Desorption kinetics of phenanthrene and lead from historically contaminated soil

Heavy metals and polycyclic aromatic hydrocarbons (PAHs) exist naturally in soils at acceptable concentrations. However, the simultaneous accumulation of PAHs and heavy metals in soils surrounding urban complexes, gas stations, metalliferous mines and major roads is growing. Thus, the purpose of this study is to determine the desorption kinetics of heavy metals and PAHs from contaminated soil samples. The influence of simultaneous contamination by heavy metals (lead (Pb)) and PAHs (phenanthrene (PHE)) on desorption kinetics was evaluated. Batch desorption tests were performed using single and composed desorption solutions, containing (ethylenedinitrilo)-tetraacetic acid disodium salt (Na-EDTA) and/or polyethylene glycol dodecyl ether (Brij® 35 P) or polyethylene glycol sorbitan monooleate (Tween® 80). Two kinetic models – empirical power function and the pseudo-second-order equation – were well adjusted to the experimental data. Extraction levels around 100% were obtained by applying EDTA or EDTA/B35 to a soil contaminated only with Pb. Moreover, extractions of 48% and 55% were obtained for Pb and PHE, respectively, with EDTA/B35 solution from a co-contaminated soil.