Adsorption of Various Amines on Titanium(IV) Oxide from Aqueous Solution

Abstract

The adsorption of various amines in aqueous solution on TiO₂ was carried out at mainly 30°C with constant stirring for several hours. The adsorptive activity of TiO₂ per specific surface area was higher than those of other metal oxides (SiO₂, ZrO₂, Fe2O₃, Al2O₃) (Fig.3). The amounts of amines adsorbed on TiO₂ were in the order of
1, 3-Propanediamine>3-Amino-1-propanol>Butylamine>Benzylamine.
The Langmuir equation was applicable to the adsorption of butylamine on TiO 2 (Fig.6). Th e activation energy was about 16.6 kJ/mol. The amount of butylamine adsorbed roughly corresponded to the amount of surface acid determined with KOH aqueous solution (Fig.7). Th ere was a almost linear relationship between the amount of adsorption and that of effective OH groups on TiO₂ calcinated above 400°C (Fig.8). The ratio of the amounts of butylamine adsorbed at higher than 400°C to those of effective surface OH groups was determined to be nearly 1: 1. Thus, the adsorptions were considered to take place not on Lewi s acid sites, b ut on the surface OH groups of TiO₂.