Degradation of the Direct Red 80 dye by chitosan bead-supported Fe/Ni nanoparticles in a fluidized bed reactor

Abstract

This study evaluated the immobilization of Fe/Ni nanoparticles (Fe/Ni-NPs) on silica, bentonite and chitosan beads (CBs). The material generated by supporting Fe/Ni-NPs on CBs (Fe/Ni-CB) presented more advantageous characteristics for application in fluidized bed reactors (FBRs) than the others, such as high mechanical resistance and chemical stability. The Gates Gaudin and Schuman mathematical model was the best one to describe the particle size distribution of the CB-Fe/Ni, presenting an excellent fit to the experimental data. The particle size distribution of this material concentrated in a narrow diameter interval, making it possible to obtain a very representative Sauter mean diameter (1.92 mm) of the sample set. The CB-Fe/Ni presented high chemical stability, low leaching of Fe and Ni to the medium and stable hydrodynamic behavior under simulated application conditions. Therefore, CB-Fe/Ni presented desirable characteristics for use in FBRs as reactive bed material. The CB-Fe/Ni was used to degrade the Direct Red 80 (DR80) dye in an FBR. The factorial experiment results determined that the initial pH does not affect the DR80 removal, only the CB-Fe/Ni dose does. A model to predict the DR80 removal based on the CB-Fe/Ni dose was obtained. The DR80 removal by the CB-Fe/Ni performed in the FBR was higher than 60% at the end of 22 h. There was low leaching of Fe and Ni from the CB-Fe/Ni to the aqueous phase under the tested conditions, which corresponds to an advance because this technology does not generate secondary pollution in the system and facilitates the recovery of the used material.