Characterization of intercalated iron(III) nanoparticles and oxidative adsorption of arsenite on them monitored by x-ray absorption fine structure combined with fluorescence spectrometry.

This paper first deals with the screening and optimization of Fe(III)-based adsorbents for arsenic adsorption from 0.2 to 16 ppm test solutions of arsenite/arsenate. The best adsorption capacity has been reported on alpha-FeO(OH) on an adsorbent weight basis. Better results were found on intercalated Fe-montmorillonites for arsenite adsorption below the equilibrium dissolved As concentration of 310 ppb and for arsenate adsorption in all of the concentrations studied. Next, the speciation of As adsorbed was performed by As K-edge x-ray absorption fine structure (XAFS) combined with high-energy-resolution fluorescence spectrometry. Major oxidative adsorption of arsenite was observed on Fe-montmorillonite from the 0.2-16 ppm test solutions. The reasons for the higher capacity of arsenic adsorption and oxidative adsorption of arsenite on Fe-montmorillonite are discussed.