Optimizing the removal of fluoride from water using new carbons obtained by modification of nut shell with a calcium solution from egg shell

Carbons loaded with specific chemical moieties were prepared from pecan nut shells employing a natural modifier agent obtained from egg shell, which is rich in calcium, for the selective adsorption of fluoride from water. A L-4 orthogonal array of the Taguchi method was used to optimize the synthesis conditions for obtaining these selective carbons. The samples obtained were characterized and the elemental composition, textural parameters and morphology were determined. Fluoride adsorption experiments were performed in synthetic and real groundwater samples. Results showed that carbons obtained from pecan nut shells modified with a calcium solution extracted from egg shells (CMPNS) were more effective for fluoride removal than those using the nut shell precursor as such. The calcium chemical species on the carbon surfaces were more important in the fluoride adsorption process than the carbon textural parameters. In addition, hydrogencarbonate was found to be the main competitor for the active sites of CMPNS during the fluoride removal process. (C) 2012 Elsevier B.V. All rights reserved.