Adsorption kinetics of methylene blue onto Fe-doped sulfated titania

Abstract

Fe-doped sulfated titania (FST) photocatalysts with high photocatalytic activity were prepared from industrial titanyl sulfate solution and characterized using N 2 adsorption–desorption technique. Adsorption kinetics and mechanism of methylene blue onto FST samples were studied at different temperatures (298, 303 and 308 K). The kinetic experimental data appropriately correlate with the pseudo-second order model. The overall rate of the adsorption process appears to be influenced by both boundary layer diffusion and intraparticle diffusion. The low adsorption activation energy (in the range of 15.59–19.31 kJ mol −1) suggests that the adsorption of methylene blue onto FST samples was conformed to the physisorption mechanism. With calcination temperature increases from 400 to 600 °C, sulfur species gradually decomposes and desorbs from the surface of FST samples, which can enhance the affinity between methylene blue and FST samples. Moreover, the specific surface decreases and the pore volume and pore diameter increase with rise in calcining temperature. All these have a significant influence on the adsorption properties of FST samples.