title: Mn(II) Oxidation in Fenton and Fenton Type Systems: Identification of Reaction Efficiency and Reaction Products.
abstract: Efficient and low-cost methods of removing aqueous Mn(II) are required to improve the quality of impacted groundwater supplies. In this work, we show that Fe(0) electrocoagulation (EC) permits the oxidative removal of Mn(II) from solution by reaction with the reactive oxidant species produced through Fe(II) oxidation. Manganese(II) removal was enhanced when the accumulation of aqueous Fe(II) was minimized, which was achieved at low Fe(II) production rates, high pH, the presence of H2O2instead of O2as the initial Fe(II) oxidant, or a combination of all three. In addition, in the EC-H2O2system, Mn(II) removal efficiency increased as pH decreased from 6.5 to 4.5 and as pH increased from 6.5 to 8.5, which implicates different reactive oxidants in acidic and alkaline solutions. Chemical analyses and X-ray absorption spectroscopy revealed that Mn(II) removal during Fe(0) EC leads to the formation of Mn(III) (0.02 to >0.26 Mn·Fe-1molar ratios) and its incorporation into the resulting Fe(III) coprecipitates (lepidocrocite and hydrous ferric oxide for EC-O2and EC-H2O2, respectively), regardless of pH and Fe(II) production rate. The Mn(II) oxidation pathways elucidated in this study set the framework to develop kinetic models on the impact of Mn(II) during EC treatment and in other Fenton type systems.
authors.affiliation: Institute of Earth Surface Dynamics, University of Lausanne , Lausanne CH-1015, Switzerland.|Department of Earth Sciences, Geochemistry, Faculty of Geosciences, Utrecht University , Utrecht 3508TA, The Netherlands.
authors.forename: Case M
authors.initials: CM
authors.lastname: van Genuchten
authors.affiliation: Institute of Earth Surface Dynamics, University of Lausanne , Lausanne CH-1015, Switzerland.
authors.forename: Jasquelin
authors.identifier: 0000-0001-7081-3873
authors.initials: J
authors.lastname: Peña
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D010084:Oxidation-Reduction; D056928:X-Ray Absorption Spectroscopy
chemical_list: D005290:Ferric Compounds; D008345:Manganese; D006861:Hydrogen Peroxide; D007501:Iron