Fluoride Ions Behavior in the Presence of Corrosion Products of Iron: Effects of Other Anions

The behavior of fluoride ions in the presence of corrosion products of iron in drinking and water solutions was analyzed and the adsorption capacities of the iron oxides (corrosion products of iron) for fluoride ions were determined. Drinking water containing naturally 2.45mg of fluoride ions per liter was characterized and the concentrations of other anions were determined. The effect of contact time, the initial concentration of fluoride ions, and the effect of other anions naturally present in the drinking water were considered. The kinetic results could be adjusted to the pseudo-second order model, which indicated that the sorption mechanism was chemisorption and the equilibrium was reached in 24 hours. The presence of bicarbonate and chloride ions diminishes the removal efficiency of the fluoride ions, whereas other anions (sulfate, phosphate, and nitrate) did not show any significant effect. The results reflect that the iron oxides products from the corrosion of a hydraulic infrastructure allow the removal of fluoride ions from water.