Avaliação das propriedades pre-concetradoras de metais das silicas modificadas para analise por fluorescencia de raios-X

AUTOR(ES)
DATA DE PUBLICAÇÃO

1997

RESUMO

Batch-wise liquid-solid extraction using chemically modified silica was studied as a pre-concentration method for non-essential heavy-metals, such as cadmium, lead and mercury, for subsequent analysis by Energy Dispersive X-Ray Fluorescence (EDXRF). Silicas modified with zirconium phosphate (SiZrP - 0.27 mmol g of phosphate) and/or propyl imidazol (Silm - 0.29 mmol g of imidazol groups) were prepared to be used as the solid extractor. The best adsorption parameters were obtained using 50 mL of aqueous phase at pH 4.5, an adsorption time of 15 minutes and 0.2 g of adsorbent. The modified silica with propyl imidazol groups showed a high selectivity for Hg (since it does not adsorb significant amount of lead and cadmium), wide linear response range (0.5 - 50 mg L), a pre-concentration factor of 107, sensitivity of 11.73 cps/mg L and detection limit of 0.089 mg L. For SiZrP the pre-concentration factors obtained for Cd, Pb and Hg were 43, 47 and 43, respectively. The linear response ranges were 0.5 to 10 mg L for cadmium, 0.5 to 50 mg L for lead and 0.5 to 116 mg L for mercury. The sensitivity depended on the emission line characteristics of each element. The detection limits were 0.071 mg L for cadmium, 0.200 mg L for lead and 0.339 mg L for mercury. From the distribution coefficients the affinity of SiZrP for the metal ions studied increases in the order: Cd(lI)

ASSUNTO(S)

silica gel fluorescencia de raio x

ACESSO AO ARTIGO

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