Applying Freundlich, Langmuir and Temkin models in Cu and Pb soil sorption experiments

Abstract

In acid soils, inputs of Cu and Pb of various origins create a high risk of environmental pollution. For this reason, batch experiments on Cu and Pb sorption and desorption in various horizons of three acid soils were performed on soil pH with 0.01 M NaNO₃ as background electrolyte. The objectives were to evaluate Cu and Pb sorption and retention capacity through the Langmuir, Freundlich and Temkin equations parameters fitted to the sorption/desorption data; to determine the coherence of the implications of these parameters; and to estimate the role of various soil characteristics in the Cu and Pb immobilization soil capacity. The results confirmed the suitability of the models parameters for studying Cu and Pb sorption and retention by acid soils. The greatest maximum sorption and retention capacities, indicated by the Langmuir parameter ß_L, corresponded to the lowest energy values required for fixation, indicated by the Temkin parameter b’. Together with the Freundlich parameter K_F, which indicates sorption and retention capacity, they made it possible to infer that the acid soil component that most influences Cu and Pb immobilization was the organic matter, followed by the Al-oxide content. High organic matter and Al-oxide contents, especially the former, gave rise to a lower energy requirement for the immobilization of metal cations, since they increased the soils’ sorption and retention capacities. Al³⁺, the dominant cation in the exchange complex in the horizons studied, and K⁺ are responsible for the influence of CEC_e on Cu and Pb immobilization in the acid soils studied.