Wolframite From Acidic System Decomposition

At present, the main method of industrial decomposition of tungsten mineral raw materials is NaOH decomposition process, which must be under extreme conditions (high temperature, high pressure and high alkali) to achieve effective decomposition of tungsten ore. However, the tendency of thermodynamic reaction of acid decomposition of tungsten ore is very high, but the decomposition is often incomplete due to the kinetic constraints.

In view of the fact that wolframite can not be effectively decomposed in various acidic systems, new technological ideas may be needed. Researchers envisage the transformation of wolframite into scheelite, which is expected to achieve efficient decomposition of tungsten in sulfuric acid-phosphoric acid system.

So the researchers improved the original method of extracting tungsten from wolframite raw materials. Wolframite is transformed into scheelite by chemical means. This method realizes the high efficient decomposition of wolframite and wolframite-scheelite mixture at normal temperature and pressure, breaking through the limitation that wolframite and wolframite-scheelite mixture can not be treated by sulfuric acid-phosphoric acid mixed acid system. The process of the leaching agent only needs to add sulfuric acid to the initial level.

Wolframite concentrate with particle size less than 250 micron (including WO₃ 71.3%) and apatite (including P₂O₅ 35.81%) were blended and added to the ball mill. The ball milling reaction lasted for 2 hours after adding water at a liquid-solid ratio of 0.5:1 mL/g. After the reaction was terminated, the tungsten-bearing ore was filtered and dried for 24 hours. During this period, the wolframite was partially converted into scheelite.

The tungsten ore was leached for 4 hours in a mixed acid solution with H₂SO₄ concentration of 250g/L and H₃PO₄ concentration of 300 g/L, and the liquid-solid ratio was 10:1 mL/g. The leaching rate of tungsten was 99.2%. After extraction of tungsten by tertiary amine extractant, mother liquor is added to the spent sulfuric acid to return to the new round of leaching. Under the same decomposition conditions, the leaching rate of tungsten is 99.1%.

This method breaks through the limitation that the sulfuric acid-phosphoric acid system can not treat wolframite and wolframite mixture, and realizes the high efficient decomposition of various tungsten mineral raw materials under normal temperature and pressure. Generally speaking, the decomposition rate of wolframite is over 98%, and that of wolframite-scheelite mixture is over 97%. Moreover, the phosphorus-containing calcium materials used in the decomposition process have a wide range of sources and low price, which can be used to make up for the consumption of phosphoric acid in the decomposition process.

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