Avaliação da imobilização do sal trissódico do ácido 1,8 -dihidróxi-2-(4-sulfofenilazol)-3,6-naftalenodisulfônico (SPADNS) em sílica gel / Evaluation of 2-(4-sulphophenylazo)-1,8-dihydroxy-3,6-napthalene disulphonic acid trisodium salt immobilization at silica gel

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

18/03/2011

RESUMO

Solid phase extraction (SPE) is a kind of procedure for preconcentration and choice of solid phase is very important to develop analytical methods because your selectivity, affinity and retention capacity. The metals preconcentration is very used in environmental samples that have metals such as Pb2+, Cd2+, Ni2+, Al3+ at μg L-1. In that sense, the main of this work was the development of complexing solid phase for metals preconcentration. SPADNS (2-(4-sulphophenylazo)-1,8-dihydroxy-3,6- napthalene disulphonic acid trisodium salt) was immobilized at sílica gel at cationic surfactant CTAB (cetyltrimethylammonium bromide) medium. Cinetic and isotherms studies were done to understand the interection between SPADNS and silica gel. The biggest amount of SPADNS adsorbed in silica gel was obtained to proportion 1 : 2,5 between SPADNS and CTAB, respectively, at pH 7. Experimental data of adsorption in function of time and SPADNS concentration were adjusted to kinetics models (pseudo-first-order, pseudo-second order and intraparticle diffusion) and isotherms (Langmuir, Freundlich and Dubinin-Radushkevich). Experimental data at 25oC were adjusted to pseudo-second-order kinetic model at specific concentration range and intraparticle diffusion was observed at highest SPADNS concentration (0,6 a 2,0 x 10-4 mol L-1). The adjustment to Langmuir, Freundlich and Dubinin- Radushkevich models demonstrated SPADNS maximum mass adsorbed per silica gel gram was (121,01,4) mg g-1; silica gel surface presents heterogeneous energetically active sites and there is physical adsorption due medium adsorption energy was obtained [(19,40,2) kJ mol-1]. The desorption of immobilized SPADNS at silica gel was evaluated and it was not significant after many washings in different acids in varied concentration medium although it was very significant at NH4OH/NH4Cl pH 9,5 buffer. Silica gel modified with SPADNS in CTAB medium was applied to Ni2+ ions retention due to this metal toxicity. The retention was 100% in 20 minutes contact between solid phase and 1,00 mg L-1 Ni2+ em pH 9. Due to lower reagent consumption and toxicity besides excellent Ni2+ ions retention, silica gel modified with SPADNS appeared to be promising like a solid phase to metals preconcentration

ASSUNTO(S)

ctab quimica adsorção spadns sílica gel ctab par iônico micela adsorption spadns silica gel ionic pair micelle

ACESSO AO ARTIGO

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