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Germanium Production


By-products of nonferrous metals, products of coke process and coal ash are used as raw feedstock for obtaining germanium. After concentration by flotation or magnetic methods germanium concentrate is processed by pyrometallurgical methods at 800-1800°C, in reducing atmosphere (CO, H2) and in the presence of S, or H2SO4, or alkali-earth metals sulphates. Germanium completely or partially passes into gaseous phase as GeO, GeO2, GeS, GeS2, Ge, which then are trapped with other volatile components and dust.

Germanium-containing dust which appears after nonferrous metals processing is subject of leaching by H2SO4 solution. Germanium concentrate is separated from solutions, usually by as well as Co-Zn codeposition with other elements, for instance, Fe as Fe(OH)3 at pH 4.8-5.4. Separated germanium is dried, roasted and treated by concentrated chlorohydric acid, distilling out the yielded GeCl4. Germanium may be isolated also by ion exchange processes with chlorohydric acid as an eluent. The solution is then distilled yielding GeCl4; or hydrolyzes by alkali liquor until GeO2.

After that GeCl4 is rectified in quartz columns, or by hydrochloric acid extraction, by thermal diffusion, by directional crystallization etc. After that GeCl4 is hydrolyzed by pure water at 20-30°C the obtained GeO2 flushed up by water and dried by spirits, ultra-high frequency currents, after which germanium is reduced by hydrogen at 600-700°C. Powder germanium is fused at 1000-1050°C and refined by zone melting, and directional crystallization. Crystals are grown by Czochralski or Stepanov crystal growth method. In this process germanium is doped in 10-3 - 10-4% by special impurities such as Sb, As, Si etc. varying semiconductor properties. The purity of produced germanium is determined through Hall's EMF or via neutron activation analysis.

Historical preparation

The metal was prepared by Winkler from argyrodite in the following way. Three parts of the finely powdered mineral were fused at a bright red heat with six parts of potassium nitrate and three parts of potassium carbonate. The alkali germanate thus formed was separated from the metallic silver by extraction with water, and the solution was evaporated with sulphuric acid till nitric acid ceased to be evolved. Most of the germanium then separated as dioxide, and the remainder was precipitated as sulphide, which was roasted and converted finally into oxide by treatment with nitric acid. This oxide was further purified by being converted into the insoluble germani-fiuoride K2GeF6, and thence into sulphide, GeS2, by fusion with potash and sulphur; the sulphide was afterwards decomposed by sulphuric acid, and so reconverted into oxide. The oxide was then reduced by heating it with carbon, and the resulting metal, after being washed with water, was purified by fusion with borax. The metal may also be obtained from potassium germanifluoride, K2GeF6, by reduction in a stream of hydrogen or with sodium; or the dioxide can be reduced by hydrogen or magnesium. Urbain, Blondel, and Obiedoff have extracted 5 grams of pure germanium from 550 kilograms of a Mexican blende.

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