Scheelite Floatation for the Fluorite Recycling

Fluorite is the most important mineral in fluorides. It has unique physical and chemical properties and it is widely used. The reserves, production and export of fluorite in China are the first class in the world.

Because the fluorite industry has always been a thin profit industry, so the mine mainly produces tungsten concentrate, accompanied by fluorite minerals is only "partial recovery". Now, with the development of the economy, the demand for fluorine in the market is increasing, and the high quality fluorite is becoming less and less, the comprehensive utilization of associated fluorite ore is on the agenda day by day.

Due to the similar floatability of calcium gangue minerals such as scheelite and fluorite ore, the addition of inhibitors in the process of floatation of wolframite has a strong inhibition on calcium containing minerals such as fluorite. Such inhibition has a negative effect on the recovery of scheelite on the one hand. On the other hand, the floatability of the fluorite is worse and the subsequent recovery is seriously affected. Therefore, it is necessary to develop the processing technology of the mixed concentrate.

Some researchers have tried to decompose fluorite minerals with sulphuric acid and add phosphoric acid at the same time, so that wolframite in the mineral is converted into heteropoly acid (or heteropoly anhydride) in the fluorogypsum residue when roasting, then a small amount of phosphoric acid is used to soak fluorogypsum, and the excess sulphuric acid in fluorogypsum is also effectively used. The tungsten is added into the solution in the form of heteropoly acid to achieve separation from calcium sulfate. The specific experimental operation process is as follows:

1kg tungsten containing fluorite concentrate (containing CaF₂ 95.6%, WO₃ 2.7%) was decomposed by sulfuric acid and phosphoric acid. The molar ratio of the concentration of 98% sulfuric acid to the mineral content is 1.2, the molar ratio of the WO₃ content of phosphoric acid to the mineral is 1, the calcination temperature is 250°C, the calcination time is 6h. The HF gas produced during the calcination process is used to prepare hydrofluoric acid, the decomposition rate of CaF₂ is 96.2%. The fluorogypsum obtained after the process of roasting junction is leached by H₃PO₄ with a concentration of 100g/L. The ratio of liquid to solid is 5:1, the leaching temperature is 80°C, the leaching rate of tungsten is 96.5%, the slag containing WO₃ is 0.056%. The filtrate obtained after the leaching process can return to a new round of leaching of tungsten containing fluorogypsum. The tungsten in the leaching solution was adsorbed on the primary amine anion exchange resin, the adsorption rate was 98.5%.

This method changes the beneficiation idea of single scheelite floatation concentrate and fluorite concentrate, obtains the high comprehensive utilization ratio of tungsten and fluorite resources. The decomposition rate of fluorite reaches more than 95%, the recovery rate of tungsten is above 90%, the WO₃ in fluorogypsum is reduced to less than 0.1%.

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