La3+-modified Activated Alumina for Fluoride Removal from Water

A La(3+)-modified activated alumina (La-AA) adsorbent was prepared for effective removal of fluoride from water. The surface properties of adsorbent were characterized with zeta potential analysis, SEM-EDS and EXAFS. Batch and column experiments were conducted to evaluate improvement of F(-) removal by the La-AA. SEM/EDS and EXAFS analyses determined the formation of La(OH)3 coating on the AA and strong bonding interactions between La(3+) and the Al atoms. The points of zero charge (pHPZC) of AA and La-AA were at pH 8.94 and 9.57, respectively. Batch experimental results indicated that the La-AA had much higher adsorption rate and capacity than the AA. The F(-) adsorption processes on La-AA and AA followed the pseudo-second-order kinetics and the Langmuir isotherm. Column filtration results shows that the La-AA and AA treated 270 and 170 bed volumes of the F(-)-spiked tap water, respectively, before F(-) breakthrough occurred. The results demonstrated that the La-AA was a promising adsorbent for effective removal of F(-) from water.