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Molecular Structures of Al/Si and Fe/Si Coprecipitates and the Implication for Selenite Removal.

Chan YT, Kuan WH, Tzou YM, Chen TY, Liu YT, Wang MK, Teah HY - Sci Rep (2016)

Bottom Line: In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse.Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates.The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates.

View Article: PubMed Central - PubMed

Affiliation: Department of Soil and Environmental Sciences, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 40227, Taiwan, R.O.C.

ABSTRACT
Aluminum and iron oxides have been often used in the coagulation processes during water purification due to their unique surface properties toward anions. In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse. In this study, surface properties and molecular structures of Al/Si and Fe/Si coprecipitates were characterized using spectroscopic techniques. Also, the selenite removal efficiency of Al/Si and Fe/Si coprecipitates in relation to their surface and structural properties was investigated. While dissolved silicate increased with increasing pH from Fe/Si coprecipitates, less than 7% of silicate was discernible from Al/Si samples over the range from acidic to alkaline conditions. Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates. In Al/Si coprecipitates, core-shell structures were developed with AlO6/AlO4 domains as the shells and Si frameworks polymerized from the SiO2 as the cores. However, Si framework remained relatively unchanged upon coprecipitation with Fe hydroxides in Fe/Si samples. The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates.

No MeSH data available.


Related in: MedlinePlus

Normalized XANES spectra at Si K-edge for (a) SiO2, Al/Si coprecipitates (Al/Si-5.0, -6.5, and -8.0), and (b) Fe/Si coprecipitates (Fe/Si-5.0, -6.5, and -8.0). The Fe K-edge XANES and k2-weighted EXAFS data for Fe/Si coprecipitates (Fe/Si-5.0, -6.5, and -8.0) were shown in (c,d).
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f6: Normalized XANES spectra at Si K-edge for (a) SiO2, Al/Si coprecipitates (Al/Si-5.0, -6.5, and -8.0), and (b) Fe/Si coprecipitates (Fe/Si-5.0, -6.5, and -8.0). The Fe K-edge XANES and k2-weighted EXAFS data for Fe/Si coprecipitates (Fe/Si-5.0, -6.5, and -8.0) were shown in (c,d).

Mentions: Normalized Si and Fe K-edge X-ray absorption near-edge structure (XANES) data for the Al/Si or Fe/Si coprecipitates synthesized at various pH were shown in Fig. 6. For the Si K-edge spectra, all samples showed a sharp white line (WL) centered at 1847.5‚ÄČeV, wherein the WL intensity for both Al/Si and Fe/Si samples tended to increased with increasing coprecipitation pH (Fig. 6a,b).


Molecular Structures of Al/Si and Fe/Si Coprecipitates and the Implication for Selenite Removal.

Chan YT, Kuan WH, Tzou YM, Chen TY, Liu YT, Wang MK, Teah HY - Sci Rep (2016)

Normalized XANES spectra at Si K-edge for (a) SiO2, Al/Si coprecipitates (Al/Si-5.0, -6.5, and -8.0), and (b) Fe/Si coprecipitates (Fe/Si-5.0, -6.5, and -8.0). The Fe K-edge XANES and k2-weighted EXAFS data for Fe/Si coprecipitates (Fe/Si-5.0, -6.5, and -8.0) were shown in (c,d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837376&req=5

f6: Normalized XANES spectra at Si K-edge for (a) SiO2, Al/Si coprecipitates (Al/Si-5.0, -6.5, and -8.0), and (b) Fe/Si coprecipitates (Fe/Si-5.0, -6.5, and -8.0). The Fe K-edge XANES and k2-weighted EXAFS data for Fe/Si coprecipitates (Fe/Si-5.0, -6.5, and -8.0) were shown in (c,d).
Mentions: Normalized Si and Fe K-edge X-ray absorption near-edge structure (XANES) data for the Al/Si or Fe/Si coprecipitates synthesized at various pH were shown in Fig. 6. For the Si K-edge spectra, all samples showed a sharp white line (WL) centered at 1847.5‚ÄČeV, wherein the WL intensity for both Al/Si and Fe/Si samples tended to increased with increasing coprecipitation pH (Fig. 6a,b).

Bottom Line: In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse.Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates.The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates.

View Article: PubMed Central - PubMed

Affiliation: Department of Soil and Environmental Sciences, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 40227, Taiwan, R.O.C.

ABSTRACT
Aluminum and iron oxides have been often used in the coagulation processes during water purification due to their unique surface properties toward anions. In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse. In this study, surface properties and molecular structures of Al/Si and Fe/Si coprecipitates were characterized using spectroscopic techniques. Also, the selenite removal efficiency of Al/Si and Fe/Si coprecipitates in relation to their surface and structural properties was investigated. While dissolved silicate increased with increasing pH from Fe/Si coprecipitates, less than 7% of silicate was discernible from Al/Si samples over the range from acidic to alkaline conditions. Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates. In Al/Si coprecipitates, core-shell structures were developed with AlO6/AlO4 domains as the shells and Si frameworks polymerized from the SiO2 as the cores. However, Si framework remained relatively unchanged upon coprecipitation with Fe hydroxides in Fe/Si samples. The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates.

No MeSH data available.


Related in: MedlinePlus