Hostname: page-component-848d4c4894-mwx4w Total loading time: 0 Render date: 2024-06-21T04:36:16.943Z Has data issue: false hasContentIssue false

An Electron Paramagnetic Resonance Spectroscopy Investigation of the Retention Mechanisms of Mn and Cu in the Nanopore Channels of Three Zeolite Minerals

Published online by Cambridge University Press:  01 January 2024

Daniel R. Ferreira*
Department of Biology and Chemistry, Southern Polytechnic State University, Building E, Suite 183, 1100 South Marietta Pkwy, Marietta, GA 30060, USA
Cristian P. Schulthess
Department of Plant Science and Landscape Architecture, University of Connecticut, 1376 Storrs Road, Storrs, CT 06269-4067, USA
James E. Amonette
Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999 Richland, WA 99352, USA
Eric D. Walter
Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999 Richland, WA 99352, USA
*E-mail address of corresponding author:


The adsorption mechanisms of divalent cations in zeolite nanopore channels can vary as a function of their pore dimensions. The nanopore inner-sphere enhancement (NISE) theory predicts that ions may dehydrate inside small nanopore channels in order to adsorb more closely to the mineral surface if the nanopore channel is sufficiently small. The results of an electron paramagnetic resonance (EPR) spectroscopy study of Mn and Cu adsorption on the zeolite minerals zeolite Y (large nanopores), ZSM-5 (intermediate nanopores), and mordenite (small nanopores) are presented. The Cu and Mn cations both adsorbed via an outer-sphere mechanism on zeolite Y based on the similarity between the adsorbed spectra and the aqueous spectra. Conversely, Mn and Cu adsorbed via an inner-sphere mechanism on mordenite based on spectrum asymmetry and peak broadening of the adsorbed spectra. However, Mn adsorbed via an outer-sphere mechanism on ZSM-5, whereas Cu adsorbed on ZSM-5 shows a high degree of surface interaction that indicates that it is adsorbed closer to the mineral surface. Evidence of dehydration and immobility was more readily evident in the spectrum of mordenite than in that of ZSM-5, indicating that Cu was not as close to the surface on ZSM-5 as it was when adsorbed on mordenite. Divalent Mn cations are strongly hydrated and are held strongly only in zeolites with small nanopore channels. Divalent Cu cations are also strongly hydrated, but can dehydrate more easily, presumably due to the Jahn-Teller effect, and are held strongly in zeolites with medium-sized nanopore channels or smaller.

Copyright © Clay Minerals Society 2012

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Alberti, A. Davoli, P. and Vezzalini, G., 1986 The crystal structure refinement of a natural mordenite Zeitschrift für Kristallographie 175 249256.CrossRefGoogle Scholar
Bergaoui, L. Lambert, J.-F. Suquet, H. and Che, M., 1995 CuII on Al13-pillared saponites: Macroscopic adsorption measurements and EPR spectra Journal of Physical Chemistry 99 21552161.CrossRefGoogle Scholar
Burgess, J., 1978 Metal Ions in Solution Sussex, England Ellis Horwood Limited.Google Scholar
Carl, P.J. and Larsen, S.C., 2000 EPR study of copper-exchanged zeolites: Effects of correlated g- and A-strain, Si/Al ratio, and parent zeolite Journal of Physical Chemistry 104 65686575.CrossRefGoogle Scholar
Collins, K.D., 1997 Charge density-dependent strength of hydration and biological structure Biophysical Journal 72 6576.CrossRefGoogle ScholarPubMed
Cotton, F.A. and Wilkinson, G., 1988 Advanced Inorganic Chemistry 5th edition New York John Wiley & Sons.Google Scholar
Doula, M.K. and Dimirkou, A., 2008 An EPR study of Cu adsorption by clinoptilolite from Cl-, NO3- and SO42- solutions Journal of Porous Materials 15 457466.CrossRefGoogle Scholar
Ferreira, D.R., 2012 The nanopore inner-sphere enhancement (NISE) effect and its role in sodium retention PhD Dissertation USA University of Connecticut 181 pp..Google Scholar
Ferreira, D.R. and Schulthess, C.P., 2011 The nanopore inner sphere enhancement effect on cation adsorption: Sodium, potassium, and calcium Soil Science Society of America Journal 75 389396.CrossRefGoogle Scholar
Ferreira, D.R. Schulthess, C.P. and Giotto, M.V., 2012 An investigation of strong sodium retention mechanisms in nanopore environments using nuclear magnetic resonance spectroscopy Environmental Science & Technology 46 300306.CrossRefGoogle ScholarPubMed
Ferreira, D.R. Schulthess, C.P. and Kabengi, N.J., 2013.Calorimetric evidence in support of the nanopore innersphere enhancement (NISE) theory on cation adsorption Soil Science Society of America JournalCrossRefGoogle Scholar
Hronský, V. Rákoš, M. Belák, J. and Kazár, D., 1978 EPR study of Mn2+ ions adsorption on silica gel Czechoslovak Journal of Physics B 28 12771286.CrossRefGoogle Scholar
Hummer, G. Pratt, L.R. and García, A.E., 1996 Free energy of ionic hydration Journal of Physical Chemistry 100 12061215.CrossRefGoogle Scholar
Larsen, S.C. Aylor, A. Bell, A.T. and Reimer, J.A., 1994 Electron paramagnetic resonance studies of copper ion-exchanged ZSM-5 Journal of Physical Chemistry 98 1153311540.CrossRefGoogle Scholar
Rabenstein, M.D. and Shin, Y.-K., 1995 Determination of the distance between two spin labels attached to a macromolecule Proceedings of the National Academy of Sciences USA 92 82398243.CrossRefGoogle ScholarPubMed
Schulthess, C.P., 2005 Soil Chemistry with Applied Mathematics Victoria, BC, Canada Trafford Publishers.Google Scholar
Schulthess, C.P. Taylor, R.W. and Ferreira, D.R., 2011 The nanopore inner sphere enhancement effect on cation adsorption: Sodium and nickel Soil Science Society of America Journal 75 378388.CrossRefGoogle Scholar
Simoncic, P. and Armbruster, T., 2004 Peculiarity and defect structure of the natural and synthetic zeolite mordenite: A single-crystal X-ray study American Mineralogist 89 421431.CrossRefGoogle Scholar
Sposito, G., 1989 Surface reactions in natural aqueous colloidal systems Chimia 43 169176.Google Scholar
Turkevich, J. Ono, Y. and Soria, J., 1972 Futher electron spin resonance studies of Cu(II) in Linde Y zeolite Journal of Catalysis 25 4454.CrossRefGoogle Scholar
Wang, Y. Bryan, C. and Xu, H., 2003 Nanogeochemistry: Geochemical reactions and mass transfer in nanopores Geology 31 387390.2.0.CO;2>CrossRefGoogle Scholar