Abstract
Selenium (Se) has become an environmental contaminant of aquatic ecosystems as a result of human activities, particularly mining, fossil fuel combustion, and agricultural activities. By leveraging the high sulfate concentrations relative to Se oxyanions (i.e., SeOn2-, n = 3, 4) present in some wastewaters, we have developed an efficient approach to Se-oxyanion removal by cocrystallization with bisiminoguanidinium (BIG) ligands that form crystalline sulfate/selenate solid solutions. The crystallization of the sulfate, selenate and selenite, oxyanions and of sulfate/selenate mixtures with five candidate BIG ligands are reported along with the thermodynamics of crystallization and aqueous solubilities. Oxyanion removal experiments with the top two performing candidate ligands show a near quantitative removal (>99%) of sulfate or selenate from solution. When both sulfate and selenate are present, there is near quantitative removal (>99%) of selenate, down to sub-ppb Se levels, with no discrimination between the two oxyanions during cocrystallization. Reducing the selenate concentrations by 3 orders of magnitude or more relative to sulfate, as found in many wastewaters, led to no measurable loss in Se removal efficiencies. This work offers a simple and effective alternative to selective separation of trace amounts of highly toxic selenate oxyanions from wastewaters, to meet stringent regulatory discharge limits.
| Original language | English |
|---|---|
| Pages (from-to) | 879-888 |
| Number of pages | 10 |
| Journal | JACS Au |
| Volume | 3 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 27 2023 |
Funding
The design of the BIG ligands, the initial X-ray structural analyses, and thermodynamics of crystallization were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. The subsequent solubility measurements, crystallization tests, and Se-oxyanion removal experiments by cocrystallization with sulfate were supported by the National Alliance for Water Innovation (NAWI). NAWI is an Energy Innovation Hub funded by DOE’s Office of Energy Efficiency and Renewable Energy’s (EERE) Advanced Manufacturing Office (AMO). The manuscript was produced by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The publisher acknowledges the U.S. Government license to provide public access under the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). The design of the BIG ligands, the initial X-ray structural analyses, and thermodynamics of crystallization were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. The subsequent solubility measurements, crystallization tests, and Se-oxyanion removal experiments by cocrystallization with sulfate were supported by the National Alliance for Water Innovation (NAWI). NAWI is an Energy Innovation Hub funded by DOE’s Office of Energy Efficiency and Renewable Energy’s (EERE) Advanced Manufacturing Office (AMO). The manuscript was produced by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The publisher acknowledges the U.S. Government license to provide public access under the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).
Keywords
- crystal engineering
- iminoguanidines
- oxyanions
- selenate
- sulfate
