How to Solve the Tungsten Tin Separation Problem

China is the world's largest tungsten producing country and the main producer of tin, millions of tons of tungsten tin symbiotic minerals are separated and enriched by the methods of general gravity separation and flotation or magnetic separation.

Some scholars have provided a kind of tungsten tin refractory symbiotic ore as raw material. The method is characterized by using chemical metallurgical means to convert tungsten tin into soluble structure, then control the different conditions and separate them into solution, then transform them into tungsten tin products such as ammonium para tungstate and two tin oxide respectively. The course is as follows:

The high purity ammonium para tungstate, or ammonium tungstate was converted to tungstate and tungsten trioxide from ammonium tungstate, was obtained by separation and desorption of ammonium tungstate and ammonium chloride or ammonia water after the ammonium tungstate was entered into the solution.

The tin slag used lignite as reducing agent and non-metallic mineral as stabilizer. After reduction and stability, the tin was leached with sulphuric acid, then two tin oxide was obtained by liquid oxidation and dehydration, or Sn sulphate, converted into stannous chloride and sodium stannate, the waste gas and waste liquid produced in the process were treated with corresponding post treatment process.

When the size of the ore is -120 > 95%, in the state of micro boiling (90~95°C), the nitric acid with a concentration of 8 ~ 10% (solid to liquid ratio 1:3) is used as an acidolysis agent, the low concentration is controlled oxidation. Under this condition, the nitrate reduction product is NH3, which can avoid excessive nitrogen oxides, cause pollution damage. At the same time, the decomposition rate of tungsten is greater than 97%.

Due to the heating of the rapid reaction rate, the decomposition of a small amount of dilute nitric acid to produce nitrogen oxides is difficult to avoid, the nitric oxide may be produced by nitric acid on some gangue. Therefore, the nitrogen oxide is used to recover the nitrogen oxide to NH₄NO₃. Using cheap ammonium bicarbonate as precipitation conversion agent, the metal ions precipitated into tungsten solution were precipitated.

For tungsten, ammonia solution is an effective purification process. Ammonium tungstate obtained by ammonia solution contains only very few impurities such as P. For tin, ammonia solution is a good way to completely remove tungsten and ammonia dissolving impurities. It can be used to separate tungsten tin refractory symbiotic ore with nitric acid conversion and ammonia leaching. The stability of cassiterite with high oxidation state is proved to be completely separated from the tungsten phase.

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