Adsorption features of Cu(II), Pb(II), and Zn(II) by an ordinary chernozem from nitrate, chloride, acetate, and sulfate solutions

The effect of Cl−,SO42−, CH3COO−, and NO3− anions on the adsorption of copper, lead, and zinc by an ordinary chernozem has been studied. The effect of the anions on the adsorption of Cu2+, Pb2+, Zn2+ ions is significant but uncertain. It has been shown that the attendant anions affect the shape of the adsorption isotherms, which are described by the Langmuir, Freundlich, or Henri equations. The constants of the adsorption from a nitrate solution calculated from the Langmuir equation (KL) decrease in the following order: Cu2+ > Pb2+ >> Zn2+. The values of the maximum adsorption (Cmax) decrease in the following order: Cu2+ ≥ Zn2+ > Pb2+ for acetate solutions and in the series Pb2+ > Zn2+ ≥ Cu2+ for nitrate solutions. The values of the Henry constants (KH) calculated for the adsorption of the same cations from chloride solutions decrease in the same order as the values of KL. The CH3COO− anion has the highest effect on the constant values. The NO3− and Cl− anions “switch their places” depending on the attendant cation, but their effect is always lower than that of the acetate anion. The values of Cmax for copper and zinc are most affected by the CH3COO− anion, and the adsorption of zinc is most affected by the Cl− and NO3− anions. The assessment of the mobility of the adsorbed cations from the extraction with ammonium acetate (pH 4.8) has shown that the content of the desorbed metals is always lower than the content of the adsorbed cations and varies from 0.025 to 83%. According to their mobility, the adsorbed metals form the following order: Zn2+ > Pb2+ > Cu2+. The effect of the attendant anions on the extractability of the adsorbed cations decreases in the following order: chlorides > sulfates > acetates > nitrates.