Applied Radiation and Isotopes 52 (2000) 27-30
Cleaning of liquid radioactive wastes using natural zeolites
N.V. Elizondo (a), E. Ballesteros (c), B.I. Kharisov (b)

a) Facultad de Ciencias Fisico-Matematicas, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, N.L.,
C.P. 66450, Mexico
b) Facultad de Ciencias Quimicas, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, N.L., C.P. 66450, Mexico
c) GE Nortek, S.A. de C.V. A.P. 1550, Monterrey, N.L., C.P. 64000, Mexico

* Corresponding author. Fax: +52-8-3753-846.
E-mail addresses: genortek@infosel.net.mx (E.Ballesteros), bkhariss@ccr.dsi.uanl.mx (B.I. Kharisov).

Received 18 May 1999; accepted 3 June 1999

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Abstract

Natural zeolite, clinoptilolite, was used to eliminate liquid radioactive wastes (LRW) 137Cs and 90 Sr. The influence of several factors (pH of solution, grain size of the zeolite, etc.) on the process effectivity was studied. It was shown that clinoptilolite is an effective filter of the nuclides above.

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1. Introduction

Natural zeolites, clinoptilolites, have been successfully used to eliminate several types of LRW. Thus, a porous clinoptilolite was applied to eliminate 137Cs, 90Sr and 60Co in the Institute of Atomic Energy of Japan. The elaborated method was recommended for industrial use (Breek, 1974). Several zeolitas, in particular, clinoptilolite, were used by Nikashina and Zaborskaya (1977) and Zaitsev et al. (1984) (Russia) to elucidate a sorption mechanisms of 137Cs and 90Sr. Clinoptilolite (Fig. 1, Table 1) belongs to family of the most widespread zeolites (Barrer, 1985), so, its wide use in enviromental protection as a 'filter' could be inexpensive and simultaneously ellective. An ideal composition of clinoptilolite is
Na6 [Al6 Si30 O72] 24H2O. A pore volumen (in cm3 of H2O per cm3 of the crystal) is approximately 0.34 (Barrer, 1985). In this work we studied dependence of cleaning of LRW by this zeolite on several experimental conditions.

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4. Conclusions

Clinoptilolite having grain size 0.25-1.0 mm is recommended to use to eliminate LRW of low activity containing 137Cs and 90Sr. The pH of used solutions should be aproximately 8 and flow velocity should not exceed 5 column volumes per hour. The present result demonstrate the effectivity of natural zeolites with high silicium contents (clinoptilolites) as fiters for above LRW.

References

Nikashina, V.A., Zaborskaya, E.Yu., 1977. Equilibrium and Cinetic Characteristics of Clinoptilolite in Selective Ion Extraction from Aqueous Solutions of Natural Zeolites on Water Vapor. Clinoptilolite. Metsniereva, Tbilisi, pp. 109-112.

Breek, D.W., 1974. Zeolite Molecular Sieves: Structure, Chemistry and Use. John Wiley & Sons.

Zaitsev, B.G., Kulakov, S.I., Chelizhev, N.F., 1984. Use of Clinoptilolite to Purify Small-Active Water. In: Waste Management Research Abstracts, Vol. 15. JAEA, Vienna, p. 294.

Barrer, R.M., 1985. Hydrothermal Chemistry of Zeolites. Academic Press, London.

Clinoptilolite: Morbidelli P., Ghiara M.R., Lonis R. and Sau A. - Zeolitic occurrences from Tertiary pyroclastic flows and related epiclastic deposits outcropping in northern Sardinia (Italy). v.68 (1999), 3, pp. 287-313.

Langella A., Cappelletti P., Pansini M., de' Gennaro M. & Colella C.: Heavy metals exchange reactions of a volcanoclastic clinoptilolite from northern Sardinia