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. (February 2016)

• Record Type: Journal Article
• Authors: Fujioka, Nanae; Suzuki, Moe; Kurosu, Shunji; Kawase, Yoshinori
• Is Part Of: Chemosphere. Volume 144(2016)
• Page Start: 1738
• Page End: 1746
• Publication Date: 2016-02
• Subjects: Nanoscale zero-valent iron -- Iron elution -- Dissolved oxygen consumption -- Reaction kinetics -- Removal of organic pollutant; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2015.10.064
• Languages: English
• ISSNs: 0045-6535

Abstract

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. Graphical abstract: Highlights: Removal of organic pollutant by nanoscale zero-valent was systematically examined. Linkage of pollutant removal with iron elution and dissolved oxygen (DO) was focused. Pollutant removal was largely controlled by the formation of iron oxide layer. The formation of iron oxide layer was linked with behaviors of Fe 2+ and DO. The proposed kinetic model could simulate the behaviors of pollutant removal.