PEPTIZATION PROCESS IN THE SOL-GEL PREPARATION OF POROUS ANATASE (TIO2)

The process variables were studied for the peptization of titania in the production of anatase membranes. The original precipitate formed by the hydrolysis of titanium ethoxide does not gel without addition of acid. An acidified (nitric or hydrochloric acid) sol peptized at room temperature leads to the formation of rutile. Under refluxing at elevated temperatures, the result is a gel that is essentially 100% anatase. Both hot and room-temperature acid peptization yield stable sols and well-crystallized systems. Less than 15 min is required for the high-temperature peptization of titania with nitric acid and increasing that time results in only the growth of the anatase particles.