Humic Acid Removal by Combining the Magnetic Property of Maghemite with the Adsorption Property of Nanosized Hydroxyapatite

Abstract

Maghemite incorporated hydroxyapatite (HAP) nanocomposite was prepared by in situ precipitation of the calcium phosphate phase in an iron oxide colloidal suspension. The resultant nanocomposite was characterized by x-ray diffraction, Fourier transform infrared spectrometer, transmission electron microscope, N2 adsorption analysis, and vibrating sample magnetometry. The potential of HAP/γ-Fe2O3 nanocomposite for HA adsorption from aqueous solution was evaluated by batch experiments and adsorption kinetic tests. HA adsorption amount on the adsorbent decreased with increasing solution pH and the presence of KNO3 and alkali-earth metal ions resulted in enhanced HA adsorption. HA adsorption onto HAP/γ-Fe2O3 nanocomposite could be well described by Freundlich and Sips models, while HA adsorption process on the adsorbent obeyed pseudo-second-order kinetics and the adsorption rates decreased with increasing initial HA concentration. This study showed that the HAP/γ-Fe2O3 nanocomposite could be used as an efficient and magnetically separable adsorbent for the removal of HA from aqueous solution. Subsequent studies demonstrated that the HA-loaded HAP/γ-Fe2O3 nanocomposite could be further applied for the highly efficient adsorption of methylene blue (MB) and separated from the medium by a simple magnetic process.