Adsorption Of Manganese On Transcarpathian Clinoptilolite
ADSORPTION OF MANGANESE ON TRANSCARPATHIAN CLINOPTILOLITE
V.O. Vasylechko, G.V. Gryshchouk, Yu.B. Kuz\’ma, Yu.O. Sulym
Lviv Ivan Franko National University, Lviv, Ukraine
In contrast to typical ion-change substances natural zeolites are characterised both by ion-exchange and molecular sieve properties. That gives wide opportunities for elaboration selective methods of concentration, separation and determination of heavy metals and some organic substances. Stability towards aggressive media, regeneration possibilities, low prices and high adsorption capacity of natural zeolites provide their use as adsorbents in solid-phase extraction. In previous works we proposed methods of concentration and separation of cadmium, copper and chloroform from aqueous solutions, based on Ukrainian Transcarpathian natural zeolites [1-3].
In the present work we have determined the possibility of use of clinoptilolite (deposit near the village Sokyrnytsya in the Ukrainian Transcarpathian region) for concentration of manganese (II) trace amounts from aqueous solutions. Adsorption properties of both non-modified and modified by acids clinoptilolite towards manganese (II) ions have been studied. Our investigations have demonstrated that manganese (II) ions were adsorbed more effectively by clinoptilolite from chloride and nitrate solutions compare to sulphate ones. Perhaps, insignificant influence of sulphates is caused by higher stability of Mn(II) sulphate complexes compared to chloride and nitrate complexes. Adsorption capacity of the clinoptilolite modified by acids depends on the nature of the acid. Maximum value of adsorption capacity was observed for clinoptilolite modified by HNO3. The highest adsorption capacity of non-modified clinoptilolite towards Mn(II) was obtained for solutions of moderate acidity (pH 5.3-6.3). The plot of the dependence of adsorption capacity of H-form of clinoptilolite from the Mn(II) solution acidity demonstrates clear maximum at pH 4.4. The similarity of mentioned curves for non-modified and modified by acids clinoptilolite indicates, that these adsorbents more effectively adsorb aqueous complexes of Mn(II).
It is known, that adsorption properties of natural zeolites depend on their previous thermal treatment. Perhaps, thermal treatment of the zeolites with gradual increasing of the temperature leads to evaporation of physically linked water, dehydroxilation of the clinoptilolite and its amorphization. Both thermally treated up to 180° C and non-treated non-modified clinoptilolites do not change their adsorption capacities towards Mn(II) and decrease the value of the capacity after treatment at higher temperatures. Maximum adsorption capacity of modified by acids clinoptilolite was observed for non thermally treated samples. The treatment of the samples even at 50° C leads to considerable decreasing of the efficiency of Mn(II) sorption. Analogous regularity was found for the H-form of clinoptilolite towards Cd(II). At optimum conditions the maximum value of adsorption capacity of non-modified clinoptilolite towards Mn(II) is 580 mg/g and of modified by acids one – 1400 mg/g. The most efficient desorbent of Mn(II) from the clinoptilolite bed is solution of hydrochloric acid (1:4). This solution removes 100 % of adsorbed Mn(II). The influence of macro-components of natural waters on the concentration of Mn(II) on Transcarpathian clinoptilolite has been studied.
The methods of concentration of trace amounts of Mn(II) from aqueous solutions has been proposed using the obtained results.
Acknowledgments
This work was partially financed by the Ministry of Education and Science of Ukraine.
References
1. Vasylechko V.O., Lebedynets L.O., Gryshchouk G.V., Leboda R., Skubishewska-Zieba J. Investigation of Usefulness of Transcarpathian Zeolites in Trace Analysis of Waters. Application of Mordenite for the Preconcentration of Trace Amounts of Copper and Cadmium // Chemia Analityczna. – 1999. – V.44. – P.1013-1024.
2. Vasylechko V.O., Lebedynets L.O., Gryshchouk G.V., Leboda R., Skubishewska-Zieba J. Badania nad przydatnoscia Zakarpackiego klinoptylolitu do adsorpcji chloroformu z roztworow wodnych // Ochrona Srodowiska. – 1998. – №R3(70). – S.27-30.
3. Vasylechko V.O., Gryshchouk G.V., Kuz’ma Yu.B., Lebedynets L.O., Oliyarnyk O.Ya. Adsorption of Cadmium on Transcarpathian Clinoptilolite // Adsorption, Science and Technology. – 2000. – V.18, №7. – P.621-630.
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