abstract
Borate anions supplied by boric acid and ammonium tetraborate solutions were intercalated into Mg-Al-A-layered double hydroxides, where A=nitrate, adipate or terephtalate, by co-precipitation and ion exchange methods at varying pH values. Elemental analyses, powder X-ray diffraction, and FUR spectra indicated that borate ion intercalating LDHs were succesfully produced by both methods. Well-textured materials were obtained by an ion-exchange technique particularly upon exchange with tetraborate solutions at pH 9. (27)Al MAS NMR studies showed that the layers retained their integrity during the exchange process although there were variations in composition and crystallinity. The nature of the intercalated borate species was deduced from (11)B MAS NMR data. The results showed that independently of the applied pH, observation of signals from both of BO(3) and BO(4), groups was consistent in all cases. The anions were intercalated as polyborate units like [B(3)O(3)(OH)(4)](-) or [B(4)O(5)(OH)(4)](2-), even at pH 12 where the monoborate anions, [B(OH)(4)](-), are expected to exist dominantly. (c) 2010 Elsevier B.V. All rights reserved.
keywords
HYDROTALCITE-LIKE COMPOUNDS; MG-AL RATIO; BORON REMOVAL; INTERCALATION CHEMISTRY; CYCLOHEXANONE-OXIME; NMR-SPECTROSCOPY; EXCHANGE; TEREPHTHALATE; COORDINATION; ADSORPTION
subject category
Chemistry; Materials Science; Mineralogy
authors
Ay, AN; Zumreoglu-Karan, B; Temel, A; Mafra, L
our authors
Luís Mafra
Principal Researcheracknowledgements
The authors gratefully acknowledge Prof. J. Rocha (Aveiro University) for providing the laboratory facilities. Ahmet Nedim Ay thanks TUBITAK research fellowship for young scientists.