(270d) Adsorption Equilibrium And Kinetics Of Fluoride On Alumina-Based Adsorbents

One of the most serious problems along the U.S.A.-Mexican border is the lack of access to adequate quality drinking water. The groundwater from wells in Columbus, NM and Palomas, Mexico border region contains significantly high levels of fluoride and arsenic that could potentially cause many serious diseases for the residents, especially young children in this border region. There is an urgent need for purifying the drinking water supplied by the municipals to protect the health of the residents in the border region. MnO2 and CaO were used to modify the sol-gel derived alumina to enhance its adsorption for fluoride. Both adsorption equilibrium and kinetics on pure alumina and MnO2 and CaO doped alumina adsorbents were investigated in batch adsorption experiments. The MnO2-AA adsorbent showed significant improvement on fluoride adsorption capacity when the fluoride concentration in water is less than 4 ppm, while the CaO-AA adsorbent exhibits higher adsorption capacity at fluoride concentration above 4 ppm. The adsorption of fluoride on the sol-gel derived adsorbent can be described by a Freundlich type of adsorption isotherm equation. The fluoride adsorption kinetics is slightly faster on MnO2-AA than CaO-AA adsorbent. The estimated effective pore diffusivities of fluoride in the MnO2-AA and fluoride in the CaO-AA are 4.5x10-7 cm2/s and 4.3x10-7 cm2/s, respectively. These values are about 10 times higher than the effective pore diffusivities of fluoride in the pure sol-gel derived alumina.