| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the amt. of industrial waste caused by waste acid discharging treatment by adding an aq. soln. contg. the fluoride of Ti with one or more kinds among potassium hydroxide, ammonium hydroxide and ammona and precipitating Ti as hydroxide. SOLUTION: The recovery of Ti from a nitric-hydrofluoric acid pickling waste soln. is executed by neutralizing treatment of pH 3 to 12 by potassium hydroxide. At this time, titanium nitrate and titanium tetrafluoride in the waste soln. are brought into reaction with potassium hydroxide to form titanium hydroxide, potassium nitrate and potassium fluoride. Potassium nitrate and potassium fluoride have high solubility and are not precipitated, and the greater part thereof dissolves into the soln. Thus, the precipitation of titanium hydroxide relatively good in purity can be obtd. Since this precipitates have relatively fine particles and are easy to be clogged into a filter cloth, or the like, a suitable coagulant is added thereto before filtration. The soln. in which the precipitates have been filtered away can be reutilized for the pickling of Ti or the like.</p> |
