Resumo

LAZO ACUNA, Pamela A  e  LAZO ACUNA, Andrea P. Spontaneous precipitation of Molybdenum compounds on Zinc in aqueous ammonia solutions. Rev. cienc. tecnol. [online]. 2015, n.24, pp.35-41. ISSN 1851-7587.

The spontaneous deposition of molybdenum over zinc in ammonia solutions with a rotatory electrode system has been studied. The effect of variables such as temperature and pH of the bath, disk rotational speed and concentration of molybdenum was analyzed. The results indicate a process with two stages, where stage 1 presents a higher rate than stage 2; the lower reaction rate in stage 2 was attributed to the nature of the film formed by a mixture of oxides and/or hydroxides of zinc and molybdenum. The analysis of the data indicates a mixed control, controlled by diffusion through the liquid film and chemical reaction; nevertheless, the results are not consistent with the diffusion of MoO4-2 because the rate of the process increases with the decrease in the concentration of molybdate, probably due to a phenomenon of proton diffusion towards the surface.

Palavras-chave : Molybdenum; Zinc; Spontaneous deposition; Oxide; Mixed Control.

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