title: Structural studies of Na-montmorillonite exchanged with Fe2+, Cr3+, and Ti4+ by N2 adsorption and EXAFS.
abstract: The structures of Fe(2+)-, Cr(3+)-, and Ti(4+)-modified montmorillonite prepared from ion exchange of the Na-clay with Fe(2+), Cr(3+), and Ti(4+) were investigated. Conventional BET surface area and spectroscopic analysis by extended adsorption fine structure (EXAFS) were applied. It was shown that the BET surface area of Na-clay was similar to that of Fe-clay, but somewhat different from those of Cr- and Ti-clay; it decreased in the order Na- > Fe- > Ti- > Cr-montmorillonite. This sequence appeared to be consistent with the ion size Na(+) (0.95 nm)>Fe(2+) (0.65 nm)>Cr(3+) (0.62 nm), except for Ti(4+) (0.69 nm). EXAFS data showed that some Si atoms within montmorillonite were replaced by Ti atoms and that a neostructure of titanium oxide was formed.
authors.affiliation: Department of Chemical Engineering, Yuan Ze University, Chung-Li 320, Taiwan.
authors.forename: Ruey-Shin
authors.initials: RS
authors.lastname: Juang
authors.forename: Su-Hsia
authors.initials: SH
authors.lastname: Lin
authors.forename: Fu-Chuang
authors.initials: FC
authors.lastname: Huang
authors.forename: Chieng-Hsien
authors.initials: CH
authors.lastname: Cheng