Adsorption Mechanism of Arsenate on Crystal γ-Fe2O3 Nanoparticles

Toxic arsenic occurs in drinking water from natural and/or anthropogenic sources. It causes health problems worldwide. Among the existing arsenic removal techniques adsorption is the commonly used one. gamma-Fe2O3 nanoparticles were found recently to be a good adsorbent for arsenate because of its relatively high adsorption capacity and simple separation of the particles from the treated water. The aim of the study was to investigate the arsenate adsorption mechanism on the crystal gamma-Fe2O3 nanoparticles. Adsorption experiments were carried out with three different kinds of maghemite nanoparticles: (i) homemade one with mechanochemical method; (ii) homemade one with sol-gel process; and (iii) a commercially available one. The adsorption process was monitored by characterizing with Fourier transform infrared, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, and zeta potential analyzer. No crystal and amorphous precipitation were found on the iron oxide surfaces. The inner-sphere complex formation was found to be the predominant mechanism of adsorption.