ADSORPTION SELECTIVITY SEQUENCE OF HEAVY METAL CATIONS BY SOME SOILS OF EGYPT

Document Type : Original Article

Author

Soil Sci. Dept. Fac. of Agric. Cairo Univ. Giza, Egypt

Abstract

 
Heavy-metal adsorption reactions, in a competitive system, areimportant to determine heavy metal availability to plants andtheir mobility throughout the soil. Therefore, this study was conductedto estimate the competitiveadsorption of several heavy metal cations in some soils of Egypt with differentchemical and physical characteristics.
 Distribution coefficients(kd) were obtained for each soil and heavy metal. On the basis of these kd, the selectivity sequence was evaluated.The most common sequences were Cr > Pb > Cu > Cd > Ni > Zn andPb> Cr > Cu > Cd > Zn > Ni. Chromium, Cu and Pb were the heavy metalcations most strongly adsorbed by all the studied soils, whereas, Cd, Niand Zn were the least adsorbed, in the competitive adsorption situation.Selectivity sequences related to valence for the trivalent Cr.For cations of the same valence, sequences did not followthe order of electronegativity. 
Statistical analysisshowed that distribution coefficient was significantly correlated to cation exchange capacity (CEC) and organic matter (O.M) for Cr; CaCO3 and pH for Cd; organicmatter and clay for Cu; pH and O.M for Ni; CEC, clay for Pb; CEC and clay for Zn.

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