For a long time, Chinese tungsten reserves, production, trade volume is ranking first in the world. In recent years, due to the rapid development of Chinese economy, China' own consumption also ranks the first in the world. Unfortunately, we pay more attention to a long-term exploitation of resources, but not enough attention to tungsten recovery and utilization due to technology, policy and other reasons. This resulted in a waste of resources and damage of the environment. Therefore, utilization of various tungsten resources is becoming urgent. People have done a lot of work on the comprehensive utilization of renewable resources of tungsten for many years. Currently, the rate of recycling waste tungsten has reached more than 20% in the consumption of our country. Sodium carbonate recycling waste tungsten smelting technology is more mature and be of wide applicability. And the annual recovery of sodium tungstate treatment was up to more than two thousand tons. But during leaching of sodium carbonate melting back waste tungsten, a large number of impurity elements also enter in the sodium tungstate solution. So the production of high purity tungsten cannot be met. So in order to effectively recover tungsten secondary resources, we should conduct impurity removal process, especially the removal of chromium.

 

There are two methods of eliminating chromium from sodium tungstate solution: 

1. The acidic solution reduction method 

In acidic solution reduction, sodium sulfite, ferrous sulfate are mainly as the reducing agent. the basic process is adjusting the solution to an acidic sodium tungstate. then   adding the sodium sulfite and ferrous sulfate reducing agent. restore Cr6+ toCr3+. 

2. The alkaline solution reduction method 

In the reduction of  alkaline solution, sodium sulfide, sodium hydrosulfide are mainly as the reducing agent. the basic process is adding sodium sulfide, sodium hydrosulfide to  an alkaline chromium-containing material to realize Cr6 + reduction reaction and form Cr (OH) 3 precipitate.

 

This paper describes the use of sodium sulfide eliminating chromium process. it's also an alkaline solution of  reduction process. Because eliminating molybdenum sulfide has been in part of the curing process of APT tungsten smelting production. so eliminating chromium can be carried out in the procee of molybdenum extraction simultaneously. But there's no vulcanization process.  it will lead to Cr (OH) 3 subsequently curing liquid phase dissolved into the tone of acid acid which resulting in extraction, stripping phase difficulties. when it enters upon stripping (NH4) 2WO4 solution,it makes the APT chromium content exceeded. so it's necessary to increase the cvulcanization processing in the part of the curing process on the basis of the original. in addition, in molybdenum sulfide production process, through adding 4 times the theoretical amount of sodium sulfide, controlling the reaction pH value of 8 to 9 and selecting  the appropriate temperature and aging time, the better effect of eliminating  chromium can be reached.