TITLE:
Adsorption of Fluoride from Water Using Aluminum Coated Sand: Kinetics, Equilibrium, Effect of pH, and Coexisting Ions
AUTHORS:
Kiana Modaresahmadi, Amid P. Khodadoust, James Wescott
KEYWORDS:
Fluoride, Removal, Adsorption, Coated Sand, Aluminum
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.10 No.12,
December
29,
2022
ABSTRACT: An aluminum coated sand (AlCS) was evaluated as a metal oxide adsorbent for
adsorption and removal of fluoride from water using a low-cost adsorbent with potential
application in continuous flow adsorber systems. Surface characterization of the
AlCS sorbent was performed using TEM, SEM/EDX, XRD and BET. The AlCS sorbent contained
mostly amorphous aluminum oxides based on adsorbent characterization results. Favorable
adsorption of fluoride onto the AlCS sorbent occurred according to the Langmuir
and Freundlich adsorption equations, while physical adsorption of fluoride onto
the AlCS sorbent was observed based on results from the Dubinin-Radushkevich equation. Fluoride
adsorption onto the AlCS sorbent followed pseudo-second order kinetics, while surface
charge analysis indicated a pHPZC of 7.1 for the AlCS sorbent. Effective
fluoride removal occurred over a broad pH range from 3 to 11 with a maximum fluoride
removal observed at pH 4 to 5. The effect of co-existing ions in water resulted
in a decrease in fluoride uptake in the presence of bicarbonate, while resulting
in an increase in fluoride uptake in the presence of calcium. The AlCS sorbent was
a low-cost and sustainable adsorbent for effective adsorption and rapid removal
of fluoride from water within an hour.