Adsorption of fluoride onto tuff varieties of the Neapolitan area

Fluoride is a natural and anthropic pollutant of ground waters that can have harmful effects on human health. Concentrations in drinking water exceeding 1.5 mg/L have been shown to cause dental fluorosis, whereas concentrations exceeding 4.0 mg/L cause fluorosis of the bone .[1]. According to the World Health Organization (WHO) recommendation and Italian drinking water standards, the maximum permissible limit of fluoride in drinking water is 1.5 mg/L F-. A recent hydrogeochemical and hydrogeological study, carried out on the groundwater of volcaniclastic aquifers of the Neapolitan area (Fig. 1), showed concentrations of F- greater than 3.0 mg/L. In this work, we intend to study the acid-base behavior of the tuff varieties Neapolitan area, (Campanian Ignimbrite and Neapolitan Yellow Tuff) and the adsorption equilibria of the fluoride at 25° C, in 0.1 M NaClO4. Furthermore the adsorbent properties of pyroclastic soils, sampled at different depths in a borehole, towards fluoride ions have been studied. Finally, a comparison was made between the adsorbent properties of stale samples with solid phases such as AlPO4(S) and Al2O3(S), used for the removal of fluoride Ion from the water (Fig.2).