＯ２還元あるいは高温高酸浸出及びヘマタイト法による亜鉛浸出残渣処理法に応用した場合のフロー図である。
【００１９】
第１工程：砒素除去及び濃縮工程
本工程には２つの方式があり、いずれの方式を用いても差し支えない。生成残渣は２法とも沈降濾過性に優れているため、シックナー等で容易に濃縮分離が可能である。
【００２０】
（Ａ）脱砒素のために、還元剤すなわち亜鉛末や鉄粉等の金属粉末を使用する。脱砒素のみが目的の場合には特に必要ないが、この工程において、インジウム，ガリウム等の有価金属類を沈殿させたくない場合には、砒化銅の生成に必要な硫酸銅がモル比（銅／砒素）で２以上、好ましくは３以上存在していた方がよい。
【００２１】
砒素は基本的には鉄と砒化鉄及び／又は単体砒素の形で沈殿し、銅存在下では砒化銅として優先的に沈殿する。
反応のｐＨは、還元剤の使用量の増大をいとわなければ、ｐＨ３以下のいかなる低ｐＨでもよく、また温度は常温でも反応は進行するが、４０℃以下では反応速度が極めて遅くなるので、好ましくは４０〜１００℃である。
【００２２】
反応は酸化還元電位を調整しながら進行させる方がよく、飽和塩化銀電極で−１５０ｍＶ以下、好ましくは−２００〜−２１０ｍＶがよい。
【００２３】
（Ｂ）砒素の濃縮には金属粉還元剤の代わりに硫化水素ガスのような硫化物を用いてもよい。このとき、砒素は硫化砒素の形で沈殿する。また、硫化剤使用の際は、飽和塩化銀電極で１５０ｍＶ程度の電位で反応を進行させるのがよい。
【００２４】
第２工程：砒素固定及び銅浸出工程
第２工程は、第１工程の２法に対して共通である。すなわち、鉄源として２価あるいは３価の鉄を加え、鉄と砒素とのモル比（以下、Ｆｅ／Ａｓあるいは砒鉄比という）が１以上となるように混合する。しかし、鉄と砒素の化合物は３＜Ｆｅ／Ａｓ＜１０の領域では沈殿形成の速度が遅くなるので、充分な砒素沈殿率を得るためには、好ましくは１＜Ｆｅ／Ａｓ＜３あるいはＦｅ／Ａｓ＞１０となるように混合する。
【００２５】
さらに、温度を１５０〜２００℃程度、好ましくは２００℃まで上げ、酸素を加え、全圧が概ね１．８〜２．０ＭＰａ（メガパスカル）となるように調整する。酸素の供給は鉄及び砒素の酸化に用いるもので、両者がＦｅ（ＩＩＩ）かつＡｓ（Ｖ）のときには必要がない。この反応によって、砒素は鉄と結晶性の安定な化合物を作り、容易に濾過分離が可能となる。
【００２６】
同時に、亜鉛や銅等の砒素あるいは鉄以外の元素は液中に浸出される。また、例えば特に湿式亜鉛製錬の亜鉛浸出残渣のＳＯ２還元あるいは高温高酸浸出から得られる硫酸鉄溶液中のように、連続的に脱砒素のための銅源を供給することが容易な場合には、この砒素固定後の液から銅を回収することは容易であるし、回収を行わずに脱砒素工程の銅源として繰り返し使用してもよい。
【００２７】
銅源を繰り返し使用する場合のフローは、図２（金属粉末還元剤使用の概念図）に明示している。次に、本発明の実施の形態を実施例と図面により説明する。
【００２８】
【発明の実施の形態】
実施例１
本実施例は、脱砒素試薬として亜鉛粉末を用いた実施例である。特に液中の銅濃度の調整は行っておらず、本発明の基本的な流れの実施例である。
砒素を含む硫酸鉄溶液（湿式亜鉛残渣のＳＯ２還元浸出とヘタマイト法による鉄処理の工程内における１段中和後液）を定量ポンプでオーバーフロー管付きの２ｌガラスビーカーに連続給液し、攪拌しながら溶液の酸化還元電位が飽和塩化銀電極で−２１０ｍＶに一定になるように亜鉛粉末を添加して、連続的に脱砒試験を行った。また、液温度は６０℃で、ｐＨは２．７の条件で試験を行った。
本試験の条件では、溶液中の銅と砒素とのモル比は１．８４で、砒素を砒化銅として沈殿させるには銅量は充分ではない条件であった。試験は、液のビーカー内滞留時間が１時間になるように給液量を調整し、液が最終ビーカーからオーバーフローし始めてから２時間後にサンプリングした。分析はオーバーフローパルプを瀘別分離して、濾液に対して行った。試験結果を表１に示す。溶液からの充分な砒素除去がなされた。一方で、インジウムの沈殿率が高く、こうしたレアメタルの回収を行う工程への適応は問題となる可能性がある。
【００２９】
【表１】
上記反応を繰り返し行うことで得た脱砒素殿物パルプを適量回収した後に、鉄源として硫酸鉄溶液（湿式亜鉛残渣のＳＯ２還元浸出とヘタマイト法による鉄処理の工程内における１段中和後液）を加え、砒鉄比が概ね４となるように充分に混合した。混合後のパルプを定量ポンプで２０ｌオートクレーブに連続給液し、攪拌しながら３Ｋｇ／ｃｍ２で加圧し２００℃まで加熱し、連続的に脱砒素試験を行った。オートクレーブの滞留時間を１．５時間とし、連続排出を開始してから３時間後に排出液をサンプリングし、反応後のパルプを濾別分離し濾液の分析を行った。その結果を表２に示す。鉄及び砒素を反応によって充分に沈殿させ、同時に有価金属である銅を液中に浸出させることができた。
【００３１】
【表２】
実施例２
本実施例は、脱砒素試薬として亜鉛粉末を用い、かつ充分な量の銅を存在させた場合の実施例である。
砒素を含む硫酸鉄溶液（湿式亜鉛残渣のＳＯ２還元浸出とヘタマイト法による鉄処理の工程内における１段中和後液）を当工程内のシックナーオーバーフローからタンクに定量的に流し込み、タンク内の液滞留時間が１時間となるように調整した。また、銅源として硫酸銅溶液を反応元液銅濃度が概ね３．０ｇ／ｌとなるように定量ポンプを用いて連続的に添加した。これは、ＳＯ２還元あるいは高温高酸浸出においては、単体硫黄あるいは亜鉛精鉱の添加を行わないことで液中に意図的に銅を残すことができ、この際の銅濃度は２．５〜３．０ｇ／ｌ程度になることが確認されているからである。溶液は攪拌しながら酸化還元電位が飽和塩化銀電極で−２１０ｍＶに一定になるように亜鉛粉末を添加して、連続的に脱砒試験を行った。
【００３３】
試験源液は添加時点で７０℃あり、反応を通じて加温の必要はなかった。本反応ではｐＨ２．０でほぼ一定に保たれ、特に調整は必要なかった。また、本試験の場合元液の銅と砒素の比は３．６であり、砒素を砒化銅として沈殿させるのに充分な銅量が確認されていた。試験結果を表３に示す。溶液からの充分な砒素除去がなされた。また、同時にインジウムの沈殿率を充分に抑えることができた。これは、液中に砒化銅生成のための充分な銅が確保されているためであり、こうした場合は亜鉛末近傍における局部的な電位低下によるインジウムの沈殿物の生成を防ぐことができるからである。従って、インジウム等のレアメタル回収を伴う工程においては、本実施例のように元液中に充分な銅が存在していた方がよい。
【００３４】
【表３】
上記脱砒素殿物に硫酸鉄溶液（湿式亜鉛残渣のＳＯ２還元浸出とヘタマイト法による鉄処理の工程内おける２段中和後液）を砒鉄比が概ね１．３となるように加え、混合後のパルプ３．５ｌを５ｌオートクレーブに送入し、攪拌しながら２００℃まで加熱後、酸素分圧５Ｋｇ／ｃｍ２で一定となるように酸素を加えながら３時間反応させた。反応後のパルプは濾別分離して濾液の分析を行った。その結果を表４に示す。鉄及び砒素を本反応によって充分に沈殿させ、同時に有価金属である銅を液中に浸出させることができた。また、反応後の液は高濃度の硫酸銅溶液であり、この溶液を再び砒素除去工程において銅源として用いても経済的に充分成り立つことが分る。
【００３６】
【表４】
実施例３
本実施例は、脱砒素試薬として硫化剤を用いることもできることを示した実施例である。
砒素を含む硫酸鉄溶液（湿式亜鉛残渣のＳＯ２還元浸出とヘタマイト法による鉄処理の工程内における１段中和後液）１ｌをガラスビーカーに採取し、攪拌しながら溶液の酸化還元電位が飽和塩化銀電極で１５０ｍＶに一定になるように硫化水素ガスをガラス製ボールフィルターで吹き込み、脱砒試験を行った。上記ビーカーで１時間反応後にサンプリングした。分析は反応後パルプを濾別分離して、濾液に対して行った。液温度は６０℃で、ｐＨは２．７の条件で試験を行った。試験結果を表５に示す。
【００３８】
【表５】
上記試験を繰り返し行い、得られた適量の脱砒素殿物に硫酸鉄溶液（湿式亜鉛残渣のＳＯ２還元浸出とヘタマイト法による鉄処理の工程内における１段中和後液）を加え、砒鉄比が概ね４．５となるように調整混合し、混合後のパルプ３．５リットルを５ｌオートクレーブに送入し、攪拌しながら２００℃まで加熱後、酸素分圧９Ｋｇ／ｃｍ２で一定となるように酸素を加えながら１．５時間反応させた。反応後のパルプは濾別分離し濾液の分析を行った。その結果を表６に示す。鉄及び砒素を本反応によって充分に沈殿させ、同時に有価金属である銅を液中に浸出させることができた。本例のように、脱砒素（砒素濃縮）試薬として硫化剤を用いた場合でも、本発明は適用できる。
【００４０】
【表６】
実施例４
実施例１〜３で得られた砒素と鉄を含有する不溶性結晶固体の環境安全性を確保するために、国で定めている埋め立て処分に関わる判定基準に準じて溶出試験を行った。
砒素と鉄を含有する不溶性の結晶固体と純水とを重量体積比１０％の割合で混合し、その混合液が５００ｍｌ以上となるようにしたものを試料液とし、常温（概ね２０℃）常圧（概ね１気圧）で、予め振とう機を用いて６時間振とうした。試験後、分析はＩＣＰ−ＭＡＳＳ（誘導結合ブラズマ質量分析装置）で行った。その結果、砒素溶出値Ｔｒ〜０．０７ｍｇ／１で規格値の０．１５ｍｇ／１を満足した。
【００４２】
【発明の効果】
数ある砒素除去及び固定方法の中で、この分野に応用される可能性をもち、特にコスト面で割りに合う方法が報告あるいは実施された例はない。しかしながら、湿式亜鉛製錬工程における亜鉛浸出残渣処理液中のように、そのままの脱砒素及び固定が困難な溶液に対し、本発明により開発された脱砒素技術を砒素の濃縮技術としても位置付ければ、コスト面でも折り合いのつくプロセスとして確立できる。例えば、湿式亜鉛残渣のＳＯ２還元あるいは高温高酸浸出とヘタマイト法による鉄処理の工程内においても、図３に示すように簡単にプロセスの中に組み込むことが出来る。
【図面の簡単な説明】
【図１】本発明に係る処理工程図の基本的概念図である。
【図２】本発明に係る処理工程図において脱砒素に際して金属粉末還元剤を用いた場合の概念図である。
【図３】本発明法をヘマタイト法に応用した実施例を示すフロー図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for removing and fixing arsenic present in an iron sulfate solution.
[0002]
[Prior art]
Conventionally, many techniques have been proposed and implemented as a method for removing arsenic present in an iron sulfate solution. As its main method,
(1) Coprecipitation and / or adsorption method with iron sulfate or iron hydroxide.
(2) Copper arsenide precipitation by electrolysis or substitution in the presence of copper ions.
(3) There is a sulfide precipitation method using a sulfurizing agent such as hydrogen sulfide and sodium sulfide.
[0003]
The method (1) is further roughly divided into the following two methods.
(A) A method in which a neutralizing agent such as slaked lime is added to an iron sulfate solution containing arsenic to produce an arsenic iron compound precipitate under atmospheric pressure.
[0004]
(B) A solution or solid content containing arsenic and a solution or solid content containing iron are put into an autoclave and heated to about 200 ° C. to precipitate a crystalline iron arsenic compound, and at the same time zinc, copper, etc. A thermodynamic precipitation method that leaches the elements in the liquid.
[0005]
The above method (a) is very general. A neutralizing agent is added to an iron sulfate solution containing arsenic so that the pH is 4 or more, and it is removed by coprecipitation and / or adsorption with iron arsenate or iron hydroxide. Yes. At this time, when arsenic is not pentavalent and / or iron is divalent, oxidation treatment is performed using air, oxygen, and / or an oxidizing agent.
[0006]
According to this method, arsenic is effectively removed, but there is a problem that the amount of final deposits becomes enormous with the use of a neutralizing agent. Moreover, enormous costs are required for processing the temples generated by this method.
[0007]
Next, the above (b) is a method for making the apparatus more compact, and is a method capable of simultaneously fixing arsenic and recovering valuable metals by a simple process.
[0008]
However, in the case of an actual iron sulfate solution, for example, an iron sulfate solution obtained from SO 2 reduction or high temperature high acid leaching of a zinc leaching residue, especially in wet zinc smelting, an overwhelmingly large amount of iron is contained in the arsenic contained. In general, arsenic could not be separated and fixed directly using this method.
[0009]
In the method (2), copper ions coexisting with arsenic present in the acidic solution are precipitated and removed as copper arsenide by reduction. However, the final precipitate copper arsenide obtained in this reaction contains a large amount of copper arsenide inside. Not only copper but also valuable metals such as indium and gallium are precipitated at the same time.
[0010]
The method (3) is the same as (2). In the case of this method, a technique for preventing arsenic elution described in Japanese Patent Publication No. 56-69627 has been proposed at the time of disposal of the final temple, but the problem of valuable metal loss has not been solved.
[0011]
In recent years, due to increasing interest in so-called environmental problems, the above-described techniques have been proposed. However, examples in which dearsenic and arsenic fixing techniques have been incorporated into actual operations are not known.
Each of the above processes is an excellent technique under each predetermined condition, but it is extremely difficult to implement them industrially due to differences in initial conditions or economic problems.
[0012]
[Problems to be solved by the invention]
The present invention has been made in view of the prior art as described above. In an iron sulfate solution, for example, an iron sulfate solution obtained from SO 2 reduction or high-temperature high acid leaching of a zinc leaching residue, particularly, wet zinc smelting. Establishing a method to remove and concentrate existing arsenic from the system without losing valuable metals such as indium and gallium, and to fix it as a stable crystalline compound with iron. It proposes a technology that can be adapted to.
[0013]
[Means for Solving the Problems]
A first invention exists in an iron sulfate solution characterized by removing and fixing arsenic present in an iron sulfate solution as a stable crystalline and non-eluting iron / arsenic compound with iron. This is a method for removing and fixing arsenic.
[0014]
In the second invention, the first step of removing arsenic by adding a dearsenic agent to the arsenic-containing iron sulfate solution, and the Fe / As ratio, temperature and oxygen partial pressure of the arsenic concentrated pulp obtained in the first step are predetermined. A second step of fixing arsenic as a stable crystalline iron / arsenic compound by adjusting to conditions, and a method for removing and fixing arsenic present in an iron sulfate solution, characterized by comprising: It is.
[0015]
In the above invention, the dearsenic agent is a metal powder such as zinc powder or iron powder, or a sulfurizing agent such as sodium hydrosulfide or hydrogen sulfide, and the liquid temperature during the dearsenic reaction is increased by adding the metal powder in the first step. It is preferable to adjust the redox potential to −150 mV at 40 to 100 ° C., and in the case of a sulfiding agent, the redox potential of the liquid is preferably about 150 mV.
[0016]
In the above invention, it is preferable to use copper leached in the solution obtained from the second step of fixing arsenic as the copper source used as necessary, and the Fe / As ratio in the second step is 1 to 3 or The iron source used is preferably an iron sulfate solution obtained from SO 2 reductive leaching of zinc leaching residue of wet zinc smelting.
[0017]
The reaction temperature in the second step in the above invention is preferably 150 to 200 ° C., and the oxygen partial pressure is preferably 1.8 to 2.0 MPa (megapascal) in total pressure with addition of oxygen. A solution containing arsenic obtained from SO 2 reductive leaching of the zinc leaching residue is preferred.
[0018]
[Action]
Hereinafter, the present invention will be described in more detail.
The present invention is composed of the following two steps, FIG. 1 is a conceptual diagram showing a basic flow according to the present invention, FIG. 2 is a conceptual diagram when a metal powder reducing agent is used as a dearsenation reagent according to the present invention, FIG. 3 is a flow chart when the present invention is applied to a zinc leaching residue treatment method by SO 2 reduction or high temperature high acid leaching and hematite method.
[0019]
First Step: Arsenic Removal and Concentration Step There are two methods in this step, and either method can be used. Since both of the produced residues are excellent in sedimentation filterability, they can be easily concentrated and separated with a thickener or the like.
[0020]
(A) For dearsenation, a reducing agent, that is, metal powder such as zinc powder or iron powder is used. Although it is not particularly necessary when only arsenic removal is intended, in this step, if it is not desired to precipitate valuable metals such as indium and gallium, the copper sulfate necessary for producing copper arsenide is in a molar ratio (copper / Arsenic) should be 2 or more, preferably 3 or more.
[0021]
Arsenic basically precipitates in the form of iron and iron arsenide and / or simple arsenic, and preferentially precipitates as copper arsenide in the presence of copper.
The pH of the reaction may be any low pH of 3 or less as long as the amount of reducing agent used is not increased, and the reaction proceeds even at room temperature, but the reaction rate is extremely slow at 40 ° C. or less, which is preferable. Is 40-100 ° C.
[0022]
The reaction is preferably allowed to proceed while adjusting the redox potential, and is −150 mV or less, preferably −200 to −210 mV with a saturated silver chloride electrode.
[0023]
(B) For the concentration of arsenic, a sulfide such as hydrogen sulfide gas may be used instead of the metal powder reducing agent. At this time, arsenic precipitates in the form of arsenic sulfide. When using a sulfiding agent, the reaction is preferably allowed to proceed at a potential of about 150 mV with a saturated silver chloride electrode.
[0024]
Second step: Arsenic fixation and copper leaching step The second step is common to the two methods of the first step. That is, divalent or trivalent iron is added as an iron source and mixed so that the molar ratio of iron to arsenic (hereinafter referred to as Fe / As or arsenic iron ratio) is 1 or more. However, since the compound of iron and arsenic has a slower rate of precipitation in the region of 3 <Fe / As <10, in order to obtain a sufficient arsenic precipitation rate, preferably 1 <Fe / As <3 or Fe / Mix so that As> 10.
[0025]
Furthermore, the temperature is raised to about 150 to 200 ° C., preferably 200 ° C., oxygen is added, and the total pressure is adjusted to be approximately 1.8 to 2.0 MPa (megapascal). The supply of oxygen is used for the oxidation of iron and arsenic, and is not necessary when both are Fe (III) and As (V). By this reaction, arsenic forms a stable crystalline compound with iron, and can be easily separated by filtration.
[0026]
At the same time, elements other than arsenic or iron such as zinc and copper are leached into the liquid. In addition, when it is easy to continuously supply a copper source for dearsenic, for example, in an iron sulfate solution obtained from SO 2 reduction or high temperature high acid leaching of a zinc leaching residue particularly in wet zinc smelting In this case, it is easy to recover copper from the arsenic-fixed solution, and it may be used repeatedly as a copper source for the arsenic removal step without performing recovery.
[0027]
The flow in the case of repeatedly using a copper source is clearly shown in FIG. 2 (conceptual diagram of using metal powder reducing agent). Next, embodiments of the present invention will be described with reference to examples and drawings.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Example 1
In this example, zinc powder was used as a dearsenic reagent. In particular, the copper concentration in the liquid is not adjusted, and this is an example of the basic flow of the present invention.
Arsenic-containing iron sulfate solution (SO 2 reductive leaching of wet zinc residue and the solution after neutralization in the iron treatment process by the hetamite method) is continuously fed into a 2 liter glass beaker with an overflow pipe with a metering pump and stirred. Then, zinc powder was added so that the oxidation-reduction potential of the solution was kept constant at −210 mV with a saturated silver chloride electrode, and a dearsenic test was continuously performed. The test was conducted under the conditions of a liquid temperature of 60 ° C. and a pH of 2.7.
Under the conditions of this test, the molar ratio of copper to arsenic in the solution was 1.84, and the amount of copper was not sufficient to precipitate arsenic as copper arsenide. In the test, the liquid supply amount was adjusted so that the residence time of the liquid in the beaker was 1 hour, and sampling was performed 2 hours after the liquid began to overflow from the final beaker. The analysis was carried out on the filtrate after separating and separating the overflow pulp. The test results are shown in Table 1. Sufficient arsenic removal from the solution was achieved. On the other hand, the precipitation rate of indium is high, and adaptation to the process of recovering such rare metals may be a problem.
[0029]
[Table 1]
After recovering an appropriate amount of dearsenic pulp obtained by repeating the above reaction, iron sulfate solution (after SO 2 reduction leaching of wet zinc residue and iron treatment by hemite method after one-step neutralization as iron source) Solution) and mixed well so that the arsenic ratio is about 4. The mixed pulp was continuously fed into a 20 l autoclave with a metering pump, pressurized with 3 Kg / cm 2 with stirring and heated to 200 ° C., and continuously subjected to a dearsenic test. The residence time of the autoclave was 1.5 hours, and after 3 hours from the start of continuous discharge, the discharged liquid was sampled, the reacted pulp was separated by filtration, and the filtrate was analyzed. The results are shown in Table 2. Iron and arsenic were sufficiently precipitated by the reaction, and at the same time, the valuable metal copper could be leached into the liquid.
[0031]
[Table 2]
Example 2
In this example, zinc powder is used as a dearsenic reagent and a sufficient amount of copper is present.
Arsenic-containing iron sulfate solution (SO 2 reductive leaching of wet zinc residue and 1st stage post-neutralization solution in the iron treatment process by the hetamite method) is quantitatively poured from the thickener overflow in this process into the tank, The liquid residence time was adjusted to 1 hour. Further, a copper sulfate solution was continuously added as a copper source using a metering pump so that the concentration of the reaction source liquid copper was approximately 3.0 g / l. In SO 2 reduction or high temperature high acid leaching, copper can be intentionally left in the liquid by not adding elemental sulfur or zinc concentrate, and the copper concentration at this time is 2.5 to This is because it has been confirmed that it is about 3.0 g / l. While stirring the solution, zinc powder was added so that the oxidation-reduction potential was kept constant at -210 mV with a saturated silver chloride electrode, and a dearsenic test was continuously performed.
[0033]
The test source solution was 70 ° C. at the time of addition, and there was no need for warming throughout the reaction. In this reaction, the pH was kept almost constant at pH 2.0, and no particular adjustment was required. In this test, the ratio of copper to arsenic in the original solution was 3.6, and a sufficient amount of copper was confirmed to precipitate arsenic as copper arsenide. The test results are shown in Table 3. Sufficient arsenic removal from the solution was achieved. At the same time, the precipitation rate of indium was sufficiently suppressed. This is because sufficient copper for copper arsenide formation is secured in the liquid, and in such a case, it is possible to prevent the formation of indium precipitates due to a local potential drop in the vicinity of the zinc powder. is there. Therefore, in a process involving recovery of a rare metal such as indium, it is preferable that sufficient copper be present in the original solution as in this embodiment.
[0034]
[Table 3]
Add the iron sulfate solution (the solution after the two-step neutralization in the iron treatment process by SO 2 reduction leaching of the wet zinc residue and the hemite process) to the dearsenic deposit so that the arsenic ratio is approximately 1.3, After mixing, 3.5 l of pulp was fed into a 5 l autoclave, heated to 200 ° C. with stirring, and reacted for 3 hours while adding oxygen so that the oxygen partial pressure was kept constant at 5 kg / cm 2 . The pulp after the reaction was separated by filtration and the filtrate was analyzed. The results are shown in Table 4. Iron and arsenic were sufficiently precipitated by this reaction, and at the same time, the valuable metal copper could be leached into the liquid. The solution after the reaction is a high-concentration copper sulfate solution, and it can be seen that even if this solution is used again as a copper source in the arsenic removal step, it is economically sufficient.
[0036]
[Table 4]
Example 3
This example is an example showing that a sulfurizing agent can also be used as a dearsenic reagent.
1 liter of iron sulfate solution containing arsenic (solution after the 1st step neutralization in the process of SO 2 reduction leaching of wet zinc residue and iron treatment by the hetamite method) is collected in a glass beaker and the redox potential of the solution is saturated while stirring Hydrogen sulfide gas was blown through a glass ball filter so as to be kept constant at 150 mV with a silver chloride electrode, and an arsenic removal test was conducted. Sampling was performed after 1 hour reaction in the above beaker. The analysis was performed on the filtrate by separating the pulp after the reaction. The test was conducted under the conditions of a liquid temperature of 60 ° C. and a pH of 2.7. The test results are shown in Table 5.
[0038]
[Table 5]
Repeat the above test, and add an appropriate amount of the dearsenic acid obtained, and then add an iron sulfate solution (the solution after the one-step neutralization in the process of SO 2 reduction leaching of wet zinc residue and iron treatment by the hetamite method). The mixture is adjusted and mixed so that the ratio is approximately 4.5, and 3.5 liters of the mixed pulp is fed into a 5 liter autoclave, heated to 200 ° C. with stirring, and becomes constant at an oxygen partial pressure of 9 kg / cm 2. The reaction was carried out for 1.5 hours while adding oxygen. The pulp after the reaction was separated by filtration and the filtrate was analyzed. The results are shown in Table 6. Iron and arsenic were sufficiently precipitated by this reaction, and at the same time, the valuable metal copper could be leached into the liquid. The present invention can be applied even when a sulfiding agent is used as a dearsenic (arsenic enrichment) reagent as in this example.
[0040]
[Table 6]
Example 4
In order to ensure the environmental safety of the insoluble crystalline solid containing arsenic and iron obtained in Examples 1 to 3, an elution test was conducted according to the criteria for landfill disposal established in the country.
An insoluble crystalline solid containing arsenic and iron and pure water are mixed at a ratio of 10% by weight, and the mixture is 500 ml or more. The sample was shaken for 6 hours at a pressure (approximately 1 atm) in advance using a shaker. After the test, the analysis was performed with ICP-MASS (inductively coupled plasma mass spectrometer). As a result, the arsenic elution value Tr to 0.07 mg / 1 satisfied the standard value of 0.15 mg / 1.
[0042]
【The invention's effect】
Among a number of arsenic removal and fixation methods, there is a possibility that they can be applied in this field, and there is no example in which a method that is particularly reasonable in terms of cost has not been reported or implemented. However, if the dearsenic technology developed according to the present invention is positioned as an arsenic concentration technology for a solution that is difficult to remove and fix as it is, such as in the zinc leaching residue treatment solution in the wet zinc smelting process, In terms of cost, it can be established as a conclusive process. For example, it can be easily incorporated into the process as shown in FIG. 3 even in the steps of SO 2 reduction of wet zinc residue or high-temperature high-acid leaching and iron treatment by the hetamite method.
[Brief description of the drawings]
FIG. 1 is a basic conceptual diagram of a process chart according to the present invention.
FIG. 2 is a conceptual diagram in the case where a metal powder reducing agent is used for dearsenication in the process diagram according to the present invention.
FIG. 3 is a flow diagram showing an embodiment in which the method of the present invention is applied to a hematite method.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12521198A JP4126415B2 (en) | 1998-03-31 | 1998-03-31 | Method for removing and fixing arsenic present in iron sulfate solution |
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| Application Number | Priority Date | Filing Date | Title |
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| JP12521198A JP4126415B2 (en) | 1998-03-31 | 1998-03-31 | Method for removing and fixing arsenic present in iron sulfate solution |
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| JPH11277075A JPH11277075A (en) | 1999-10-12 |
| JP4126415B2 true JP4126415B2 (en) | 2008-07-30 |
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| JP2010202443A (en) * | 2009-03-03 | 2010-09-16 | Dowa Metals & Mining Co Ltd | Iron arsenate powder and method for producing the same |
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| CN115385477A (en) * | 2022-08-23 | 2022-11-25 | 长春黄金研究院有限公司 | Method for removing arsenic in contaminated acid |
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