The defluoridation of drinking water using multi-walled carbon nanotubes

In this study, the potential sorption capacity of multi-walled carbon nanotubes (MWCNTs) was investigated as a means of removing fluoride from the drinking water of a number of regions in Iran and from experimental solutions. The test was conducted in both batch and continuous operation modes. Batch mode experiments were used to study the effect of parameters such as pH, contact time, ionic strength, adsorbent dose, adsorbent capacity, and the presence of foreign anions on the efficiency of fluoride removal. The results showed that the highest level of sorption occurs at pH 5 (about 94% at 18 min). The ionic strength of the solutions and the presence of co-anions such as chloride, nitrate, sulfate, hydrogen carbonate, perchlorate had a negligible effect on the sorption of F− onto MWCNTs. Sorption capacity measurements revealed that MWCNTs have a saturation capacity of 3.5 mg of F− per gram. Sorption data were best fitted with the Fruendlich sorption isotherm equation, which indicates that F− tends to be adsorbed on MWCNTs in a multilayered manner. Experiments using Kohbanan city drinking water, which contains the highest level of F− among the drinking water samples studied, showed that MWCNTs can remove over 85% of fluoride content.

Graphical abstractMWCNTs with high surface area, stability in various conditions are interesting materials for removing fluoride from drinking water. MWCNTs are more powerful than Fullerene C60 and activated charcoal to remove fluoride from aqueous media.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► MWCNTs have been used for the first time to remove fluoride from drinking water. ► MWCNTs are more efficient than Fullerene C60 and activated carbon. ► MWCNTs can remove fluoride from the water in concentrations of less than 2 mg/ml. ► Sorption data were more fitted to Fruendlich isotherm model than Langmuir model.