The Behavior Of Germanium In The Germanium-rich Sphalerite Acid Pressure Leaching Process

As a rare metal, germanium is very important material because of its good physic-chemical characteristics, used in high-tech field. The behavior of germanium in acid pressure oxidative leaching of germanium-bearing sphalerite was investigated for the sake of the later industrial application, and to further understanding of pressure leaching.After review of plenty of literature home and abroad, most of experiments were carried out in Technology Center of Yunnan Metallurgy Group Co., Ltd, Kunming. The experiment was constituted of six partS。(1) study on acid pressure oxidative leaching of germanium-bearing sphalerite; (2) study on mechanism of acid pressure oxidative of germanium sphalerite; (3) study on difference of leaching kinetics of germanium and zinc in pressure leaching; (4) leaching kinetics of germanium in acid pressure oxidative leaching of germanium-bearing; (5) catalytic role of silver, iron and manganese in pressure leaching of germanium-rich sphalerite; (6) study on the process to deal with pressure leaching liquor of germanium-bearing sphalerite. The former five parts was the main body, and the latter one part is a supplement. Analysis and determination was done by Yunnan Non-Ferrous Metals & Products Quality Supervision and Analysis Center.In the first part, Lab-scale Orthogonal experiment of autoclave oxidation of germanium-bearing sphalerite concentrate was carried out in a 2-L autoclave to investigate the variables such as leaching temperature, leaching duration, oxygen pressure, granularity, molar ratio of acid to zinc and stirring rate on the dissolution of germanium. In the second part, artificial zinc sulfide crystal was prepared via pre-leaching of nature bearing-sphalerite. Such relatively "pure" sphalerite concentrate was leached in a pressure autoclave, with or without iron ion added. In the third part, the difference in dissolution between germanium and zinc during oxidative pressure leaching of germanium-bearing sphalerite was evaluated in laboratory-scale experiments. The effect of temperature and time on germanium hydrolysis, co-precipitation with silica, and co-precipitation with iron oxides was investigated. In the fourth part, Germanium-bearing zinc sulfide crystal was synthesized; it's acid pressure oxidative leaching kinetics was investigated under condition with and without sulfur dispersion agent (sodium lignosulfonate) addition. In the fifth part, Catalytic role of dissolved silver, iron and manganese in acid pressure oxidative leaching of germanium-bearing sphalerite was studied. Factors affecting it were investigated. In the sixth part, two processes to deal with pressure leach liquor were studied. One is germanium co-precipitation with ferric hydroxides, factors were investigated. The other is how to scale tannins'utilization.In the first part study on acid pressure oxidative leaching of germanium-bearing sphalerite, variables affecting germanium-bearing sphalerite were investigated such as leaching temperature, leaching duration, oxygen pressure, granularity, molar ratio of acid to zinc and rotation speed on the dissolution of germanium. Orthogonal experiment results showed that leaching temperature and oxygen pressure are major factors affecting the dissolution of germanium, followed by granularity, rotation speed, and molar ratio of acid to ore and leaching duration. The most reasonable conditions were:leaching temperate,150℃, oxygen pressure,1.2MPa, granularity-320mess,98.2%(grind time,9min), stirring rate,700rpm, acid-to-ore ratio,1.5。under such condition, zinc and germanium dissolution yield was above 99%and 90%above, respectively; 80%above sulfur was conversed to elemental sulfur; the final acidity is about 20g/L; iron concentration was about 5g/L. in the second part Study on mechanism of acid pressure oxidative leaching of germanium-bearing sphalerite, a new method was used to investigate the mechanism. Experimental result obtained showed dissolution of sphalerite increased with increased dissolved iron addition, and at medium temperature, the mechanism of hydrogen sulfide is the medium was fitted to experimental result well. In the third part Study on difference of leaching kinetics of germanium and zinc in pressure leaching, the difference of dissolution yield of zinc and germanium was investigated in term of germanium hydrolysis, co-precipitation with silicon, co-precipitation with iron. Experimental results obtained showed the most important factor is co-precipitation with silica, followed by co-precipitation with iron, the finally germanium hydrolysis, and containing 9%,5%and 2%of germanium loss respectively. In the three iron precipitation, jarosite is the most important factor, followed by goethite and hematite. In the forth part leaching kinetics of germanium in acid pressure oxidative leaching of germanium-bearing, attempt to find the kinetics model was tried. When without sodium lignosulphonate addition, diffusion in sulfur lay is the rate-controlling step, and dissolution of germanium is fitted to the model "ash diffusion control-dense-constant size-spherical particles", the equation is When with sodium lignosulphonate addition, chemical reaction is the rate-controlling step, fit the model "chemical reaction control-dense-constant size or shrinking spherical particles" well, the equation From the fitting resuls, most germanium-bearing sphalerite is spherical particles, maybe some are cylindrical particles. In the fifth part catalytic role of silver, iron and manganese in pressure leaching of germanium-rich sphalerite, catalytic role of silver, iron and manganese was investigated. In a given condition, silver ion can accelerate the leaching of sphalerite. In simultaneous leaching of sphalerite and neutral leach residue, they can accelerate each other. Divalent manganese can accelerate the manganese rapidly, and catalytic effect is stronger than iron. In the sixth Study on the process to deal with pressure leaching liquor of germanium-bearing sphalerite, the process of co-precipitation of ferric hydrolysis, germanium precipitation with tannins was investigated. The favor to Ge/Fe co-precipitation conditions are:high initial germanium concentration, high Fe/Ge molar ratio, high final solution pH, and low iron strength, low neutralization temperature. High germanium precipitation yield was achieved in an easy-go condition, which indicated the process has good industrial applicative potential. Tannins can complex with nearly all metal ions. Re-use and multi-use of tannins can scale tannins'utilization.It is technologically feasible to deal with geranium-bearing sphalerite with acid pressure oxidative leaching of sphalerite. Using the process friendlily to environment, higher germanium/zinc can be achieved. To increase germanium recovery yield, it was recommend that pre-treatment, rigid operation condition was done. To shorten the leaching of germanium-bearing sphalerite, manganese and sulfur sphere agency should be added, and guard sulfur sphere agency from being oxidized.