Equilibrium and kinetic study of the biosorption of chromium(III) by two brown algae: Macrocystis pyrifera and Undaria pinnatifida

PLAZA CAZÓN JOSEFINA; BENÍTEZ LEONARDO; VIERA MARISA; DONATI EDGARDO

ENGINEERING IN LIFE SCIENCES

WILEY-V C H VERLAG GMBH

Año: 2012 vol. 12 p. 95 - 103

1618-0240

Abstract Two brown algae, Macrocystis pyrifera and Undaria pinnatifida were employed to remove Cr(III) from aqueous solutions. Both seaweeds were characterized in terms of alginate yields. The alginate contents were 20% and 30% of the dry weight for M. pyrifera and U. pinnatifida, respectively. Kinetics experiments were carried out at different initial pH values. Cr(III) biosorption was affected by the solution pH. The highest metal uptake was found at pH 4.0 for both biosorbents. Different models were applied to elucidate the rate?controlling mechanism: pseudo first order, pseudo second order, external mass transfer and intra- particle diffusion. The application of Langmuir, Freundlich and Dubinin?Radushkevich models to the equilibrium data showed a better fitting to the first model. The maximum Cr(III) sorption capacity and the affinity coefficient were very similar for both biosorbents: qm=0.77 mmol.g-1 and b= 1.20 L.mmol-1 for M. pyrifera and 0.74 mmol.g-1 and 1.06 L.mmol-1 for U. pinnatifida. The free energy of the sorption process was estimated using the Dubinin?Radushkevich isotherm. The values found indicate that the processes are chemical sorptions. To evaluate the significance of the ion exchange mechanism, the light metals (Ca2+, Na+, Mg2+ and K+) and pH were measured during the experiments.