Sorption of Cu(II) by Soil and Soil Components: Sorption Experiments and Surface Complexation Modeling

Sorption of Cu(II) by different horizons of a podzolic soil (A(O)EL, EL, and IIBD) was studied in model laboratory experiments and described using surface complexation models. To elucidate the role of individual components, Cu(II) sorption was investigated before and after sequential removal of organic matter and non-silicate iron compounds from the soil. It was established that in the A(O)EL sample, organic matter plays the principal role in Cu(II) sorption. According to the modeling results, solid-phase organic matter accounts for ≈25 to 50% of copper sorption depending on the concentration of the applied solution, whereas water-soluble organic matter retains ≈40% of Cu(II) in the equilibrium liquid phase. In the EL and IIBD samples, clay minerals are the main carriers of sorption sites, with their contribution to total sorption ranging from ≈5 to 40% and from ≈95 to 99%, respectively. Within the pH range characteristic of the studied podzolic soils, non-silicate iron compounds do not make a significant contribution to Cu(II) sorption. The selected models generally adequately described the distribution of Cu(II) among sorption sites—both in the initial samples and after removal of organic matter and FeDCB.