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International Journal of Environment Science and Technology
Center for Environment and Energy Research and Studies (CEERS)
ISSN: 1735-1472
EISSN: 1735-2630
Vol. 11, No. 3, 2014, pp. 633-644
Bioline Code: st14063
Full paper language: English
Document type: Research Article
Document available free of charge

International Journal of Environment Science and Technology, Vol. 11, No. 3, 2014, pp. 633-644

 en Desorption of tetracycline from montmorillonite by aluminum, calcium, and sodium: an indication of intercalation stability
Chang, P.-H.; Li, Z.; Jean, J.-S.; Jiang, W.-T.; Wu, Q.; Kuo, C.-Y. & Kraus, J.

Abstract

As the uptake of cationic drugs, such as tetracycline (TC), was attributed to cation exchange, the stability of adsorbed TC on a Ca-montmorillonite SAz-2 was studied using cationic solutions of different valence charges under different pH conditions. At the initial loading of 356 mg g-1, the amounts of TC desorbed by 0.05 M AlCl3, CaCl2, and NaCl were 133 ± 4, 83 ± 6, and 50 ± 4 mg g-1, respectively, or 37, 23, and 14 %. However, when the amount or percentage of TC desorbed was normalized to the equivalence of each cation, the values were in the range of 44–50 mg g-1 or 11–14 % per 10 mmol of charge. The kinetics of TC desorption were moderately fast and almost reached equilibrium in 6 h. The results followed the pseudo-second-order kinetic model with reaction rate in the order of AlCl3>CaCl2>NaCl at a higher initial TC loading level. The total amount of TC desorbed after five desorption cycles followed the order of AlCl3>CaCl2>NaCl, too, suggesting that cations with higher positive charges, thus, less hydrated, are preferred to remove adsorbed cationic drugs. The FTIR analyses showed larger band shift when Al3+ was used as the desorbing reagent. The XRD patterns before and after TC desorption revealed no changes in basal spacing, even after five desorption cycles, suggesting that the removal of TC from SAz-2 was largely from the external surfaces.

Keywords
Ca-montmorillonite; Cation exchange; Complexation; Desorption; Metal cations; Tetracycline

 
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