Removal of Selenium Oxyanions from Aqueous Solutions by Ion Exchange: Equilibrium, Kinetics, and Mechanistic Modeling

Z. Zeng; Z. Shen; J. D. Einkauf; A. P. Ladshaw; R. Custelcean; C. Tsouris; S. Yiacoumi

doi:10.1021/acsestwater.5c01136

Removal of Selenium Oxyanions from Aqueous Solutions by Ion Exchange: Equilibrium, Kinetics, and Mechanistic Modeling

Z. Zeng
, Z. Shen
, J. D. Einkauf
, A. P. Ladshaw
, R. Custelcean
, C. Tsouris
, S. Yiacoumi

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

Abstract

Selenium (Se) is an essential micronutrient but toxic at high concentrations, posing challenges for water treatment. This study investigated the removal of selenate (SeO₄^2–) and selenite (SeO₃^2–) using the strong-base anion-exchange resin IRA-900, particularly in the presence of competing sulfate (SO₄^2–). The performance of the commercially available resin IRA-900 was systematically investigated. The batch equilibrium behavior was studied in both single- and binary-component systems, and the kinetic behavior was investigated in single-component systems. Results confirmed a selectivity order of SeO₄^2– > SO₄^2– > SeO₃^2–, indicating preferential SeO₄^2– removal over competing SO₄^2– but lower affinity for SeO₃^2–. The maximum total exchange capacity was determined to be 2.04 mequiv/g. Furthermore, SeO₃^2– uptake was found to be pH-dependent, whereas SeO₄^2– uptake remained stable across a broad pH range. From a modeling perspective, the Law of Mass Action model effectively described equilibrium data, and a transport–reaction modeling framework captured removal kinetics of oxyanions including film and intraparticle diffusion. Finally, X-ray photoelectron spectroscopy confirmed ion exchange between chloride and Se oxyanions as the primary removal mechanism. These findings provide fundamental insights into the removal of Se oxyanions from aqueous solutions by ion exchange.

Original language	English
Pages (from-to)	438-454
Number of pages	17
Journal	ACS ES and T Water
Volume	6
Issue number	1
DOIs	https://doi.org/10.1021/acsestwater.5c01136
State	Published - Jan 9 2026

Funding

This material is based upon work supported by the National Alliance for Water Innovation (NAWI), funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE), under Funding Opportunity Announcement DE-FOA-0001905. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. This work was performed in part at the Materials Characterization Facility (MCF) at Georgia Tech. The MCF is jointly supported by the Georgia Tech Institute for Materials (IMat) and the Institute for Electronics and Nanotechnology (IEN), which is a member of the National Nanotechnology Coordinated Infrastructure supported by the National Science Foundation (Grant ECCS-2025462). The authors are also thankful to Dr. Harry Meyer III (Oak Ridge National Laboratory) for assisting with the XPS analysis.

Keywords

IRA-900
ion exchange
ion-exchange modeling
selenate
selenite
selenium oxyanions

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10.1021/acsestwater.5c01136

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title = "Removal of Selenium Oxyanions from Aqueous Solutions by Ion Exchange: Equilibrium, Kinetics, and Mechanistic Modeling",

abstract = "Selenium (Se) is an essential micronutrient but toxic at high concentrations, posing challenges for water treatment. This study investigated the removal of selenate (SeO42–) and selenite (SeO32–) using the strong-base anion-exchange resin IRA-900, particularly in the presence of competing sulfate (SO42–). The performance of the commercially available resin IRA-900 was systematically investigated. The batch equilibrium behavior was studied in both single- and binary-component systems, and the kinetic behavior was investigated in single-component systems. Results confirmed a selectivity order of SeO42– > SO42– > SeO32–, indicating preferential SeO42– removal over competing SO42– but lower affinity for SeO32–. The maximum total exchange capacity was determined to be 2.04 mequiv/g. Furthermore, SeO32– uptake was found to be pH-dependent, whereas SeO42– uptake remained stable across a broad pH range. From a modeling perspective, the Law of Mass Action model effectively described equilibrium data, and a transport–reaction modeling framework captured removal kinetics of oxyanions including film and intraparticle diffusion. Finally, X-ray photoelectron spectroscopy confirmed ion exchange between chloride and Se oxyanions as the primary removal mechanism. These findings provide fundamental insights into the removal of Se oxyanions from aqueous solutions by ion exchange.",

keywords = "IRA-900, ion exchange, ion-exchange modeling, selenate, selenite, selenium oxyanions",

author = "Z. Zeng and Z. Shen and Einkauf, \{J. D.\} and Ladshaw, \{A. P.\} and R. Custelcean and C. Tsouris and S. Yiacoumi",

note = "Publisher Copyright: {\textcopyright} 2025 The Authors. Published by American Chemical Society",

year = "2026",

month = jan,

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doi = "10.1021/acsestwater.5c01136",

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T1 - Removal of Selenium Oxyanions from Aqueous Solutions by Ion Exchange

T2 - Equilibrium, Kinetics, and Mechanistic Modeling

AU - Zeng, Z.

AU - Shen, Z.

AU - Einkauf, J. D.

AU - Ladshaw, A. P.

AU - Custelcean, R.

AU - Tsouris, C.

AU - Yiacoumi, S.

PY - 2026/1/9

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N2 - Selenium (Se) is an essential micronutrient but toxic at high concentrations, posing challenges for water treatment. This study investigated the removal of selenate (SeO42–) and selenite (SeO32–) using the strong-base anion-exchange resin IRA-900, particularly in the presence of competing sulfate (SO42–). The performance of the commercially available resin IRA-900 was systematically investigated. The batch equilibrium behavior was studied in both single- and binary-component systems, and the kinetic behavior was investigated in single-component systems. Results confirmed a selectivity order of SeO42– > SO42– > SeO32–, indicating preferential SeO42– removal over competing SO42– but lower affinity for SeO32–. The maximum total exchange capacity was determined to be 2.04 mequiv/g. Furthermore, SeO32– uptake was found to be pH-dependent, whereas SeO42– uptake remained stable across a broad pH range. From a modeling perspective, the Law of Mass Action model effectively described equilibrium data, and a transport–reaction modeling framework captured removal kinetics of oxyanions including film and intraparticle diffusion. Finally, X-ray photoelectron spectroscopy confirmed ion exchange between chloride and Se oxyanions as the primary removal mechanism. These findings provide fundamental insights into the removal of Se oxyanions from aqueous solutions by ion exchange.

AB - Selenium (Se) is an essential micronutrient but toxic at high concentrations, posing challenges for water treatment. This study investigated the removal of selenate (SeO42–) and selenite (SeO32–) using the strong-base anion-exchange resin IRA-900, particularly in the presence of competing sulfate (SO42–). The performance of the commercially available resin IRA-900 was systematically investigated. The batch equilibrium behavior was studied in both single- and binary-component systems, and the kinetic behavior was investigated in single-component systems. Results confirmed a selectivity order of SeO42– > SO42– > SeO32–, indicating preferential SeO42– removal over competing SO42– but lower affinity for SeO32–. The maximum total exchange capacity was determined to be 2.04 mequiv/g. Furthermore, SeO32– uptake was found to be pH-dependent, whereas SeO42– uptake remained stable across a broad pH range. From a modeling perspective, the Law of Mass Action model effectively described equilibrium data, and a transport–reaction modeling framework captured removal kinetics of oxyanions including film and intraparticle diffusion. Finally, X-ray photoelectron spectroscopy confirmed ion exchange between chloride and Se oxyanions as the primary removal mechanism. These findings provide fundamental insights into the removal of Se oxyanions from aqueous solutions by ion exchange.

KW - IRA-900

KW - ion exchange

KW - ion-exchange modeling

KW - selenate

KW - selenite

KW - selenium oxyanions

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JO - ACS ES and T Water

JF - ACS ES and T Water

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ER -

Removal of Selenium Oxyanions from Aqueous Solutions by Ion Exchange: Equilibrium, Kinetics, and Mechanistic Modeling

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Keywords

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