Detinning Process of APT Production- Precipitation Method

Precipitation method in APT production is a common method of separation science. As the tin exists as precipitate forms in the weakly acidic, neutral, weakly alkaline environment, people take a variety of precipitation methods, such as hydrolysis precipitation, tin sulfide precipitation to remove tin of the tungsten solution.

Hydrolysis precipitation method
This is a classic method remove tin. Its basic principle is tin in solution can be hydrolyzed into tin hydroxide precipitate at a pH of about 2 to 11 (depending on the concentration of tin in the solution) to separate tungsten. The main reaction is:
SnO3 2-+3H2O= Sn(OH)4↓+20H-.

Specific operating conditions: add dilute acid(typically sulfuric acid) to sodium tungstate solution (pH is about 14), adjust pH of the solution to 9 to 10, stirring for 10 ~ 15 min, at room temperature (in the case of boiling , the advantage is not very obvious), to stand for aging. The longer the standing time, the higher the tin hydrolysis precipitation rate. It’s believed in the literature that it needs to stand for 96 h.

Hydrolysis detinning rate rises with the tin mass concentration of solution increased. However, when hydrolysing detinning, and the solution is often turbid, the precipitation is difficult to cake filter. Easy to form a tin-containing hydrolysis solution lower gum, gum nucleosome its low concentration, dispersion and strong, easy reunion. It is also above the longer the standing time, the higher the rate of hydrolysis precipitation in addition to tin reasons. Production, the use of tin content in the concentrate within the range of 0.03% to 0.2%, tin in solution concentration of 0.0012 ~ 0.033g / L, therefore, in addition to use of hydrolytic precipitation when tin is difficult to obtain the desired results. Moreover, the operation of acid sodium tungstate were to spend a lot of acid, and the introduction of a large number of impurities anion, seriously affecting the subsequent ion exchange process, difficult to apply to the current tungsten metallurgy most advanced "tungsten concentrate decompose an ion exchange an evaporative crystallization "technology.