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Interaction between glycine and Na-, Ca-and Cu-rich smectites

Department of Earth Sciences, University of Modena and Reggio Emilia, Via S. Eufemia 19, I 41100, Modena, Italy

^* E-mail: brigatti{at}unimo.it

(Received 11 May 1999; revised 27 March 2000)

The interactions between glycine and two Na-, Ca- and Cu-exchanged smectites with different layer-charge location were studied. The sorption of glycine depends on the nature of the interlayer cations (Ca < Na < Cu), and on the type of smectite. Sequential extraction procedures were carried out in order to test the possibility of removing metals and/or glycine from the smectite interlayer. By the end of the treatments, the release of the amino acid from the substrates, with the exception of Cu-rich smectite, was virtually complete. The thermal curves of glycine-smectites confirm the stronger bonding of the amino acid with Cu-exchanged samples, and FTIR spectra indicate that glycine is mainly sorbed in the zwitterionic form. The data obtained suggest that in investigations into mechanisms of the binding of metals by minerals and their subsequent mobilization, amino acids merit close attention.

KEYWORDS: glycine, homoionic smectites, layer charge, FTIR, thermal analysis