I.R. evidence for migration of protons in H- and organo-montmorillonites

An investigation of Cu(II) adsorption by raw and acid-activated bentonite: A combined potentiometric, thermodynamic, XRD, IR, DTA study

“…The examination of DTA curves for the RB and Cu-RB samples indicates that the dehydroxylation of Cu-RB occurs at low temperature (612 • C) as compared to RB sample (624 • C), revealing the stronger interaction between OH and the Cu(II) ions, and a different composition of the octahedral sheet after Cu(II) adsorption [25,26]. This result show that the structure of the dehydroxylation product depends on the acidity of the adsorbed Cu(II) cation [27,28]. The dehydroxylation peak of Cu-AAB in temperature range 600-700 • C was not showed due to the dehydroxylation process started at low temperature (Fig.…”

Bleaching Properties of Alumina-Pillared Acid-Activated Montmorillonite

“…Hydrophobicity is a common characteristic of pillared clays (Yariv and Heller-Kalai, 1973). The acid activation of the clay framework is observed to further increase the hydrophobicity of the Al-pillared acid-activated montmorillonite (Schutz et al, 1987).…”

Perturbation of Structural Fe3+ in Smectites by Exchange Ions

“…3B), suggesting that the protons have penetrated the hexagonal holes of the structure upon dehydration. Pro_ tons of H30 + montmorillonite are known to migrate to structural OH groups associated with Mg 2+ (Russell and Fraser, 1971;Yariv and Heller-Kallai, 1973). This process is especially pronounced when dehydration by heating decomposes the hydronium ions, and the bare protons easily migrate through surface hexagonal holes to the source of negative charge--hydroxyl groups and oxygen atoms coordinated to octahedral Mg 2+.…”

“…This mechanism explains the effective neutralization of octahedral charge as observed by esr, while the divalent charge localized on Ca 2+ causes the perturbation of structural OH that is greater than that for Na+-clay. Structural OH groups approached by protons are so influenced as to demonstrate no observable OH deformation band (Yariv and Heller-Kallai, 1973). The proposed mechanism should be reversible so that rehydration of the clay reverses the equation described above.…”