| 摘要 |
PURPOSE:To recover waste chromate soln. by a simple method, by alkalizing waste chromate soln. to a prescribed pH so as to remove zinc hydroxide, then by acidulating the waste soln. to a prescribed pH. CONSTITUTION:To the waste soln. obtained from chromate soln. having been used for forming chromate coating on the surface of zinc-galvanized product are added one or more members of alkali metal hydroxide, for example, sodium hydroxide, potassium hydroxide etc. to increase its pH to 9-12. By this process, zin contained in the waste soln. is removed as hydroxide precipitate without decreasing the oxidizing power of the waste soln. To the waste soln. having been liberated from zinc hydroxide is added a strong mineral acid such as nitric acid, sulfuric acid etc to decrease its pH to 2 or lower. Reutilization of the chromate soln. hereby regenerated permits to form excellent chromate coating. |
