With the shortage of tungsten ore resources, the utilization of tungsten resources becomes more and more urgent.
Waste tungsten alloy is one of the main sources of tungsten recovery, according to statistics, about 35% of the tungsten in Europe and America developed from waste tungsten alloy recycling. With the emphasis on tungsten resources in China, the recycle rate of tungsten resources in China has been increasing year by year, and it has reached 20%.
In the tungsten recycling process, the sodium carbonate melting method of waste tungsten recycle process technology is more mature and wide applicability of the program, but it is inevitable that the leaching process in recycling of waste tungsten, scrap tin, phosphorus, chromium, molybdenum and other impurities may also enter coarse sodium tungstate solution, thus affecting the purity of tungsten products. The main impurities of the waste alloy are different, the treatment method varies according to material, here to introduce tin removal from crude sodium tungstate solution method of tin rich impurities.
In the alkaline process, the purification of sodium tungstate from waste alloy is usually made by magnesium ammonium phosphate method or phosphorus arsenic magnesium salt method. In the impure sodium tungstate solution, a small amount of soluble magnesium salt is added to produce ammonium phosphate, and generated magnesium salt or phosphorus arsenic magnesium salt, so as to remove arsenic and phosphorus.
In the impure sodium tungstate solution, a small amount of soluble magnesium salt is added to produce ammonium phosphate, magnesium salt or phosphorus arsenic magnesium salt, so as to remove arsenic and phosphorus. In the process of pH, silicon can simultaneously remove from the solution, but it can not effectively remove tin and tin, the best filtering stage only in the crude sodium tungstate solution phase, the follow-up process is very difficult to deal with.
For the treatment of tin in crude sodium tungstate solution from waste tungsten alloy recycle, some foreign scholars have proposed the scheme, which can be roughly divided into four stages. (1) Adding ammonium or hydrogen hydroxide to sodium tungstate solution. (2) Adding sulfuric acid, transfer PH to 9.5-10 and stir for half an hour. (3) Adding magnesium chloride into the solution which has been ammoniation and adjusted the pH value, and then the mixture is stirred for a period of about 12 hours to form a slightly soluble tin, arsenic, phosphorus and silicon compounds. (4) Stand aside for about 3 hours. A substance containing tin compounds can be precipitated.
When the insoluble substance is removed, the filter can be used to filter the insoluble matter in the solution and to obtain the purified solution containing tungsten, the content of tin obtained by the purified solution can reach or better than the purity of APT - 0, and it is very economical and feasible to evaluate the content of the waste alloy by the recycling standard of APT.
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