The effect of particle size and crystal structure of titanium dioxide nanoparticles on the photocatalytic properties

Titanium dioxide nanoparticles with different average diameter of particles (8, 18 and 27 nm) and different crystal structure (anatase and rutile) were used for degradation of C.I. Acid Red 88 (AR88) as a model compound. The degree of degradation of AR88 by TiO2 nanoparticles under irradiation of UV-light (254nm) with TiO2-UV100 (8 nm diameter and 100% anatase) is lower than TiO2-Merck (27 nm diameter and 95% anatase). TiO2-P25 with structure of anatase and rutile (80:20) combination shows higher photoactivity than other samples such as TiO2-UV100 and TiO2-Merck. Kinetics of removal of AR88 with all of nanosized-TiO2 particles is pseudo-first-order. The apparent reaction rate constant (kap) for removal of AR88 in the presence of different nanosized-TiO2 particles decreases with increasing of AR88 initial concentration. For TiO2-P25 and TiO2-UV100 a linear relation and for TiO2-Merck a nonlinear relation between kap and light intensity were obtained.