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High Efficiency Adsorption and Removal of Selenate and Selenite from Water Using Metal−Organic Frameworks
Summary:
The authors from Northwestern University, Argonne National Laboratory, and King Abdulaziz University developed zirconium-based metal-organic frameworks (Zr-MOFs, especially NU-1000) with high surface area, porosity, and water stability, achieving efficient adsorption and removal of selenate and selenite from water.
Background:
1. To address the problem of controlling bioavailable selenium in drinking water (narrow range between deficiency and toxicity, EPA limit 50 ppb), previous researchers used vertical flow wetlands, bioreactors (high cost, large size) and iron oxides (low surface area, poor selenate removal), yet there are limitations.
2. The authors proposed using Zr-MOFs as adsorbents, leveraging their tunable properties and Zr(IV) affinity for oxo-anions, obtaining high adsorption capacity and fast kinetics with NU-1000.
Research Content:
1.Synthesis: UiO-66, UiO-66-(NH₂)₂, etc., were synthesized via literature methods; NU-1000 via a modified recent procedure.
2.Characterizations:
1) BET: NU-1000 had 1035±5 m²/cm³ (volumetric) and 2130±5 m²/g (gravimetric) surface area before adsorption, decreasing slightly after.
2) SEM-EDX: Se was evenly distributed in NU-1000 post-adsorption.
3) DRIFTS: Peaks at 3670 cm⁻¹ (terminal -OH) and 2745 cm⁻¹ (H-bonding) weakened/disappeared post-adsorption.
3.Application: NU-1000 adsorbed 98% of 1 ppm selenate/selenite in <5 min (residue ~20 ppb, meeting EPA standard); max capacity 95 mg/g (selenite) and 85 mg/g (selenate).
4.Mechanism: Selenate/selenite bound to Zr₆ nodes via η₂μ₂ mode, replacing terminal -OH; large pores of NU-1000 accelerated diffusion.
Outlook:
This research identifies NU-1000 as a promising adsorbent for selenium remediation, providing a basis for MOFs in removing harmful oxyanions, with significance for water treatment.
High Efficiency Adsorption and Removal of Selenate and Selenite from Water Using Metal−Organic Frameworks
Authors: Ashlee J. Howarth, Michael J. Katz, Timothy C. Wang, Ana E. Platero-Prats, Karena W. Chapman, Joseph T. Hupp, Omar K. Farha
DOI: 10.1021/jacs.5b03904
Link: https://pubs.acs.org/doi/10.1021/jacs.5b03904
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