Role of Fe(II) and phosphate in arsenic uptake by coprecipitation

Nita Sahai; Young J. Lee; Huifang Xu; Mark Ciardelli; Jean Francois Gaillard

doi:10.1016/j.gca.2007.04.008

Role of Fe(II) and phosphate in arsenic uptake by coprecipitation

Nita Sahai^*, Young J. Lee, Huifang Xu, Mark Ciardelli, Jean Francois Gaillard

^*Corresponding author for this work

Civil and Environmental Engineering

Research output: Contribution to journal › Article › peer-review

58 Scopus citations

Abstract

Natural attenuation of arsenic by simple adsorption on oxyhydroxides may be limited due to competing oxyanions, but uptake by coprecipitation may locally sequester arsenic. We have systematically investigated the mechanism and mode (adsorption versus coprecipitation) of arsenic uptake in the presence of carbonate and phosphate, from solutions of inorganic composition similar to many groundwaters. Efficient arsenic removal, >95% As(V) and ∼55% in initial As(III) systems, occurred over 24 h at pHs 5.5-6.5 when Fe(II) and hydroxylapatite (Ca₅(PO₄)₃OH, HAP) "seed" crystals were added to solutions that had been previously reacted with HAP, atmospheric CO_2(g) and O_2(g). Arsenic adsorption was insignificant (<10%) on HAP without Fe(II). Greater uptake in the As(III) system in the presence of Fe(II) was interpreted as due to faster As(III) to As(V) oxidation by molecular oxygen in a putative pathway involving Fe(IV) and As(IV) intermediate species. HAP acts as a pH buffer that allows faster Fe(II) oxidation. Solution analyses coupled with high-resolution transmission electron microscopy (HRTEM), X-ray Energy-Dispersive Spectroscopy (EDS), and X-Ray Absorption Spectroscopy (XAS) indicated the precipitation of sub-spherical particles of an amorphous, chemically-mixed, nanophase, Fe^III[(OH)₃(PO₄)(As^VO₄)]·nH₂O or Fe^III[(OH)₃( PO₄)(As^VO₄)(As^IIIO₃)_minor]·nH₂O, where As^IIIO₃ is a minor component. The mode of As uptake was further investigated in binary coprecipitation (Fe(II) + As(III) or P), and ternary coprecipitation and adsorption experiments (Fe(II) + As(III) + P) at variable As/Fe, P/Fe and As/P/Fe ratios. Foil-like, poorly crystalline, nanoparticles of Fe^III(OH)₃ and sub-spherical, amorphous, chemically-mixed, metastable nanoparticles of Fe^III[(OH)₃, PO₄]·nH₂O coexisted at lower P/Fe ratios than predicted by bulk solubilities of strengite (FePO₄·2H₂O) and goethite (FeOOH). Uptake of As and P in these systems decreased as binary coprecipitation > ternary coprecipitation > ternary adsorption. Significantly, the chemically-mixed, ferric oxyhydroxide-phosphate-arsenate nanophases found here are very similar to those found in the natural environment at slightly acidic to circum-neutral pHs in sub-oxic to oxic systems, such phases may naturally attenuate As mobility in the environment, but it is important to recognize that our system and the natural environment are kinetically evolving, and the ultimate environmental fate of As will depend on the long-term stability and potential phase transformations of these mixed nanophases. Our results also underscore the importance of using sufficiently complex, yet systematically designed, model systems to accurately represent the natural environment.

Original language	English (US)
Pages (from-to)	3193-3210
Number of pages	18
Journal	Geochimica et Cosmochimica Acta
Volume	71
Issue number	13
DOIs	https://doi.org/10.1016/j.gca.2007.04.008
State	Published - Jul 1 2007

Funding

We thank Brian Majestic, Environmental Chemistry and Technology Program, University of Wisconsin (UW)-Madison, for training and use of the ICP–OES; Prof. Eric Roden for use of the UV–Vis spectrophotometer and DO probe; Kaya Delak, Tim Oleson and Mark Stevens for general assistance in the laboratory; Dr. Stephan Hug, EAWAG, for initially motivating N.S. to work on arsenic-contamination problems and for helpful discussions. Financial support for portions of this work was provided by NSF EAR CAREER Grant # 0346689 and faculty “start-up” and WARF grants from UW-Madison to N.S., and UW-Madison’s faculty “start-up” funds to H.X. The XAS work was performed at the DND-CAT Synchrotron Research Center, Sector 5 of the Advanced Photon Source, Argonne, IL. DND-CAT is supported by the E.I. DuPont de Nemours & Co., The Dow Chemical Company, the U.S. NSF through Grant DMR-9304725 and the State of Illinois through the Department of Commerce and the Board of Higher Education Grant IBHE HECA NWU 96. Use of the APS was supported by the U. S. DOE, Office of Science, Office of BES, under Contract No. W-31-109-Eng-38, to J.-F. G. Many thanks to Dr. Ian Saratovsky and Dr. Qin Ma for the collection of XAS data, and to Dr. Xiao-Zhou Liao, University of Chicago and Dr. Ying-Bing Jiang, University of New Mexico-Albuquerque, for assistance with the HRTEM analysis. NS thanks the two anonymous reviewers and the AE, Carrick Eggleston, for their thoughtful and critical remarks, that helped improve the quality of this manuscript.

ASJC Scopus subject areas

Geochemistry and Petrology

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1016/j.gca.2007.04.008

Cite this

@article{207b9133830b4df9bb86f91fdac9e82e,

title = "Role of Fe(II) and phosphate in arsenic uptake by coprecipitation",

abstract = "Natural attenuation of arsenic by simple adsorption on oxyhydroxides may be limited due to competing oxyanions, but uptake by coprecipitation may locally sequester arsenic. We have systematically investigated the mechanism and mode (adsorption versus coprecipitation) of arsenic uptake in the presence of carbonate and phosphate, from solutions of inorganic composition similar to many groundwaters. Efficient arsenic removal, >95% As(V) and ∼55% in initial As(III) systems, occurred over 24 h at pHs 5.5-6.5 when Fe(II) and hydroxylapatite (Ca5(PO4)3OH, HAP) {"}seed{"} crystals were added to solutions that had been previously reacted with HAP, atmospheric CO2(g) and O2(g). Arsenic adsorption was insignificant (<10%) on HAP without Fe(II). Greater uptake in the As(III) system in the presence of Fe(II) was interpreted as due to faster As(III) to As(V) oxidation by molecular oxygen in a putative pathway involving Fe(IV) and As(IV) intermediate species. HAP acts as a pH buffer that allows faster Fe(II) oxidation. Solution analyses coupled with high-resolution transmission electron microscopy (HRTEM), X-ray Energy-Dispersive Spectroscopy (EDS), and X-Ray Absorption Spectroscopy (XAS) indicated the precipitation of sub-spherical particles of an amorphous, chemically-mixed, nanophase, FeIII[(OH)3(PO4)(AsVO4)]·nH2O or FeIII[(OH)3( PO4)(AsVO4)(AsIIIO3)minor]·nH2O, where AsIIIO3 is a minor component. The mode of As uptake was further investigated in binary coprecipitation (Fe(II) + As(III) or P), and ternary coprecipitation and adsorption experiments (Fe(II) + As(III) + P) at variable As/Fe, P/Fe and As/P/Fe ratios. Foil-like, poorly crystalline, nanoparticles of FeIII(OH)3 and sub-spherical, amorphous, chemically-mixed, metastable nanoparticles of FeIII[(OH)3, PO4]·nH2O coexisted at lower P/Fe ratios than predicted by bulk solubilities of strengite (FePO4·2H2O) and goethite (FeOOH). Uptake of As and P in these systems decreased as binary coprecipitation > ternary coprecipitation > ternary adsorption. Significantly, the chemically-mixed, ferric oxyhydroxide-phosphate-arsenate nanophases found here are very similar to those found in the natural environment at slightly acidic to circum-neutral pHs in sub-oxic to oxic systems, such phases may naturally attenuate As mobility in the environment, but it is important to recognize that our system and the natural environment are kinetically evolving, and the ultimate environmental fate of As will depend on the long-term stability and potential phase transformations of these mixed nanophases. Our results also underscore the importance of using sufficiently complex, yet systematically designed, model systems to accurately represent the natural environment.",

author = "Nita Sahai and Lee, {Young J.} and Huifang Xu and Mark Ciardelli and Gaillard, {Jean Francois}",

note = "Funding Information: We thank Brian Majestic, Environmental Chemistry and Technology Program, University of Wisconsin (UW)-Madison, for training and use of the ICP–OES; Prof. Eric Roden for use of the UV–Vis spectrophotometer and DO probe; Kaya Delak, Tim Oleson and Mark Stevens for general assistance in the laboratory; Dr. Stephan Hug, EAWAG, for initially motivating N.S. to work on arsenic-contamination problems and for helpful discussions. Financial support for portions of this work was provided by NSF EAR CAREER Grant # 0346689 and faculty “start-up” and WARF grants from UW-Madison to N.S., and UW-Madison{\textquoteright}s faculty “start-up” funds to H.X. The XAS work was performed at the DND-CAT Synchrotron Research Center, Sector 5 of the Advanced Photon Source, Argonne, IL. DND-CAT is supported by the E.I. DuPont de Nemours & Co., The Dow Chemical Company, the U.S. NSF through Grant DMR-9304725 and the State of Illinois through the Department of Commerce and the Board of Higher Education Grant IBHE HECA NWU 96. Use of the APS was supported by the U. S. DOE, Office of Science, Office of BES, under Contract No. W-31-109-Eng-38, to J.-F. G. Many thanks to Dr. Ian Saratovsky and Dr. Qin Ma for the collection of XAS data, and to Dr. Xiao-Zhou Liao, University of Chicago and Dr. Ying-Bing Jiang, University of New Mexico-Albuquerque, for assistance with the HRTEM analysis. NS thanks the two anonymous reviewers and the AE, Carrick Eggleston, for their thoughtful and critical remarks, that helped improve the quality of this manuscript. ",

year = "2007",

month = jul,

day = "1",

doi = "10.1016/j.gca.2007.04.008",

language = "English (US)",

volume = "71",

pages = "3193--3210",

journal = "Geochimica et Cosmochimica Acta",

issn = "0016-7037",

publisher = "Elsevier Ltd",

number = "13",

}

TY - JOUR

T1 - Role of Fe(II) and phosphate in arsenic uptake by coprecipitation

AU - Sahai, Nita

AU - Lee, Young J.

AU - Xu, Huifang

AU - Ciardelli, Mark

AU - Gaillard, Jean Francois

N1 - Funding Information: We thank Brian Majestic, Environmental Chemistry and Technology Program, University of Wisconsin (UW)-Madison, for training and use of the ICP–OES; Prof. Eric Roden for use of the UV–Vis spectrophotometer and DO probe; Kaya Delak, Tim Oleson and Mark Stevens for general assistance in the laboratory; Dr. Stephan Hug, EAWAG, for initially motivating N.S. to work on arsenic-contamination problems and for helpful discussions. Financial support for portions of this work was provided by NSF EAR CAREER Grant # 0346689 and faculty “start-up” and WARF grants from UW-Madison to N.S., and UW-Madison’s faculty “start-up” funds to H.X. The XAS work was performed at the DND-CAT Synchrotron Research Center, Sector 5 of the Advanced Photon Source, Argonne, IL. DND-CAT is supported by the E.I. DuPont de Nemours & Co., The Dow Chemical Company, the U.S. NSF through Grant DMR-9304725 and the State of Illinois through the Department of Commerce and the Board of Higher Education Grant IBHE HECA NWU 96. Use of the APS was supported by the U. S. DOE, Office of Science, Office of BES, under Contract No. W-31-109-Eng-38, to J.-F. G. Many thanks to Dr. Ian Saratovsky and Dr. Qin Ma for the collection of XAS data, and to Dr. Xiao-Zhou Liao, University of Chicago and Dr. Ying-Bing Jiang, University of New Mexico-Albuquerque, for assistance with the HRTEM analysis. NS thanks the two anonymous reviewers and the AE, Carrick Eggleston, for their thoughtful and critical remarks, that helped improve the quality of this manuscript.

PY - 2007/7/1

Y1 - 2007/7/1

N2 - Natural attenuation of arsenic by simple adsorption on oxyhydroxides may be limited due to competing oxyanions, but uptake by coprecipitation may locally sequester arsenic. We have systematically investigated the mechanism and mode (adsorption versus coprecipitation) of arsenic uptake in the presence of carbonate and phosphate, from solutions of inorganic composition similar to many groundwaters. Efficient arsenic removal, >95% As(V) and ∼55% in initial As(III) systems, occurred over 24 h at pHs 5.5-6.5 when Fe(II) and hydroxylapatite (Ca5(PO4)3OH, HAP) "seed" crystals were added to solutions that had been previously reacted with HAP, atmospheric CO2(g) and O2(g). Arsenic adsorption was insignificant (<10%) on HAP without Fe(II). Greater uptake in the As(III) system in the presence of Fe(II) was interpreted as due to faster As(III) to As(V) oxidation by molecular oxygen in a putative pathway involving Fe(IV) and As(IV) intermediate species. HAP acts as a pH buffer that allows faster Fe(II) oxidation. Solution analyses coupled with high-resolution transmission electron microscopy (HRTEM), X-ray Energy-Dispersive Spectroscopy (EDS), and X-Ray Absorption Spectroscopy (XAS) indicated the precipitation of sub-spherical particles of an amorphous, chemically-mixed, nanophase, FeIII[(OH)3(PO4)(AsVO4)]·nH2O or FeIII[(OH)3( PO4)(AsVO4)(AsIIIO3)minor]·nH2O, where AsIIIO3 is a minor component. The mode of As uptake was further investigated in binary coprecipitation (Fe(II) + As(III) or P), and ternary coprecipitation and adsorption experiments (Fe(II) + As(III) + P) at variable As/Fe, P/Fe and As/P/Fe ratios. Foil-like, poorly crystalline, nanoparticles of FeIII(OH)3 and sub-spherical, amorphous, chemically-mixed, metastable nanoparticles of FeIII[(OH)3, PO4]·nH2O coexisted at lower P/Fe ratios than predicted by bulk solubilities of strengite (FePO4·2H2O) and goethite (FeOOH). Uptake of As and P in these systems decreased as binary coprecipitation > ternary coprecipitation > ternary adsorption. Significantly, the chemically-mixed, ferric oxyhydroxide-phosphate-arsenate nanophases found here are very similar to those found in the natural environment at slightly acidic to circum-neutral pHs in sub-oxic to oxic systems, such phases may naturally attenuate As mobility in the environment, but it is important to recognize that our system and the natural environment are kinetically evolving, and the ultimate environmental fate of As will depend on the long-term stability and potential phase transformations of these mixed nanophases. Our results also underscore the importance of using sufficiently complex, yet systematically designed, model systems to accurately represent the natural environment.

AB - Natural attenuation of arsenic by simple adsorption on oxyhydroxides may be limited due to competing oxyanions, but uptake by coprecipitation may locally sequester arsenic. We have systematically investigated the mechanism and mode (adsorption versus coprecipitation) of arsenic uptake in the presence of carbonate and phosphate, from solutions of inorganic composition similar to many groundwaters. Efficient arsenic removal, >95% As(V) and ∼55% in initial As(III) systems, occurred over 24 h at pHs 5.5-6.5 when Fe(II) and hydroxylapatite (Ca5(PO4)3OH, HAP) "seed" crystals were added to solutions that had been previously reacted with HAP, atmospheric CO2(g) and O2(g). Arsenic adsorption was insignificant (<10%) on HAP without Fe(II). Greater uptake in the As(III) system in the presence of Fe(II) was interpreted as due to faster As(III) to As(V) oxidation by molecular oxygen in a putative pathway involving Fe(IV) and As(IV) intermediate species. HAP acts as a pH buffer that allows faster Fe(II) oxidation. Solution analyses coupled with high-resolution transmission electron microscopy (HRTEM), X-ray Energy-Dispersive Spectroscopy (EDS), and X-Ray Absorption Spectroscopy (XAS) indicated the precipitation of sub-spherical particles of an amorphous, chemically-mixed, nanophase, FeIII[(OH)3(PO4)(AsVO4)]·nH2O or FeIII[(OH)3( PO4)(AsVO4)(AsIIIO3)minor]·nH2O, where AsIIIO3 is a minor component. The mode of As uptake was further investigated in binary coprecipitation (Fe(II) + As(III) or P), and ternary coprecipitation and adsorption experiments (Fe(II) + As(III) + P) at variable As/Fe, P/Fe and As/P/Fe ratios. Foil-like, poorly crystalline, nanoparticles of FeIII(OH)3 and sub-spherical, amorphous, chemically-mixed, metastable nanoparticles of FeIII[(OH)3, PO4]·nH2O coexisted at lower P/Fe ratios than predicted by bulk solubilities of strengite (FePO4·2H2O) and goethite (FeOOH). Uptake of As and P in these systems decreased as binary coprecipitation > ternary coprecipitation > ternary adsorption. Significantly, the chemically-mixed, ferric oxyhydroxide-phosphate-arsenate nanophases found here are very similar to those found in the natural environment at slightly acidic to circum-neutral pHs in sub-oxic to oxic systems, such phases may naturally attenuate As mobility in the environment, but it is important to recognize that our system and the natural environment are kinetically evolving, and the ultimate environmental fate of As will depend on the long-term stability and potential phase transformations of these mixed nanophases. Our results also underscore the importance of using sufficiently complex, yet systematically designed, model systems to accurately represent the natural environment.

UR - http://www.scopus.com/inward/record.url?scp=34250199724&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34250199724&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2007.04.008

DO - 10.1016/j.gca.2007.04.008

M3 - Article

AN - SCOPUS:34250199724

SN - 0016-7037

VL - 71

SP - 3193

EP - 3210

JO - Geochimica et Cosmochimica Acta

JF - Geochimica et Cosmochimica Acta

IS - 13

ER -

Role of Fe(II) and phosphate in arsenic uptake by coprecipitation

Abstract

Funding

ASJC Scopus subject areas

UN SDGs

Access to Document

Other files and links

Fingerprint

Cite this