title: Monitoring the role of Mn and Fe in the As-removal efficiency of tetravalent manganese feroxyhyte nanoparticles from drinking water: An X-ray absorption spectroscopy study.
abstract: The implementation of amorphous tetravalent manganese feroxyhyte (TMFx) nanoparticles, prepared via co-precipitation synthesis, as an efficient As(V)-removal material is investigated using X-ray absorption fine structure (XAFS) spectroscopy at the Fe-, Mn- and As-K-edges. The optimum synthesis conditions and chemical composition of the TMFx adsorbent were determined by the degree of polymerization in the adsorbents' microstructure. Under synthesis into mildly acidic conditions, the change in the polymerization of the metal-oxyhydroxyl chains (metal=Fe, Mn) provides more adsorption sites at edges and corner sites in the bonding environment of Fe and Mn, respectively, thereby enhancing As uptake. After exposure to As-polluted water, similar microstructural changes related to As-bidentate and monodentate geometries are generated: As(V) preferentially occupies the high energy adsorption sites ((2)C complexes) available in the Mn-oxyhydroxyl groups and the low energy edge sites offered by Fe ((2)E complexes). It is revealed that optimum arsenic-removal by TMFx occurs into mildly acidic synthesis pH and for iron to manganese molar ratio equal to 3.
authors.affiliation: Aristotle University of Thessaloniki, Department of Chemical Engineering, Analytical Chemistry Laboratory, 54124 Thessaloniki, Greece.
authors.forename: F
authors.initials: F
authors.lastname: Pinakidou
authors.affiliation: Aristotle University of Thessaloniki, School of Physics, Section of Solid State Physics, 54124 Thessaloniki, Greece.
authors.forename: M
authors.initials: M
authors.lastname: Katsikini
authors.affiliation: Aristotle University of Thessaloniki, School of Physics, Section of Solid State Physics, 54124 Thessaloniki, Greece.
authors.forename: E C
authors.initials: EC
authors.lastname: Paloura
authors.affiliation: Aristotle University of Thessaloniki, School of Physics, Section of Solid State Physics, 54124 Thessaloniki, Greece.
authors.forename: K
authors.initials: K
authors.lastname: Simeonidis
authors.affiliation: Aristotle University of Thessaloniki, Department of Chemical Engineering, Analytical Chemistry Laboratory, 54124 Thessaloniki, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Mitraka
authors.affiliation: Aristotle University of Thessaloniki, Department of Chemical Engineering, Analytical Chemistry Laboratory, 54124 Thessaloniki, Greece. Electronic address: manasis@eng.auth.gr.
authors.forename: M
authors.initials: M
authors.lastname: Mitrakas
keywords: Adsorbent; Arsenic removal; Drinking water; EXAFS; FeMn(IV)OOH; XANES