TiO2 hollow microspheres were synthesized by a simple hydrothermal method followed by calcination at different temperatures ranging from 400 to 800 degrees C. The prepared samples were characterized by XRD, SEM, TEM, SAED, HRTEM, N-2 adsorption, and UV-vis spectroscopy. The photocatalytic activities of the hollow microspheres were evaluated by photocatalytic decomposition of 4-chloronitrobenzene (4-CNB). Results showed that the TiO2 hollow microspheres, which had an average external diameter of 1.75 mu m were composed of numerous TiO2 nanoparticles. Photocatalysis experiments indicated that the TiO2 hollow microspheres calcined at 500 degrees C exhibited the highest photocatalytic activity, which was nearly 2 and 1.5 times higher than that of the uncalcined sample and Degussa P25, respectively. The catalyst crystallinity, catalyst dosage and 4-CNB concentration were found to have a significant impact on the degradation efficiency whereas solution pH has relatively less effect. The removal of total organic carbon (TOC) and formation of chloride, nitrate (V) anions were monitored to follow the mineralization process of 4-CNB. In addition, it was demonstrated that these TiO2 hollow microspheres could be recycled easily without decreasing their photocatalytic activities. (C) 2010 Elsevier B.V. All rights reserved.