Estudo do comportamento de Cr(III) na precipitação do PbCrO4

AUTOR(ES)

Rosa Lina Gomes do Nascimento

DATA DE PUBLICAÇÃO

1983

RESUMO

The behavior of Cr(III) in the precipitation of Cr(VI) as PbCrO4, using Cr as tracer; was studied to gain information about the process of Cr(III) incorporation in the precipitate. The Cr(III) coprecipitation with PbCrO4 from. aqueous solution having Cr(III) and Cr(VI), at pH 8-10, shows a great dependence on the storage time of the solution at 36,5°C, before the addition of the precipitating agent Pb(NO3)2 on the pH of the solution during storage and at the moment of precipitation as well as on the pH of the wash solution. It was noted that in each studied case, the incorporation increases with the storage time. The analysis of the present species in the solution, by Cationic Exchange Chromatography after 24 hours both without precipitating agent and with it, indicate that the Cr(III) - distribution (i.e., the relative proportion of the monomer -, dimer-, and polymer - species) does not change. This indicate that each species coprecipitates with PbCrO4 at the same rate (i.e., with equal incorporation efficiences) and/or is stored in a precipitate, before liberation by adicification. ln contrast with previous descritions of the overall process, it can be concluded that the Cr(III) probably doesn t go into the PbCrO4 - Crystal lattice as a doping species, but that it precipitates separately as chromium - chromate and/or chromium hidroxide.

ASSUNTO(S)

cromo compostos de chumbo

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