Fluoride removal from aqueous solution by Zirconium-Chitosan/Graphene Oxide Membrane

A Zirconium-Chitosan/Graphene Oxide (Zr-CTS/GO) Membrane adsorbent was applied for fluoride removal from aqueous solution. The effects of different compositions, dose, pH, and initial fluoride concentration were investigated. Results showed that the membrane could effectively remove fluoride within a wide pH range of 3-11. The data fitted the Freundlich isotherm model well, indicating that fluoride adsorption occurred on heterogeneous Zr-CTS/GO membrane surfaces probably in a multilayer form. The kinetic studies showed that the adsorption reached equilibrium within 45 min, and the maximum adsorption capacity was calculated to be 29.0588 mg/g by Two-site Langmuir isotherm model. X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure spectroscopy (EXAFS) were used to elucidate the adsorption mechanism. The results revealed that Zr(IV) species reacted with oxygen functional groups from the CTS/GO complex, and Zr-F species formed partly through fluoride ions exchanged with chloride ions and-OH and partly through chemical rearrangement. The findings indicate that Zr-CTS/GO is a promising adsorbent for fluoride removal with a quite short contact time and a wide optimum pH range. (C) 2017 Elsevier B.V. All rights reserved.