Adsorption of copper and cadmium from aqueous solution by various types of sediments under static and dynamic conditions
Bulletin of Geosciences, volume 78, issue 3;
pages: 169 - 178;
Accepted in revised form 5 May 2003;
sequential extraction analysis,
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The mobility of heavy metals in sediments and soils depends strongly on physical properties and chemical and mineralogical composition of such environments. Five types of samples with different amounts of carbonates, organic matter, chemical composition and various grain sizes were chosen. Experimental sorption data from batch tests were evaluated by Langmuir and Freundlich type isotherms, which provided main sorption characteristics of sediment samples for heavy metals (Cu, Cd). In order to simulate natural conditions more realistically, several leaching column tests were also performed. The sample sorption capacities under static and dynamic conditions were evaluated. All chosen samples bonded Cu more efficiently and firmly than Cd. Distilled water washed out about 6% of Cu and 44%of Cd from HBS 2 (quartz-dominated sample with 74 wt% of sand-sized fraction) and 6% of Cu and 9 % of Cd from HBS 6 (finer-grained sample with some amount of organic matter and carbonates). Carbonates proved to be crucial for the mobility of heavy metals in natural samples. Free metals were washed out of pores at the very beginning of the desorption experiments. Then, weakly adsorbed metals (electric double layer) were washed out and finally, a low stationary metal concentration was established. Such behaviour should result in a slow release of small amounts of a heavy metal, which should therefore not represent significant danger to the environment.