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Selenium(VI) Removal from Challenge Waters by Continuous-Flow-Through Iron Electrocoagulation
Xicheng He1, Yihang Yuan1, Maya Mehrotra1
1Department of Energy, Environmental and Chemical Engineering, Washington University at St. Louis, St. Louis, Missouri 63130, United States.
Environmental Science & Technology
|August 11, 2025
Summary
Iron electrocoagulation effectively removes selenate from water, but bicarbonate and sulfate significantly inhibit the process by altering iron solid reactivity. Optimizing iron dosage and sulfate pretreatment are key for real-world applications.
Area of Science:
- Environmental Science
- Water Treatment Technologies
- Inorganic Chemistry
Background:
- Selenium(VI) (selenate) is a contaminant of concern in various water bodies.
- Iron electrocoagulation (EC) shows potential for selenate removal.
- Understanding water matrix effects is crucial for effective EC application.
Purpose of the Study:
- To investigate the performance of flow-through iron EC for selenate removal under environmentally relevant conditions.
- To determine the influence of water composition on selenate removal efficiency.
- To elucidate the mechanisms by which water components affect selenate removal.
Main Methods:
- Flow-through iron electrocoagulation experiments were conducted.
- The effects of major anions (bicarbonate, sulfate, nitrate) and humic acid were examined individually and in complex water matrices.
- Analysis of iron solids formation, redox properties, and adsorption mechanisms was performed.
Main Results:
- Bicarbonate inhibited selenate removal by forming less reactive iron solids (green rust).
- Sulfate hindered iron solid oxidation and transformation, reducing reactivity with selenate.
- Sulfate and high ionic strength were major inhibitors in real wastewater, requiring higher iron doses.
- Sulfate pretreatment improved EC performance for agricultural and mining wastewater but not for FGD wastewater.
Conclusions:
- Water composition significantly impacts iron electrocoagulation efficiency for selenate removal.
- Bicarbonate and sulfate are key inhibitory species requiring management strategies.
- Insights into solids formation, redox, and adsorption provide guidance for practical water treatment design.
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