MONO AND COMPETITIVE ADSORPTION OF Zn, Cu AND Mn IN DIFFERENT CALCAREOUS SOILS

Abstract

Soil carbonate is considered an effective adsorbent to trace element retention. Many researchers have studied the preferential adsorption of those heavy metals on calcareous soils. In 2021- 2022, an experiment was conducted in agriculture college laboratories to assess the mono and competitive of three trace elements (Cu, Zn, Mn) on three calcareous soils that differ in their CaCO3 content. Calcareous representative soil samples were collected from different Nineveh governorate and north Iraq locations. The adsorption experiment was carried out using the batch method by equilibrating 2.5 gm soil with 25 ml of a solution containing concentrations of (1.5, 10, 20, 30, 40, 50, 60 and 70 mg. L-1) of all traced elements in the same concentrations. Sorption isotherms were characterized using linear Langmuir and Freundlich equations. Results showed huge differences in sorptions capacities and other studied parameters. All studied soils showed a high maximum adsorption capacity Qmax and strength binding for Cu than Zn and Mn. On the basis of Qmax and distribution coefficient values (Σkd) for each studied soil and element, the selectivity sequence was as follows Cu>Zn >Mn. Gibbs free energy (-ΔG) values were decreased as the sorption capacity decreased too. In mono and ternary adsorption system, Langmuir isotherms were of H-type whereas Freundlich isotherms were of C-type. The soil properties such as CaCO3, pH, Clay, C.E.C, and O.M were significantly related to trace elements adsorption.

Keywords

• Qmax
• Σkd
• Adsorption capacity
• Adsorption tendency
• Co-existence