engleski

Adsorption properties of clays from deposits in loess formations of NW Croatia

In northwestern Croatia a large number of clay deposits are emplaced in loess formations of Pleistocene age. The loess formations have been mainly described as marshy or acarbonatic continental loess (BASCH, 1980). The clay deposits are largely silty with a subordinate content of clay fraction. They have been generally exploited for brick production. In the present study adsorption properties of the clays originating from the deposits in northwestern Croatia were evaluated by determination of cation exchange capacity(CEC). The CEC values were related to mineral composition, especially to the content of clay minerals. The clays were sampled in the clay deposits in the eastern part of Zagreb County (Kraljevečki Novaki, Dugo Selo, Luka), in Bedekovčđina, and at several spots in Međimurje County (Belica, Šenkovec, Vukanovec). The sampling sites in Bedekovčina and Šenkovec belong to still active clay quarries mined for brick production. The clay deposits are situated within the Pleistocene loess accumulations (BASCH, 1980 ; ŠIMUNIĆ et al., 1981 ; MARKOVIĆ & MIOČ, 1989, 1996), except those from the Vukanovec area which are situated within the Upper Pontian sediments (MARKOVIĆ & MIOČ, 1996). The mineral composition of the clays was determined by X-ray diffraction being supported by heating and swelling tests for clay mineral identification. Cation exchange capacity was measured by application of copper ethylendiamine complex (AMMAN et al., 2005) and subsequent determination by UV–VIS spectrophotometry. The mineralogical analysis yielded the following phase composition for all the samples: quartz, plagioclase, illitemuscovite and chlorite. Additionally, kaolinite is present in approximately half of the samples. All CEC values were measured at pH~7. The clay samples from Zagreb County have CEC values between 11 and 18 meq/100 g, the sample from Bedekov~ina around 19 meq/100 g, and those from Me|imurje County between 7 and 28 meq/100 g (Tab. 1). The measured CEC v lues correspond well to the observed mineral composition. The identified clay minerals, being of a great importance for adsorption of trace elements in sediment, have CEC values ranging from 5 to 25 meq/100 g (VAN OLPHEN & FRIPIAT, 1979). A future study will relate the investigated clay sediments with overlying soil as well as to content of iron and manganese oxyhydroxides and organic matter.

clays; loess; CEC; NW Croatia

nije evidentirano