Synthesis of Hydrous $TiO_2$ Powder by Dropping Precipitant Method and Photocatalytic Properties

침전제 적하법을 이용한 $TiO_2$ 분말 제조 및 광촉매 특성

Hydrous titanium oxide particles with anatase phase were prepared from 0.05 mol TiCl4 solution using NH4HCO3 as precipitant by the droopping precipitant method. The sequential change of pH is completed by a sudden and steep increase in a pH value of the range of 6~7 to which the concentration of adsorbed OH- and H+ ions on TiO2 surface is equal. Rutile phase started precipitating with anatase phase as an increase of reaction temperature above 6$0^{\circ}C$ in aqueous 0.05mol TiCl4 solution and its specific surface area was found to decrease from 452 $m^2$/g($25^{\circ}C$) to 164$m^2$/g(8$0^{\circ}C$). Specific surface area decreased rapidly when anatase powders precipitated at 4$0^{\circ}C$ were heat-treated at temperature higher 40$0^{\circ}C$. FT-IR result confirmed that it was due to the decrease of OH species within hydrous titanium oxides. The loss of ethanol after illumination of the powder heated at $600^{\circ}C$ and $700^{\circ}C$ for 4 h was 66 and 68.8%, respectively.