Navegando por Palavras-chave "Copper and lead complex"

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    Estudos voltamétrico e espectroscópico da interação dos íons metálicos cobre e chumbo com o pesticida paration metílico
    (Universidade Federal de São Paulo, 2017-12-07) Cardoso, Daisy Alves [UNIFESP]; Oliveira, Lucia Codognoto de [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The objective of this work was to analyze the interaction between the pesticide methyl parathion molecule and the copper and lead metal ions that may be present in soil and water. Initially, electrochemical studies were performed using cyclic voltammetry with a carbon electrode reused from the zinc cell for characterization of the species. Methyl parathion (PM) in 0.4 mol L-1 BR buffer had a cathode peak at approximately -0.57 V, corresponding to the reduction of the nitro group to hydroxylamine. This process was followed by a couple of peaks at -0.02 V and -0.04 V, corresponding to reversible oxidation of the hydroxylamine. In buffer BR 0.4 mol L-1 the copper metal ion showed a cathode peak at -0.09 V and an anode peak at -0.14 V corresponding to the reduction / oxidation of the copper ion and the lead ion in 0.1 mol L-1 KNO3 had a cathode peak at -0.65 V and an anode peak at - 0.44 V corresponding to the reduction / oxidation of the lead ion. Both presented a process controlled by the diffusion of the species on the surface of the electrode. The evaluation of the formation of the complex was performed by cyclic voltammetry and anodic redissolution voltammetry by differential pulse at pH 6.0. The studies of the evaluation of the interaction between PM and Cu(II) did not present satisfactory evidence on the formation of a new species in solution. A new peak at -0.60 V corresponding to the formation of a new species in solution with 1:2 stoichiometry (Pb: PM) was observed for the PM-Pb(II) studies. The stability constant for this new species was calculated (log K'=7.6) from the Langmuir linearization method. Comparative studies using UV-Vis indicated the formation of a new species in solution with increased absorbance of the band of the PM ligand in alkaline medium when in the presence of lead. In the interaction between the PM and Cu (II) by differential the changes in the peak potentials appear in close potential interval hindering an adequate definition of the formation of a new species in solution, already in the interaction between the PM and the Pb (II) was evidenced the formation of a new peak. The studies by voltammetry presented more satisfactory results compared to the technique by UV-Vis.