Adsorção de corantes em turfa de origem Magalhânica / Absorption dyes om Magallanic peat

AUTOR(ES)
DATA DE PUBLICAÇÃO

2011

RESUMO

The aim of this work was to study the removal of dyes Naphthol Blue Black (NBB) and Maxilon Blue 5G (MB) in the aqueous phase by adsorption on Magellan peat. According to the peat physicochemical characterization, the carboxylic, phenolic, hydroxyl and methyl amines were identified as the main functional groups, that giving it a preferably negative charge and a Point of Zero Charge (PZC) equal to 3.68. The results of batch experiments showed that the adsorption of the NBB dye is strongly dependent on surface charge of the peat, but it did not happen with the MB dye. The Langmuir, Freundlich and Sips isotherm models were well correlated to equilibrium experimental data of both dyes. The maximum adsorption capacities (qm) and the Langmuir energy parameter (b) of the NBB and MB dyes obtained were 33.7 and 33.1 mg/g and 0.031 and 0.139 L/mg, respectively. On the kinetic experiments in stirred tank, the removal rate and the adsorption capacities were 81 and 97%, 12 and 30 mg/g for NBB and MB dyes, respectively. The kinetic models of second order and Langmuir were well fitted to experimental data for low initial concentrations of dye. The system modeling showed that happens pore and surface diffusion and was the rate-determining step of the adsorption process. The diffusion coefficients were estimated in 1.08 to 3.5.10-10 m2/s in the pore and 0.2 to 1.5.10-11 m2/s on the surface. From tests in fixed bed columns, the adsorption capacities at saturation ranged between 17.1 and 30.1 mg/g for MB dye in the selected conditions. The mass transfer height was dependent on the concentration and flow rate of feeding from 14 to 23 cm. In the other side, the adsorption capacities of the NBB dye ranged between 2 and 3 mg/g, equivalent to 20 - 30% of equilibrium capacity in batch tests. These results were attributed to the low energies of the dye adsorption on peat. The THOMAS model showed a good quality in prediction of the dye concentration in initial portion of the breakthrough curves (C/Co <0.5), when the MB dye were adsorbed on a peat bed. However, the model failed to predict the behavior of the NBB dye

ASSUNTO(S)

adsorção corantes turfa adsorption dyes peat

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