Isotermas de Langmuir e de Freundlich na descrição da adsorção de zinco em solos do Estado da Paraíba J.D. Fernandes

In environmental studies it is necessary to know the adsorption behavior of zinc by soils.This behavior can be evaluated by mathematical models described by Langmuir and Freundlich equations. The objective of this study was to evaluate Langmuir and Freundlich isotherms applied to zinc adsorption in surface samples of ten soil from Paraíba State, Brazil, with a wide range of chemical properties. In order to quantify the adsorbed zinc, 2 g of air-dried soil were equilibrated with 20 mL of a NaCl (0.01 mol L-1) solution containing different quantities of zinc (5, 20, 30, 40, 50, 60, 70, 90 mg L-1). Zinc adsorption by soils, with exception of the PAd, was well described by both Langmuir and Freundlich models. For Zn concentrations up to 30 mg L-1, applied in the soils, the two models estimated low values than the experimental values; above 70 mg L-1 of Zn, Freundlich model overestimated the experimental values.