JP4204235B2 - Silver recovery method - Google Patents
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- JP4204235B2 JP4204235B2 JP2002026422A JP2002026422A JP4204235B2 JP 4204235 B2 JP4204235 B2 JP 4204235B2 JP 2002026422 A JP2002026422 A JP 2002026422A JP 2002026422 A JP2002026422 A JP 2002026422A JP 4204235 B2 JP4204235 B2 JP 4204235B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description
【０００１】
【発明の属する技術分野】
本発明は、電子機器半導体産業などで使用済みとなった基板部品類から、有価金属をリサイクルする目的で湿式処理した際に発生する硝酸性銀溶液に含まれる銀を、不溶性タンニンを用いて回収する方法に関するものである。
【０００２】
【従来の技術】
パーソナルコンピューターや携帯電話などは、モデルチェンジの期間が短いため短サイクルで廃棄されている。それらに使用されている半導体基板などには銀や白金、パラジウムなどの貴金属類が含まれており、この希少な有価金属類を回収する方法がいくつか考案されている。
先ず、半導体基板などから有価金属を回収するには、廃棄部品であるボード類を一旦適当な大きさに粉砕、裁断し、次いで高温焼却処理して金属以外は熱分解する。熱分解後に酸化物として残った金属にはメッキ部材などの銀、結線などに用いられている金やパラジウムなどの白金族類を含んでいる。それらの有価金属の中で、銀は硝酸性溶液に対して比較的溶解度が高い。一方、金や白金族類は硝酸性溶液に対して溶解度が低く、王水などにより溶解される。この化学的特性を利用して銀とその他の有価金属類とを分離できる。
【０００３】
従来、銀を含む硝酸性溶液より銀を回収する方法には、銀がハロゲン元素とハロゲン化銀の固形物を生成する特性を利用して固液分離する方法が採用されていた。この方法では主にハロゲン元素に塩素を用いて固体の塩化銀を生成させる。硝酸性溶液より分離回収した塩化銀は再度溶解されて脱塩が行われ、粗銀材として回収される。粗銀材は精製処理されて、産業へとリサイクルされる。
【０００４】
【発明が解決しようとする課題】
しかしながら、上記硝酸性溶液に溶解させた銀を塩化銀として回収する方法では、塩素を用いるため耐食性設備が必要となる、塩化銀の固液分離操作や回収した塩化銀を更に脱塩処理するなど粗銀材を作るまでの工程が多いなどの問題があった。
【０００５】
本発明の目的は、塩素を用いることなく銀を含む硝酸性溶液から銀のみを選択的に分離し、銀をリサイクルし得る銀の回収方法を提案することにある。
【０００６】
【課題を解決するための手段】
請求項１に係る発明は、銀を含む硝酸性溶液にアルカリ水溶液を添加して溶液をｐＨ値２〜７に調整して中和処理する工程と、中和した溶液に粒状の不溶性タンニンを添加混合する工程と、溶液の温度を３０℃以上に保温して溶液に含まれる銀を不溶性タンニンに吸着する工程と、銀を吸着した不溶性タンニンを溶液から分離する工程と、銀を吸着した不溶性タンニンを焼却処理して銀を回収する工程とを含み、不溶性タンニンが末端Ｈ型不溶性タンニン、懸濁蒸発型不溶性タンニン又はＮＨ 3 型不溶性タンニンであることを特徴とする銀の回収方法である。
請求項２に係る発明は、銀を含む硝酸性溶液にアルカリ水溶液を添加して溶液をｐＨ値２〜７に調整して中和処理する工程と、中和した溶液の温度を３０℃以上に保温する工程と、粒状の不溶性タンニンを充填したカラムを３０℃以上に保温してカラムに３０℃以上に保温した溶液を通して溶液に含まれる銀を不溶性タンニンに吸着する工程と銀を吸着した不溶性タンニンを焼却処理して銀を回収する工程とを含み、不溶性タンニンが末端Ｈ型不溶性タンニン、懸濁蒸発型不溶性タンニン又はＮＨ 3 型不溶性タンニンであることを特徴とする銀の回収方法である。
請求項１又は２に係る発明では、銀を含む硝酸性溶液を３０℃以上、好ましくは４０℃以上に保温することにより、不溶性タンニンは銀に対して非常に高い吸着特性が現れ、不溶性タンニン表面に銀を吸着して、硝酸性溶液から容易に銀を分離できる。また、硝酸性溶液の組成によってはアンモニアなどの還元促進剤を更に添加してｐＨ値を２〜７に調整することにより、より一層の吸着特性が得られる。
【０００７】
銀鏡反応に代表されるように、硝酸性銀溶液はアンモニアの存在下で還元銀として容器表面へ析出することが知られているが、この方法では内壁面へ付着した銀を回収するのに手間がかかる。これに対して本発明の不溶性タンニンを用いる方法では、大部分の銀が不溶性タンニンの表面上に析出するので、銀の回収に手間がかからない。また、銀は析出が一箇所に集中すると難溶解性の塊を生成し易い傾向にあるが、不溶性タンニンに吸着する場合には一箇所には集中せずに分散して吸着するので、その後の処理に適した微粒子状の銀として回収することができる。
【０００８】
不溶性タンニンに吸着した銀は、有機物の還元力により還元状態で吸着している。吸着した銀の純度が９９．９％を越える場合、電気炉により焼却する際に微量の還元性雰囲気で焼却処理を行うことにより、金属銀として回収できる。一方、吸着した銀の純度が９９．９％未満の場合、電気炉により焼却する際に酸化性雰囲気で酸化することにより、酸化銀の形態で回収される。この酸化銀は硝酸性溶液に容易に溶けるため電析法(Electrodeposition)などにより精錬処理し易い。
【０００９】
【発明の実施の形態】
本発明に供される不溶性タンニンは特許第３０３３７９６号に示される不溶性タンニンのうち、縮合性タンニン粉末を苛性ソーダで溶解し、この溶液にホルマリン水溶液を混合してゲル状組成物を生成し、このゲル状組成物を室温下で熟成、又は加熱して安定化することにより作られる不溶性タンニンで吸着基の末端構造が−ＯＮａ型となる不溶性タンニン、この吸着基の末端構造が−ＯＮａ型の不溶性タンニンを硝酸などの鉱酸に浸漬することにより、吸着基の末端構造を−ＯＨ型に置換して作られる不溶性タンニン（以下、末端Ｈ型不溶性タンニンという。）、特願平１１−２５２５４９号公報に示される方法で製造される不溶性タンニン（以下、懸濁蒸発型不溶性タンニンという。）が適している。この懸濁蒸発型不溶性タンニンは、アルカリ水溶液に縮合型タンニン粉末を溶解し、この溶液にアルデヒド水溶液を添加混合し、ポリエーテル型非イオン性界面活性剤を含む疎水性溶媒を加熱温度下で撹拌させながらこの混合液を添加して液滴の形態で前記疎水性溶媒中に分散させた後、液滴から水分を蒸発させることにより作られる。
【００１０】
また、特許第３０３３７９６号に示される不溶性タンニンのうち、縮合性タンニン粉末をアンモニア水で溶解し、この溶液にホルムアルデヒド水溶液を混合してゲル状組成物を生成し、このゲル状組成物を室温下で熟成又は加熱することにより安定化して作られる不溶性タンニン（以下、ＮＨ3型不溶性タンニンという。）も銀の回収用として使用される。このＮＨ3型不溶性タンニンは銀以外の不純物元素が硝酸性溶液中に含まれる場合は、その他の不純物元素も吸着するため、銀のみを回収する目的には適さず、様々な工程を経て、溶液の最終的な廃液処理として使用する場合に適している。
上述した「不溶性タンニン」はいずれも、水、酸又はアルカリのいずれに対しても溶解しないタンニンである。この不溶性タンニンは粒径が好ましくは０．５ｍｍ以上のものが選ばれる。
【００１１】
本発明の処理対象となる溶液は、製品のライフサイクルが短いパーソナルコンピューターや携帯電話などの電子機器関係で使用済みとなった廃棄基板を粉砕、酸化処理して得られる金属酸化物を硝酸性溶液に溶解した銀やニッケル、銅を含む溶液である。この銀を含む硝酸性溶液に苛性ソーダ等のアルカリ水溶液を添加して、不溶性タンニンの吸着に適したｐＨ値２〜７の範囲に中和する。硝酸性溶液に含まれるニッケルや銅がほとんど不溶性タンニンに吸着しないｐＨ値３〜４が好ましい。硝酸性溶液の中和処理に用いるアルカリ水溶液には銀の吸着・還元効果を向上するアンモニア水が好ましい。この中和した溶液に末端Ｈ型不溶性タンニンを添加し撹拌するか、又は振り混ぜる方法により、溶液の温度を３０℃以上好ましくは４０℃以上に保温して、銀のみを選択的に不溶性タンニンにて吸着し、還元回収する。
【００１２】
中和した溶液と不溶性タンニンの接触方法には、バッチ式とカラム式がある。請求項１に係る方法はバッチ式であって、中和した溶液を容器に入れ不溶性タンニンを溶液に添加した後、溶液の温度を３０℃以上に保温した状態で撹拌するか、又は振り混ぜる方法である。請求項２に係る方法はカラム式であって、不溶性タンニンをカラムに充填した後、中和した溶液だけでなく、カラムも３０℃以上に保温した状態で中和した溶液を通過させる方法である。
バッチ式の場合、中和した溶液に対する上記不溶性タンニンの添加量は、溶液中に含まれる金属元素の濃度に依存するが、好ましくは溶液１０〜１００ｍｌに対して湿潤重量で１ｇである。粒状の不溶性タンニンを中和した溶液に添加した後、３０℃以上の保温した状態で好ましくは２時間以上十分に撹拌するか、或いは振り混ぜる。
銀を吸着した不溶性タンニンを硝酸性溶液から分離する方法としては、濾紙、可燃性ポリプロピレン製のフィルタ、或いは不溶性タンニンのみ通過できない目開きを有するステンレス鋼製のスクリーンが採用される。濾紙や可燃性フィルタで不溶性タンニンを分離した場合には、濾紙やフィルタとともに不溶性タンニンを焼却することにより銀のみを酸化物として回収することができる。ステンレス鋼製スクリーンを使用する場合には、不溶性タンニンの粒径が０．５ｍｍ以上あれば、目開きが０．２〜０．３ｍｍ程度のスクリーンが選ばれ、分離した不溶性タンニンを直接焼却することにより、銀のみを回収することができる。
【００１３】
【実施例】
次に本発明の実施例を比較例とともに説明する。
＜実施例１〜９＞
銀の濃度が５０ｐｐｍ、硝酸濃度が２．０Ｎの水溶液１８００ｍｌを用意した。先ずこの水溶液をそれぞれ５等分し、各溶液にアンモニア水を異なる量添加して、ｐＨ値をおおよそ２，３，４，５及び６に調整した液を用意した。次いでｐＨ値をおおよそ２，３，４，５及び６に調整した液をそれぞれ更に９等分した。
ｐＨを変えた５種類の溶液に末端Ｈ型不溶性タンニンをそれぞれ添加し、４０℃に保温した状態で振り混ぜた（実施例１）。
ｐＨを変えた５種類の溶液にＮＨ3型不溶性タンニンをそれぞれ添加し、４０℃に保温した状態で振り混ぜた（実施例２）。
ｐＨを変えた５種類の溶液に懸濁蒸発Ｈ型不溶性タンニンをそれぞれ添加し、４０℃に保温した状態で振り混ぜた（実施例３）。
【００１４】
ｐＨを変えた５種類の溶液に末端Ｈ型不溶性タンニンをそれぞれ添加し、５０℃に保温した状態で振り混ぜた（実施例４）。
ｐＨを変えた５種類の溶液にＮＨ3型不溶性タンニンをそれぞれ添加し、５０℃に保温した状態で振り混ぜた（実施例５）。
ｐＨを変えた５種類の溶液に懸濁蒸発Ｈ型不溶性タンニンをそれぞれ添加し、５０℃に保温した状態で振り混ぜた（実施例６）。
【００１５】
ｐＨを変えた５種類の溶液に末端Ｈ型不溶性タンニンをそれぞれ添加し、６０℃に保温した状態で振り混ぜた（実施例７）。
ｐＨを変えた５種類の溶液にＮＨ3型不溶性タンニンをそれぞれ添加し、６０℃に保温した状態で振り混ぜた（実施例８）。
ｐＨを変えた５種類の溶液に懸濁蒸発Ｈ型不溶性タンニンをそれぞれ添加し、６０℃に保温した状態で振り混ぜた（実施例９）。
各溶液には、不溶性タンニンを溶液２０ｍｌに対して湿潤重量で１ｇの割合でそれぞれ添加し、４８時間振とう試験器で振り混ぜた。
【００１６】
＜比較例１〜３＞
実施例１〜９と同じ銀の濃度が５０ｐｐｍ、硝酸濃度が２．０Ｎの水溶液を６００ｍｌ用意した。先ずこの水溶液をそれぞれ５等分し、各溶液にアンモニア水を異なる量添加して、ｐＨ値をおおよそ２，３，４，５及び６に調整した液を用意した。次いでｐＨ値をおおよそ２，３，４，５及び６に調整した液をそれぞれ更に３等分した。
ｐＨを変えた５種類の溶液に末端Ｈ型不溶性タンニンをそれぞれ添加し、２５℃に保温した状態で振り混ぜた（比較例１）。
ｐＨを変えた５種類の溶液にＮＨ3型不溶性タンニンをそれぞれ添加し、２５℃に保温した状態で振り混ぜた（比較例２）。
ｐＨを変えた５種類の溶液に懸濁蒸発Ｈ型不溶性タンニンをそれぞれ添加し、２５℃に保温した状態で振り混ぜた（比較例３）。
各溶液には、不溶性タンニンを溶液２０ｍｌに対して湿潤重量で１ｇの割合でそれぞれ添加し、４８時間振とう試験器で振り混ぜた。
【００１７】
＜比較評価＞
実施例１〜９及び比較例１〜３の３種類の不溶性タンニンによる吸着平衡後の６０種類の溶液のｐＨを測定した。その結果を図１の横軸に示す。図１の縦軸には不溶性タンニン１ｇ（乾燥重量）当りの銀の吸着容量を示す。
図１から明らかなように、２５℃の保温条件で末端Ｈ型不溶性タンニン及び懸濁蒸発型不溶性タンニンを用いた比較例１，３ではほとんど吸着できていない。これに対して保温条件を４０℃、５０℃及び６０℃にそれぞれ加温した実施例１，３，４，６，７及び９では温度が上がるにつれて徐々に吸着容量が大きくなっている。３０℃の保温条件でＮＨ3型不溶性タンニンを用いた比較例２は、銀が吸着しているが、保温条件を４０℃、５０℃及び６０℃にそれぞれ上げた実施例２，５及び８では更に吸着容量が大きくなっていることが判る。
【００１８】
＜実施例１０＞
銀濃度１００００ｐｐｍ、硝酸濃度２．０Ｎの水溶液４０ｍｌを用意した。この溶液に湿潤状態で２ｇのＮＨ3型不溶性タンニンを添加して、６０℃に保温して４８時間振とう試験器で振り混ぜた。この溶液のｐＨ値はおおよそ６に調整した。
【００１９】
この実施例１０における銀の吸着容量は、不溶性タンニン１ｇ（乾燥重量）当り最大２５０ｍｇの吸着量が得られた。また、銀は容器表面へはほとんど付着せず、不溶性タンニンの表面に吸着されていることが判った。不溶性タンニンの表面より採取した小片を測定試料としてＸ線回折分析(X-ray Difracion analysis：ＸＲＤ)による定性分析を行った。その結果を図２に示す。図２に示すように、金属銀を分析したときのピークと同じピークが表れたことから不溶性タンニンの表面より採取した測定試料のほとんどが還元銀の形で吸着されていることが確認された。
【００２０】
【発明の効果】
以上述べたように、本発明によれば、銀を含む硝酸性溶液にアルカリ水溶液を添加して溶液をｐＨ値を２〜７、好ましくは３〜４に調整して中和し、この中和した溶液に粒状の末端Ｈ型不溶性タンニン、懸濁蒸発型不溶性タンニン又はＮＨ 3 型不溶性タンニンである不溶性タンニンを添加混合し、溶液の温度を３０℃以上、好ましくは４０℃以上に保温して溶液に含まれる銀を不溶性タンニンに吸着させ、銀を吸着した不溶性タンニンを溶液から分離し、銀を吸着した不溶性タンニンを焼却処理して銀を回収することにより、塩素を用いることなく銀を含む硝酸性溶液から銀のみを選択的に分離し、銀をリサイクルすることができる。また、銀を含む硝酸性溶液にアルカリ水溶液を添加して溶液をｐＨ値を２〜７に調整して中和し、この中和した溶液を３０℃以上に保温して、粒状の末端Ｈ型不溶性タンニン、懸濁蒸発型不溶性タンニン又はＮＨ 3 型不溶性タンニンである不溶性タンニンを充填したカラムを３０℃以上に保温してカラムに溶液を通して溶液に含まれる銀を不溶性タンニンに吸着させ、銀を吸着した不溶性タンニンを焼却処理して銀を回収する方法を用いても同様の効果が得られる。
【図面の簡単な説明】
【図１】実施例１〜９及び比較例１〜３の３種類の不溶性タンニンへの銀の吸着容量と吸着後のｐＨ値を示す図。
【図２】実施例１０のＸ線回折分析によるスペクトル図。[0001]
BACKGROUND OF THE INVENTION
The present invention recovers silver contained in a nitrate silver solution generated by wet processing for the purpose of recycling valuable metals using insoluble tannins from substrate parts that have been used in the electronic device semiconductor industry and the like. It is about how to do.
[0002]
[Prior art]
Personal computers and mobile phones are discarded in a short cycle because the model change period is short. Semiconductor substrates and the like used in these materials contain noble metals such as silver, platinum, and palladium, and several methods for recovering these rare valuable metals have been devised.
First, in order to recover valuable metals from a semiconductor substrate or the like, boards, which are waste parts, are once pulverized and cut to an appropriate size and then subjected to high-temperature incineration to thermally decompose other than the metal. Metals remaining as oxides after pyrolysis include silver such as plating members, and platinum groups such as gold and palladium used for connection. Among these valuable metals, silver is relatively soluble in nitrate solutions. On the other hand, gold and platinum groups have low solubility in a nitrate solution and are dissolved by aqua regia. Using this chemical property, silver and other valuable metals can be separated.
[0003]
Conventionally, as a method for recovering silver from a nitrate-containing solution containing silver, a method in which silver is solid-liquid separated by utilizing the property that silver forms a solid of a halogen element and a silver halide has been adopted. In this method, solid silver chloride is produced mainly using chlorine as a halogen element. Silver chloride separated and recovered from the nitrate solution is dissolved again, desalted, and recovered as a crude silver material. Crude silver is refined and recycled to industry.
[0004]
[Problems to be solved by the invention]
However, in the method of recovering silver dissolved in the above-mentioned nitrate solution as silver chloride, corrosion resistance equipment is required because chlorine is used, silver chloride solid-liquid separation operation, recovered silver chloride is further desalted, etc. There were problems such as many processes to make coarse silver material.
[0005]
An object of the present invention is to propose a silver recovery method capable of selectively separating only silver from a nitrate solution containing silver without using chlorine and recycling the silver.
[0006]
[Means for Solving the Problems]
The invention according to
The invention according to
In the invention according to
[0007]
As represented by the silver mirror reaction, nitrate silver solution is known to deposit on the container surface as reduced silver in the presence of ammonia, but this method takes time and effort to recover the silver adhering to the inner wall surface. It takes. On the other hand, in the method using the insoluble tannin of the present invention, most of the silver is deposited on the surface of the insoluble tannin, so that it does not take time to recover the silver. In addition, silver tends to form a hardly soluble lump when precipitation is concentrated in one place, but when adsorbing to insoluble tannin, it is dispersed and adsorbed without being concentrated in one place. It can be recovered as fine silver particles suitable for processing.
[0008]
Silver adsorbed on insoluble tannin is adsorbed in a reduced state by the reducing power of organic matter. When the purity of the adsorbed silver exceeds 99.9%, it can be recovered as metallic silver by incineration in a small amount of reducing atmosphere when incinerated by an electric furnace. On the other hand, when the purity of the adsorbed silver is less than 99.9%, it is recovered in the form of silver oxide by being oxidized in an oxidizing atmosphere when incinerated by an electric furnace. Since this silver oxide is easily dissolved in a nitric acid solution, it is easy to refine by an electrodeposition method (Electrodeposition) or the like.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Among the insoluble tannins disclosed in Japanese Patent No. 3033796, the insoluble tannin used in the present invention is prepared by dissolving a condensable tannin powder with caustic soda and mixing this solution with a formalin aqueous solution to form a gel composition. Insoluble tannin produced by aging at room temperature or stabilizing by heating to form an insoluble tannin in which the terminal structure of the adsorptive group becomes -ONa type, insoluble tannin in which the terminal structure of the adsorbing group is -ONa type Insoluble tannin (hereinafter referred to as terminal H-type insoluble tannin), which is produced by immersing the terminal group of the adsorbing group with —OH type by immersing in a mineral acid such as nitric acid, Japanese Patent Application No. 11-252549. Insoluble tannin produced by the method shown (hereinafter referred to as suspension evaporation type insoluble tannin) is suitable. This suspension evaporation type insoluble tannin is obtained by dissolving condensed tannin powder in an alkaline aqueous solution, adding an aldehyde aqueous solution to this solution, mixing, and stirring a hydrophobic solvent containing a polyether type nonionic surfactant at a heating temperature. The mixed solution is added while being dispersed in the hydrophobic solvent in the form of droplets, and then water is evaporated from the droplets.
[0010]
Also, among the insoluble tannins shown in Japanese Patent No. 3033796, a condensable tannin powder is dissolved in aqueous ammonia, and a formaldehyde aqueous solution is mixed with this solution to form a gel composition. Insoluble tannins (hereinafter referred to as NH 3 type insoluble tannins) which are made stable by aging or heating in the above are also used for silver recovery. This NH 3 type insoluble tannin is not suitable for the purpose of recovering only silver, because it contains other impurity elements when nitrate elements other than silver are contained in the nitrate solution. It is suitable for use as a final waste liquid treatment.
Any of the above-mentioned “insoluble tannins” is a tannin that does not dissolve in any of water, acid, or alkali. The insoluble tannin having a particle size of preferably 0.5 mm or more is selected.
[0011]
The solution to be treated according to the present invention is a nitrate solution of a metal oxide obtained by pulverizing and oxidizing a waste substrate that has been used in connection with electronic devices such as personal computers and mobile phones having a short product life cycle. It is a solution containing silver, nickel and copper dissolved in. An alkaline aqueous solution such as caustic soda is added to this silver-containing nitrate solution to neutralize it to a pH value range of 2 to 7 suitable for adsorption of insoluble tannin. A pH value of 3 to 4 where nickel and copper contained in the nitric acid solution hardly adsorb to insoluble tannin is preferable. The aqueous alkaline solution used for the neutralization treatment of the nitrate solution is preferably aqueous ammonia that improves the silver adsorption / reduction effect. By adding terminal H-type insoluble tannin to this neutralized solution and stirring or shaking, the temperature of the solution is kept at 30 ° C. or higher, preferably 40 ° C. or higher, so that only silver is selectively converted into insoluble tannin. Adsorbed and reduced and recovered.
[0012]
There are batch and column methods for contacting the neutralized solution with insoluble tannin. The method according to
In the case of a batch system, the amount of the insoluble tannin added to the neutralized solution depends on the concentration of the metal element contained in the solution, but is preferably 1 g in a wet weight with respect to 10 to 100 ml of the solution. After adding the granular insoluble tannin to the neutralized solution, it is preferably sufficiently stirred or shaken for 2 hours or more while keeping the temperature at 30 ° C. or higher.
As a method for separating the insoluble tannin adsorbing silver from the nitrate solution, a filter paper, a filter made of flammable polypropylene, or a stainless steel screen having an opening through which only insoluble tannin cannot pass is employed. When insoluble tannin is separated by a filter paper or a flammable filter, only silver can be recovered as an oxide by burning the insoluble tannin together with the filter paper or filter. When using a stainless steel screen, if the particle size of insoluble tannin is 0.5 mm or more, a screen with an opening of about 0.2 to 0.3 mm is selected, and the separated insoluble tannin is directly incinerated. Thus, only silver can be recovered.
[0013]
【Example】
Next, examples of the present invention will be described together with comparative examples.
<Examples 1-9>
1800 ml of an aqueous solution having a silver concentration of 50 ppm and a nitric acid concentration of 2.0 N was prepared. First, each of the aqueous solutions was divided into 5 equal parts, and different amounts of aqueous ammonia were added to each solution to prepare liquids having pH values adjusted to approximately 2, 3, 4, 5, and 6. Next, the liquids whose pH values were adjusted to approximately 2, 3, 4, 5 and 6 were further divided into 9 equal parts.
The terminal H-type insoluble tannin was added to each of the five types of solutions having different pHs, and the mixture was shaken and kept at 40 ° C. (Example 1).
NH 3 type insoluble tannin was added to each of the five types of solutions having different pHs, and the mixture was shaken and mixed at a temperature of 40 ° C. (Example 2).
Suspension evaporation H-type insoluble tannin was added to each of the five types of solutions with different pHs, and the mixture was shaken and kept at 40 ° C. (Example 3).
[0014]
The terminal H-type insoluble tannin was added to each of the five types of solutions having different pHs, and the mixture was shaken and mixed at a temperature of 50 ° C. (Example 4).
NH 3 -type insoluble tannin was added to each of the five types of solutions having different pHs, and the mixture was shaken and kept at 50 ° C. (Example 5).
Suspension evaporation H-type insoluble tannin was added to each of the five types of solutions having different pHs, and the mixture was shaken and kept at 50 ° C. (Example 6).
[0015]
The terminal H-type insoluble tannin was added to each of the five types of solutions having different pHs, and the mixture was shaken and kept at 60 ° C. (Example 7).
NH 3 -type insoluble tannin was added to each of the five types of solutions with different pHs, and the mixture was shaken and kept at 60 ° C. (Example 8).
Suspension evaporation H-type insoluble tannin was added to each of the five types of solutions with different pHs, and the mixture was shaken and kept at 60 ° C. (Example 9).
To each solution, insoluble tannin was added in a ratio of 1 g in a wet weight to 20 ml of the solution, and the mixture was shaken with a shaking tester for 48 hours.
[0016]
<Comparative Examples 1-3>
600 ml of the same aqueous solution having a silver concentration of 50 ppm and a nitric acid concentration of 2.0 N as in Examples 1 to 9 was prepared. First, each of the aqueous solutions was divided into 5 equal parts, and different amounts of aqueous ammonia were added to each solution to prepare liquids having pH values adjusted to approximately 2, 3, 4, 5, and 6. Next, the liquids whose pH values were adjusted to approximately 2, 3, 4, 5, and 6 were further divided into three equal parts.
The terminal H-type insoluble tannin was added to each of the five types of solutions having different pHs, and the mixture was shaken and kept at 25 ° C. (Comparative Example 1).
NH 3 -type insoluble tannin was added to each of the five types of solutions having different pHs, and the mixture was shaken and kept at 25 ° C. (Comparative Example 2).
Suspension evaporation H-type insoluble tannin was added to each of the five types of solutions with different pHs, and the mixture was shaken and kept at 25 ° C. (Comparative Example 3).
To each solution, insoluble tannin was added in a ratio of 1 g in a wet weight to 20 ml of the solution, and the mixture was shaken with a shaking tester for 48 hours.
[0017]
<Comparison evaluation>
The pH of 60 types of solutions after adsorption equilibrium with the three types of insoluble tannins of Examples 1 to 9 and Comparative Examples 1 to 3 was measured. The result is shown on the horizontal axis of FIG. The vertical axis of FIG. 1 shows the adsorption capacity of silver per 1 g of insoluble tannin (dry weight).
As is apparent from FIG. 1, in Comparative Examples 1 and 3 using terminal H-type insoluble tannin and suspension evaporation-type insoluble tannin under a temperature maintaining condition of 25 ° C., almost no adsorption was possible. On the other hand, in Examples 1, 3, 4, 6, 7 and 9 in which the heat retaining conditions were heated to 40 ° C., 50 ° C. and 60 ° C., respectively, the adsorption capacity gradually increased as the temperature increased. In Comparative Example 2 in which NH 3 type insoluble tannin was used at 30 ° C., silver was adsorbed, but in Examples 2, 5 and 8 where the temperature was increased to 40 ° C., 50 ° C. and 60 ° C., respectively. Further, it can be seen that the adsorption capacity is increased.
[0018]
<Example 10>
40 ml of an aqueous solution having a silver concentration of 10,000 ppm and a nitric acid concentration of 2.0 N was prepared. To this solution, 2 g of NH 3 type insoluble tannin was added in a wet state, and the mixture was kept at 60 ° C. and shaken for 48 hours with a shaking tester. The pH value of this solution was adjusted to approximately 6.
[0019]
The maximum adsorption amount of 250 mg per 1 g (dry weight) of insoluble tannin was obtained as the silver adsorption capacity in Example 10. Further, it was found that silver hardly adhered to the container surface and was adsorbed on the surface of insoluble tannin. Qualitative analysis by X-ray diffraction analysis (XRD) was performed using a small piece collected from the surface of insoluble tannin as a measurement sample. The result is shown in FIG. As shown in FIG. 2, it was confirmed that most of the measurement sample collected from the surface of the insoluble tannin was adsorbed in the form of reduced silver because the same peak as the peak when metal silver was analyzed appeared.
[0020]
【The invention's effect】
As described above, according to the present invention, an aqueous alkaline solution is added to a nitric acid solution containing silver to neutralize the solution by adjusting the pH value to 2 to 7, preferably 3 to 4. Insoluble tannin which is granular terminal H type insoluble tannin, suspension evaporation type insoluble tannin or NH 3 type insoluble tannin is added to and mixed with the solution, and the temperature of the solution is kept at 30 ° C or higher, preferably 40 ° C or higher. Nitric acid containing silver without using chlorine by adsorbing the silver contained in the insoluble tannin, separating the insoluble tannin adsorbing the silver from the solution, and incinerating the insoluble tannin adsorbing the silver to recover the silver. It is possible to selectively separate only silver from the aqueous solution and recycle the silver. Further, an aqueous alkaline solution is added to a nitrate-containing solution containing silver to neutralize the solution by adjusting the pH value to 2 to 7, and the neutralized solution is kept at 30 ° C. or higher to form a granular terminal H type. A column packed with insoluble tannin that is insoluble tannin, suspension evaporative insoluble tannin or NH 3 type insoluble tannin is kept at 30 ° C or higher, and the silver contained in the solution is adsorbed to the insoluble tannin by passing the solution through the column. The same effect can be obtained by using a method in which the insoluble tannin is incinerated to recover silver.
[Brief description of the drawings]
FIG. 1 is a graph showing the adsorption capacity of silver on three types of insoluble tannins of Examples 1 to 9 and Comparative Examples 1 to 3 and the pH value after adsorption.
2 is a spectrum diagram obtained by X-ray diffraction analysis of Example 10. FIG.
Claims (2)
前記中和した溶液に粒状の不溶性タンニンを添加混合する工程と、
前記溶液の温度を３０℃以上に保温して前記溶液に含まれる銀を前記不溶性タンニンに吸着する工程と、
前記銀を吸着した不溶性タンニンを前記溶液から分離する工程と、
前記銀を吸着した不溶性タンニンを焼却処理して銀を回収する工程と
を含み、
前記不溶性タンニンが末端Ｈ型不溶性タンニン、懸濁蒸発型不溶性タンニン又はＮＨ 3 型不溶性タンニンであることを特徴とする銀の回収方法。Adding an aqueous alkaline solution to a silver-containing nitrate solution to adjust the solution to a pH value of 2 to 7 and neutralizing the solution;
Adding and mixing granular insoluble tannin to the neutralized solution; and
Maintaining the temperature of the solution at 30 ° C. or higher and adsorbing silver contained in the solution to the insoluble tannin;
Separating the insoluble tannin adsorbed with silver from the solution;
See containing and recovering the silver incinerated insoluble tannin having adsorbed the silver,
The method for recovering silver, wherein the insoluble tannin is terminal H type insoluble tannin, suspension evaporation type insoluble tannin or NH 3 type insoluble tannin .
前記中和した溶液の温度を３０℃以上に保温する工程と、
粒状の不溶性タンニンを充填したカラムを３０℃以上に保温して前記カラムに前記３０℃以上に保温した溶液を通して前記溶液に含まれる銀を前記不溶性タンニンに吸着する工程と
前記銀を吸着した不溶性タンニンを焼却処理して銀を回収する工程と
を含み、
前記不溶性タンニンが末端Ｈ型不溶性タンニン、懸濁蒸発型不溶性タンニン又はＮＨ 3 型不溶性タンニンであることを特徴とする銀の回収方法。Adding an aqueous alkaline solution to a silver-containing nitrate solution to adjust the solution to a pH value of 2 to 7 and neutralizing the solution;
Maintaining the temperature of the neutralized solution at 30 ° C. or higher;
A step of keeping a column packed with granular insoluble tannin at 30 ° C. or higher and adsorbing silver contained in the solution to the insoluble tannin through a solution kept at 30 ° C. or higher in the column; the incineration process to look at containing and recovering the silver,
The method for recovering silver, wherein the insoluble tannin is terminal H type insoluble tannin, suspension evaporation type insoluble tannin or NH 3 type insoluble tannin .
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| WO2007023521A1 (en) * | 2005-08-22 | 2007-03-01 | Saga University | Method of separating gold |
| CN100434548C (en) * | 2007-03-08 | 2008-11-19 | 同济大学 | Method of reclaiming silver from silver containing solution by poly m-phenylenediamine as adsorbent |
| CN100434547C (en) * | 2007-03-08 | 2008-11-19 | 同济大学 | Method of reclaiming silver from silver containing solution by poly o-phenylenediamine as adsorbent |
| CN100434546C (en) * | 2007-03-08 | 2008-11-19 | 同济大学 | Method of reclaiming silver from silver ion containing solution by polydiaminoanthraquinone as adsorbent |
| JP5093883B2 (en) * | 2007-04-12 | 2012-12-12 | オルガノ株式会社 | Separation membrane modification method and apparatus, separation membrane modified by the method, and separation membrane operation method and apparatus |
| JP5184838B2 (en) * | 2007-07-31 | 2013-04-17 | 富士シリシア化学株式会社 | Tannin-containing porous body, method for producing tannin-containing porous body, and method for recovering metal |
| JP5644250B2 (en) * | 2010-08-18 | 2014-12-24 | 三菱マテリアル株式会社 | Method for recovering platinum group elements |
| JP5644251B2 (en) * | 2010-08-18 | 2014-12-24 | 三菱マテリアル株式会社 | Method for recovering platinum group elements |
| CN102534211B (en) * | 2012-01-20 | 2013-08-28 | 北京科技大学 | Method for selectively adsorbing and extracting gold by using mangosteen slag |
| JP2016047505A (en) * | 2014-08-28 | 2016-04-07 | 元基 井上 | Noble metal adsorbent using polyphenol derived from grape seeds as raw material |
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