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Bifunctional NH₂-MIL-88(Fe) metal–organic framework nanooctahedra for highly sensitive detection and efficient removal of arsenate in aqueous media
Summary:
The authors from Institute of Solid State Physics, Chinese Academy of Sciences, University of Science and Technology of China, and Griffith University developed NH₂-MIL-88(Fe) nanooctahedra with dual functions of highly sensitive detection and efficient removal of arsenate, achieving a detection limit of 4.2 ppb and a saturated adsorption capacity of 125 mg/g in the field of arsenic pollution control in aqueous media.
Background:
1. To address the problem of arsenic's high toxicity and widespread pollution, previous researchers developed separate detection (e.g., fluorescence, electrochemistry) and removal (e.g., adsorption, coagulation) techniques. However, these methods lack integration, limiting practical application efficiency.
2. The authors proposed an innovative method by synthesizing amino-functionalized iron-based MOF nanooctahedra via a one-step solvothermal route, realizing simultaneous sensitive detection and efficient removal of arsenate, overcoming the limitations of single-function materials.
Research Content:
1. Synthesis:
The authors synthesized NH₂-MIL-88(Fe) nanooctahedra using a solvothermal method: FeCl₃·6H₂O and 2-aminoterephthalic acid (NH₂-BDC) were dissolved in DMF, reacted at 120°C for 20 hours, then washed and freeze-dried.
2. Characterizations:
1) BET and pore size distribution: BET surface area is 201 m²/g, average pore size is 1.4 nm, and total pore volume is 0.273 cm³/g.
2) SEM/TEM tests show the particle size of the material: The material is octahedral with an average edge length of ~150 nm, well-dispersed.
3) Other tests: XRD confirms the crystalline structure matching NH₂-MIL-88(Fe); FT-IR identifies amino groups (3456 cm⁻¹, 3373 cm⁻¹) and Fe-O bonds (537 cm⁻¹); fluorescence spectra show emission at 450 nm under 350 nm excitation; XPS verifies As-O-Fe bond formation after adsorption.
3. Application:
The material was tested in arsenate detection and removal:
- Detection: Shows a linear range of 0.1-50 μM, a detection limit of 4.2 ppb, and a response time <1 min. It exhibits excellent selectivity against interfering ions (e.g., PO₄³⁻, SO₄²⁻) and acceptable recoveries (80-94%) in real water samples (tap water, lake water).
- Removal: Achieves a saturated adsorption capacity of 125 mg/g, reducing arsenate from 5 mg/L to below the WHO drinking water standard (<10 ppb) within 60 min. It maintains >75% removal efficiency after 3 regeneration cycles.
4. Mechanism:
- Detection mechanism: Arsenate coordinates with Fe₃-μ₃-oxo clusters in NH₂-MIL-88(Fe), causing partial release of fluorescent NH₂-BDC ligands, leading to fluorescence enhancement at 450 nm.
- Removal mechanism: Arsenate is adsorbed via chemisorption, forming As-O-Fe bonds with Fe₃-μ₃-oxo clusters, as confirmed by FT-IR (new peak at 828 cm⁻¹) and XPS (As 3d peak at 45.7 eV).
Outlook:
This research realizes the integration of arsenate detection and removal using MOFs, providing a new strategy for designing dual-functional environmental materials. The excellent performance of NH₂-MIL-88(Fe) in sensitivity, efficiency, and reusability highlights its potential in practical arsenic pollution monitoring and remediation, and offers reference for the development of multifunctional MOF materials.
Bifunctional NH₂-MIL-88(Fe) metal–organic framework nanooctahedra for highly sensitive detection and efficient removal of arsenate in aqueous media
Authors: Donghua Xie, Yue Ma, Yue Gu, Hongjian Zhou, Haimin Zhang, Guozhong Wang, Yunxia Zhang, Huijun Zhao
DOI: 10.1039/c7ta07934f
Link: https://pubs.rsc.org/en/content/articlelanding/2017/ta/c7ta07934f
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