On the photocatalytic properties of elongated TiO2 nanoparticles for phenol degradation and Cr(VI) reduction

Elongated TiO2 nanoparticles with high aspect ratio have specific advantages in separation processes. In this study, TiO2 nanofiber was prepared via a hydrothermal reaction, and TiO2 nanoparticles with varied structural properties were obtained using hydrothermal and calcination post-treatments. Photocatalytic phenol degradation and Cr(VI) reduction over these catalysts was investigated. Results showed that hydrothermally prepared TiO2 nanofiber consisted of titanate with high aspect ratio. Calcining the as-prepared TiO2 nanofiber at 400 and 600 degrees C led to the crystalline phase transformation from titanate to TiO2-B and to the presence of mixed crystalline phases composed of TiO2-B and anatase. In contrast, hydrothermal post-treatment results in the generation of pure anatase TiO2 nanoparticles. For photocatalytic phenol degradation, calcining the as-prepared TiO2 nanofiber resulted in an enhanced catalytic activity, where as TiO2 nanoparticles obtained by calcination post-treatment showed lower catalytic activities for photocatalytic Cr(VI) reduction compared to as-prepared TiO2 nanofiber. TiO2 nanofiber modified using the hydrothermal post-treatment, however, exhibited the highest catalytic activity among TiO2 nanoparticles examined for both photocatalytic phenol degradation and Cr(VI) reduction. Furthermore, TiO2 nanoparticles obtained by hydrothermal post-treatment showed the best sedimentation efficiency, highlighting its prominent potential as a readily separable and recoverable photocatalyst. (C) 2009 Elsevier B.V. All rights reserved.