Lead Sorption and Dessorption in Oxisols from Paraná-Brazil.

This work aimed to evaluate the sorption and desorption of lead in Oxisols of Paraná. Initially were selected six Paraná State Oxisols where samples of your horizon A and Bw were collected. In these soils were carried out physical, chemical and mineralogical and these data correlated with the values of sorption and desorption of lead. In the lead sorption process in soil were obtained remaining and adsorbed amounts of lead, maximum lead adsorption capacity (CMAPb), binding energy (EL), distribution coefficient (Kd), Gibbs free energy (ΔG₀) and adsorption envelope. In the desorption process, the effects of pH on the adsorption of lead sequential desorption with CaCl₂ and Mehlich-1 which is an acid extractant (pH = 1.5). Lead adsorbed has formed outer sphere complex-CEE and inner sphere complex with the surfaces of soil particles. The values of CMAPb, EL, Kd and DG_0, varied from  (5555 to 934 mg kg^-1), (0,047 to 0,9 L mg^-1), (16,9 to 2876,1 L kg^-1), (-9536 to -847 J mol^-1), respectively. The values of desorption with CaCl₂ 0,01M varied from 1,4 to 70% and with Mehlich-1 varied from 14 to 97%. Through the Pearson linear correlation was observed that the primary responsibility for the highest sorption of lead in soil were the chemical properties (pH, SB, CTC, V%, P e C) and mineralogical (Mgh, Hm e Fe_t). Based on the correlation data it was observed that the primary responsibility for a lower desorption of lead with CaCl₂ are chemical (pH, CTC, P, C, SB and V%) and mineralogical (Mgh, Hm, Fet and Feo). Already percentage desorbed with Mehlich-1 showed the opposite correlation obtained for CaCl₂ and showed a negative correlation the relation F_d / F_t, indicating a smaller percentage of lead desorption in weathered soils.