Competitive Adsorption of Cu, Zn and Mn on Compost Amended Soils with Variable Clay Content

THE AIM of this study was to assess the effects of a single application of compost derived from crop wastes, and incubated for 60 days, on the competitive adsorption of Cu, Zn and Mn on four soil samples with different clay contents (2%, 10%, 20% and 40%, hereafter referred to S2, S10, S20 and S40) in terms of their physical and chemical properties.The competitive sorption isotherms of copper (Cu), zinc (Zn) and manganese (Mn) in multi-metal batch experiments were characterized using linear, Freundlich and Langmuir equations. All soils showed greater sorption capacity and binding strength for Cu than the other trace elements. On the basis of distribution (partition) coefficient (Kd) values for the metal concentration and maximum sorption capacity (Q) for each soil and trace element, the selectivity sequence was obtained. The greatest adsorption sequence found was Cu>Zn>Mn. Cu was the trace element most strongly adsorbed by all soils, whereas Zn and Mn were the least adsorbed in the competitive situation. The relationships between maximum adsorption and partitioning coefficients of Cu, Zn and Mn and clay content were quantitatively modeled.