Research on removal of fluoride in aqueous solution by alumina-modified expanded graphite composite

Amorphous Alumina-modified Expanded Graphite (Al2O3/EG) composite was prepared via a facile solution method followed by thermal treatment at 450 degrees C for 2 h, which was used to remove trace F in aqueous solution. Alumina nano-peas (with a diameter of 10-30 nm) were observed on the surface of EG by Field Scanning Electron Microscope (FSEM). The X-ray powder diffraction (XRD) results dominated the Alumina was amorphous. FTIR spectra analysis indicated that Al-F bends appeared after adsorption. The effect of pH and adsorbent dose were studied in a series of batch adsorption experiments. The Effect of pH results showed that the solution pH had no significant effect on F removal between pH = 3.0-7.0. The superior adsorbent properties of Al2O3/EG proved highly effective in absorbing F , where the removal rate reached 94.4% and the adsorption capacity reached 1.18 mg/g. The results showed that Al2O3/EG could removed trace amounts of F in solution effectively and the residual F concentrate could decreased to less than 0.28 ppm. The isotherms and thermodynamics parameters were calculated which displayed that the adsorption was a multi-molecular layer adsorption between the adsorbed molecules, and the process was spontaneous endothermic. (C) 2014 Elsevier B.V. All rights reserved.