Adsorption study of selenium ions from aqueous solutions using MgO nanosheets synthesized by ultrasonic method

- Ultrasonic fabrication of MgO nanosheets by an one-step ultrasonic method.
- Both Se(IV) and Se(VI) adsorption by MgO nanosheets from aqueous solutions.
- High adsorption Qmax for Se(IV) (103.52 mg g−1) and Se(VI) (10.28 mg g−1).
- Inner-sphere surface complexes formation (SeO32−/SeO42−) on the surface of MgO nanosheets.

MgO nanosheets with thickness ranges of 3-10 molecule layers and high specific area (166.44 m2 g−1) were successfully fabricated by an ultrasound-assisted exfoliation method and used as adsorbent for the removal of both selenite (Se(IV)) and selenate (Se(VI)) from aqueous solutions. The resulting MgO nanosheets displayed high maximum adsorption capacities of 103.52 and 10.28 mg g−1 for Se(IV) and Se(VI), respectively. ATR-FTIR and XPS spectroscopic results suggested that both Se(IV) and Se(VI) formed inner-sphere surface complexes on MgO nanosheets under the present experimental conditions. Furthermore, high adsorption capacity for Se(IV/VI) in the presence of coexistent anions (SO42−, PO43−, Cl−, and F−) and efficient regeneratability of adsorbent by NaOH solution were observed in the competitive adsorption and regeneration steps. The simple one-step synthesis process of MgO nanosheets and high adsorption capacities offer a promising method for Se(IV/VI) removal in water treatment.

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