Studies on the defluoridation of water using conducting polymer/montmorillonite composites.

Conducting polymer/inorganic hybrid composites have large surface areas, which makes the adsorbent properties of the polymer composites as good the constituents. Polyaniline/montmorilonite (PANi-MMT) and polypyrrole/montmorillonite (PPy-MMT) composites were prepared, characterized (Fourier transform infrared, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction patterns) and were employed as adsorbents for the removal of fluoride ions from aqueous solution by the batch sorption method. The spectral studies of the adsorbents before and after the adsorption are recorded to get better insight into the mechanism of the adsorption process. The results indicated that the removal of fluoride ions from water by these composites occurs via the combined effect of both the constituents, that is, through a physico-chemical mechanism. The amount of fluoride ion adsorbed by PANi-MMT and PPy-MMT at 30 degrees C is observed to be 2.3 and 5.1 mg g(-1), respectively, when compared to 0.77 and 2.66 mg g(-1), respectively, for the polymers alone. The Langmuir, Freundlich and Dubinin-Radushkevich isotherms were used to describe the adsorption equilibrium.