Tetracycline adsorption on montmorillonite: pH and ionic strength effects

Authors
Parolo, Maria Eugenia; Savini, Monica Claudia; Valles, Jorge Manuel; Baschini, Miria Teresita; Avena, Marcelo Javier
Publication Year
2008
Language
English
Format
article
Status
Published version
Description
The adsorption of tetracycline (TC) on a Patagonian montmorillonite is studied as a function of pH, ionic strength and TC concentration by using X-ray diffraction, UV-Visible spectroscopy, ATR-FTIR spectroscopy, batch experiments and adsorption modeling. X-ray diffraction reveals that TC species can intercalate into the interlayer space of montmorillonite as deduced from the change in the basal spacing from 12.6 Å to 19.5 Å, in the absence or presence of TC respectively. UV-Visible and ATR-FTIR spectroscopies show that the corresponding spectra of TC change upon adsorption, suggesting important montmorillonite-TC interactions in the adsorbed state. Batch experiments, on the other hand, reveal that there is an important adsorption of TC in a wide range of pH. Since at low pH (pH < 4) the prevailing species of TC is a cation with a net charge of + 1, the adsorption is rather high at this pH, reaching nearly the cation exchange capacity of the mineral. The adsorption then decreases as the pH is increased and eventually becomes negligible at pH 11. Experiments and modeling suggest that not only the cationic species but also the neutral and monoanionic species of TC adsorb on the negatively charged montmorillonite surface. Although there is a significant electrostatic interaction between TC and montmorillonite, a rather strong non-electrostatic interaction also exists. At all pH values TC species compete with sodium ions for surface sites, and thus there is an important effect of ionic strength on the adsorption. © 2007 Elsevier B.V. All rights reserved.
Fil: Parolo, Maria Eugenia. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Química; Argentina
Fil: Savini, Monica Claudia. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Química; Argentina
Fil: Valles, Jorge Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Química; Argentina
Fil: Baschini, Miria Teresita. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Química; Argentina
Fil: Avena, Marcelo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina
Subject
ADSORPTION
ATR-FTIR
MONTMORILLONITE
TETRACYCLINES
UV-VISIBLE SPECTROSCOPY
XRD
Otras Ciencias Químicas
Ciencias Químicas
CIENCIAS NATURALES Y EXACTAS
Access level
Restricted access
License
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Repository
CONICET Digital (CONICET)
Institution
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identifier
oai:ri.conicet.gov.ar:11336/66052