Effects of Anions on Local Structure of Al and Si in Aluminosilicates

✍ Scribed by Akane Miyazaki; Takushi Yokoyama

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 62 KB
• Volume: 214
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1999.6194

✦ Synopsis

Three kinds of amorphous aluminosilicates were synthesized by coprecipitation of silicic acid with aluminum hydroxide in the presence of different inorganic ions: sulfate, chloride, and nitrate. Although the bulk composition of the aluminosilicates obtained was not affected by anion species, their DTA spectra were significantly different, suggesting that their structures also differ. The local structure of Al and Si in the aluminosilicates was studied in detail by 27 Al and 29 Si MAS NMR. From the 27 Al MAS NMR spectra and comparison between 29 Si HD-and CP-MAS NMR spectra, it was concluded that the aluminosilicate obtained in the presence of sulfate ions has only a montmorillonite-like structure, whereas in the cases of chloride and nitrate, the solids are composed of three phases: aluminum hydroxide, silica, and the montmorillonite-like aluminosilicate. The difference in the local structure of Al and Si in the aluminosilicates was explained by the difference in interaction between the anions and aluminum ions.