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

•We have grafted amorphous alumina nano-peas with a diameter of 10–30 nm.•The Al2O3/EG adsorbent showed a considerably high adsorption efficiency over a relatively wide pH range of 3.0–7.0.•Al2O3/EG can remove trace amounts of F− in solution effectively.•The final F− concentrate can be decreased to less than 0.28 ppm.

Amorphous Alumina-modified Expanded Graphite (Al2O3/EG) composite was prepared via a facile solution method followed by thermal treatment at 450 °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 AlF 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.

Graphical abstractAmorphous Alumina-modified Expanded Graphite (Al2O3/EG) were prepared through mass appropriate Al(NO3)3 solution and EG, then calcinating at 450 °C for 2 h and used for F− adsorption. Al2O3/EG can remove trace amounts of F− in solution effectively and the final F− concentrate can be decreased to less than 0.28 ppm. The isotherms and thermodynamics parameters indicate that the adsorption is a multi-molecular layer adsorption between the adsorbed molecules, and the process is spontaneous endothermic.Figure optionsDownload full-size imageDownload as PowerPoint slide