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Title: Pb, Cu, and Zn distributions at humic acid-coated metal-oxide surfaces

Abstract

Mineral surfaces are often coated by natural organic matter (NOM), which has a major influence on metal-ion sorption and sequestration because of the abundance of binding sites in such coatings and the changes they cause in local nanoscale environments. The effects of NOM coatings on mineral surfaces are, however, still poorly understood at the molecular level due to the complexity of these systems. We have applied long-period X-ray standing wave-fluorescence yield (LP-XSW-FY) spectroscopy to measure the partitioning of naturally present Cu(II) (0.0226%), Zn(II) (0.009%), and Pb(II) (similar to 0.0004%) between Elliott Soil Humic Acid (ESHA) coatings and three model single-crystal metal-oxide substrates: alpha-Al2O3 (00 01), alpha-Al2O3 (1-102), and alpha-Fe2O3 (0001). The competitive sorption effects among these metal ions for binding sites in the ESHA coatings and on the metal-oxide surfaces were investigated as a function of reaction time, calcium content, and solution pH. Pb(II) ions present in the ESHA coatings were found to redistribute to reactive alpha-Al2O3 (1-102) and alpha-Fe2O3 (0001) surfaces after 3 h of reaction (pH = 6.0, [Ca(II)] = 2 mM). Pb(II) partitioning onto these reactive metal-oxide surfaces increased with increasing reaction time (up to 7 d). Additionally, the partitioning of Cu(II) and Zn(II) from the ESHAmore » coating to the alpha-Fe2O3 (0001) substrate increased slightly with reaction time (2.4% and 3.7% for Cu(II) and Zn(II), respectively, after 3 h and 6.4% and 7.7% for Cu(II) and Zn(II), respectively, after 72 h of reaction time). However, no changes in the partitioning of Cu(II) and Zn(II) onto the alpha-Al2O3 (1-102) surface were observed with increasing reaction time, suggesting that these ions strongly complex with functional groups in the ESHA coatings. Similar results were obtained for Cu(II) and Zn(II) on the ESHA-coated alpha-Al2O3 (1-102) surfaces in samples without the addition of calcium. However, the amounts of Pb(II) mobilized from the ESHA coatings onto the alpha-Al2O3 (1-102) surfaces increased from 40% (no added Ca) to 58% (with 2 mM Ca) after 72 h of reaction time, possibly due to displacement of Pb(II) by Ca(II) from binding sites in the ESHA coatings. In contrast, Pb(II), Cu(II), and Zn(II) present in the ESHA coatings were found to be unreactive with the alpha-Al2O3 (0001) surface. The reactivities of the three ESHA-coated metal-oxide surfaces that we observed, with respect to metal-ion sorption, are consistent with the trend observed for the uncoated metal-oxide surfaces: alpha-Fe2O3 (0001) > alpha-Al2O3 (1-102) > alpha-Al2O3 (0001). In addition, Pb(II) partitioning onto alpha-Al2O3 (1-102) surfaces increased with increasing pH from 4.0 to 9.0 as a result of the increasingly negative surface charge. Our results show that intrinsic properties (nature of binding sites, binding affinities, and surface charge) of the ESHA coatings and metal-oxide surfaces, as well as external parameters such as pH and competing ions, are key factors governing the distribution and speciation of metal ions at complex NOM/mineral interfaces.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [9]
  1. Stanford Univ., Stanford, CA (United States)
  2. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
  4. Univ. of Chicago, Chicago, IL (United States)
  5. Stanford Univ., Stanford, CA (United States); CEREGE, Europole Mediterraneen de l'Arbois, Cedex (France)
  6. Stanford Univ., Stanford, CA (United States); Ben-Gurion Univ. of the Negev, Midreshet Ben-Gurion (Israel)
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  8. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  9. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)
OSTI Identifier:
1327773
Alternate Identifier(s):
OSTI ID: 1340232; OSTI ID: 1430546
Grant/Contract Number:  
AC05-00OR22725; AC02-06CH11357; FG02-94ER14466; AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 188; Journal Issue: C; Journal ID: ISSN 0016-7037
Publisher:
The Geochemical Society; The Meteoritical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; humic acid; Pb; Cu; Zn; Ca; metal-oxide surfaces; single crystal; X-ray standing wave; LP-XSW-FY; metal partitioning; hematite; alumina; pH effect; 36 MATERIALS SCIENCE; 58 GEOSCIENCES; X-RAYS; COMPETITIVE ADSORPTION; ION-BINDING; MINERAL SURFACES; NATURAL ORGANIC-MATTER; RAY STANDING WAVES

Citation Formats

Wang, Yingge, Michel, F. Marc, Choi, Yongseong, Eng, Peter J., Levard, Clement, Siebner, Hagar, Gu, Baohua, Bargar, John R., and Brown, Gordon E. Pb, Cu, and Zn distributions at humic acid-coated metal-oxide surfaces. United States: N. p., 2016. Web. doi:10.1016/j.gca.2016.05.009.
Wang, Yingge, Michel, F. Marc, Choi, Yongseong, Eng, Peter J., Levard, Clement, Siebner, Hagar, Gu, Baohua, Bargar, John R., & Brown, Gordon E. Pb, Cu, and Zn distributions at humic acid-coated metal-oxide surfaces. United States. https://doi.org/10.1016/j.gca.2016.05.009
Wang, Yingge, Michel, F. Marc, Choi, Yongseong, Eng, Peter J., Levard, Clement, Siebner, Hagar, Gu, Baohua, Bargar, John R., and Brown, Gordon E. Mon . "Pb, Cu, and Zn distributions at humic acid-coated metal-oxide surfaces". United States. https://doi.org/10.1016/j.gca.2016.05.009. https://www.osti.gov/servlets/purl/1327773.
@article{osti_1327773,
title = {Pb, Cu, and Zn distributions at humic acid-coated metal-oxide surfaces},
author = {Wang, Yingge and Michel, F. Marc and Choi, Yongseong and Eng, Peter J. and Levard, Clement and Siebner, Hagar and Gu, Baohua and Bargar, John R. and Brown, Gordon E.},
abstractNote = {Mineral surfaces are often coated by natural organic matter (NOM), which has a major influence on metal-ion sorption and sequestration because of the abundance of binding sites in such coatings and the changes they cause in local nanoscale environments. The effects of NOM coatings on mineral surfaces are, however, still poorly understood at the molecular level due to the complexity of these systems. We have applied long-period X-ray standing wave-fluorescence yield (LP-XSW-FY) spectroscopy to measure the partitioning of naturally present Cu(II) (0.0226%), Zn(II) (0.009%), and Pb(II) (similar to 0.0004%) between Elliott Soil Humic Acid (ESHA) coatings and three model single-crystal metal-oxide substrates: alpha-Al2O3 (00 01), alpha-Al2O3 (1-102), and alpha-Fe2O3 (0001). The competitive sorption effects among these metal ions for binding sites in the ESHA coatings and on the metal-oxide surfaces were investigated as a function of reaction time, calcium content, and solution pH. Pb(II) ions present in the ESHA coatings were found to redistribute to reactive alpha-Al2O3 (1-102) and alpha-Fe2O3 (0001) surfaces after 3 h of reaction (pH = 6.0, [Ca(II)] = 2 mM). Pb(II) partitioning onto these reactive metal-oxide surfaces increased with increasing reaction time (up to 7 d). Additionally, the partitioning of Cu(II) and Zn(II) from the ESHA coating to the alpha-Fe2O3 (0001) substrate increased slightly with reaction time (2.4% and 3.7% for Cu(II) and Zn(II), respectively, after 3 h and 6.4% and 7.7% for Cu(II) and Zn(II), respectively, after 72 h of reaction time). However, no changes in the partitioning of Cu(II) and Zn(II) onto the alpha-Al2O3 (1-102) surface were observed with increasing reaction time, suggesting that these ions strongly complex with functional groups in the ESHA coatings. Similar results were obtained for Cu(II) and Zn(II) on the ESHA-coated alpha-Al2O3 (1-102) surfaces in samples without the addition of calcium. However, the amounts of Pb(II) mobilized from the ESHA coatings onto the alpha-Al2O3 (1-102) surfaces increased from 40% (no added Ca) to 58% (with 2 mM Ca) after 72 h of reaction time, possibly due to displacement of Pb(II) by Ca(II) from binding sites in the ESHA coatings. In contrast, Pb(II), Cu(II), and Zn(II) present in the ESHA coatings were found to be unreactive with the alpha-Al2O3 (0001) surface. The reactivities of the three ESHA-coated metal-oxide surfaces that we observed, with respect to metal-ion sorption, are consistent with the trend observed for the uncoated metal-oxide surfaces: alpha-Fe2O3 (0001) > alpha-Al2O3 (1-102) > alpha-Al2O3 (0001). In addition, Pb(II) partitioning onto alpha-Al2O3 (1-102) surfaces increased with increasing pH from 4.0 to 9.0 as a result of the increasingly negative surface charge. Our results show that intrinsic properties (nature of binding sites, binding affinities, and surface charge) of the ESHA coatings and metal-oxide surfaces, as well as external parameters such as pH and competing ions, are key factors governing the distribution and speciation of metal ions at complex NOM/mineral interfaces.},
doi = {10.1016/j.gca.2016.05.009},
journal = {Geochimica et Cosmochimica Acta},
number = C,
volume = 188,
place = {United States},
year = {Mon May 09 00:00:00 EDT 2016},
month = {Mon May 09 00:00:00 EDT 2016}
}

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Works referencing / citing this record:

Fulvic acid in foliar spray is more effective than humic acid via soil in improving coffee seedlings growth
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Fulvic acid in foliar spray is more effective than humic acid via soil in improving coffee seedlings growth
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Fulvic acid in foliar spray is more effective than humic acid via soil in improving coffee seedlings growth
text, January 2019