Removal of Fluoride by Graphene Oxide/Alumina Nanocomposite: Adsorbent Preparation, Characterization, Adsorption Performance and Mechanisms
Naicai Xu, Sixia Li, Wu Li, Zhong Liu
Abstract
Abstract GO/Al 2 O 3 was successfully prepared by using hydrothermal method which was used to study the removing of fluoride from water. The characterization results of X‐ray diffraction (XRD), transmission electron microscope (TEM) and Fourier transform infrared (FT‐IR) spectra indicated that γ‐Al 2 O 3 had been modified onto GO nanosheets. The BET surface area of GO/Al 2 O 3 is 326.22 m 2 g −1 and the corresponding pore size center at 3.7 nm. A batch of fluoride adsorption experiments were employed to investigate the effects of various factors such as solution pH values, contact time, fluoride initial concentrations, temperature, adsorbent dose, co‐existing anions, and recycling on fluoride removal. The results showed that the adsorption capacity (4.68 mg g ‐1 ) of GO/Al 2 O 3 is higher than that of γ‐Al 2 O 3 (3.04 mg g −1 ). In addition, the modified adsorbent had a wide range of pH applications. Adsorption kinetics is well represented by the pseudo‐second‐order model, which indicating the adsorption processes are involved in chemisorption with ion exchange. The influences of co‐existing anions on fluoride removal followed the decreasing order of PO 4 3‐ >HCO 3 ‐ >SO 4 2‐ >Cl ‐ >NO 3 ‐ , which was related to the charge and radius of ions. The recycle performance of GO/Al 2 O 3 is not so good owing to the poor strength of GO during the cycle process. Fluoride adsorption onto GO/Al 2 O 3 could be attributed to electrostatic attraction, ligand exchange, ion exchange and hydrogen‐bond interaction between fluoride and OH groups.