Arsenate Adsorption From Aqueous Solutions On Magnetite Nanoparticles.

Arsenic is highly toxic to humans and other living organisms, and is ubiquitous in natural environment from both natural and anthropogenic sources. Arsenate is a predominant inorganic anion of arsenic in natural surface water. Therefore, effective removal of arsenate from water is important to reducing arsenic environmental exposure. Magnetite (Fe₃O₄) nanoparticles have the great potential to be used as novel adsorbent for arsenate removal because of its large surface area and easy magnetic separation. In this study, the adsorption of arsenate on Fe₃O₄ nanoparticles from aqueous solutions was investigated to better understand mechanisms and influencing factors of arsenate adsorption using batch adsorption experiments, aided with spectroscopic analyses. The adsorption kinetics, isotherms, and influence of solution pH, ionic strength, and temperature were examined in detail. In addition, the Fe₃O₄ nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) analyses before and after the arsenate adsorption. The adsorption experiment results showed that Fe₃O₄ nanoparticles had high arsenate adsorption capacity, indicating its excellent potential as a highly effective adsorbent for arsenate removal in water treatment. The results of XPS and XAS suggested that arsenate formed inner-sphere surface complexes on the metal-oxide surface of Fe₃O₄ nanoparticles, which implied that the major arsenate adsorption mechanism on Fe₃O₄ nanoparticles was surface complexation.