The effect of substrate type and 2,2{prime}-bipyridine on the sorption of copper(II) on silica and alumina
- Stanford Univ., CA (United States)
The authors have studied the co-adsorption of Cu(II) and an organic ligand, 2,2{prime}-bipyridine (bipy), on amorphous silica (am-SiO{sub 2}) and {gamma}-Al{sub 2}O{sub 3} ({gamma}-alumina). This study focuses on two fundamental questions: (1) how bipy affects the macroscopic uptake behavior and molecular-scale characteristics of Cu(II) sorption complexes formed on each oxide; and (2) how and why the uptake behavior and the characteristics 9f Cu(II) sorption complexes differ for the two oxides. Solution uptake experiments and X-ray Absorption Fine Structure (XAFS) spectroscopy were used to answer these questions. In the absence of bipy and at a surface loading of approximately 0.05 {micro}M/m{sup 2}, Cu(II) adsorbs predominantly as a dimeric complex on am-SiO{sub 2} surfaces but as a monomeric complex on {gamma}-Al{sub 2}O{sub 3}. At low Cu(II) to solid ratio, bipy shifts the pH of Cu(II) sorption on am-SiO{sub 2} to lower values, but it shifts the pH of Cu(II) sorption on {gamma}-Al{sub 2}O{sub 3} to higher values. Uptake experiments and XAFS measurements on the wet sorption samples indicate that sorption of aqueous Cu(bipy){sub 2} on {gamma}-Al{sub 2}O{sub 3} displaces one bipy from the aqueous Cu(bipy){sub 2} complex, while sorption on am-SiO{sub 2} does not disrupt the complex. More detailed XAFS analysis suggests an inner-sphere Cu(bipy){sub 1} complex on {gamma}-Al{sub 2}O{sub 3} and a stronger Cu-surface oxygen interaction when Cu(bipy){sub 2} adsorbs on {gamma}-Al{sub 2}O{sub 3} than am-SiO{sub 2}.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG03-93ER14347
- OSTI ID:
- 501010
- Report Number(s):
- CONF-960401--; ISBN 1-55899-335-5
- Country of Publication:
- United States
- Language:
- English
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