*3.3. Selenium Desorption*

In the present study, 0.25 M KCl was used to extract adsorbed Se(IV). As is stated by Dhillon and Dhillon [34] and Zhu et al. [38], chloride ion can replace non-specifically adsorbed Se through ion exchange and mass action mechanisms. The desorption pattern was almost identical for all soils, i.e., increasing the initial Se(IV) solution concentration resulted in increasing the Se amounts desorbed from the soils (Figure 3). For all initial Se(IV) concentrations, less Se desorbed from acid soils, a trend more pronounced for initial solution concentrations up to 40 mg Se(IV)/L. Depending on the initial Se(IV) solution concentration, desorbed Se ranged between 2.6 and 117.6 and 0.2 and 84 mg kg−<sup>1</sup> for alkaline and acid soils respectively (Figure 3).

**Figure 3.** Se(IV) desorption from the studied soils (**a**) alkaline and (**b**) acid. Contact time 24 h, agitation rate 125 rpm, sorbent/solution ratio 1 g/0.03 L, temperature 22 ◦C.
