JP3838743B2

JP3838743B2 - Method for producing high purity cadmium

Info

Publication number: JP3838743B2
Application number: JP15150797A
Authority: JP
Inventors: 喜志雄田山; 一山内
Original assignee: Dowa Holdings Co Ltd; Dowa Mining Co Ltd
Current assignee: Dowa Holdings Co Ltd
Priority date: 1997-05-26
Filing date: 1997-05-26
Publication date: 2006-10-25
Anticipated expiration: 2017-05-26
Also published as: JPH10324930A

Description

【０００１】
【発明の属する技術分野】
本発明は、純度９９．９９％程度の市販金属カドミウム等から真空蒸留精製により、純度９９．９９９９％以上の高純度カドミウムを製造する方法と装置に関する。
【０００２】
【従来の技術】
一般に金属カドミウムは、カドミウムを含む硫酸浴を不溶性陽極とアルミニウム陰極で電解して、陰極上に純金属カドミウムを析出させて得る電解法が知られている。この方法は、原料として亜鉛製錬煙灰や亜鉛電解で発生する精製滓の中に含有される数％〜数十％のカドミウムを硫酸液で溶解し、再び亜鉛板や亜鉛末で置換析出した海綿状のものからＣｄ５０〜６０ｇ／ｌの純電解液を作り、電流密度１．５Ａ／ｄｍ² で電解して純カドミウムを得る方法である。これらの方法によって得られた粗カドミウムを原料として、帯溶融法や電解精製法によって純度を上げ、現在では９９．９９％の純度を有する金属カドミウムが市販されている。
【０００３】
【発明が解決しようとする課題】
上述の帯溶融法や、電解精製法によって得られる金属カドミウムの純度は９９．９〜９９．９９％程度であり不純物として含有される銅、銀、鉛はいずれも１０ppm 以上含まれていた。上記の金属をさらにゾーン精製法によって精製する手段もあるが、精製後の切断加工の必要性と汚染の危険があることから、精製時の処理量の制約や精製カドミウムをインゴットにする場合には鋳造時の不純物の混入による汚染の問題があった。
【０００４】
したがって本発明の目的は、従来の電解溶融法ではカドミウムとの完全分離が困難でった銅、銀、タリウム、鉛等を分離できる新規な精製手段を開発することによって純度９９．９９９９％以上の高純度カドミウムを直接インゴット状で製造できる製造方法と製造装置を提供することにある。
【０００５】
【課題を解決するための手段】
本発明者らは上記目的を達成すべく鋭意研究の結果、外筒と内筒からなる二重の石英筒で封体した内部に原料カドミウムが装入される原料るつぼとこれに連接して設けられる回収鋳型を配置して真空蒸留を行い、蒸発したカドミウムを石英筒面に凝縮させ、これを回収鋳型に回収するようにすれば、従来よりも簡易な構造でしかも精製から鋳造までを一回の連続工程で処理できる上、汚染が少ないので、含有する不純物が１ppm 未満の純度９９．９９９９％以上の高純度カドミウムが得られることを見いだし本発明に到達した。
【０００６】
すなわち本発明は、カドミウム原料を真空溶解して高純度カドミウムを製造する方法において、電気炉内で原料るつぼと回収鋳型を耐熱材からなる内筒と外筒の二重の筒内に封体し、該原料るつぼに装入された原料カドミウムを温度３５０℃以上、真空度１×１０^-2Ｔｏｒｒ以下で真空蒸留することにより、蒸発させたカドミウムを該原料るつぼ上の前記内筒の表面に接触させて凝縮させ該原料るつぼ下方の該回収鋳型に回収してインゴットとし、さらに前記凝縮後のガスを該回収鋳型の下方で冷却して固化し、銅、銀、鉛、タリウムの含有量がそれぞれ０.０１ｐｐｍ未満で、かつガス成分以外の不純物量が１ｐｐｍ未満である純度９９.９９９９％以上の高純度カドミウムを得ることを特徴とする高純度カドミウムの製造方法を提供するものである。
【０００７】
【発明の実施の形態】
本発明の高純度カドミウムの製造装置は、一例として図１の概略図に示す構造とすることができる。すなわち電気炉１内に配置された石英製外筒３内を真空排気装置２により真空排気を行えるよう、上記外筒３内に原料るつぼ５、回収鋳型６、鋳型中央部に設けた吸入台９、吸入台下の冷却トラップ８、これを冷却する水冷フランジ７を脱着可能に連接し、さらに原料るつぼ上面に石英製内筒４を設けて外筒３と共に二重構造となって封体されている。
【０００８】
この場合、原料カドミウムとして市販金属カドミウム（純度９９．９９％程度）を原料るつぼ５に適量入れ、電気炉で３５０℃以上、好ましくは３５０〜５００℃の温度範囲にすると共に、真空度を１×１０^-2Ｔｏｒｒ以下、好ましくは１×１０^-2〜１×１０^-3Ｔｏｒｒの範囲に制御すると原料るつぼ内の原料カドミウムが融解・蒸発し、該るつぼ５と上部の内筒４との間に落下して、るつぼ底部に連接する回収鋳型６の中に回収される。
【０００９】
原料カドミウム中に含有される不純物のうち、カドミウムより蒸気圧の低いアルミニウム、ケイ素、カルシウム、鉄、ニッケル、銅、銀、亜鉛、タリウム、鉛、ビスマスは原料るつぼ５内に残留し、逆に蒸気圧の高いナトリウム、硫黄、塩素、カリウムは凝縮することなく気体状で真空排気装置２によってるつぼ底部に設けられた吸入孔を通って冷却トラップ８内に吸収され、水冷フランジ７の働きにより冷却されて固化する。
【００１０】
本発明においては、予め、回収用の鋳型の形状を精製後の次工程で用いる鋳型の形状にしてあるため、従来法のように精製されたカドミウムを再度鋳造する必要はなく、このため汚染の少ない高純度カドミウム製品を精製・鋳造の工程を区別することなく一回の処理で製造できる。
【００１１】
このようにして得られた高純度カドミウムをグロー放電質量分析装置で分析したところ、カルシウムが０．０３ppm 未満であり、ナトリウム、アルミニウム、ケイ素、硫黄、塩素、カリウム、鉄、ニッケル、銅、銀、亜鉛、タリウム、鉛、ビスマスがそれぞれ０．０１ppm 未満で、かつガス成分以外の不純物が１ppm 未満の値を示していた。
【００１２】
したがって、本発明においては測定対象元素をＮａ、Ａｌ、Ｓｉ、Ｓ、Ｃｌ、Ｋ、Ｃａ、Ｆｅ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｔｌ、Ｐｂ、Ｂｉとし、グロー放電質量分析装置により定量分析を行い、得られた不純物含有量の総和を１００％から差し引いて得られる数値が９９．９９９９％以上の場合をもって純度９９．９９９９％以上の高純度カドミウムと定義した。
【００１３】
以下、実施例により本発明をさらに説明するが、本発明の範囲はこれらに限定されるものではない。
【００１４】
【実施例１】
図１の高純度カドミウム製造装置を参照して以下説明する。先ず、純度９９．９９％の市販金属カドミウム１００ｇを原料るつぼ５に入れ、回収鋳型６中央部に設置した吸入台９上に固定した後、図１に示すように電気炉１内に装入した。この場合、原料るつぼ５と回収鋳型６の上面には、石英製の外筒３と内筒４とが設けられ、真空排気装置２によって内筒４内部が真空状態となる構造である。真空排気装置２で排気して内筒４の真空度を１×１０^-2Ｔｏｒｒとすると共に、炉温を３５０℃一定で５時間精製したところ、原料中のカドミウムはいったん蒸発した後、原料るつぼ５上の内筒４の面に接触して次第に凝縮し始め、粒状になって原料るつぼ５の底部に設けた回収鋳型６の中に落下した。この粒状カドミウム９９ｇを回収し、その品位を表１に示した。
【００１５】
一方、カドミウムより蒸気圧の高いものはガス状のまま排気装置２で吸引され、吸入台９の上部に設けられた吸入孔を通過して、冷却トラップ８内に吸引され、水冷フランジ７により冷却され固化した。この固化物を分析したところ、その主成分はナトリウム、硫黄、塩素、カリウムなどいずれも蒸気圧の高い物質であることがわかった。併せて原料るつぼ内に残っている金属を分析したところ、その主成分はアルミニウム、ケイ素、カルシウム、鉄、ニッケル、銅、銀、亜鉛、タリウム、鉛、ビスマスなどの蒸気圧の低い物質であることがわかった。
【００１６】
【表１】

【００１７】
【実施例２】
純度９９．９９％の市販金属カドミウム１００ｇを原料るつぼ５に入れて、真空度を１×１０^-3Ｔｏｒｒ、加熱温度を４５０℃として実施例１と同様に精製を行い、精製カドミウム９９ｇを得た。この品位を表１に併せて示した。
【００１８】
【比較例１】
比較のため、純度９９．９９％の市販金属カドミウムの品位を表１に併せて示した。
【００１９】
【発明の効果】
上述のように、本発明の方法に基づく製造装置によれば、原料るつぼで溶解したカドミウムは蒸発して内筒表面に凝縮し、鋳型に回収されてインゴットを形成するので、従来必要とされていた鋳造や後処理等の複雑な工程に代わって、本発明の簡易な構造の製造装置を用いることにより、精製から鋳造までの一連の工程を汚染の危険が少ない一回の工程で行なえるようになり、従来よりも分離精度が高くしかもコスト低減可能な精製手段を提供できる。
【図面の簡単な説明】
【図１】本発明に係る高純度カドミウムの製造装置の概要を示す概略断面図である。
【符号の説明】
１電気炉
２真空排気装置
３石英製外筒
４石英製内筒
５原料るつぼ
６回収鋳型
７水冷フランジ
８冷却トラップ
９吸入台[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for producing high-purity cadmium having a purity of 99.9999% or more by vacuum distillation purification from commercially available metal cadmium having a purity of about 99.99%.
[0002]
[Prior art]
Generally, an electrolysis method is known in which metal cadmium is obtained by electrolyzing a sulfuric acid bath containing cadmium with an insoluble anode and an aluminum cathode, and depositing pure metal cadmium on the cathode. This method is a sponge in which several percent to several tens percent of cadmium contained in zinc smelting smoke ash and refined soot generated by zinc electrolysis is dissolved as a raw material with sulfuric acid solution, and replaced with zinc plate or zinc powder again. In this method, a pure electrolytic solution having a Cd of 50 to 60 g / l is prepared from the product and electrolyzed at a current density of 1.5 A / dm ² to obtain pure cadmium. Using crude cadmium obtained by these methods as a raw material, the purity is increased by a zone melting method or an electrolytic purification method, and metal cadmium having a purity of 99.99% is now commercially available.
[0003]
[Problems to be solved by the invention]
The purity of the metal cadmium obtained by the above-mentioned zone melting method or electrolytic purification method is about 99.9 to 99.99%, and copper, silver, and lead contained as impurities are all contained at 10 ppm or more. Although there is a means to further refine the above metals by zone purification, there is a need for post-purification cutting and the risk of contamination, so when processing volume restrictions during purification and purified cadmium is used as an ingot There was a problem of contamination due to contamination of impurities during casting.
[0004]
Therefore, the object of the present invention is to develop a novel purification means capable of separating copper, silver, thallium, lead, etc., which has been difficult to completely separate from cadmium by the conventional electrolytic melting method, and has a purity of 99.9999% or more. An object of the present invention is to provide a production method and a production apparatus capable of producing high-purity cadmium directly in an ingot shape.
[0005]
[Means for Solving the Problems]
As a result of diligent research to achieve the above object, the present inventors have provided a raw material crucible filled with a raw material cadmium enclosed in a double quartz cylinder composed of an outer cylinder and an inner cylinder, and connected thereto. If the recovered mold is placed and vacuum distilled to condense the evaporated cadmium onto the quartz cylinder surface and collect it in the recovery mold, the structure is simpler than before and the process from refining to casting is performed once. Thus, the present inventors have found that high-purity cadmium having a purity of less than 1 ppm and having a purity of 99.9999% or more can be obtained because it can be processed in a continuous process.
[0006]
That is, the present invention relates to a method for producing high-purity cadmium by vacuum melting a cadmium raw material, wherein the raw material crucible and the recovery mold are sealed in a double cylinder of an inner cylinder and an outer cylinder made of a heat-resistant material in an electric furnace. The raw material cadmium charged in the raw material crucible is vacuum distilled at a temperature of 350 ° C. or higher and a vacuum degree of 1 × 10 ⁻² Torr or lower, so that the evaporated cadmium contacts the surface of the inner cylinder on the raw material crucible. And condensed into the recovery mold below the raw material crucible to form an ingot, and further, the condensed gas is cooled and solidified below the recovery mold so that the contents of copper, silver, lead, and thallium are respectively There is also provided a method for producing high-purity cadmium, characterized by obtaining high-purity cadmium having a purity of 99.9999% or more which is less than 0.01 ppm and the amount of impurities other than gas components is less than 1 ppm. It is.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The high-purity cadmium production apparatus of the present invention can have the structure shown in the schematic diagram of FIG. 1 as an example. That is, the raw material crucible 5, the recovery mold 6, and the suction table 9 provided at the center of the mold are arranged in the outer cylinder 3 so that the inside of the quartz outer cylinder 3 disposed in the electric furnace 1 can be evacuated by the evacuation apparatus 2. A cooling trap 8 under the suction table and a water cooling flange 7 for cooling the cooling trap 8 are connected in a detachable manner, and a quartz inner cylinder 4 is provided on the upper surface of the raw material crucible so that it is enclosed in a double structure together with the outer cylinder 3. Yes.
[0008]
In this case, a commercially available metal cadmium (purity of about 99.99%) as a raw material cadmium is put in an appropriate amount in the raw material crucible 5, and the temperature is set to 350 ° C. or higher, preferably 350 to 500 ° C. in an electric furnace, and the degree of vacuum is 1 ×. When controlled to 10 ⁻² Torr or less, preferably in the range of 1 × 10 ⁻² to 1 × 10 ⁻³ Torr, the raw material cadmium in the raw material crucible melts and evaporates, and between the crucible 5 and the upper inner cylinder 4 It falls and is recovered in the recovery mold 6 connected to the bottom of the crucible.
[0009]
Of the impurities contained in the raw material cadmium, aluminum, silicon, calcium, iron, nickel, copper, silver, zinc, thallium, lead, and bismuth, whose vapor pressure is lower than that of cadmium, remain in the raw material crucible 5 and vice versa. High pressure sodium, sulfur, chlorine, and potassium are absorbed in the cooling trap 8 through the suction hole provided at the bottom of the crucible by the vacuum evacuation device 2 without being condensed, and cooled by the action of the water cooling flange 7. Solidify.
[0010]
In the present invention, since the shape of the recovery mold is preliminarily made into the shape of the mold to be used in the next step after purification, there is no need to re-cast cadmium purified as in the conventional method. A few high-purity cadmium products can be produced in a single process without distinguishing the purification and casting processes.
[0011]
When the high-purity cadmium thus obtained was analyzed by a glow discharge mass spectrometer, the calcium content was less than 0.03 ppm, sodium, aluminum, silicon, sulfur, chlorine, potassium, iron, nickel, copper, silver, Zinc, thallium, lead, and bismuth each had a value of less than 0.01 ppm, and impurities other than gas components showed values of less than 1 ppm.
[0012]
Therefore, in the present invention, Na, Al, Si, S, Cl, K, Ca, Fe, Ni, Cu, Ag, Zn, Tl, Pb, and Bi are used as measurement target elements, and quantitative analysis is performed by a glow discharge mass spectrometer. When the numerical value obtained by subtracting the total impurity content obtained from 100% was 99.9999% or higher, it was defined as high purity cadmium having a purity of 99.9999% or higher.
[0013]
EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these.
[0014]
[Example 1]
This will be described below with reference to the high-purity cadmium production apparatus in FIG. First, 100 g of a commercially available metal cadmium having a purity of 99.99% was put in a raw material crucible 5 and fixed on a suction table 9 installed in the central portion of the recovery mold 6 and then charged in an electric furnace 1 as shown in FIG. . In this case, a quartz outer cylinder 3 and an inner cylinder 4 are provided on the upper surfaces of the raw material crucible 5 and the recovery mold 6, and the inside of the inner cylinder 4 is evacuated by the vacuum exhaust device 2. When the vacuum of the inner cylinder 4 is evacuated by the vacuum evacuation device 2 to 1 × 10 ⁻² Torr and the furnace temperature is refined at a constant 350 ° C. for 5 hours, the cadmium in the raw material once evaporates and then the raw material crucible. 5 began to condense gradually in contact with the surface of the inner cylinder 4 on the upper surface 5, and became granular and dropped into the recovery mold 6 provided at the bottom of the raw material crucible 5. 99 g of this granular cadmium was recovered and the quality is shown in Table 1.
[0015]
On the other hand, those having a vapor pressure higher than that of cadmium are sucked by the exhaust device 2 in a gaseous state, passed through a suction hole provided in the upper part of the suction table 9, sucked into the cooling trap 8, and cooled by the water cooling flange 7. And solidified. When this solidified product was analyzed, it was found that its main component was a substance having a high vapor pressure such as sodium, sulfur, chlorine and potassium. In addition, when the metal remaining in the raw material crucible was analyzed, the main component was a substance with a low vapor pressure such as aluminum, silicon, calcium, iron, nickel, copper, silver, zinc, thallium, lead, bismuth, etc. I understood.
[0016]
[Table 1]

[0017]
[Example 2]
100 g of a commercially available metal cadmium having a purity of 99.99% was put into the raw material crucible 5 and purified in the same manner as in Example 1 at a vacuum of 1 × 10 ⁻³ Torr and a heating temperature of 450 ° C. to obtain 99 g of purified cadmium. . This quality is also shown in Table 1.
[0018]
[Comparative Example 1]
For comparison, the quality of commercially available metal cadmium having a purity of 99.99% is also shown in Table 1.
[0019]
【The invention's effect】
As described above, according to the manufacturing apparatus based on the method of the present invention, the cadmium dissolved in the raw material crucible evaporates and condenses on the inner cylinder surface, and is collected in the mold to form an ingot. Instead of complicated processes such as casting and post-processing, the manufacturing apparatus of the simple structure of the present invention can be used to perform a series of processes from refining to casting in a single process with little risk of contamination. Thus, it is possible to provide a purification means that has higher separation accuracy than conventional ones and can reduce costs.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an outline of an apparatus for producing high-purity cadmium according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electric furnace 2 Vacuum exhaust apparatus 3 Quartz outer cylinder 4 Quartz inner cylinder 5 Raw material crucible 6 Recovery mold 7 Water cooling flange 8 Cooling trap 9 Suction stand

Claims

In a method for producing high-purity cadmium by vacuum melting a cadmium raw material, a raw material crucible and a recovery mold are sealed in a double tube of an inner cylinder and an outer cylinder made of a heat-resistant material in an electric furnace, and the raw material crucible The raw material cadmium is vacuum distilled at a temperature of 350 ° C. or higher and a vacuum degree of 1 × 10 ⁻² Torr or less, so that the evaporated cadmium is brought into contact with the surface of the inner cylinder on the raw material crucible and condensed. Recovered in the recovery mold below the raw material crucible to make an ingot, and further, the condensed gas was cooled and solidified below the recovery mold, and the contents of copper, silver, lead and thallium were less than 0.01 ppm respectively. A method for producing high-purity cadmium, characterized by obtaining high-purity cadmium having a purity of 99.9999% or more in which the amount of impurities other than gas components is less than 1 ppm.