The roles of the surface charge and hydroxyl group on a Fe-Al-Ce adsorbent in fluoride adsorption were studied. Fluoride adsorption at different initial solution pH was investigated. An external voltage was applied to an adsorbent-coated electrode to examine the adsorption characteristics due to the surface charge. The capability of accepting or providing H + of the hydroxyl on the adsorbent surface was determined through the titration of NaOH solution, and the change of the hydroxyl before and

more »

... after adsorption was analyzed by FTIR. Fluoride adsorption was rapid during the initial stage but slowed down later. Fluoride ions were transferred to the adsorbent surface by Coulombic attraction and/or thermal motion, forming a temporary and nonspecific adsorption. The enriched fluoride ions reacted with the hydroxyl groups on the adsorbent surface, forming a stable adsorption. The surface charge on the adsorbent and ion exchange between surface hydroxyl groups and fluoride ions have a large effect on the adsorption rate and efficiency.