JP5200588B2 - Method for producing high purity silver - Google Patents

Method for producing high purity silver Download PDF

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JP5200588B2
JP5200588B2 JP2008054713A JP2008054713A JP5200588B2 JP 5200588 B2 JP5200588 B2 JP 5200588B2 JP 2008054713 A JP2008054713 A JP 2008054713A JP 2008054713 A JP2008054713 A JP 2008054713A JP 5200588 B2 JP5200588 B2 JP 5200588B2
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silver
silver chloride
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JP2009209421A (en
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善昭 真鍋
靖志 一色
隆至 橋川
聡 浅野
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住友金属鉱山株式会社
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    • YGENERAL 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

本発明は、高純度銀の製造方法に関し、さらに詳しくは、難溶性銀化合物と不純物元素を含有する精錬中間物から金属銀を得る際に、乾式精製又は電解による再精製処理を行うことなく湿式精製のみで、99.999質量%の高純度の金属銀を得ることができる銀の製造方法に関する。   The present invention relates to a method for producing high-purity silver. More specifically, when obtaining metallic silver from a refining intermediate containing a sparingly soluble silver compound and an impurity element, wet purification is performed without performing dry refining or electrorefining treatment. The present invention relates to a method for producing silver by which 99.999 mass% high-purity metallic silver can be obtained only by purification.
従来、銀の製錬方法の一つとして、銅、鉛等の製錬プロセスにおいて電解精製工程で発生するアノードスライムから回収することが行われている。例えば、前記アノードスライムから銀を分離精製する方法として、前記アノードスライムを乾式処理し、粗銀を得て、これを電解精製する方法が広く用いられている。
前記乾式処理および電解精製する方法として、例えばメービアス銀電解法によれば、99.999質量%(以下、5Nと呼称する場合がある。)以上の純度を得ることが可能であることが知られている。
Conventionally, as one of the methods for smelting silver, recovery from anode slime generated in the electrolytic purification step in a smelting process of copper, lead or the like has been performed. For example, as a method for separating and purifying silver from the anode slime, a method is widely used in which the anode slime is dry-treated to obtain crude silver, which is electrolytically purified.
As a method for the dry treatment and electrolytic purification, it is known that, for example, a purity of 99.999% by mass (hereinafter sometimes referred to as 5N) can be obtained according to the Mevias silver electrolysis method. ing.
ところが、前記乾式処理においては、環境面では、粉塵及び排ガスが発生し、作業面では、暑熱作業及び火傷のリスクが潜在するという問題点がある。このような状況の中で、湿式法による効率的な銀の分離回収方法が注目されており、例えば、下記の(1)〜(3)の工程からなる方法により高純度の塩化銀を製造し、得られた塩化銀をアルカリ水溶液中で還元剤により処理して金属銀粉を得る湿式方法(例えば、特許文献1参照。)が提案されている。
(1)前記精錬中間物を亜硫酸塩水溶液中で浸出し、銀を該液中に抽出して、銀を含む浸出液と不溶解残渣を形成する浸出工程、
(2)前記浸出液を中和して酸性にし、塩化銀を析出して、該塩化銀と母液を形成する塩化銀生成工程、及び
(3)前記塩化銀を酸性水溶液中で酸化剤を添加して酸化処理し、不純物元素を溶出分離して、精製された塩化銀と不純物元素を含む溶液を形成する塩化銀精製工程
However, in the dry process, there are problems that dust and exhaust gas are generated on the environment side, and there is a risk of hot work and burns on the work side. Under such circumstances, an efficient method for separating and recovering silver by a wet method has attracted attention. For example, high-purity silver chloride is produced by a method comprising the following steps (1) to (3). There has been proposed a wet method (see, for example, Patent Document 1) in which the obtained silver chloride is treated with a reducing agent in an alkaline aqueous solution to obtain metallic silver powder.
(1) A leaching step of leaching the refining intermediate in a sulfite aqueous solution and extracting silver into the liquid to form a leachate containing silver and an insoluble residue.
(2) a step of neutralizing the leachate to make it acidic, precipitating silver chloride to form a mother liquor with the silver chloride, and (3) adding an oxidizing agent to the silver chloride in an acidic aqueous solution. The silver chloride refining process that forms a solution containing the purified silver chloride and impurity elements by oxidizing and separating the impurity elements to form a solution containing the purified silver chloride and impurity elements
この方法によれば、乾式処理を行い、銀アノードを経て銀電解精製を行なう従来の方法と比較して、環境面及び作業面の軽減化がなされることのみならず、製品化日数の短縮のほか、設備面においても、熔解炉や乾式特有の排ガスを処理するための除塵設備、及び電解槽や整流器などの大型機器が不要であること、液を搬送するためのポンプと反応槽の組み合わせで構成されるので集中管理システムを導入した自動化が可能であること等の大きな利点がある。このため、人員も少なく、設備コストと製造コストの面においても有利な方法であると言える。しかしながら、この方法では、99.99質量%(以下、4Nと呼称する場合がある。)の純度が得られるものの、5Nの純度のものは得られないという課題があった。   According to this method, compared to the conventional method in which dry treatment is performed and silver electrolytic purification is performed through a silver anode, not only environmental and work aspects are reduced, but also the number of days for commercialization is shortened. In addition, on the equipment side, there is no need for large-scale equipment such as melting furnaces and dry-type exhaust gas treatment equipment, and electrolyzers and rectifiers, and a combination of pumps and reaction tanks for transporting liquids. Since it is configured, there are significant advantages such as the possibility of automation using a centralized management system. For this reason, it can be said that it is an advantageous method also in terms of equipment cost and manufacturing cost with a small number of personnel. However, this method has a problem that a purity of 99.99% by mass (hereinafter sometimes referred to as 4N) is obtained, but a purity of 5N cannot be obtained.
以上の状況から、難溶性銀化合物と不純物元素とを含有する精錬中間物を原料として、湿式精製のみで、99.999質量%の高純度の金属銀を得ることができる、効率的な銀の製造方法が求められている。   From the above situation, 99.999 mass% high-purity metallic silver can be obtained only by wet refining using a refining intermediate containing a sparingly soluble silver compound and an impurity element as a raw material. There is a need for a manufacturing method.
再公表特許WO2005/023716号公報(第1頁、第2頁)Republished patent WO2005 / 023716 (first page, second page)
本発明の目的は、上記の従来技術の問題点に鑑み、難溶性銀化合物と不純物元素を含有する精錬中間物から金属銀を得る際に、乾式精製又は電解による再精製処理を行うことなく湿式精製のみで、99.999質量%の高純度の金属銀を得ることができる銀の製造方法を提供することにある。   The object of the present invention is to solve the above-mentioned problems of the prior art, when obtaining metallic silver from a refining intermediate containing a sparingly soluble silver compound and an impurity element, without performing refining treatment by dry refining or electrolysis. An object of the present invention is to provide a silver production method capable of obtaining 99.999 mass% high-purity metallic silver only by purification.
本発明者らは、上記目的を達成するために、難溶性銀化合物と不純物元素とを含有する精錬中間物から、高純度の銀を製造する方法について、鋭意研究を重ねた結果、上記湿式方法において、浸出液を中和して酸性にし、塩化銀を析出して、該塩化銀と母液を形成する塩化銀生成工程で、酸を添加する際に、pHを特定の値に調整し、かつ、塩化銀の析出後に直ちに母液から析出物を分離したところ、99.999質量%の高純度の金属銀を得ることができることを見出し、本発明を完成した。   In order to achieve the above object, the present inventors have conducted extensive research on a method for producing high-purity silver from a refined intermediate containing a sparingly soluble silver compound and an impurity element. In the silver chloride production step of neutralizing the leachate to make it acidic and depositing silver chloride to form a mother liquor with the silver chloride, the pH is adjusted to a specific value when adding acid, and When the precipitate was separated from the mother liquor immediately after the silver chloride was precipitated, it was found that 99.999 mass% high-purity metallic silver could be obtained, and the present invention was completed.
すなわち、本発明の第1の発明によれば、難溶性銀化合物と不純物元素とを含有する精錬中間物から、下記の(1)〜(4)の工程により銀を製造する方法であって、
前記(2)の工程において、前記(1)の工程で得られた銀を含む浸出液に酸を添加する前に、前記銀を含む浸出液を目開きが1μm以下のフィルターで精密ろ過し、酸を添加する際に、pHを3.5〜5.5に調整し、かつ、塩化銀の析出後、60分以内に母液と析出物の全量をろ過し、母液から析出物を分離することを特徴とする銀の製造方法が提供される。
(1)前記精錬中間物を亜硫酸塩水溶液中で浸出して、銀を該亜硫酸塩水溶液中に抽出し、次いで生成した不溶解残渣を分離して、銀を含む浸出液を得る。
(2)前記浸出液に酸を添加して、塩化銀を析出させ、次いで母液を分離して、塩化銀を含む析出物を得る。
(3)前記析出物を酸性水溶液中で酸化処理して、不純物元素を溶出させ、次いで不純物元素を含む液を分離して、精製された塩化銀を得る。
(4)前記塩化銀をアルカリ水溶液中で還元して、銀粉を得る。
That is, according to the first invention of the present invention, a method for producing silver from a refining intermediate containing a hardly soluble silver compound and an impurity element by the following steps (1) to (4),
In the step (2), before adding acid to the leaching solution containing silver obtained in the step (1), the leaching solution containing silver is microfiltered with a filter having an opening of 1 μm or less, and the acid is removed. During the addition, the pH is adjusted to 3.5 to 5.5, and after precipitation of silver chloride, the whole amount of the mother liquor and the precipitate is filtered within 60 minutes to separate the precipitate from the mother liquor. A method for producing silver is provided.
(1) The refining intermediate is leached in an aqueous sulfite solution, silver is extracted into the aqueous sulfite solution, and then the insoluble residue formed is separated to obtain a leachate containing silver.
(2) An acid is added to the leaching solution to precipitate silver chloride, and then the mother liquor is separated to obtain a precipitate containing silver chloride.
(3) The precipitate is oxidized in an acidic aqueous solution to elute the impurity element, and then the liquid containing the impurity element is separated to obtain purified silver chloride.
(4) The silver chloride is reduced in an alkaline aqueous solution to obtain silver powder.
また、本発明の第の発明によれば、第1の発明において、前記(2)の工程において、母液と析出物の全量が抜き出せる構造を有する反応槽を用いて、母液と析出物をろ過する際に、該反応槽から母液と析出物の全量を抜き出すことを特徴とする銀の製造方法が提供される。 According to the second invention of the present invention, in the first invention, in the step (2), the mother liquor and the precipitate are removed using a reaction tank having a structure capable of extracting the whole amount of the mother liquor and the precipitate. When filtering, the silver manufacturing method characterized by extracting the whole quantity of mother liquid and a precipitate from this reaction tank is provided.
また、本発明の第の発明によれば、第1又は2の発明において、前記難溶性銀化合物は、塩化銀であることを特徴とする銀の製造方法が提供される。 According to a third aspect of the present invention, there is provided the method for producing silver according to the first or second aspect , wherein the hardly soluble silver compound is silver chloride.
本発明の高純度銀の製造方法は、難溶性銀化合物と不純物元素とを含有する精錬中間物から金属銀を得る際に、乾式精製又は電解による再精製処理を行うことなく湿式精製のみで、99.999質量%の高純度の金属銀を得ることができるので、その工業的価値は極めて大きい。   The method for producing high-purity silver according to the present invention, when obtaining metallic silver from a refining intermediate containing a hardly soluble silver compound and an impurity element, only by wet refining without performing dry refining or electrorefining treatment, Since 99.999 mass% high-purity metallic silver can be obtained, its industrial value is extremely high.
以下、本発明の高純度銀の製造方法を詳細に説明する。
本発明の高純度銀の製造方法は、難溶性銀化合物と不純物元素とを含有する精錬中間物から、下記の(1)〜(4)の工程により銀を製造する方法であって、前記(2)の工程において、酸を添加する際に、pHを3.5〜5.5に調整し、かつ、塩化銀の析出後に、直ちに母液と析出物の全量をろ過し、母液から析出物を分離することを特徴とする。
(1)前記精錬中間物を亜硫酸塩水溶液中で浸出して、銀を亜硫酸塩水溶液中に抽出し、次いで生成した不溶解残渣を分離して、銀を含む浸出液を得る。
(2)前記浸出液に酸を添加して、塩化銀を析出させ、次いで母液を分離して、塩化銀を含む析出物を得る。
(3)前記析出物を酸性水溶液中で酸化処理して、不純物元素を溶出させ、次いで不純物元素を含む液を分離して、精製された塩化銀を得る。
(4)前記塩化銀をアルカリ水溶液中で還元して、銀粉を得る。
Hereinafter, the manufacturing method of the high purity silver of this invention is demonstrated in detail.
The method for producing high-purity silver according to the present invention is a method for producing silver from a refined intermediate containing a hardly soluble silver compound and an impurity element by the following steps (1) to (4), In the step 2), when adding the acid, the pH is adjusted to 3.5 to 5.5, and immediately after the precipitation of silver chloride, the whole amount of the mother liquor and the precipitate is filtered, and the precipitate is removed from the mother liquor. It is characterized by separating.
(1) The refining intermediate is leached in a sulfite aqueous solution, silver is extracted into the sulfite aqueous solution, and the insoluble residue thus formed is separated to obtain a leachate containing silver.
(2) An acid is added to the leaching solution to precipitate silver chloride, and then the mother liquor is separated to obtain a precipitate containing silver chloride.
(3) The precipitate is oxidized in an acidic aqueous solution to elute the impurity element, and then the liquid containing the impurity element is separated to obtain purified silver chloride.
(4) The silver chloride is reduced in an alkaline aqueous solution to obtain silver powder.
本発明において、上記(2)の工程において、浸出液に酸を添加して、塩化銀を析出させ、次いで母液を分離して、塩化銀を含む析出物を得るとき、酸を添加する際に、pHを3.5〜5.5に調整すること、及び塩化銀の析出後に、直ちに母液と析出物の全量をろ過し、母液から析出物を分離することを確実に実施することに重要な意義を有する。これによって、従来の工程を用いる高純度銀の製造方法よりも、さらに高純度の、5Nの純度を有する銀を製造することができる。
ここで、本発明に用いる精錬中間物と各工程について説明する。なお、各工程の説明において、作用とその技術的意義についても説明する。
In the present invention, in the step (2), an acid is added to the leachate to precipitate silver chloride, and then the mother liquor is separated to obtain a precipitate containing silver chloride. Significant importance to adjust the pH to 3.5 to 5.5 and to ensure that after the silver chloride is precipitated, the mother liquor and the total amount of the precipitate are immediately filtered and the precipitate is separated from the mother liquor. Have As a result, it is possible to produce silver having a purity of 5N, which is higher than that of the conventional method for producing high purity silver.
Here, the refining intermediate used for this invention and each process are demonstrated. In the description of each process, the action and its technical significance will also be described.
1.精錬中間物
本発明の原料である精錬中間物は、難溶性銀化合物として塩化銀と不純物元素とを含有するものであり、それが産出されるプロセスとしては、特に限定されるものではないが、銅、ニッケル、鉛等の精錬プロセスの電解精製工程で発生するアノードスライムを始め、めっき液及び写真現像液等の銀含有液の処理工程、貴金属の精錬工程等で発生する中間物が含まれる。
ここで、不純物元素としては、銅、ニッケル、鉛、鉄、コバルト、マンガン、硫黄、亜鉛、カドミウム、スズのほか、ヒ素、アンチモン、ビスマス等の15族元素、セレン、テルル等の16族元素、及び金、白金族元素等が挙げられる。
1. Refining intermediate The refining intermediate that is a raw material of the present invention contains silver chloride and an impurity element as a hardly soluble silver compound, and the process for producing it is not particularly limited. Intermediates generated in the processing step of silver-containing liquid such as plating solution and photographic developer, refining step of noble metal, etc. are included, including anode slime generated in the electrolytic refining step of refining processes such as copper, nickel and lead.
Here, as impurity elements, in addition to copper, nickel, lead, iron, cobalt, manganese, sulfur, zinc, cadmium, tin, group 15 elements such as arsenic, antimony, and bismuth, group 16 elements such as selenium and tellurium, And gold and platinum group elements.
2.(1)の工程
上記(1)の工程は、上記精錬中間物を亜硫酸塩水溶液中で浸出して、銀を亜硫酸塩水溶液中に抽出し、次いで生成した不溶解残渣を分離して、銀を含む浸出液を得る工程である。ここで、上記精錬中間物を亜硫酸塩水溶液に懸濁する。
上記工程の浸出反応は、亜硫酸塩が亜硫酸ナトリウムであり、難溶性銀化合物が塩化銀であるとき、下記の式1に従い、銀は選択的に浸出される。
2. Step (1) In the step (1), the refining intermediate is leached in an aqueous sulfite solution, silver is extracted into the aqueous sulfite solution, and then the insoluble residue produced is separated to remove silver. It is a step of obtaining a leachate containing. Here, the refining intermediate is suspended in a sulfite aqueous solution.
In the leaching reaction in the above step, when the sulfite is sodium sulfite and the hardly soluble silver compound is silver chloride, silver is selectively leached according to the following formula 1.
式1:AgCl+NaSO→Na[AgSO]+NaCl
ここで、式1は、塩化銀が亜硫酸ナトリウムと反応して、安定な銀のスルフィト錯塩:Na[AgSO]を生成する反応である。
Formula 1: AgCl + Na 2 SO 3 → Na [AgSO 3 ] + NaCl
Here, Formula 1 is a reaction in which silver chloride reacts with sodium sulfite to produce a stable silver sulfite complex salt: Na [AgSO 3 ].
上記工程で用いる亜硫酸塩水溶液の亜硫酸イオン濃度は、特に限定されるものではないが、70〜160g/Lが好ましく、95〜130g/Lがより好ましい。すなわち、70g/L未満では、亜硫酸塩水溶液中への銀化合物の溶解量が少なく、設備容量が大きくなる。亜硫酸イオン濃度は、高いほど銀化合物の溶解量が増加する。しかし、亜硫酸塩の水溶液への溶解量は、水溶液中の亜硫酸塩以外の塩の存在量にもよるが、工業的に実施可能な範囲としては亜硫酸イオン濃度が160g/L以下である。   The sulfite ion concentration of the sulfite aqueous solution used in the above step is not particularly limited, but is preferably 70 to 160 g / L, and more preferably 95 to 130 g / L. That is, if it is less than 70 g / L, the amount of silver compound dissolved in the sulfite aqueous solution is small, and the equipment capacity is increased. The higher the sulfite ion concentration, the higher the amount of silver compound dissolved. However, the amount of sulfite dissolved in the aqueous solution depends on the amount of salt other than sulfite in the aqueous solution, but the sulfite ion concentration is 160 g / L or less as an industrially feasible range.
上記工程で用いる亜硫酸塩としては、特に限定されるものではなく、水溶性の亜硫酸塩であればいずれも使用することができ、例えば、亜硫酸カリウム、亜硫酸ナトリウム、亜硫酸カルシウム、亜硫酸アンモニウム、亜硫酸セシウム、亜硫酸ルビジウム、アミンの亜硫酸塩等が用いられるが、この中で、特に経済性と入手容易性から亜硫酸ナトリウムが好ましい。   The sulfite used in the above step is not particularly limited, and any water-soluble sulfite can be used. For example, potassium sulfite, sodium sulfite, calcium sulfite, ammonium sulfite, cesium sulfite, Rubidium sulfite, amine sulfite and the like are used, and among these, sodium sulfite is particularly preferable from the viewpoint of economy and availability.
上記工程で用いる亜硫酸塩水溶液の製造方法としては、特に限定されるものではなく、上記亜硫酸塩を水に溶解する方法のほか、アルカリ金属及び/又は土類金属の水酸化物及び/又は炭酸塩の水溶液又はスラリーに二酸化硫黄ガスを反応させることで製造することができる。この中で、特に金属製錬の硫酸製造工程において、熔錬工程から発生した二酸化硫黄ガスを水酸化アルカリ金属及び/又炭酸アルカリ金属塩の水溶液に吸収させて得られる吸収液を用いることが、工業的に安価に利用できるので好ましい。特に、製錬ガスより硫酸を製造する際に、転化されずに残存した二酸化イオウを除害塔で吸収して得られる亜硫酸塩含有廃液を有効活用すれば、より経済的である。   The method for producing the aqueous sulfite solution used in the above step is not particularly limited. In addition to the method for dissolving the above sulfite in water, alkali metal and / or earth metal hydroxides and / or carbonates. It can manufacture by making sulfur dioxide gas react with the aqueous solution or slurry of this. Among them, particularly in the sulfuric acid production process of metal smelting, it is possible to use an absorbent obtained by absorbing the sulfur dioxide gas generated from the smelting process into an aqueous solution of alkali metal hydroxide and / or alkali metal carbonate, This is preferable because it can be used industrially at low cost. In particular, when sulfuric acid is produced from a smelting gas, it is more economical to effectively utilize a sulfite-containing waste liquid obtained by absorbing sulfur dioxide remaining without being converted by a detoxification tower.
上記工程のpHは、8〜12が好ましく、10〜11がより好ましい。すなわち、pHが8未満では、亜硫酸塩が重亜硫酸塩に急速に変化し始め、銀化合物の溶解が不十分となり、一方pHが12を越えると、銀のスルフィト錯塩から金属銀が析出し、銀の見かけ上の浸出率が低下する。   8-12 are preferable and, as for the pH of the said process, 10-11 are more preferable. That is, when the pH is less than 8, sulfite begins to rapidly change to bisulfite and the silver compound is insufficiently dissolved. On the other hand, when the pH exceeds 12, metallic silver is precipitated from the silver sulfite complex, The apparent leaching rate is reduced.
上記工程の温度は、20〜80℃が好ましく、30〜60℃がより好ましい。すなわち、20℃未満では、亜硫酸イオンの溶解度が低下するので亜硫酸塩水溶液の亜硫酸塩濃度を70g/L以上にすることが難しい。一方、80℃を超えると、銀のスルフィト錯塩の分解反応によって金属銀に還元される。   20-80 degreeC is preferable and the temperature of the said process has more preferable 30-60 degreeC. That is, when the temperature is lower than 20 ° C., the solubility of sulfite ions decreases, so that it is difficult to set the sulfite concentration of the sulfite aqueous solution to 70 g / L or more. On the other hand, when it exceeds 80 ° C., it is reduced to metallic silver by the decomposition reaction of the silver sulfite complex salt.
上記工程で得られる浸出液には、銀のスルフィト錯塩のほかに、上記精錬中間物に含有される不純物元素も微量ではあるが、アルカリ塩又は亜硫酸塩により溶解され、含有される。   In the leachate obtained in the above step, in addition to the silver sulfite complex salt, the impurity elements contained in the refining intermediate are also contained in a small amount, but are dissolved and contained with an alkali salt or sulfite.
3.(2)の工程
上記(2)の工程は、上記(1)の工程で得られた浸出液に酸を添加して、塩化銀を析出させ、次いで母液を分離して、塩化銀を含む析出物(以下、粗塩化銀と呼称する場合がある。)を得る工程である。ここで、酸を添加する際に、pHを3.5〜5.5に調整し、かつ、塩化銀の析出後に、直ちに母液と析出物の全量をろ過し、母液から析出物を分離することが重要である。
また、ここで、原料として用いる精錬中間物に塩化物以外の難溶性銀化合物を含む場合には、塩化銀として析出させるため所定量の塩化物イオンを添加することができる。前記塩化物イオンの供給源としては、塩酸、食塩等の水溶性塩化物を用いるのが好ましい。
3. Step (2) In the step (2), an acid is added to the leachate obtained in the step (1) to precipitate silver chloride, and then the mother liquor is separated to obtain a precipitate containing silver chloride. (Hereinafter referred to as crude silver chloride). Here, when adding the acid, the pH is adjusted to 3.5 to 5.5, and after the precipitation of silver chloride, the mother liquor and the total amount of the precipitate are immediately filtered to separate the precipitate from the mother liquor. is important.
Here, when the refining intermediate used as a raw material contains a hardly soluble silver compound other than chloride, a predetermined amount of chloride ion can be added for precipitation as silver chloride. As a supply source of the chloride ions, water-soluble chlorides such as hydrochloric acid and sodium chloride are preferably used.
上記工程において、酸を添加する際に、pHとしては、3.5〜5.5に調整する。すなわち、pHが3.5未満では、析出する塩化銀中の不純物元素品位が高くなり、後工程の(3)の工程で、析出物を酸性水溶液中で酸化処理する際に、不純物元素が充分に除去されないため、5N以上の純度の銀粉が得られない。一方、pHが5.5を超えると、より不純物元素の含有量が少ない粗塩化銀が回収されるが、銀の析出量が少なくなり、実収率の点から好ましくない。   In the said process, when adding an acid, as pH, it adjusts to 3.5-5.5. That is, when the pH is less than 3.5, the impurity element quality in the precipitated silver chloride is high, and the impurity element is sufficient when the precipitate is oxidized in an acidic aqueous solution in the subsequent step (3). Therefore, silver powder having a purity of 5N or more cannot be obtained. On the other hand, when the pH exceeds 5.5, crude silver chloride having a smaller impurity element content is recovered, but the amount of silver deposited is reduced, which is not preferable from the standpoint of actual yield.
このpHと不純物元素の挙動について、より詳細に説明する。
まず、従来の条件で、上記浸出液に酸を添加してpHを下げると、一般に、銀のスルフィト錯塩が分解されて銀が塩化銀として析出する。ここで、pHが低いほど、母液中の銀濃度が低下して銀の回収率が増加するが、同時に溶解していた金、セレン、テルル、鉛等の不純物元素も銀とともに共沈する。特に、金は、pHの依存性が高いので、pH5未満では、急激にスルフィト錯塩の分解が進み、粗塩化銀に混入する。また、酸の添加による亜硫酸塩の分解によって生じた亜硫酸ガスがセレン等の不純物元素の還元を促進させ、粗塩化銀に混入する。このような不純物元素が、粗塩化銀に含まれる程度は、原料の難溶性銀化合物により異なるが通常、数十〜数千ppmが混入される。
The behavior of the pH and impurity elements will be described in more detail.
First, when an acid is added to the above leachate under a conventional condition to lower the pH, generally the silver sulfite complex is decomposed and silver is precipitated as silver chloride. Here, the lower the pH, the lower the silver concentration in the mother liquor and the higher the silver recovery rate. At the same time, the dissolved impurity elements such as gold, selenium, tellurium, and lead coprecipitate with the silver. In particular, since gold is highly dependent on pH, if the pH is less than 5, decomposition of the sulfito complex salt rapidly proceeds and is mixed into the crude silver chloride. In addition, the sulfurous acid gas generated by the decomposition of sulfite by the addition of acid accelerates the reduction of impurity elements such as selenium and is mixed into the crude silver chloride. The extent to which such impurity elements are contained in the crude silver chloride varies depending on the raw material poorly soluble silver compound, but usually several tens to several thousand ppm are mixed.
上記工程で粗塩化銀を製造する際の不純物元素の挙動例を、図を用いて説明する。
図1は、粗塩化銀回収時のpHと母液中の銀濃度の関係を表す図である。また、図2は、粗塩化銀回収時のpHと析出した粗塩化銀中の金品位の関係を表す図である。図1、2より、母液中の銀は、pH4程度までにその殆んどが析出するが、一方、析出した粗塩化銀中の金品位は、pH5以下で急激に増加することが分かる。
An example of the behavior of an impurity element when producing crude silver chloride in the above process will be described with reference to the drawings.
FIG. 1 is a graph showing the relationship between the pH during recovery of crude silver chloride and the silver concentration in the mother liquor. Moreover, FIG. 2 is a figure showing the relationship between pH at the time of rough | crude silver chloride collection | recovery, and the gold quality in the precipitated rough | crude silver chloride. 1 and 2, it can be seen that most of the silver in the mother liquor is precipitated by about pH 4, while the gold quality in the precipitated crude silver chloride increases rapidly at pH 5 or lower.
また、pHが3.5〜5.5程度の範囲では、塩化銀が析出した後、亜硫酸塩が除々に分解する不安定な領域にあり、不純物元素も時間経過に伴い除々に析出することが観察される。図3は、酸をpH5まで添加し、塩化銀を析出させた後の保持時間(塩化銀回収保持時間)と粗塩化銀中の金、鉛、鉄、セレン及びテルル等の不純物元素品位の関係を示す図である。ここで、不純物元素は、時間とともに増加し、特に、鉛とセレンが顕著に増加することが分かる。すなわち、塩化銀を析出させた後、時間とともに不純物元素が沈殿するので、できるだけ短時間で、母液と析出物を分離することが望ましく、塩化銀の析出後60分以内に母液と分離することが好ましい。   In addition, when the pH is in the range of about 3.5 to 5.5, after silver chloride is precipitated, it is in an unstable region where sulfite gradually decomposes, and impurity elements may gradually precipitate over time. Observed. Fig. 3 shows the relationship between the retention time after adding acid to pH 5 and precipitating silver chloride (silver chloride recovery retention time) and the quality of impurity elements such as gold, lead, iron, selenium and tellurium in crude silver chloride. FIG. Here, it can be seen that the impurity elements increase with time, and in particular, lead and selenium increase significantly. That is, since the impurity element precipitates with time after the silver chloride is precipitated, it is desirable to separate the mother liquor and the precipitate in as short a time as possible, and within 60 minutes after the silver chloride is precipitated, the mother liquor is separated. preferable.
以上の説明から、本発明の方法により、酸を添加する際に、pHを3.5〜5.5に調整し、かつ、塩化銀の析出後に、直ちに母液と析出物の全量をろ過し、母液から析出物を速やかに分離することが、不純物元素の含有量が少ない塩化銀を析出させるため、有効な手段であることが分かる。   From the above explanation, when adding acid by the method of the present invention, the pH is adjusted to 3.5 to 5.5, and immediately after the precipitation of silver chloride, the total amount of the mother liquor and the precipitate is filtered, It can be seen that the rapid separation of the precipitate from the mother liquor is an effective means for precipitating silver chloride with a low impurity element content.
また、このとき、母液が反応槽に残留すると、不純物元素の多い塩化銀となり、新しく析出した塩化銀の純度を下げることとなる。したがって、1回の反応毎に、母液と析出物の全量をろ過し、母液と析出物を分離することが好ましい。このため、反応形態としては、バッチ法で行い、反応槽の形状としては、母液と析出物の全量を反応槽から抜き出せる構造とすることが好ましい。すなわち、母液と析出物の全量が抜き出せる構造を有する反応槽を用いて、母液と析出物をろ過する際に、該反応槽から母液と析出物の全量を抜き出すことが好ましい。
例えば、反応槽の底がコーン状又は傾斜のあるものが使用される。また、通常、固体が含まれたスラリー状の液には、ワーマンポンプ等が使用できるが、ここでは、母液を最後まで抜取れる自給式タイプのホースポンプ、エアークッションポンプ等が好適である。
At this time, if the mother liquor remains in the reaction vessel, it becomes silver chloride with a large amount of impurity elements, and the purity of newly precipitated silver chloride is lowered. Therefore, it is preferable to filter the whole amount of the mother liquor and the precipitate for each reaction to separate the mother liquor and the precipitate. For this reason, as a reaction form, it is preferable to carry out by a batch method, and as a shape of a reaction tank, it is preferable to set it as the structure which can draw out the whole quantity of mother liquid and a deposit from a reaction tank. That is, when the mother liquor and the precipitate are filtered using a reaction tank having a structure in which the whole amount of the mother liquor and the precipitate can be extracted, it is preferable to extract the entire amount of the mother liquor and the precipitate from the reaction tank.
For example, a reaction vessel having a cone-shaped or inclined bottom is used. Usually, a Werman pump or the like can be used for the slurry-like liquid containing the solid. However, a self-contained type hose pump or an air cushion pump that can draw out the mother liquor to the end is suitable here.
上記工程において、浸出液に酸を添加する前に、例えば、目開きが1μm以下のフィルターで精密ろ過することが好ましい。これにより、析出物への不純物元素の含有量を低減することができる。すなわち、通常、工業的には、浸出後の不溶解残渣との分離にフィルタープレス、遠心分離機等の固液分離装置が用いられているが、これらの装置では、通気度の小さなろ布を使用しても、通常微量の不溶解残渣の洩れが生じる。この不溶解残渣の主成分としては、硫酸鉛であり、後工程の(3)の工程で、析出物を酸性水溶液中で酸化処理する際にも、溶解除去できない。また、亜硫酸塩水溶液で浸出した液を放置すると、不純物元素が除々に析出する。   In the above step, before adding the acid to the leachate, for example, it is preferable to perform microfiltration with a filter having an opening of 1 μm or less. Thereby, content of the impurity element to a precipitate can be reduced. In other words, industrially, solid-liquid separation devices such as filter presses and centrifuges are usually used for separation from insoluble residue after leaching. In these devices, filter cloth with a low air permeability is used. Even if it is used, leakage of a small amount of insoluble residue usually occurs. The main component of the insoluble residue is lead sulfate, which cannot be dissolved and removed even when the precipitate is oxidized in an acidic aqueous solution in the subsequent step (3). Further, when the solution leached with the aqueous sulfite solution is left, the impurity elements gradually precipitate.
したがって、浸出液に酸を添加し、塩化銀が析出する前に、目開きが1μm以下のフィルターを用いて精密ろ過することにより、微量含まれる固体分を除去することが有効である。ここで、ろ過機としては、通常、得られる固体成分は10〜50mg/L程度であり、安価であり、かつ小スペースでろ過面積が大きいカートリッジフィルターを用いるとことが好ましい。   Therefore, it is effective to remove a solid content contained in a trace amount by adding an acid to the leachate and performing microfiltration using a filter having an opening of 1 μm or less before silver chloride is precipitated. Here, as a filter, it is preferable to use a cartridge filter which is usually about 10 to 50 mg / L of the obtained solid component, is inexpensive, and has a small space and a large filtration area.
上記工程の酸としては、特に限定されるものではなく、硫酸、塩酸等の鉱酸が用いられるが、硫酸がより好ましい。
上記工程の反応温度は、特に限定されるものではないが、20〜100℃が好ましい。
The acid in the above step is not particularly limited, and mineral acids such as sulfuric acid and hydrochloric acid are used, but sulfuric acid is more preferable.
Although the reaction temperature of the said process is not specifically limited, 20-100 degreeC is preferable.
以上の本発明の(1)と(2)工程とを経過して得られる塩化銀からは、上記原料中に含有する大部分の元素が分離されているが、一部亜硫酸塩水溶液に溶解するセレン、テルル、鉛等の不純物元素の一部が含有される。   Although most of the elements contained in the raw material are separated from the silver chloride obtained through the steps (1) and (2) of the present invention, some of them are dissolved in the sulfite aqueous solution. Part of impurity elements such as selenium, tellurium and lead are contained.
4.(3)の工程
上記(3)の工程は、上記工程で得られる析出物を酸性水溶液中で酸化処理して、不純物元素を溶出させ、次いで不純物元素を含む液を分離して、精製された塩化銀を得る工程である。上記工程では、塩化銀を含む析出物は酸性水溶液中に懸濁され、さらに酸化還元電位を調整しながら酸化剤が添加される。
4). Step (3) In step (3), the precipitate obtained in the step was oxidized in an acidic aqueous solution to elute the impurity element, and then the liquid containing the impurity element was separated and purified. This is a step of obtaining silver chloride. In the above step, the precipitate containing silver chloride is suspended in an acidic aqueous solution, and an oxidizing agent is added while adjusting the redox potential.
上記工程の懸濁液のスラリー濃度は、特に限定されるものではないが、スラリーの分散性の向上と溶出された不純物元素の再吸着防止から、100〜500g/Lが好ましい。
上記工程で用いる酸性水溶液としては、特に限定されるものではなく、各種の鉱酸が用いられるが、この中で、特に、酸化剤により塩素を生成して金属形態で存在する不純物元素を溶解しやすく、また想定される不純物元素の塩化物の水に対する溶解度が大きいので、塩酸が好ましい。
The slurry concentration of the suspension in the above step is not particularly limited, but is preferably 100 to 500 g / L from the viewpoint of improving the dispersibility of the slurry and preventing resorption of the eluted impurity elements.
The acidic aqueous solution used in the above step is not particularly limited, and various mineral acids are used. Among them, in particular, chlorine is generated by an oxidizing agent to dissolve impurity elements present in a metal form. Hydrochloric acid is preferred because it is easy and the solubility of the assumed impurity element chloride in water is high.
上記工程の酸化還元電位(銀/塩化銀電極規準)は、特に限定されるものではなく、800〜1200mVに調整することが好ましく、900〜1000mVがより好ましい。すなわち、酸化還元電位(銀/塩化銀電極規準)を800mV以上とすることにより、金属又は金属間化合物として存在し、酸化により酸性水溶液に可溶となる元素、例えばセレン、テルル等を溶解することができる。   The oxidation-reduction potential (silver / silver chloride electrode standard) in the above step is not particularly limited, and is preferably adjusted to 800 to 1200 mV, more preferably 900 to 1000 mV. That is, by setting the oxidation-reduction potential (silver / silver chloride electrode standard) to 800 mV or higher, elements that exist as metals or intermetallic compounds and become soluble in an acidic aqueous solution by oxidation, such as selenium and tellurium, are dissolved. Can do.
上記工程で用いる酸化剤としては、特に限定されるものではなく、塩化銀への汚染が少ない塩素ガス、過酸化水素水、塩素酸塩等が用いられる。
上記工程の反応温度は、特に限定されるものではなく、高温ほど反応速度を促進することができるが、40〜80℃が好ましい。すなわち、40℃未満では、不純物の溶解反応が遅い。一方、80℃を超えると、過酸化水素水又は塩素酸塩を用いるときにはこれらの自己分解も促進され、薬品使用量が増加する。
The oxidizing agent used in the above step is not particularly limited, and chlorine gas, hydrogen peroxide solution, chlorate, etc. with little contamination to silver chloride are used.
The reaction temperature in the above step is not particularly limited, and the reaction rate can be accelerated as the temperature increases, but 40 to 80 ° C. is preferable. That is, at a temperature lower than 40 ° C., the impurity dissolution reaction is slow. On the other hand, when the temperature exceeds 80 ° C., when hydrogen peroxide solution or chlorate is used, the self-decomposition is promoted and the amount of chemicals used increases.
5.(4)の工程
上記(4)の工程は、上記塩化銀をアルカリ水溶液中で還元して、99.999質量%の高純度の銀粉を得る工程である。上記工程では、高純度塩化銀をアルカリ水溶液中で懸濁して行なうことができる。
5. Step (4) The step (4) is a step in which the silver chloride is reduced in an alkaline aqueous solution to obtain 99.999 mass% high-purity silver powder. In the above step, high-purity silver chloride can be suspended in an alkaline aqueous solution.
上記工程の高純度塩化銀の初期スラリー濃度は、特に限定されるものではなく、スラリーの分散性から、100〜500g/Lが好ましい。   The initial slurry concentration of the high purity silver chloride in the above step is not particularly limited, and is preferably 100 to 500 g / L from the dispersibility of the slurry.
上記工程で用いるアルカリ水溶液としては、特に限定されるものではないが、銀に対して1〜5当量の水酸化アルカリ及び/又は炭酸アルカリを用いて調製されるものが好ましい。すなわち、1当量以上の添加によって、未還元の塩化銀が残留して、得られる金属銀を汚染することを防止する。一方、5当量を超えても、それ以上の効果が得られないので経済的でない。特に、アルカリ水溶液のpHを13以上となるようにアルカリ分を添加することが、より好ましい。
また、前記水酸化アルカリ又は炭酸アルカリとしては、特に限定されるものではなく、水溶性のアルカリ金属塩、アンモニウム塩等が用いられるが、排水処理の負担が少なく、かつ経済的コストである水酸化ナトリウムが好ましい。
Although it does not specifically limit as aqueous alkali solution used at the said process, What is prepared using 1-5 equivalent alkali hydroxide and / or alkali carbonate with respect to silver is preferable. That is, addition of 1 equivalent or more prevents unreduced silver chloride from remaining and contaminating the resulting metallic silver. On the other hand, even if it exceeds 5 equivalents, it is not economical because no further effect can be obtained. In particular, it is more preferable to add an alkali component so that the pH of the aqueous alkali solution is 13 or more.
Further, the alkali hydroxide or alkali carbonate is not particularly limited, and water-soluble alkali metal salts, ammonium salts, and the like are used. Sodium is preferred.
上記工程で用いる還元剤としては、特に限定されるものではないが、銀への汚染が少ないヒドラジン、糖類、ホルマリン等が用いられる。上記工程で還元剤の添加量は、溶液の酸化還元電位を測定することにより調整することができる。すなわち、酸化還元電位(銀/塩化銀電極規準)が−700mV以下で安定したところが終点となる。   Although it does not specifically limit as a reducing agent used at the said process, Hydrazine, saccharides, formalin, etc. with little contamination to silver are used. The amount of reducing agent added in the above step can be adjusted by measuring the redox potential of the solution. That is, the end point is when the oxidation-reduction potential (silver / silver chloride electrode standard) is stable at −700 mV or less.
上記工程の還元温度は、特に限定されるものではなく、反応速度を促進することができる70〜100℃が好ましく、90〜100℃がより好ましい。すなわち、温度が70℃未満では塩化銀の残留が多くなる。一方、100℃を超えると、加圧容器を用いることが必要である。特に塩化銀の残留を抑制するためには、アルカリ水溶液のpHが13以上となるようにアルカリ分を添加し、かつ90℃以上に加熱して還元処理することがさらに好ましい。また、塩化銀の残留をさらに低減するためには、再度還元処理を行なうことが有効である。この場合、還元する塩化銀量が微量であるため、薬品の添加量はごくわずかで充分である。   The reduction temperature in the above step is not particularly limited, and is preferably 70 to 100 ° C, more preferably 90 to 100 ° C, which can accelerate the reaction rate. That is, when the temperature is less than 70 ° C., the residual silver chloride increases. On the other hand, when the temperature exceeds 100 ° C., it is necessary to use a pressurized container. In particular, in order to suppress the residual of silver chloride, it is more preferable to add an alkali component so that the pH of the aqueous alkali solution is 13 or more and to perform the reduction treatment by heating to 90 ° C or higher. In order to further reduce the residual silver chloride, it is effective to perform the reduction treatment again. In this case, since the amount of silver chloride to be reduced is very small, a very small amount of chemical is sufficient.
以下に、本発明の実施例及び比較例によって本発明をさらに詳細に説明するが、本発明は、これらの実施例によってなんら限定されるものではない。なお、実施例及び比較例で用いた金属の分析は、PdがICP−MS法で、その他の元素が発光分光法で行った。   Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the analysis of the metal used by the Example and the comparative example was performed by Pd for the ICP-MS method, and other elements by the emission spectroscopy.
(実施例1)
原料として、銅電解工程で産出されたアノードスライムを塩素浸出して得た難溶性銀化合物を含む精錬中間物(以下、塩素浸出残渣と呼称する。)を用いて、以下に示す方法で処理し、産出した銀粉の純度を分析した。なお、塩素浸出残渣の組成を、表1に示す。
Example 1
Using a refining intermediate (hereinafter referred to as chlorine leaching residue) containing a sparingly soluble silver compound obtained by chlorine leaching of anode slime produced in the copper electrolysis process as a raw material, the raw material was treated by the following method. The purity of the produced silver powder was analyzed. The composition of the chlorine leaching residue is shown in Table 1.
(1)の工程
まず、亜硫酸塩水溶液として、金属製錬の熔錬工程において発生する二酸化硫黄ガスを水酸化ナトリウム水溶液に吸収させて得られた吸収液を容量10mの浸出槽に受け入れ、浸出液とした。この浸出の亜硫酸ソーダの濃度を測定すると、210g/Lであった。
次に、浸出液中に、表1に示す組成の塩素浸出残渣を湿量で1.2トン投入した。このとき、塩素浸出残渣に付着していた酸により亜硫酸塩水溶液のpHが下がったため、18質量%濃度の苛性ソーダで浸出液のpHを9に調整した。1時間の攪拌の後に、フィルタープレスを用いて、銀の浸出液と不溶解残渣を分離した。
Step (1) First, as a sulfite aqueous solution, an absorption liquid obtained by absorbing a sulfur dioxide gas generated in a smelting process of metal smelting in an aqueous sodium hydroxide solution is received in a leaching tank having a capacity of 10 m 3 , and the leaching liquid It was. The concentration of this leached sodium sulfite was measured and found to be 210 g / L.
Next, 1.2 tons of a chlorine leaching residue having the composition shown in Table 1 was introduced into the leachate in a wet amount. At this time, since the pH of the aqueous sulfite solution was lowered by the acid adhering to the chlorine leaching residue, the pH of the leaching solution was adjusted to 9 with caustic soda having a concentration of 18% by mass. After stirring for 1 hour, the silver leachate and the insoluble residue were separated using a filter press.
(2)の工程
上記工程で得られた浸出液を目開き1μmのカートリッジフィルターを通してから、容量5mの塩化銀生成槽に受け入れた。なお、塩化銀生成槽の底は、傾斜した構造であり、槽の底からホースポンプで析出物と母液を全量フィルタープレスに送液できる構造になっている。
次に、塩化銀生成槽に薄硫酸を投入し、pHを3.5〜5.5に調整後、直ぐに析出物と母液の全量をフィルタープレスへ送液し、析出物と母液をろ過分離し、粗塩化銀を回収した。なお、フィルタープレスのろ過時間は、約60分で終了した。
次いで、この操作を再度行った。その後、得られた粗塩化銀を回収し、分析した。ここで、粗塩化銀の分析としては、粗塩化銀を水と水酸化ナトリウムを加えてpH10に調整し、濃度60質量%のヒドラジンを酸化還元電位が安定するまで添加し、得られた銀粉を分析した。結果を表2に示す。なお、回収した粗塩化銀は湿量で263kgであり、銀の回収率は95%であった。
Step (2) The leachate obtained in the above step was passed through a cartridge filter having an opening of 1 μm and then received in a silver chloride production tank having a capacity of 5 m 3 . In addition, the bottom of the silver chloride production tank has an inclined structure, and the deposit and the mother liquor can be fed from the bottom of the tank to the filter press with a hose pump.
Next, after adding thin sulfuric acid to the silver chloride production tank and adjusting the pH to 3.5 to 5.5, the whole amount of the precipitate and the mother liquor is immediately fed to the filter press, and the precipitate and the mother liquor are separated by filtration. The crude silver chloride was recovered. The filter press filtration time was about 60 minutes.
This operation was then performed again. Thereafter, the obtained crude silver chloride was recovered and analyzed. Here, for analysis of the crude silver chloride, the crude silver chloride was adjusted to pH 10 by adding water and sodium hydroxide, hydrazine having a concentration of 60% by mass was added until the oxidation-reduction potential became stable, and the obtained silver powder was analyzed. The results are shown in Table 2. The recovered crude silver chloride was 263 kg in terms of moisture, and the silver recovery rate was 95%.
(3)、(4)の工程
上記工程で得られた粗塩化銀263kgを、濃度8mol/Lの塩酸溶液1mに懸濁し、このスラリーを60℃に昇温後、濃度35質量%の過酸化水素水60Lを約1時間かけて全量を添加するように滴下して、酸化処理を行なった。ここで、スラリーの酸化還元電位(銀/塩化銀電極規準)は、1000mV以上であった。40℃まで冷却後、遠心分離機にて固液分離し、続いて水で洗浄を行い、精製塩化銀を回収した。
その後、得られた湿量で263kgの精製塩化銀を、濃度8.6質量%の水酸化ナトリウム水溶液1mに懸濁し、温度70℃に加温後、濃度60質量%のヒドラジンを酸化還元電位が−700mV以下で安定するまで添加し、塩化銀を銀粉に還元した。還元後、40℃以下に冷却し、遠心分離機でろ過し、銀粉を遠心分離機内で洗浄し、得られた銀粉を分析した。結果を表3に示す。
Steps (3) and (4) 263 kg of the crude silver chloride obtained in the above step was suspended in 1 m 3 of hydrochloric acid solution having a concentration of 8 mol / L, and this slurry was heated to 60 ° C. An oxidizing treatment was performed by adding 60 L of hydrogen oxide water dropwise over about 1 hour so as to add the entire amount. Here, the oxidation-reduction potential (silver / silver chloride electrode standard) of the slurry was 1000 mV or more. After cooling to 40 ° C., solid-liquid separation was performed with a centrifuge, followed by washing with water to recover purified silver chloride.
Thereafter, 263 kg of purified silver chloride in the obtained wet amount was suspended in 1 m 3 of an aqueous solution of sodium hydroxide having a concentration of 8.6% by mass, heated to a temperature of 70 ° C., and then hydrazine having a concentration of 60% by mass was converted into a redox potential. Was added until it became stable at −700 mV or less, and silver chloride was reduced to silver powder. After the reduction, the mixture was cooled to 40 ° C. or lower, filtered with a centrifuge, the silver powder was washed in the centrifuge, and the obtained silver powder was analyzed. The results are shown in Table 3.
表3より、上記塩素浸出残渣を本発明の工程で処理して得られた銀粉は、純度99.999質量%を有することが分かる。   From Table 3, it turns out that the silver powder obtained by processing the said chlorine leaching residue at the process of this invention has a purity of 99.999 mass%.
(比較例1)
原料として、実施例1で用いた塩素浸出残渣を用いて、以下に示す方法で処理し、産出した銀粉の純度を分析した。
(1)の工程
まず、亜硫酸塩水溶液として、金属製錬の熔錬工程において発生する二酸化硫黄ガスを水酸化ナトリウム水溶液に吸収させて得られた吸収液を用いた。これを浸出液として、その容量400mlに塩素浸出残渣45gを懸濁し、水酸化ナトリウムでpH10に調整した。調整後、1時間攪拌して銀の浸出を行なった後、ガラス製のろ過機でろ過を行い、銀の浸出液と不溶解残渣を回収した。なお、浸出液の亜硫酸ソーダの濃度は、200g/Lであった。
(Comparative Example 1)
Using the chlorine leaching residue used in Example 1 as a raw material, it was processed by the method shown below, and the purity of the silver powder produced was analyzed.
Step (1) First, as an aqueous sulfite solution, an absorbent obtained by absorbing a sulfur dioxide gas generated in a smelting step of metal smelting in an aqueous sodium hydroxide solution was used. Using this as a leaching solution, 45 g of chlorine leaching residue was suspended in a volume of 400 ml, and the pH was adjusted to 10 with sodium hydroxide. After the adjustment, the mixture was stirred for 1 hour and silver was leached, followed by filtration with a glass filter to recover the silver leaching solution and insoluble residue. The concentration of sodium sulfite in the leachate was 200 g / L.
(2)の工程
上記工程で得られた浸出液に、薄硫酸を添加し、pHを1に調整後、1時間保持した。ここで、反応中は、亜硫酸ナトリウムが分解して二酸化硫黄ガスが発生するため、ドラフト内で行なった。析出した粗塩化銀と母液とをガラス製のろ過機でろ過して、粗塩化銀を回収し、分析した。ここで、粗塩化銀の分析としては、粗塩化銀を水と水酸化ナトリウムを加えてpH10に調整し、濃度60質量%のヒドラジンを酸化還元電位が安定するまで添加し、得られた銀粉を分析した。結果を表4に示す。
Step (2) Thin sulfuric acid was added to the leachate obtained in the above step, the pH was adjusted to 1, and then held for 1 hour. Here, during the reaction, sodium sulfite was decomposed to generate sulfur dioxide gas. The precipitated crude silver chloride and the mother liquor were filtered with a glass filter, and the crude silver chloride was recovered and analyzed. Here, for analysis of the crude silver chloride, the crude silver chloride was adjusted to pH 10 by adding water and sodium hydroxide, hydrazine having a concentration of 60% by mass was added until the oxidation-reduction potential became stable, and the obtained silver powder was analyzed. The results are shown in Table 4.
表4より、酸を添加する際のpHが1で、塩化銀の析出後に1時間保持であり、酸を添加する際のpHと、塩化銀の析出後の母液中での保持時間が本発明のこれらの条件に合わないので、得られた塩化銀は、実施例1と比較して、多くの不純物元素を含むことが分かる。   From Table 4, the pH when adding the acid is 1 and is maintained for 1 hour after the precipitation of silver chloride, and the pH when adding the acid and the holding time in the mother liquor after the precipitation of silver chloride is the present invention. Since these conditions are not met, it can be seen that the obtained silver chloride contains more impurity elements than Example 1.
(3)、(4)の工程
上記工程で得られた塩化銀:湿量で250gを、濃度8mol/Lの塩酸溶液500mlに懸濁し、このスラリーを60℃に昇温後、濃度35質量%の過酸化水素水50mlを約1時間かけて全量を添加するように滴下して、酸化処理を行った。ここで、スラリーの酸化還元電位(銀/塩化銀電極規準)は、1000mV以上であった。冷却後、ガラス製のろ過器でろ過を行い、精製塩化銀を回収した。
得られた湿量で250gの精製塩化銀を、濃度8.6質量%の水酸化ナトリウム水溶液1000mlに懸濁し、温度70℃に加温後、濃度60質量%のヒドラジンを酸化還元電位が−700mV以下で安定するまで添加し塩化銀を銀粉に還元した。冷却後、ガラス製のろ過器でろ過し、洗浄し、得られた銀粉を分析した。結果を表5に示す。
Steps (3) and (4) Silver chloride obtained in the above step: 250 g in a wet amount is suspended in 500 ml of hydrochloric acid solution having a concentration of 8 mol / L, and the slurry is heated to 60 ° C. Then, 50 ml of hydrogen peroxide solution was added dropwise over about 1 hour so as to add the whole amount, and oxidation treatment was performed. Here, the oxidation-reduction potential (silver / silver chloride electrode standard) of the slurry was 1000 mV or more. After cooling, it was filtered with a glass filter to recover purified silver chloride.
The obtained wet amount of 250 g of purified silver chloride was suspended in 1000 ml of an aqueous solution of sodium hydroxide having a concentration of 8.6% by mass and heated to a temperature of 70 ° C. Silver chloride was reduced to silver powder by adding until stable below. After cooling, it was filtered and washed with a glass filter, and the resulting silver powder was analyzed. The results are shown in Table 5.
表5より、比較例1では、99.999質量%を超える純度の銀粉を得ることができない。すなわち、(2)の工程で得られた塩化銀の不純物元素の含有量が高いので、その後の(3)、(4)の工程による不純物元素の除去に限界があるためである。   From Table 5, in the comparative example 1, the silver powder of the purity exceeding 99.999 mass% cannot be obtained. That is, since the content of the impurity element of silver chloride obtained in the step (2) is high, there is a limit to the removal of the impurity element in the subsequent steps (3) and (4).
以上より明らかなように、本発明の高純度銀の製造方法は、難溶性銀化合物と不純物元素とを含有する精錬中間物から金属銀を得る際に、乾式精製又は電解による再精製処理を行うことなく湿式精製のみで、99.999質量%の高純度の金属銀を得ることができるので、精錬中間物、特に塩化銀を含む精錬中間物から、経済的に高純度銀を製造する方法として、好適である。   As is clear from the above, the high purity silver production method of the present invention performs dry refining or electrorefining when obtaining metallic silver from a refined intermediate containing a sparingly soluble silver compound and an impurity element. As a method for producing high-purity silver economically from refining intermediates, particularly refining intermediates containing silver chloride, 99.999 mass% high-purity metallic silver can be obtained only by wet refining. Is preferable.
粗塩化銀回収時のpHと母液中の銀濃度の関係を表す図である。It is a figure showing the relationship between pH at the time of rough | crude silver chloride collection | recovery, and the silver concentration in a mother liquid. 粗塩化銀回収時のpHと析出した粗塩化銀中の金品位の関係を表す図である。It is a figure showing the relationship between pH at the time of rough | crude silver chloride collection | recovery, and the gold quality in the precipitated rough | crude silver chloride. 酸をpH5まで添加し、塩化銀を析出させた後の保持時間(塩化銀回収保持時間)と粗塩化銀中の金、鉛、鉄、セレン及びテルル等の不純物元素品位の関係を示す図である。The figure which shows the relationship between the retention time after adding an acid to pH 5 and precipitating silver chloride (silver chloride recovery retention time) and the quality of impurity elements such as gold, lead, iron, selenium and tellurium in crude silver chloride is there.

Claims (3)

  1. 難溶性銀化合物と不純物元素とを含有する精錬中間物から、下記の(1)〜(4)の工程により銀を製造する方法であって、
    前記(2)の工程において、前記(1)の工程で得られた銀を含む浸出液に酸を添加する前に、前記銀を含む浸出液を目開きが1μm以下のフィルターで精密ろ過し、酸を添加する際に、pHを3.5〜5.5に調整し、かつ、塩化銀の析出後、60分以内に母液と析出物の全量をろ過し、母液から析出物を分離することを特徴とする銀の製造方法。
    (1)前記精錬中間物を亜硫酸塩水溶液中で浸出して、銀を亜硫酸塩水溶液中に抽出し、次いで生成した不溶解残渣を分離して、銀を含む浸出液を得る。
    (2)前記浸出液に酸を添加して、塩化銀を析出させ、次いで母液を分離して、塩化銀を含む析出物を得る。
    (3)前記析出物を酸性水溶液中で酸化処理して、不純物元素を溶出させ、次いで不純物元素を含む液を分離して、精製された塩化銀を得る。
    (4)前記塩化銀をアルカリ水溶液中で還元して、銀粉を得る。
    A method for producing silver from a refining intermediate containing a hardly soluble silver compound and an impurity element by the following steps (1) to (4),
    In the step (2), before adding acid to the leaching solution containing silver obtained in the step (1), the leaching solution containing silver is microfiltered with a filter having an opening of 1 μm or less, and the acid is removed. During the addition, the pH is adjusted to 3.5 to 5.5, and after precipitation of silver chloride, the whole amount of the mother liquor and the precipitate is filtered within 60 minutes to separate the precipitate from the mother liquor. A method for producing silver.
    (1) The refining intermediate is leached in a sulfite aqueous solution, silver is extracted into the sulfite aqueous solution, and the insoluble residue thus formed is separated to obtain a leachate containing silver.
    (2) An acid is added to the leaching solution to precipitate silver chloride, and then the mother liquor is separated to obtain a precipitate containing silver chloride.
    (3) The precipitate is oxidized in an acidic aqueous solution to elute the impurity element, and then the liquid containing the impurity element is separated to obtain purified silver chloride.
    (4) The silver chloride is reduced in an alkaline aqueous solution to obtain silver powder.
  2. 前記(2)の工程において、母液と析出物の全量が抜き出せる構造を有する反応槽を用いて、母液と析出物をろ過する際に、該反応槽から母液と析出物の全量を抜き出すことを特徴とする請求項1に記載の銀の製造方法。   In the step (2), when the mother liquor and the precipitate are filtered using a reaction tank having a structure capable of extracting the whole amount of the mother liquor and the precipitate, the whole amount of the mother liquor and the precipitate is extracted from the reaction tank. The method for producing silver according to claim 1, characterized in that:
  3. 前記難溶性銀化合物は、塩化銀であることを特徴とする請求項1又は2に記載の銀の製造方法。 The method for producing silver according to claim 1 or 2 , wherein the hardly soluble silver compound is silver chloride.
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