Chemical Engineering Journal, Vol.175, 144-149, 2011
Defluoridation by freshly prepared aluminum hydroxides
The exposure to fluoride via drinking water is a great issue globally. This study investigates the adsorptive capability of the freshly prepared aluminum hydroxide, i.e., in-situ Al2O3 center dot xH(2)O, towards fluoride. The maximum adsorption of above 110 mg F/g Al is observed in pH ranges from 5.0 to 7.2. The adsorption equilibrium is achieved within 120 min, and pseudo-second-order model may well describe the adsorption kinetics (R-2 = 0.999), indicating the involvement of chemisorptions in. The characteristics of low particle diameter, high surface area, and the surface reactivity of the amorphous in-situ Al2O3 center dot xH(2)O enables its superior to remove fluoride for the in-situ Al2O3 center dot xH(2)O. pH impacts the distribution of Al species and the quantity of solid-state Al available for fluoride. The ratios of monomeric Al, i.e., Al-a, are below 4% in pH from 6 to 8, and then increase to 19.2% at pH 4 and to 28.9% at pH 10. Al-c, showing adverse trends to Ala, is the main species for fluoride removal. In cases that the amount of in-situ Al2O3 center dot xH(2)O available is the same, surface charge is dominant to affect the removal of fluoride. FTIR indicates the replacement of surface hydroxyl groups by fluoride. (C) 2011 Elsevier B.V. All rights reserved.
Keywords:Defluoridation;In-situ Al2O3 center dot xH(2)O;Zeta potential;Al species distribution;Solid-phase Alc