Competitive Adsorption and Desorption of Cadmium, Chromium, Copper, Nickel, Lead, and Zinc by Humic Umbrisols

Abstract

The objective of this study was the evaluation of the selectivity sequences of adsorption and retention of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in four Humic Umbrisols from the province of Pontevedra, Spain. The characteristics of the surface horizons of the soils showed significant differences in the components and properties that influence adsorption capacity and mobility of metals and, therefore, their retention by the soils. The most adsorbent and retentive soil after desorption has the highest content of manganese (Mn), iron (Fe), and aluminum (Al) oxides. The least adsorbent has the lowest content of oxides and organic matter. The metal adsorbed in greater amount by the soils was Pb, followed by Cu and Cr, which competed favorably for adsorption sites with Cd, Ni, and Zn. After desorption, Cr is the most retained metal. The greater retention of Cr seems to indicate that the relation charge-to-radius is the most influential factor in the retention of this element. In general, the properties and components of the soils have more influence on the adsorption and retention of the metals than the properties of the metallic ions.