Adsorption of fluoride by magnetic Li-Al layered double hydroxide

The use of adsorbents to uptake hazardous ions from water and wastewater has attracted the attention of researchers due to their high effectiveness.1 Magnetite-containing materials possess interesting magnetic properties and the layered double hydroxides (LDHs) are known to be excellent ion exchangers. Core@shell structures, such as Fe3O4@LDH-Li/Al, possess the advantage of combining physico-chemical properties of two different materials.2 The magnetic LDH was evaluated in the fluoride ion (F-) uptaken from water. Despite its comprehensive use for dental health, depending on its concentration, F- ion is considered highly toxic and may cause dental fluorosis. According to the Ministerial Decree # 2914/2011, the maximum limit of fluoride ion in the water is 1.5 mg/L.3 The magnetic material was prepared by a simple synthetic route and characterized by XRD and FTIR. Then, it was evaluated in batch experiments for the fluoride ion uptaken from water. The fluoride adsorption better fitted the pseudo-second order kinetics model with k2 of 10.73 g.mg-1.min-1. The adsorption data were fitted by Langmuir (Eq. 1) and Freundlich (Eq. 2) isotherm models (Table 1) and the maximum adsorption capacity was 5.58 mg.g-1 (Figure 1).