| 摘要 |
PURPOSE:To remove SO2-4, Ba<2+> and Sr<2+> substantially completely and to purify phosphoric acid by filtering off BaSO4 formed by adding a Ba compd. to phosphoric acid produced by the wet process contg. SO4<2-> and treating the phosphoric acid with cation exchange resin. CONSTITUTION:Preferably, phosphoric acid produced by the wet process and freed of cationic impurities by extracting using an org. solvent such as slcohol from crude phosphoric acid obtd. by the decomposition of rock phosphate with H2SO4 is treated by the following process. Thus, H3PO4 content in the wet process phosphoric acid is held at >=75wt%, and a Ba compd. such as BaCO3, etc. is added to the phosphoric acid. Formed BaSO4 is filtered off to reduce the concn. of dissolved SO4<2-> to <=20ppm (by weight). Then, the phosphoric acid freed of BaSO4 is allowed to contact with cation exchange resin such as polystyrenic ion exchange resin. As the result, remaining SO4<2->, Ba<2+>, and Sr<2+> in the phosphoric acid are removed and the phosphoric acid is purified.
|
