Structural variation of precipitates formed by Fe(II) oxidation and impact on the retention of phosphate.
File(s)
Supporting information
Author(s)
Type
Journal Article
Abstract
The oxidation-precipitation process of Fe(II) is ubiquitous in the environment and critically affects the fate of contaminants and nutrients in natural systems where Fe(II) is present. Here, we explored the effect of H2O2 concentration on the structure of precipitates formed by Fe(II) oxidation and compared the precipitates to those formed by Fe(III) hydrolysis. Additionally, the phosphate retention under different H2O2 concentrations was evaluated. XRD, TEM, PDA, XPS, and UV-visible absorbance spectroscopy were used to characterize the structure of the formed precipitates; UV-visible absorbance spectroscopy was also used to determine the residual phosphate and Fe(II) in solution. It was found that the predominant precipitates in Fe(II) solution changed from planar-shaped crystalline lepidocrocite (γ-FeOOH) to poor short-range order (poorly crystalline) spherical-shaped hydrous ferric oxide (HFO) with increasing H2O2 concentrations. Although the HFO precipitates formed from Fe(II) resembled those formed from Fe(III) hydrolysis, the former was larger and had clearer lattice fringes. During the formation of γ-FeOOH, both Fe(II)-Fe(III) complexes and ligand-to-metal charge transfer processes were observed, and it was found that Fe(II) was present in the planar-shaped precipitates. Fe(II) might be present in the interior of precipitates as Fe(OH)2, which could serve as a nucleus for the epitaxial growth of γ-FeOOH. In addition, the extent of phosphate retention increased with the H2O2 concentration, indicating the increased reactivity of formed precipitates with H2O2 concentration. More phosphate was retained via coprecipitation with Fe than adsorption on the preformed Fe precipitates due to the incorporation of phosphate within the structure of the formed Fe hydroxyphosphate via coprecipitation.
Date Issued
2022-03-23
Date Acceptance
2022-03-11
Citation
Environmental Science and Technology (Washington), 2022, 56 (7)
ISSN
0013-936X
Publisher
American Chemical Society
Journal / Book Title
Environmental Science and Technology (Washington)
Volume
56
Issue
7
Copyright Statement
© 2022 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environ. Sci. Technol., after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.est.1c06256
Sponsor
Engineering & Physical Science Research Council (E
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/35319869
Grant Number
144356 (EP/N010124/1)
Subjects
Fe(II) oxidation
H2O2
LMCT
hydrous ferric oxide
lepidocrocite
phosphate retention
Publication Status
Published online
Coverage Spatial
United States
Date Publish Online
2022-03-23