A Method for Tungsten Extraction in Alkaline Medium

Pressure leaching and water leaching are two mature methods for industrial leaching of tungsten from tungsten ore. The leachate obtained by the above two leaching methods is a mixed solution of sodium tungstate and sodium carbonate, which usually contains a small amount of impurities such as P, As, Si, etc. and this solution is a soda leaching solution containing a tungsten material.

An important method for preparing ammonium tungstate (APT) solution from soda leaching solution is solvent extraction. The industrial extraction method currently uses a weakly basic polymeric amine (such as a polymer tertiary amine, a primary amine, a secondary amine, etc.) as an extractant to extract tungsten under acidic conditions (pH 2 to 4), and the organic phase is supported. Ammonia water is stripping to obtain an APT solution. This extraction method is called acid extraction.

The acidic extraction method has the following disadvantages: (1) The leachate containing a large amount of free sodium carbonate must be adjusted to be acidic (pH 2 to 4), at which free sodium carbonate in the leachate is wasted and a large amount of inorganic acid (sulfuric acid or hydrochloric acid)was consumed, and the inorganic salts produced by neutralization of acid and alkali can pollute the environment; (2) P, As, Si can form heteropolyacids with tungsten under acidic conditions, so the acid extraction method does not have the function of removing impurities containing P, As, Si, etc. These impurities need to be removed by a chemical precipitation method (magnesium salt method or ammonium magnesium salt method) in a sodium tungstate solution, which consumes a large amount of chemicals and has a loss of tungsten.

In response to the problem of acid extraction, Zhang Qixiu et al. proposed a preparation method to centrifugally extract ammonium tungstate solution from a tungsten ore leaching solution. The operation procedure is as follows:

1) Composition of soda leaching solution containing tungsten material: WO3 10.0g/L, Na2CO3 20.5g/L, P0.02g/L, As0.01g/L, Si0.03g/L;

Organic phase: pre-formed an organic phase consisting of 60% N263 + 20% octanol + 20% sulfonated kerosene (volume percent concentration), wherein N263 is the commercial code of quaternary ammonium salt extractant, which is a methyl three Alkyl ammonium chloride.

2) The organic phase is contacted with the sodium carbonate solution several times before the extraction to convert the methyltrialkylammonium chloride in the organic phase to the methyltrialkylammonium carbonate, and the extractant in the organic phase is organic The volume percentage concentration in the phase was 60%, and the organic phase was used as the extracted organic phase.

3) Operation: The above organic phase and the tungsten ore leaching solution are subjected to 7-stage countercurrent extraction under the condition of a flow ratio of 1/10, the extraction device is an annular gap centrifugal extractor, and the negative tungsten organic phase is treated with deionized water by flow ratio 3.After washing, it was mixed with ammonium solution (2.5 mol/L NH4HCO3 + 1.0 mol/L (NH4)2CO3) to have a 10-stage countercurrent striping. The striping equipment was also an annular gap centrifugal extractor with a striping flow ratio of 2/1. The post-organic phase was returned to the extraction after a single-stage regeneration treatment with a 2 mol/L NaOH aqueous solution at 1.5/1.

Results: The stripping solution was a high-purity ammonium tungstate solution with a WO3 concentration of 190.0 g/L, P < 0.0001 g/L, As < 0.0006 g/L, and Si < 0.006 g/L.

In the process, the extracting agent is a methyltrialkylammonium carbonate, and the extracting agent is combined with a polarity improving agent (such as octanol, tributyl phosphate) and a diluent (such as sulfonated kerosene) to form an organic phase; The feed liquid is a leaching solution of tungsten ore, and the solution is a mixed solution of sodium tungstate and sodium carbonate, which usually contains a small amount of impurities such as P, As, Si, etc. In the multi-stage centrifugal extractor connected by countercurrent flow, rapid mixing and phase separation are carried out to realize a multi-stage countercurrent extraction process. In this process, tungsten is extracted into the organic phase, and impurities such as P, As, Si, etc. are discharged with the raffinate. Tungsten separation. After the organic phase is washed by detergent (such as deionized water), the mixed solution of ammonium hydrogencarbonate and ammonium carbonate is used as a stripping agent for rapid mixing and phase separation in a plurality of centrifugal extractors connected in a countercurrent manner at a certain flow ratio. A multi-stage countercurrent stripping process is realized to obtain a higher purity ammonium tungstate solution. The organic phase after the stripping is regenerated by a solution containing free sodium hydroxide and then returned to the extraction. The main component of the raffinate produced by the extraction process is sodium carbonate solution, which can be returned to leaching.

The above process of tungsten extraction is carried out directly in an alkaline medium, without the need to consume inorganic acid to neutralize the free base in the soda leaching solution of the tungsten ore and to adjust the acidity; the separation of impurities P, As, Si, etc. can be simultaneously achieved. The process of removing P, As, Si by chemical precipitation method is cut. The waste water discharge is reduced, and it is easy to be scaled application.

• < Prev
• Next >