Adsorption of phosphate from water by easily separable Fe3O4@SiO2 core/shell magnetic nanoparticles functionalized with hydrous lanthanum oxide.

Hydrous lanthanum oxide was loaded onto the surface of Fe3O4@SiO2 core/shell magnetic nanoparticles to obtain an easily separable adsorbent (abbreviated as Fe-Si-La) for efficient separation of phosphate from water. Fe-Si-La was characterized with XRF, XRD, TEM, specific surface area and magnetization and their performance for phosphate removal was investigated. The Fe3O4@SiO2 core/shell structure was confirmed and the hydrous lanthanum oxide was successfully loaded onto its surface. The newly developed adsorbent had magnetization of 51.27emu/g. The Langmuir adsorption capacity of phosphate by Fe-Si-La reached 27.8mg/g by loading only 1mmol lanthanum per gram of magnetite. The adsorption was fast; nearly 99% of phosphate could be removed within 10min. The removal of phosphate was favored within the pH range 5.0-9.0. The adsorption on Fe-Si-La was not significantly influenced by ionic strength and by the coexistence of the anions of chloride and nitrate but sulfate, bicarbonate and humic acid showed slightly greater negative effects. Phosphate removal efficiency of higher than 95% was attained for real effluent of a wastewater treatment plant when the dose of adsorbent was >0.2kg/ton. The results showed that adsorbed phosphate could be nearly completely desorbed with NaOH solution for further use. In conclusion, Fe-Si-La is a promising adsorbent for the removal and recovery of phosphate from water.