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Title: Heterogeneous Lead Phosphate Nucleation at Organic–Water Interfaces: Implications for Lead Immobilization

Abstract

Phosphate is added to Pb-contaminated soils to induce lead immobilization through lead phosphate precipitation. Organic coatings on soils, which may affect heterogeneous lead phosphate nucleation, can impact the effectiveness of lead immobilization. SiO 2 surfaces were coated with silanol self-assembled thin films terminated with -COOH and -OH functional groups to act as model organic coatings on soil particles. Using grazing incidence small-angle X-ray scattering (GISAXS), heterogeneous lead phosphate nucleation on coatings was measured from mixed Pb(NO 3) 2 and Na 2HPO 4/NaH 2PO 4 solutions at pH 7 with varied ionic strengths (IS = 0.58, 4, and 11 mM). Raman spectroscopy identified the homogeneous precipitates in solution as hydroxylpyromorphite (Pb 5(PO 4) 3OH). The smallest lead phosphate nuclei (4.5 ± 0.5 nm) were observed on -COOH coatings, which resulted from the highest level of lead and phosphate ion adsorption on -COOH coatings. The IS of the solution also affected the sizes of the heterogeneous precipitates on -COOH coating, with smaller nuclei (1.3 ± 0.4 nm) forming under higher IS (4 and 11 mM). Finally, this study provided new findings that can improve our understanding of lead immobilization in contaminated soil environments.

Authors:
 [1];  [1]; ORCiD logo [2];  [3];  [4]; ORCiD logo [1]
  1. Univ. of Houston, TX (United States). Dept. of Civil & Environmental Engineering
  2. Washington Univ., St. Louis, MO (United States). Dept. of Energy, Environmental and Chemical Engineering
  3. Washington Univ., St. Louis, MO (United States). Dept. of Earth and Planetary Sciences
  4. Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Houston, TX (United States); Washington Univ., St. Louis, MO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
OSTI Identifier:
1484682
Grant/Contract Number:  
AC02-06CH11357; 1604042; 1603717
Resource Type:
Accepted Manuscript
Journal Name:
ACS Earth and Space Chemistry
Additional Journal Information:
Journal Volume: 2; Journal Issue: 9; Journal ID: ISSN 2472-3452
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; critical nuclei sizes; heterogeneous nucleation; hydroxylpyromorphite; ion adsorption; local supersaturation near substrates; organic coatings; recrystallization

Citation Formats

Dai, Chong, Zhao, Juntao, Giammar, Daniel E., Pasteris, Jill D., Zuo, Xiaobing, and Hu, Yandi. Heterogeneous Lead Phosphate Nucleation at Organic–Water Interfaces: Implications for Lead Immobilization. United States: N. p., 2018. Web. doi:10.1021/acsearthspacechem.8b00040.
Dai, Chong, Zhao, Juntao, Giammar, Daniel E., Pasteris, Jill D., Zuo, Xiaobing, & Hu, Yandi. Heterogeneous Lead Phosphate Nucleation at Organic–Water Interfaces: Implications for Lead Immobilization. United States. doi:10.1021/acsearthspacechem.8b00040.
Dai, Chong, Zhao, Juntao, Giammar, Daniel E., Pasteris, Jill D., Zuo, Xiaobing, and Hu, Yandi. Fri . "Heterogeneous Lead Phosphate Nucleation at Organic–Water Interfaces: Implications for Lead Immobilization". United States. doi:10.1021/acsearthspacechem.8b00040. https://www.osti.gov/servlets/purl/1484682.
@article{osti_1484682,
title = {Heterogeneous Lead Phosphate Nucleation at Organic–Water Interfaces: Implications for Lead Immobilization},
author = {Dai, Chong and Zhao, Juntao and Giammar, Daniel E. and Pasteris, Jill D. and Zuo, Xiaobing and Hu, Yandi},
abstractNote = {Phosphate is added to Pb-contaminated soils to induce lead immobilization through lead phosphate precipitation. Organic coatings on soils, which may affect heterogeneous lead phosphate nucleation, can impact the effectiveness of lead immobilization. SiO2 surfaces were coated with silanol self-assembled thin films terminated with -COOH and -OH functional groups to act as model organic coatings on soil particles. Using grazing incidence small-angle X-ray scattering (GISAXS), heterogeneous lead phosphate nucleation on coatings was measured from mixed Pb(NO3)2 and Na2HPO4/NaH2PO4 solutions at pH 7 with varied ionic strengths (IS = 0.58, 4, and 11 mM). Raman spectroscopy identified the homogeneous precipitates in solution as hydroxylpyromorphite (Pb5(PO4)3OH). The smallest lead phosphate nuclei (4.5 ± 0.5 nm) were observed on -COOH coatings, which resulted from the highest level of lead and phosphate ion adsorption on -COOH coatings. The IS of the solution also affected the sizes of the heterogeneous precipitates on -COOH coating, with smaller nuclei (1.3 ± 0.4 nm) forming under higher IS (4 and 11 mM). Finally, this study provided new findings that can improve our understanding of lead immobilization in contaminated soil environments.},
doi = {10.1021/acsearthspacechem.8b00040},
journal = {ACS Earth and Space Chemistry},
number = 9,
volume = 2,
place = {United States},
year = {2018},
month = {7}
}

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