Preparation of Fly Ash/CeO2 Composite and its Adsorption Kinetics for Congo Red Dye from Aqueous Solution

Abstract

Fly ash/CeO2 composite (FA/CeO2) was prepared by acid modification and precipitation method using a low-cost waste fly ash (FA) as a raw material and characterized by X-ray diffraction (XRD) and the BET surface analysis. The adsorption of FA and FA/CeO2 for Congo Red (CR) from simulated dye wastewater was studied. The different regeneration methods for the CR-saturated FA/CeO2 were investigated. The results show that the adsorption capacity and removal rate of CR on FA/CeO2 can respectively reach 175.35mg/g and 97.42%, 4.5 times higher than those on FA. The adsorption process of FA/CeO2 for CR at different temperatures (25°C~55°C) can well be described by the pseudo-second-order adsorption model and is mainly controlled by intraparticle diffusion. The adsorption rate decreased slightly with increasing temperature, and the obtained adsorption apparent activation energy is 15.08kJ/mol. This indicates that CR is easily adsorbed on FA/CeO2, and the adsorption of the process is mainly physical adsorption with exothermic nature. The room temperature is favorable to the adsorption and actual operation. NaOH solution of 0.01 mol/L can make CR-saturated FA/CeO2 regenerated three times, and corresponding removal rate for CR can reach 97.82%, 80.21% and 66.04%, respectively. As a new kind of low-cost and high-efficient adsorbent, FA/CeO2 composite has the potential value in the application of wastewater treatment.