Fluoride removal with electro-activated alumina

A new activation technique using alumina was developed for the removal of fluoride from water. This technique is based on an electro-activation by means of an electrical field. The optimum activation parameters (potential and contact time) were determined, and an activation time of about 120 min and a potential of +100 mV/SCE were then selected. The effect of various experimental parameters - ionic strength, pH hardness, and fluoride-alumina concentration ratio (C-Fo/C-A)- was determined for the adsorption capacities of the electro-activated alumina. The effect of these parameters on the fluoride adsorption capacities of both electro-activated adsorbent and conventional alumina was essentially the same, except for the ionic strength parameter. Indeed, ionic strength did not have a considerable effect on the performance of the conventional alumina. However, for the electro-activated alumina, an increase in ionic strength induced a slight increase in the fluoride adsorption capacity of the electro-activated adsorbent. The optimum conditions, determined in the batch mode, gave an optimal pH ranging from 3.5 to 5 and a C-Fo/C-A ratio of about 4. At a NaCl concentration of 800 mg dm(-3), the fluoride adsorption capacity of the electro-activated alumina was about 55% better than that of conventional alumina.