MATHEMATICAL-DESCRIPTION OF THE DESORPTIO N OF ZINC FROM RIVER SEDIMENTS BY NTA USING FREUNDLICH AND LANGMUIR EQUATIONS

Remobilization of zinc from sediments from Rhine and Neckar rivers wit h nitrilotriacetic acid (NTA) in water has been studied in order to ob tain a mathematical relation between quantities of mobilized zinc on s ediments and concentration of zinc and NTA in aqueous solution. Remobi lization has been measured by stirring the sediments for 70 hours in p olyethylene flasks and analyzing dissolved zinc by AAS. Concentration of free zinc ions in solution is correlated with amount of zinc fixed on the sediments in form of adsorption equations by Freundlich and Lan gmuir and the linear equation. Whereas for the Rhine river sediment al l correlations are of similar quality, the standard deviation for the linear correlation with the Neckar sediment is about twice as large as for the others. The adsorption energies on both sediments are similar , however, the adsorption capacity and therefore, the remobilized amou nt of zinc is larger for the Rhine sediment. For mathematical modellin g of technical processes, eg., for technical decontamination of sedime nts the linear correlation may be recommended.