O. Yavuz Ataman a b & Harry B. Mark Jr. a a Department of Chemistry, University of

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1 This article was downloaded by: [Orta Dogu Teknik Universitesi] On: 10 October 2014, At: 03:50 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Analytical Letters Publication details, including instructions for authors and subscription information: Ion Exchange Between Ammonium Zeolite and the Supporting Matrix in KBr Pellets O. Yavuz Ataman a b & Harry B. Mark Jr. a a Department of Chemistry, University of Cincinnati, Cincinnati, Ohio, b Dept. of Chemistry, Middle East Technical University, Ankara, Turkey Published online: 06 Dec To cite this article: O. Yavuz Ataman & Harry B. Mark Jr. (1976) Ion Exchange Between Ammonium Zeolite and the Supporting Matrix in KBr Pellets, Analytical Letters, 9:12, , DOI: / To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the Content ) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.

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3 ANALYTICAL LETTERS, 9 (12), (1976) ION EXCHANGE BETWEEN AMMONIUM ZEOLITE AND THE SUPPORTING MATRIX IN KBr PELLETS Key Words: Infrared, Zeolite, Ion Exchange, KBr Pellet t 0. Yavuz Ataman and Harry B. Mark, Jr." Department of Chemistry University of Cincinnati Cincinnati, Ohio A R S T RA C T An investigation of the solid state ion exchange of NH4' adsorbed by Zeolite with the Kf carried out. of the KBr pellets has been This ion exchange process can be a source of serious error in using infrared measurement for the quantita- tive analysis of species adsorbed on solid matrix. Methods for avoiding this error are described. Alkali Halide Pelleting is a very commonly used technique for the infrared investigation of solid samples Anoma- lies in the infrared spectra arising from ion exchange in alkali 3-7 halide pellets have been reported in several cases. An un- *To whom correspondence should be addressed. tpresent address: Dept. of Chemistry, Middle East Technical University, Ankara, Turkey 1135 Copyright by Marcel Dekker, Inc. All Rights Reserved. Neither this work nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical. including photocopying, microfilming, and recording, or by any information storage ;and retrieval system. without permission in writing from the publisher.

4 1136 ATAMAN AND MARK usual example of this arose from experimental difficulty encountered during the development of a new technique for the determination of ammonia in aqueous solutions by infrared spectroscopy following a preconcentration step on zeolite matrix 8* 9. In our particular application solutions having concentrations be- tween 1-14 ppm NH3-N were treated with zeolite AAA, whose formula is Na.(A102).(SiO2)3.,-,.3.9H20, to preconcentrate the NH4+ species on the zeolite matrix, by using a batch process yielded irreproducible results. The source of the error was investigated and is disclosed here. This particular phenomena would be a general source of unsuspected loss in accuracy and precision for any method using a porous preconcentration matrix with IR measurement. During the preliminary experiments it was observed that 1402 cm-l bending vibration band of the NH4+ species exhibited a marked increase in intensity with time. This growth of peak intensity was found to be more rapid when the KBr pellets normally stored in a dessicator were exposed to the air. Typical example results illustrating the rate of peak growth in air are shown in Figure 1. It is obvious that the rate of growth was sufficiently high to be observed when repetitive spectra were taken only a few days after the preparation of KBr pellets. As the object of this type of preconcentration sampling is to give stable sample system for direct nondestructive analysis, this time dependence of the spectra resulted in a large source of error. It was also noted that the precision of duplicate determinations was poor

5 AMMONIUM ZEOLITE AND KBr PELLET ION EXCHANGE 1137 Lo t Peak littensity (Arbitrary Unitsl I L 1 L $ Time (Days) FIG. 1 NH4' bending vibration peak growth with time. The data were taken 'n with four KBr pellets from the same batch. Several trials with different KBr pellet groups, which were kept in and out of the dessicators, suggested that humidity possibly affects the growth in peak intensities. In order to verify the effect of humidity, one of the sample pellets was tested in a very humid environment. A vacuum dessicator containing water in its bottom was used as a high humidity atmosphere. The pellet was placed inside the dessicator, without touching water, and the valve at the top of the dessicator was opened to air. The combination was left overnight on the lab bench, before the infrared spectrum of the pellet was taken. After humidity treatment, 1402 cm-l peak showed a significant increase in intensity (Fig. 2). The change in the slope of the background is due to an intense 1640 cm-l H20 bending vibration

6 1138 ATAMAN AND MARK 0.5 L;I 0 z 0.4 Q in CT 0 cr) L cm FIG. 2 Humidity treatment for KBr pellets containing NH4+-Zeolite a) KBr pellet before humidity treatment. b) KBr pellet after humidity treatment. band arising from the high humidity environment in which the pellet was kept. Also, as the surface of the pellet was slightly damaged by high humidity, its transparency was lowered by surface reflections, resulting in a higher background noise in the spectrum.

7 AMMONIUM ZEOLITE AND KBr PELLET ION EXCHANGE 1139 This experiment clearly demonstrated that whatever the change is caused by, the amount of moisture in the KBr affects it. As the moist KBr pellet is somewhat analogous to concen- trated aqueous systems, it was reasonable to suggest that an ion exchange reaction is taking place. As the moisture content is raised, NH4' which is in the interior cavities of the amorphous zeolite becomes more mobile and NH4' diffused out of the cavities and NH4Br formed in the matrix with the K' ions diffusing into the zeolite matrix. In order to check the validity of the ion exchange hypothesis, self supporting pellets of several zeolites containing NH4' in their matrix were prepared. About 3 mg of zeolite was pressed in a hole in the middle of a paper circle 13 mm in diameter using the standard pressing technique in the pellet die. Although these self supporting pellets did not give quantitative results, examinations of the band positions for NH4' were sufficient to answer to the problem. The values of the NH4' bending vibration band for the self supporting pellets and KBr pellets shown in Table I are distinctly different. A KBr pellet containing pure NH4Br also exhibits a peak at 1402 cm-'. Therefore, the 1402 cm-' peak observed in the KBr zeolite pellets is representative of HN4Br, not NHb'-zeolite. The poor precision of duplicate determinations is, thus, a function non-uniformity of particle size of the zeolite. Control of the zeolite partical size resulted in excellent precision (approximately 6% mean deviation for samples containing l to 15 ppm NH3-N).

8 1140 ATAMAN AND MARK TABLE I. Wavenumbers for NHk' Bending Vibration on Several Zeolites Wavenumbers (cm- l) Zeolite Self Supporting Pellets KBr-Zeolite Pellets 3A A A 13X AAA ACKNOWLEDGMENT One of us, 0. Yavuz Ataman, gratefully acknowledges the support of the Agency for International Development. search was supported in part by the National Science Foundation, Grant No. MPS REFERENCES This re- 1. R. G. J. Miller and B. C. Stace, Editors, "Laboratory Methods in Infrared Spectroscopy, Heyden and Son, Ltd., New York, Y. Ataman and H. B. Mark, Jr., "Alkali Halide Pelleting Technique for Solid Sampling in Infrared Spectroscopy. A Review. It, to be published. 3. L. F. Power and A. M. Tait. Anal. Chem. 5, 1721 (1975). 4. F. Vratny, J. Inorg. Nucl. Chem. 10, 328 (1959).

9 AMMONIUM ZEOLITE AND KBr PELLET ION EXCHANGE R. 0. French, M. E. Wadsworth, M. A. Cook and I. B. Cuttler, J. Phys. Chem. 58, 805 (1954) W. A. Pliskin andr. P. Eischens, ibid., (1955). 7. V. W. Meloche, G. E. Kalbus, J. Inorg. Nucl. Chem. - 6, 104 (1958) Y. Ataman and H. B. Mark, Jr., "Determination of Ammonia in Aqueous Solutions by Infrared Spectroscopy Following Preconcentration on Zeolite, I' to be published Y. Ataman, Ph. D. thesis, 1975, Received October 15, 1976 Accepted October 19, 1976