In this review is presented an innovative technology for use of animal and vegetable waste with high pollution levels in microbial fuel cell (MFC) as an alternative to waste remediation and simultaneously producing electricity and fertilizer for agriculture. A brief history of MFC, the studies about the electron transfer mechanisms, discussion of the biological nanowires in bacteria and the use of chemical mediators or carriers of electrons are explained. The factors influencing the performance of MFCs, the application in waste and sewage treatment and power generation are also discussed.

Neste trabalho estudou-se a eletrodeposição de ligas de Fe-Mo e Ni-Mo sobre eletrodos de Pt em meio de citrato de sódio em pH 4,0. O comportamento das ligas foi avaliado por voltametria ciclica em diferentes razões dos íon metálicos. Os depósitos foram caracterizados por MEV, EDX e difração de raios-X. Nos voltamogramas cíclicos os picos de dissolução só aparecem para soluções com maior concentração de íons Fe ou Ni. Análises de MEV mostraram morfologias diferentes para as duas ligas estudadas sendo que as de Ni-Mo são mais uniformes e espessas. O conteúdo de Mo e O nas ligas Ni-Mo é maior do que na de Fe-Mo. A deposição das ligas de Ni-Mo é do tipo anômala.

This paper reports on a study of the electrodeposition of Ni-Mo and Fe-Mo alloys on Pt electrodes in a sodium citrate solution at pH 4.0. The alloys were subjected to cyclic voltammetry at different ion concentration ratios to identify their behavior. The electrodeposited coatings were analyzed by SEM, EDX and XRD. The results of the cyclic voltammetry tests indicated the presence of dissolution peaks only with high Ni or Fe ion concentrations. The SEM analysis revealed that the two alloys had dissimilar morphologies and the Ni-Mo alloys were homogeneous and thick. The Mo and O contents were higher in the Ni-Mo than in the Fe-Mo alloys. Anomalous deposition was found to occur in the co-deposition of Ni and Mo.

The <FONT FACE="Symbol">e</font> phase of electrolytic manganese dioxide (EMD) is the structural form most easily converted in the LiMn2O4 spinel used as cathode in lithium batteries. Thus, employing titanium as anode, a study of electrolysis parameters was carried out in order to determine the best conditions to produce an <FONT FACE="Symbol">e</font>-EMD suitable for that spinel preparation. The influence of solution temperature (65oC and 90oC) and current density (between 1 mA/cm2 and 17.5 mA/cm2) on the anode potential and the EMD properties was investigated using an aqueous 2.0 mol/L MnSO4 + 0.30 mol/L H2SO4 solution. In any of the electrolysis conditions tested only the e-EMD structure was obtained, but its specific surface area varied with the applied current density and temperature. Drying the <FONT FACE="Symbol">e</font>-EMD at temperatures between 60oC and 120oC did not cause any phase changes. To produce a suitable EMD at the highest current density possible without passivation of the titanium anode, the best electrolysis parameters were determined to be 90oC and 15 mA/cm2. The <FONT FACE="Symbol">e</font>-EMD thus obtained had a specific surface area (BET) of ca. 65 m2/g.