Resumo (PT):
Abstract (EN):
This work focuses on assessing the feasibility of cathodic iron extraction from the magnetite based
precursors. For this, electrochemical processes at Fe3O4/alkaline electrolyte interface were screened by
cycling voltammetry. Based on these results, one obtained guidelines for selecting the conditions (i.e.,
potential and temperature) where efficient direct electrochemical reduction of magnetite ceramics to
metallic iron occurs. Electrochemical conversion of relatively dense magnetite samples yields a
polycrystalline Fe scale, formed at the surface of the magnetite pellet in direct contact with the bulk
electrolyte. Still, the onset of slightly open porosity results in formation of intermediate layers with
coexisting magnetite and metallic Fe; this is ascribed to gradual development of additional porosity,
which promotes sample impregnation with the electrolyte, extends the effective electrochemically active
area, and facilitates dissolution of soluble species in the inner pores. This is clearly demonstrated by
transient response behavior, with remarkable increase in the current density. The key roles of porosity
and effective Fe3O4/electrolyte area are also emphasized by the enhanced kinetics of electrochemical
reduction observed for highly porous magnetite samples, with nearly homogeneous distribution of
reactant (Fe3O4) and product (metallic Fe), without a clear surface scale of metallic iron. In this case, the
final productis very porous and fragile. The conversion of highly porous magnetite samples also proceeds
with much higher Faradaic efficiency compared to nearly dense ceramics.
Idioma:
Inglês
Tipo (Avaliação Docente):
Científica
Nº de páginas:
9