Application of TiO2-containing mesoporous spherical activated carbon in a fluidized bed photoreactor-Adsorption and photocatalytic activity

A TiO2-containing mesoporous spherical activated carbon (meso-TiO2/SAC) with high adsorption capacity and photocatalytic activity was prepared using ion-exchange method and heat-treatment process. The prepared meso-TiO2/SAC was characterized by SEM, TEM, EDS, XRD, and BET analysis. Results obtained showed that meso-TiO2/SAC had a smooth spherical shape (0.30-0.45 mm) and TiO2 with crystalline size of 10-30 nm was well dispersed on the spherical activated carbon. XRD study confirmed that TiO2 existed in a mixture of anatase (83%) and rutile (17%) phase. The meso-TiO2/SAC presented a high specific surface area of 1649 m(2)/g. The meso-TiO2/SAC was used for the removal of humic acid (HA) in a fluidized bed photoreactor, the rate of adsorption reaction of HA by meso-TiO2/SAC followed the pseudo second-order kinetic, the adsorption isotherm fitted well to the Freundlich and Langmuir isotherm models. The maximum adsorption capacity of meso-TiO2/SAC determined from Langmuir isotherm was 2.92 mg/g. The effect of the photocatalysis of HA by meso-TiO2/SAC under UV irradiation was investigated under various conditions of varying catalyst dosage, initial HA concentration, and coexisting anion. HA was mineralized up to 80.3% under optimal experimental conditions for a catalyst dosage of 9 g/L and at an initial HA concentration of 20 mg/L. In the presence of coexisting anions, the degradation efficiency of HA was reduced to 72.1% and 72.8% for SO42- and NO3-, respectively. In the cyclic reuse experiment, over 85% of the initial TOC and COD were removed after the eighth cycles, indicating the relatively high photocatalytic stability of meso-TiO2/SAC. TiO2 was not released from the spherical activated carbon during the photocatalytic reaction. The meso-TiO2/SAC developed, therefore has potentials for practical applications in water treatment. (C) 2012 Elsevier B.V. All rights reserved.