TY - JOUR
T1 - Structural Variation of Precipitates Formed by Fe(II) Oxidation and Impact on the Retention of Phosphate
AU - Li, Xian
AU - Graham, Nigel J.D.
AU - Deng, Wensheng
AU - Liu, Mengjie
AU - Liu, Ting
AU - Yu, Wenzheng
N1 - Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/4/5
Y1 - 2022/4/5
N2 - 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 H2O2concentration 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 H2O2concentrations 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 (?-FeOOH) to poor short-range order (poorly crystalline) spherical-shaped hydrous ferric oxide (HFO) with increasing H2O2concentrations. 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 ?-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 ?-FeOOH. In addition, the extent of phosphate retention increased with the H2O2concentration, indicating the increased reactivity of formed precipitates with H2O2concentration. 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.
AB - 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 H2O2concentration 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 H2O2concentrations 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 (?-FeOOH) to poor short-range order (poorly crystalline) spherical-shaped hydrous ferric oxide (HFO) with increasing H2O2concentrations. 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 ?-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 ?-FeOOH. In addition, the extent of phosphate retention increased with the H2O2concentration, indicating the increased reactivity of formed precipitates with H2O2concentration. 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.
KW - Fe(II) oxidation
KW - HO
KW - LMCT
KW - hydrous ferric oxide
KW - lepidocrocite
KW - phosphate retention
UR - http://www.scopus.com/inward/record.url?scp=85127559279&partnerID=8YFLogxK
U2 - 10.1021/acs.est.1c06256
DO - 10.1021/acs.est.1c06256
M3 - Article
C2 - 35319869
AN - SCOPUS:85127559279
SN - 0013-936X
VL - 56
SP - 4345
EP - 4355
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 7
ER -