Modified natural magnetite with Al and La ions for the adsorption of fluoride ions from aqueous solutions

Natural magnetite ore (Fe3O4) was modified with aluminum and lanthanum ions to increase the fluoride removal efficiency from aqueous solutions. The modified and unmodified magnetite samples were characterized by X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), infrared spectroscopy (IR), surface area (BET) and zeta potential (zeta). The adsorption and stability of fluoride on magnetite were investigated using modified magnetite in batch systems. The SEM results indicate the formation of a lanthanum oxide layer around the magnetite and that aluminum oxide is dispersed between the particles. Al and La were deposited as hydroxides (IR), which increased the surface area by 7.5 and 9.5 times higher than natural magnetite and shifted the surface potential toward positive values. The IR results indicated that fluoride replaces a hydroxyl group from the aluminum hydroxides whereas no such replacement was detected for materials with La. Batch tests showed that adsorption increased from 30 to 90% and 96% for the aluminum and lanthanum modified materials, respectively. (C) 2016 Elsevier B.V. All rights reserved.