ABSTRACT
TiO2 particles of various sizes were prepared by grinding in cyclohexanone, and TiO2 particulate films were obtained by depositing these TiO2 particles with various sizes onto a glass or quartz substrate. The effect of the particle size and thickness on the photocatalytic properties of the films was evaluated via oxidative degradation of gaseous 2-propanol. The initial rate of 2-propanol degradation under UV light irradiation for the films deposited with 30 nm TiO2 particles increased with increasing film thickness up to 600 nm, and reached a saturated value above this film thickness. Photocatalytic activity for the films with thickness below 600nm was larger when smaller TiO2 particles were deposited onto the substrate, due to the increase in the surface area of the particulate films. Furthermore, saturated values of the photocatalytic activity for thick films were smaller for the films deposited with smaller particles, which is mainly attributed to the change in crystal form of the particles during the grinding treatment.
Subject(s)
Titanium/chemistry , 2-Propanol/chemistry , 2-Propanol/radiation effects , Catalysis , Cyclohexanones , Membranes, Artificial , Oxidation-Reduction , Particle Size , Photochemistry , Solvents , Surface Properties , Suspensions , Ultraviolet Rays , X-Ray DiffractionABSTRACT
The effect of pH on the surface charge density of the O/W-type microemulsion formed in solutions of an amphoteric surfactant, (N alpha , N alpha -dimethyl-N epsilon -lauroyllysine, DMLL)/n -octane/1-pentanol/CaCl2 or AlCl3 , has been investigated. A novel equation for the surface charge densities in the presence of a multivalent cation (Ca2+ and/or Al3+ ) has been derived taking account of the number of DMLL molecules bound to a multivalent cation (q ). By applying a numerical analysis of this equation, it is possible to determine the intrinsic binding constants (K ) of the multivalent cation and the monovalent anion to the hydrophilic groups of DMLL and the adsorption density (N ) of DMLL molecules on the oil/water interface. Furthermore, N has been found to show pH dependence. N has a maximum value around the isoelectric region (in particular, pH 5-7) of DMLL molecules in the presence of CaCl2 , whereas N increases with increasing pH in the presence of AlCl3 . The surfactant (DMLL) numbers per O/W-type microemulsion droplet, i.e., the aggregation numbers, are successfully obtained as a function of pH in the presence of CaCl2 and/or AlCl3 .
