title: Linkage of iron elution and dissolved oxygen consumption with removal of organic pollutants by nanoscale zero-valent iron: Effects of pH on iron dissolution and formation of iron oxide/hydroxide layer.
abstract: The iron elution and dissolved oxygen (DO) consumption in organic pollutant removal by nanoscale zero-valent iron (nZVI) was examined in the range of solution pH from 3.0 to 9.0. Their behaviors were linked with the removal of organic pollutant through the dissolution of iron and the formation of iron oxide/hydroxide layer affected strongly by solution pH and DO. As an example of organic pollutants, azo-dye Orange II was chosen in this study. The chemical composition analyses before and after reaction confirmed the corrosion of nZVI into ions, the formation of iron oxide/hydroxide layer on nZVI surface and the adsorption of the pollutant and its intermediates. The complete decolorization of Orange II with nZVI was accomplished very quickly. On the other hand, the total organic carbon (TOC) removal was considerably slow and the maximum TOC removal was around 40% obtained at pH 9.0. The reductive cleavage of azo-bond by emitted electrons more readily took place as compared with the cleavage of aromatic rings of Orange II leading to the degradation to smaller molecules and subsequently the mineralization. A reaction kinetic model based on the Langmuir-Hinshelwood/Eley-Rideal approach was developed to elucidate mechanisms for organic pollutant removal controlled by the formation of iron oxide/hydroxide layer, the progress of which could be characterized by considering the dynamic concentration changes in Fe(2+) and DO. The dynamic profiles of Orange II removal linked with Fe(2+) and DO could be reasonably simulated in the range of pH from 3.0 to 9.0.
authors.affiliation: Research Center for Biochemical and Environmental Engineering, Department of Applied Chemistry, Toyo University, Kawagoe, Saitama 350-8585, Japan.
authors.forename: Nanae
authors.initials: N
authors.lastname: Fujioka
authors.affiliation: Research Center for Biochemical and Environmental Engineering, Department of Applied Chemistry, Toyo University, Kawagoe, Saitama 350-8585, Japan.
authors.forename: Moe
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Bio-Nano Electronics Research Centre, Toyo University, Kawagoe, Saitama 350-8585, Japan.
authors.forename: Shunji
authors.initials: S
authors.lastname: Kurosu
authors.affiliation: Research Center for Biochemical and Environmental Engineering, Department of Applied Chemistry, Toyo University, Kawagoe, Saitama 350-8585, Japan. Electronic address: ykawase@toyonet.toyo.ac.jp.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kawase
mesh_terms: D000327:Adsorption; D001391:Azo Compounds / Q000737:chemistry* / Q000302:isolation & purification; D001557:Benzenesulfonates / Q000737:chemistry* / Q000302:isolation & purification; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D010100:Oxygen / Q000737:chemistry*; D012995:Solubility; D012996:Solutions; D013499:Surface Properties; D062065:Wastewater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; D005290:Ferric Compounds; D005296:Ferrous Compounds; D007501:Iron; D010100:Oxygen; D012996:Solutions; D062065:Wastewater; D014874:Water Pollutants, Chemical; C021024:ferric hydroxide; C034236:ferrous oxide; C014722:2-naphthol orange
keywords: Dissolved oxygen consumption; Iron elution; Nanoscale zero-valent iron; Reaction kinetics; Removal of organic pollutant