title: Optimization of tetravalent manganese feroxyhyte's negative charge density: A high-performing mercury adsorbent from drinking water.
abstract: This study demonstrates an optimization procedure for the development of an Hg-specified adsorbent able to comply with the regulation limit for drinking water of 1μg/L. On this purpose, the synthesis of Mn(IV)-feroxyhyte was modified to achieve high negative charge density by combining alkaline and extreme oxidizing conditions. In particular, precipitation of FeSO4at pH9 and excess of KMnO4follows a very fast nucleation step providing a product with very small nanocrystal size (1-2nm), high specific surface area (300m2/g) and maximum negative charge density (1.8mmol H+/g). The adsorbent was validated for Hg removal in batch experiments and column tests using natural-like water indicating an adsorption capacity as high as 2.5μg/mg at equilibrium concentration 1μg/L under reliable conditions of application. Importantly, the adsorption is an exothermic spontaneous process, resulting in the formation of inner sphere complexes by sharing both A-type and B-type oxygen atoms with the metal surface octahedral as revealed by the X-ray absorption fine structure results.
authors.affiliation: Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Kokkinos
authors.affiliation: Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece.
authors.forename: K
authors.initials: K
authors.lastname: Simeonidis
authors.affiliation: Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece.
authors.forename: F
authors.initials: F
authors.lastname: Pinakidou
authors.affiliation: Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
authors.forename: M
authors.initials: M
authors.lastname: Katsikini
authors.affiliation: Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece. Electronic address: manasis@eng.auth.gr.
authors.forename: M
authors.initials: M
authors.lastname: Mitrakas
keywords: Adsorption; Column tests; Fe/Mn oxy-hydroxides; Mercury; Surface charge; XAFS