Mesoporous 2-line ferrihydrite was synthesized through a facile precipitation method and was characterized by X-ray diffraction

Mesoporous 2-line ferrihydrite was synthesized through a facile precipitation method and was
characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption–
desorption isotherms. The surface area of the obtained mesoporous 2-line ferrihydrite was 331.0 m2 g1
.
The fluoride adsorption performance was investigated. Batch adsorption experiments were conducted to
study the influence of various factors such as contact time, initial fluoride concentration, temperature,
pH value and co-existing anions on the adsorption of fluoride. The fluoride adsorption process fitted
well with the Langmuir model, and the maximum adsorption capacity was 23.89 mg g1 at pH 7.0. It is
worth mentioning that this adsorbent performed well over a considerably wide pH range of 3–9. The
fluoride adsorption kinetics over the adsorbent can be well described by a pseudo-second-order kinetic
model. Thermodynamic parameters including the Gibbs free energy, standard enthalpy and standard
entropy were calculated, and the results suggested that the adsorption of fluoride on the mesoporous 2-
line ferrihydrite was thermodynamically favorable and exothermic in nature. Furthermore, Fourier
transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that the
surface hydroxyl groups play an important part in the fluoride removal process.