Comprehensive recovery of molybdenum and tungsten from oxidized ore

China is the country with the largest tungsten reserves in the world. On the cause of formation, most of them belong to gasification high temperature hydrothermal deposits. Among them, quartz vein type is the most valuable and most important tungsten deposit. Tungsten ore, the mineral composition is very complex, in addition to the main metal minerals wolframite, scheelite, there is still associated cassiterite, more mineral molybdenite ore brass, bismuthinite like. The associated sulphide mineral content often reaches the value of comprehensive recovery. In tungsten ore containing a variety of sulfide minerals, there are two relationships between tungsten and molybdenum:
(1) Molybdenum enters the tungsten mineral by partially replacing the tungsten with the isomorphism. In view of the rare mineralization of tungsten, the isomorphous products are often molybdenum-containing scheelite or tungsten-molybdenum-calcium ore (molybdenum-tungstenite or tungsten-containing molybdenum-calcium ore is tungsten-substituted molybdenum-calcium ore). The product of molybdenum). At this time, molybdenum exists as a valuable companion element in the tungsten mineral.
(2) Molybdenum minerals are associated with tungsten minerals. At this time, molybdenum minerals exist as valuable associated minerals in tungsten ore.
Molybdenum, which has entered the tungsten minerals, cannot be separated by conventional beneficiation ; the oxidized molybdenum minerals associated with tungsten ore are also difficult to separate by conventional beneficiation processes. They are sorted into tungsten concentrates with tungsten minerals and separated and extracted during deep processing.
A tungsten ore containing a plurality of sulfide minerals, the associated molybdenum ore is selected from a mixed concentrate produced by total sulfur flotation to obtain a qualified molybdenum concentrate. Since tungsten minerals are the main valuable minerals, the beneficiation process should first consider the recovery of tungsten minerals. Usually, the combination of heavy, floating, magnetic, and electrical means can achieve the purpose of sorting. The combination of process types is different depending on the type, particle size, and inlay relationship of the tungsten minerals, as shown in the figure below.
Figure Flow chart of tungsten ore beneficiation principle containing polymetallic sulphides
Among them: Figure a is suitable for ore with high tungsten mineral content, coarse particle size and simple mineral composition. The recovery of tungsten from the slime can be carried out by flotation, or by re-election (turning bed, belt chute, etc.). Figure b is suitable for tungsten ore with fine particle inlays, complex mineral composition or high sulfide mineral content. The process of recovering tungsten minerals from flotation tailings can also be carried out by flotation or re-election. Figure c is suitable for the symbiosis of tungsten minerals and sulfur minerals, and is a tungsten ore that is easily selected by assembly. Tungsten ores containing large amounts of iron ore magnet, magnetic separation process should be added to the process. For rare metal oxides (such as monazite), heavy sand must be separated and recycled.
Separation of mixed sulfur concentrate produced by total sulfur flotation. Inhibit added cyanide copper, zinc, iron sulfide minerals, molybdenum flotation, mixed concentrate bismuth (lead) in a basic medium; Gargano Fox re suppression or bismuth, lead and chromium by weight sodium acid medium, Flotation molybdenum ore; use of lime to suppress the collection of copper minerals. Thereby, the sulfides of Mo, Bi, Cu, and Fe are separated. The molybdenum products have been selected several times to obtain qualified molybdenum concentrates. And can get a variety of sulfide concentrates. [next]
The tungsten-containing molybdenum ore, in the flotation of molybdenum ore, can also be recovered from the flotation tailings by re-election or flotation, and the associated scheelite or wolframite is comprehensively recovered, and the process is relatively simple.
Separation of the tungsten-molybdenum component in the same mineral often has to be done in deep processing.
When used as an alloying additive for steel, the associated molybdenum (or tungsten) is also a beneficial component of steel and is usually applied without further separation.
As a metal or chemical raw material, molybdenum in tungsten products, or tungsten in molybdenum products, is often strictly controlled as a harmful element. Therefore, the tungsten-molybdenum separation at this time is not only a means of comprehensive recovery, but also a necessary means for purifying the product.
Industrially, an effective method for separating tungsten molybdenum from a tungsten-molybdenum leachate is to precipitate molybdenum trisulfide (MoS 3 ).
When an immersion liquid containing both MoO 4 2- and WO 4 2- ions is added to sodium sulfide (Na 2 S), the following reaction occurs:
Na 2 WO 4 + 4NaHS ←→ Na 2 WS 4 + 4NaOH
Na 2 MoO 4 + 4NaHS ←→ Na 2 MoS 4 + 4NaOH
 

K (equilibrium constant)

=

[ Na 2 RS 4 ][ NaOH ] 4

[ Na 2 RO 4 ][ NaHS ] 4

The formation of sodium thiomolybdate by K Mo "K W is much easier than the production of sodium thiotungstate. When the amount of sodium sulfide (Na 2 S) added is only sufficient to vulcanize Na 2 MoO 4 to Na 2 MoS 4 , sodium tungstate is rarely vulcanized. The immersion liquid is acidified to adjust the pH to 2.5 to 3.0. At this time, the sodium thiomolybdate is decomposed to precipitate a molybdenum trisulfide (MoS 3 ) having a low solubility:
Na 2 MoS 4 + 2HCl → MoS 3 + 2NaCl + H 2 S↑
In order to prevent the formation of sodium thiotungstate and precipitate tungsten trisulfide (WS 3 ), the amount of Na 2 S added is only 82% to 83% of the theoretical value (alloyed to form oxygenated molybdenum sulfide (MoO x due to acidification ) S 3~x ).
When the molybdenum is precipitated from the solution containing 8~10g/tMo and 100~120g/t WO 3 , the precipitated sulfide contains 5%~10% WS 3 . After the precipitate was dissolved in soda and then repeatedly precipitated with Na 2 S, MoS 3 was obtained , and WO 3 <2% of MoS 3 was obtained , and the loss of tungsten was only about 0.3% of that in the ore.
The solution was de-molybdenum may be added caustic soda (NaOH) boiling, destruction metatungstate, and then the addition of silicon and phosphorus in addition, allows the production of tungstic acid, ammonium paratungstate or other chemical product.
The tungstic acid or ammonium paratungstate produced at this time also contains a small amount of molybdic acid or ammonium paramolybdate. For further purification, concentrated and fractional crystallization is usually used: the solubility of the paratungstate is smaller than that of the ammonium paramolybdate, and after the solution is evaporated to 60% liquid, 55% of ammonium paratungstate crystallizes, and the molybdenum only precipitates 12%. Repeated concentration and stepwise crystallization can reduce the molybdenum in ammonium paratungstate to a very low level.
The separation of tungsten-molybdenum can be satisfactorily obtained by the above process. It is not only suitable for tungsten-molybdenum-like minerals, but also for various tungsten concentrates containing molybdenum.

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