Removal of acid dye by ZnFe2O4/TiO2-immobilized granular activated carbon under visible light irradiation in a recycle liquid-solid fluidized bed

The photocatalytic oxidation of acid dye under visible light irradiation was carried out in a recycle fluidized bed reactor. ZnFe2O4/TiO2-immobilized granular activated carbon (ZnFe2O4/TiO2-GAC) was employed as the photocatalyst, and the lamp (CDM-T, 150 W) was used as the light source. The fluidized bed reactor, involving contact among liquid and solid phases, has gained an increasing importance in a wide range of industrial application. ZnFe2O4/TiO2-GAC with different characteristics and degradation ability of pollutant was prepared by hydrolysis of titanium n-butoxide, combined with zinc ferrite solution and calcined at different temperatures. The crystalline structures and morphologies of the samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and diffuse reflectance spectroscopy (DRS). The photocatalytic degradation follows the pseudo-first-order reaction kinetics with respect to the concentration of acid dye. The apparent first-order rate constant decreases with increasing initial acid dye concentration and particle size of photocatalyst, as well as increases with increasing ZnFe2O4/TiO2-GAC loading amount.