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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

Results of zeta potential for SiO2, Al-, Fe-hydroxides, and Al/Si, Fe/Si coprecipitates synthesized at (a) pH 5.0 and (b) pH 8.0 under an electrolyte concentration of 0.01 M NaNO3.
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f3: Results of zeta potential for SiO2, Al-, Fe-hydroxides, and Al/Si, Fe/Si coprecipitates synthesized at (a) pH 5.0 and (b) pH 8.0 under an electrolyte concentration of 0.01 M NaNO3.

Mentions: Trends of zeta potential as a function of pH for pure hydroxides and that coprecipitated with silica are showed in Fig. 3. In general, the coprecipitation with silica tended to decrease the PZC for both Al and Fe hydroxides. While hydrolyzed at pH 5.0, for example, the PZC of Fe hydroxide was 7.4, and that was decreased to 6.4 for the Fe/Si-5.0 sample. Similar trend was also found in the systems that hydrolyzed and coprecipitated at pH 8.0 (Fig. 3b). From the perspective of coprecipitation pH, however, the PZC for samples prepared at pH 8.0 were lower than that prepared at pH 5.0. For example, the PZC of Fe/Si-8.0 is 2.4 units less than that of Fe/Si-5.0.


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)

Results of zeta potential for SiO2, Al-, Fe-hydroxides, and Al/Si, Fe/Si coprecipitates synthesized at (a) pH 5.0 and (b) pH 8.0 under an electrolyte concentration of 0.01 M NaNO3.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Results of zeta potential for SiO2, Al-, Fe-hydroxides, and Al/Si, Fe/Si coprecipitates synthesized at (a) pH 5.0 and (b) pH 8.0 under an electrolyte concentration of 0.01 M NaNO3.
Mentions: Trends of zeta potential as a function of pH for pure hydroxides and that coprecipitated with silica are showed in Fig. 3. In general, the coprecipitation with silica tended to decrease the PZC for both Al and Fe hydroxides. While hydrolyzed at pH 5.0, for example, the PZC of Fe hydroxide was 7.4, and that was decreased to 6.4 for the Fe/Si-5.0 sample. Similar trend was also found in the systems that hydrolyzed and coprecipitated at pH 8.0 (Fig. 3b). From the perspective of coprecipitation pH, however, the PZC for samples prepared at pH 8.0 were lower than that prepared at pH 5.0. For example, the PZC of Fe/Si-8.0 is 2.4 units less than that of Fe/Si-5.0.

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