8. Sorption of zinc on suspended particles along a salinity gradient: a laboratory study using illite and suspended matter from the river Rhine.


The adsorption of zinc on suspended matter from the river Rhine has been studied. High rates of adsorption were apparent during the first hours of the experiments, but during the next few days adsorption kinetics were much slower. The adsorption could be described by a Freundlich isotherm, indicating surface heterogeneity. In subsequent experiments, desorption of previously adsorbed Zn was investigated in solutions of various salinities. These experiments showed that the largest desorption effect occurs in the low salinity range (S=0-5). It was also found that the adsorption reaction is not completely reversible.
Our results indicate that desorption of Zn is to be expected in an estuary due to the presence of a salinity gradient. In field measurements, however, adsorption of zinc is often observed. This apparent contradiction is caused by additional processes that are not taken into account in laboratory studies.

This chapter was published in:

Netherlands Journal of Sea Research. Year 1992, Volume 28, number 4, pages 285-292.
W.J.M. Hegeman (*), C.H. Van Der Weijden (*), J.J.G. Zwolsman (**)

(*) Department of Geochemistry
Institute of Earth Sciences
University of Utrecht
P.O. Box 80021
3508 TA Utrecht
The Netherlands

(**) Delft Hydraulics
P.O. Box 177
2600 MH Delft
The Netherlands

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