In the process of decomposition of tungsten ore alkali, the impurity molybdenum will enter the sodium tungstate solution. Therefore, how to remove molybdenum from tungsten alkali leaching liquid and achieve the deep purification of the crude sodium tungstate solution are the major issues of improving the quality of tungsten products and expanding the comprehensive utilization of resources. The classic sulfide precipitation of purifying the sodium tungstate solution is still widely used in the tungsten metallurgy. The advantage of this method is simpleness and easily removing part of molybdenum in the solution. Its shortcomings are emitting toxic gases of hydrogen sulfide unavoidably in the process of molybdenum sulfide precipitation to pollute environment. The effect of eliminating molybdenum is not good enough and has great lost of tungsten. Typical extraction agent, which is used by Solvent extraction method for the purification of crude sodium tungstate solution, has a neutral phosphorous extraction agent, acid phosphorus extraction, nitrogen extraction agent, containing sulfur extraction agent, oxygen extraction agent, etc. Due to effect of selective, split phase, toxicity, economic problems, above-mentioned extraction agent has not been widely used. Eliminating molybdenum of sodium tungstate solution by using precipitating agent with copper sulfate is a kind of simple and practical method.

 

About operation process of this method is as follows: the first react with sodium sulfide sodium molybdate formed glucosinolates molybdate, tungsten compounds are still in the form of tungstate in solution. After vulcanization joined the crude sodium tungstate solution of copper sulfate, sulphur molybdenum acid radical generation and the generation of the combination of undissolved compound precipitate, realize the separation of tungsten and molybdenum. Then see the test method, first with dilute sulphuric acid and dilute sodium hydroxide solution of sodium tungstate solution to the required pH value, add a certain amount, sodium sulfide control proper curing temperature and time of vulcanization. Add a certain amount, after the completion of sulfide copper sulfate, control the appropriate temperature and time of reaction. 

 

After the completion of reaction heat filtration, the filtrate third tungsten and molybdenum oxide content can learn by experiment: 

1. Using sodium sulphide for vulcanizing agent, copper sulfate as precipitant, precipitated sulfur generation of molybdenum acid radical, can achieve effective separation of molybdenum and tungsten. During vulcanization, better conditions for the amount of sodium sulfide three times the amount on the theory of curing temperature 70 ℃, the curing time of 90 min, the sodium tungstate solution pH 7.

2, when precipitation temperature is 80 ℃, precipitation time is 120 minutes, precipitating agent dosage of copper sulfate for theory is five times of the amount of precipitation, it’s efficiency is highest. 

3. The sediment can be recycled molybdenum oxide treatment of residual copper compounds can be treated to return to the precipitation process. With copper sulfate precipitation despite the molybdenum of crude sodium tungstate solution, has the reagent was cheap, generating hydrogen sulfide gas, the operating conditions, grasp the advantages of easy to control. This method is not only simple, easily controlled but also has little pollution.