<報文>アンモニア・アルカリ性チオ硫酸ソーダ溶液への金の溶解について : 浸出残渣中の金銀の回収について(第2報)

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The complex sulfide ore (Kuroko) and the concentrate obtained from leaching residue of zinc plant were examined by microphotographic method. As the results, it was determined that gold exists in a native form, but silver and sulfide minerals will probably form solid solution. It is known that thiosulfate ions are produced during ammonia pressure leaching of sulfide ores. Therefore, we have considered the use of these thiosulfate ions to extract gold and silver in the leaching residue. The following reaction occurs, when gold dissolves in thiosulfate solutions in the presence of oxygen : [chemical formula] Studies of the above reaction, carried out under a variety of conditions, suggest that the dissolution of gold is accelerated by the presence of cupric ammine complex ions and proceeds in the following four stages with the rise of temperature : (1) dissolution rate increases up to 65℃ ; (2) dissolution rate decreases between 65 and 100℃, because the gold surface receives copper sulfide coating by the reaction [chemical formula] (3) gold redissolves above 100℃, because gold reacts immediately with S_2O_3^<2-> ion formed on the gold surface by the reaction [chemical formula] and (4) dissolution rate decreases above 140℃, because of the decrease of S_2O_3^<2-> concentration by oxidation. Oxygen partial pressure and stirring velocity have the limits to avoid the oxidation of thiosulfate. Ammonia concentration is enough to form cupric ammine complex ion. The conditions determined as optimum for dissolving gold in ammoniacal sodium thiosulfate solution at 65℃ are as follows : oxygen pressure 1 atm ; stirring velocity 200 r.p.m. ; NH_3 0.5 M, Na_2S_2O_3 0.5 M ; and addition of 0.04 M CuSO_4.
東北大学の論文
1972-11-15

<報文>アンモニア・アルカリ性チオ硫酸ソーダ溶液への金の溶解について : 浸出残渣中の金銀の回収について(第2報)

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