Copper and zinc adsorption in tropical soils

Copper and zinc are essential elements acting in the biochemical processes of plants and animals, however, the knowledge of the mobility and retention of these ions at the presence of other competitive metals, in different soils, is essential to predict their fate in the soil system and evaluate a possible contamination of surface and groundwater. Thus, the objective of this study was to evaluate the adsorption isotherms of copper and zinc in mono- and multi-component systems, for the tropical soils Oxisol, Inceptisol and Entisol Quartzipsamment. The evaluated isotherm models were Langmuir, Freündlich, multi-component Langmuir and multi-component Freündlich. The initial concentrations of the evaluated and accompanying ions were 10, 15, 30, 40 and 50 mg L-1, and the Gibbs free energy and separation factor were determined. Copper was the most adsorbed ion by the porous medium in a mono-component system and the least adsorbed was the zinc in a multi-component system. The best-fit isotherm model was Freündlich for mono-component systems and Langmuir for multi-component systems. The Incentisol showed higher adsorption capacity, favoring the reduction of ion leaching, which leads to the attenuation of groundwater contamination, which may allow the application of copper and zinc-based wastewater or fertilizers to be a viable alternative for this soil. On the other hand, Entisol Quartzipsamment showed lower ion adsorption capacity and consequently greater ion leaching potential.