Contaminant Adsorption on Nanoscale Particles: Structural and Theoretical Characterization of Cu2+ Bonding on the Surface of Keggin-Type Polyaluminum (Al30) Molecular Species

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• 作者：Samangi Abeysinghe ; Katie W. Corum ; Diane L. Neff ; Sara E. Mason ; Tori Z. Forbes
• 刊名：Langmuir
• 出版年：2013
• 出版时间：November 19, 2013
• 年：2013
• 卷：29
• 期：46
• 页码：14124-14134
• 全文大小：628K
• 年卷期：v.29,no.46(November 19, 2013)
• ISSN：1520-5827

文摘

The adsorption of contaminants onto metal oxide surfaces with nanoscale Keggin-type structural topologies has been well established, but identification of the reactive sites and the exact binding mechanism are lacking. Polyaluminum species can be utilized as geochemical model compounds to provide molecular level details of the adsorption process. An Al₃₀ Keggin-type species with two surface-bound Cu²⁺ cations (Cu₂Al₃₀-S) has been crystallized in the presence of disulfonate anions and structurally characterized by single-crystal X-ray diffraction. Density functional theory (DFT) calculations of aqueous molecular analogues for Cu₂Al₃₀-S suggest that the reactivity of Al₃₀ toward Cu²⁺ and SO₄^{2鈥?/sup> shows opposite trends in preferred adsorption site as a function of particle topology, with anions preferring the beltway and cations preferring the caps. The bonding competition was modeled using two stepwise reaction schemes that consider Cu₂Al₃₀-S formation through initial Cu2+ or SO₄2鈥?/sup> adsorption. The associated DFT energetics and charge density analyses suggest that strong electrostatic interactions between SO₄2鈥?/sup> and the beltway of Al₃₀ play a vital role in governing where Cu2+ binds. The calculated electrostatic potential of Al₃₀ provides a theoretical interpretation of the topology-dependent reactivity that is consistent with the present study as well as other results in the literature.}