The pattern of the sorption isotherm affected the variation range of the Kd values, which is apparent with the minimum (Kd,min) and maximum (Kd,max) values obtained within the range
of tested concentrations, as shown in Table 2 and in Fig. 2, which also presents their related sorption percentages. Although only a few cases could be associated with linear sorption (constant partition isotherms) in a straightforward manner, the range of Kd variation was
often less than one order of magnitude. The changes in Kd were over one order of magnitude for the majority of metals only for the BF, BS and GW materials. Therefore, a single Kd value estimating the sorptive capacity of the materials could not be directly
deduced from the raw sorption data. Among the studied metals, Pb typically had the highest Kd values except for DOM and OWH, and Ni typically possessed the lowest Kd values. For the rest of
the target metals, the Kd (Cu) values were always in the upper range with Kd (Zn) and Kd (Cd) exhibiting lower values