Estudo das propriedades de troca ionica de silicofosfato de zirconio (IV)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

Zirconium (IV) phosphosilicate (HZPS) was prepared by mixing solutions of sodium metasilicate with solutions of zirconium(IV) oxychloride. The resulting precipitates were further treated with phosphoric acid. Precipitation reactions were carried out at pH~9-10 and pH~6. The HZPS obtained at each pH showed similar exchange capacities. Thermogravimetric analysis showed low degree of hydration, the solids having nearly 10% of adsorved water. Exchange reactions with Ni (II), Cu (II), Zn (II), Cd (II), Hg (II) and Pb (II) were carried out in batch. Exchange capacities were determined from the values of Nf (amount of M (II) exchanged per gram of HZPS) In the limit of infinite concentrations of M(II) in solution. The exchange capacities so obtained were (in mmol g): Ni (II) = 0.45, Cu (II) = 0.83, Zn (II) = 0.72, Cd (II) = 0.68, Hg (II) = 1.70 and Pb (II) = 1.80. Selectivity coefficients were calculated for each point along the exchange isotherms, and using the Gaines-Thomas approach, the selectivity constants were also calculated: Ni (II) = 0.25 x 10, Cu (II) = 1.0 x 10, Zn (II) = 0.40 x 10 Cd (II) = 0.79 x 10, Hg (II) = 0.10 and Pb (II) = 0.16. HZPS is highly selective for all studied metal ions selectivity higher for those ions having larger volume. In the exchange process, the entalpy of transference of the metal ion from the aqueous solution to the exchanger phase, appears to play important role for this class of materiaIs. HZPS is a rigid, thermally and mechanically resistant material; these properties, in addition with its high selectivity, qualify this materiaIs for use in several technological applications.

ASSUNTO(S)

zirconio troca ionica silicatos

ACESSO AO ARTIGO

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