Influence of Ca2+ on tetracycline adsorption on montmorillonite

• Published in: Journal of colloid and interface science 2012-02, Vol.368 (1), p.420-426
• Main Authors: Parolo, M. Eugenia, Avena, Marcelo J., Pettinari, Gisela R., Baschini, Miria T.
• Format: Article
• Language: English
• Subjects: Adsorption; Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - metabolism; Antibiotics; Bentonite - chemistry; Bentonite - metabolism; calcium; Calcium - pharmacology; cation exchange; Cation exchanging; Chemistry; Clays; Diffraction; Electron microscopy; Exact sciences and technology; General and physical chemistry; Hydrogen-Ion Concentration; Intercalation; Microscopy, Electron, Transmission; Montmorillonite; sodium chloride; Surface physical chemistry; Tetracycline; Tetracycline - chemistry; Tetracycline - metabolism; Tetracyclines; transmission electron microscopy; X-Ray Diffraction; X-rays
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2011.10.079

[Display omitted] ► The adsorption of TC on montmorillonite was studied as a function of pH and Ca2+. ► In the presence of Ca2+, two different TC adsorption processes took place. ► TC adsorption became independent of Ca2+ concentration only at pH 5. ► XRD and TEM indicate that TC was intercalated in the interlayer space. The adsorption of tetracycline (TC) on montmorillonite was studied as a function of pH and Ca2+ concentration using a batch technique complemented with X-ray diffraction and transmission electron microscopy. In the absence of Ca2+, TC adsorption was high at low pH and decreased as the pH increased. In the presence of Ca2+, at least two different adsorption processes took place in the studied systems, i.e., cation exchange and Ca-bridging. Cation exchange was the prevailing process at pH5, and thus, TC adsorption increased by increasing Ca2+ concentration. The pH 5 represents an isoadsorption pH where both adsorption processes compensate each other. TC adsorption became independent of Ca2+ concentration at this pH. For TC adsorption on Ca2+-montmorillonite in 0.01M NaCl experiments, the ratio adsorbed TC/retained Ca2+ was close to 1 in the pH range of 5–9, indicating an important participation of Ca2+ in the binding of TC to montmorillonite. X-ray diffraction and transmission electron microscopy showed that TC adsorption induced intercalation between montmorillonite layers forming a multiphase system with stacking of layers with and without intercalated TC.