The synthesis of Fe-Al hydroxides coated with EDTA-Cross-linked β-Cyclodextrin and adsorption mechanism for As (III)

The adsorption mechanism of As (III) uptake onto Fe-Al hydroxides (FA) coated with EDTA-Cross-linked β-Cyclodextrin (FA-ECD) was investigated. Characterization of FA-ECD and FA was studied by SEM, BET, FTIR, XRD, TG and XPS. Results indicated the framework integrity of FA was kept after modification, but the surface chemical properties have changed in the comparison of FA and FA-ECD, which could enhance the adsorption capacity for As (III). Besides, various parameters including contact time, pH, adsorbent dosage and initial concentration were systematically studied. The results showed that the adsorption process was pH dependent, and the maximum adsorption capacity of As (III) was approximately 6.64 mg/g at pH 6. Moreover, the equilibrium data better fitted the Freundlich model, and the lower value of χ2 in Freundlich also demonstrated the availability of model. In addition, the pseudo-second-order kinetic model was found to be more propitious for the adsorption of As (III). The analysis of thermodynamic study proved the adsorption process was endothermic and spontaneous.