Preparação e caracterização de filmes de PbO2 sobre diferentes substratos e MnO2 sobre fibra de carbono para aplicação no tratamento eletroquímico de efluentes simulados
IRIKURA, Kallyni. Preparation and characterization of PBO2 films on different substracts and MNO2 film on carbon fibre for application in the electrochemical treatment of simulated wastewaters. 2008. 104 f. Dissertação (Mestrado em Ciências Exatas e da Terra) - Universidade Federal de São Carlos, São Carlos, 2008.
PbO2 films were grown on different substrates (Ti-Pt, ADE, FC and Pb), at constant current density of 20 mA cm-2, using two methodologies: electrodepositon from 0.1 mol L-1 Pb(NO3)2, 1.7 mmol L-1 LSS and 0.1 mol L-1 HNO3 solution and lead anodization in 3 mol L-1 H2SO4 solution. All PbO2 films presented important characteristics such as: homogeneous and compact morphology, quite uniform growth and good adherence. MnO2-composite film was prepared from electrolytic MnO2 powder [80 % (m/m)], carbon black [10 % (m/m)] e PVDF [10 % (m/m)] and then applied on carbon fibre (FC). The physical and electrochemical properties of these different electrode materials were characterized by scanning electronic microscopy, X-ray diffratometry, linear potential scan and cyclic voltammetry. The PbO2 films obtained by electrodeposition presented mainly the tetragonal phase â-PbO2, while the PbO2 film obtained by anodization presented an oxide mixture with the following phases: tetragonal â-PbO2, orthorhombic á-PbO2, PbO and also PbSO4. The electrolytic MnO2 was obtained mainly with the phase å- MnO2. The Pb/PbO2 electrode presented the best performance regarding OER. Among the electrodes obtained by electrodeposition (Ti-Pt/PbO2, ADE/PbO2 and FC/PbO2), the FC/PbO2 electrode presented higher values of superficial area and overpotential for the OER. The FC/MnO2 did not present good performance regarding OER. The Pb/PbO2 electrode was applied, at constant current density of 5 mA cm-2, in the oxidation of 0.05 mol L-1 Cr3+ ions solution, presenting a conversion efficiency of Cr3+ to Cr6+ ions of 90 %. The FC/PbO2 was also applied in the decolorization of the BR 19 dye solution (100 mg L-1), using a filter-press reactor. A decolorization efficiency of 99.5 % was obtained in the following experimental conditions: flow rate of 7.0 L min-1, current density of 30 mA cm-2 and chloride concentration of 70 mmol L-1. At the end of the oxidation process, a value of the German parameter DFZ 10 times lower than the maximum value (3 m-1) established before discarding in the environment was found.