Preparation of activated carbons from banana leaves by chemical activation with phosphoric acid. adsorption of methylene blue

Abstract

Banana leaves, which represent the second major residue generated in banana cultivations, were used as raw material for the preparation of six different activated carbons. The adsorbents were developed from this lignocellulosic precursor by means of chemical activation with phosphoric acid, modifying the concentration of the activating agent and the carbonization temperature during the production process. The obtained activated carbons presented slightly acid points of zero charge, high specific surface areas (798.51-1227.60 m(2)/g) and large total pore volumes (0.831.29 cm(3)/g), resulting mainly mesoporous. These adsorbents were employed for the adsorption of Methylene Blue in batch process. The dynamic experimental data were adjusted to pseudo-first and pseudo-second order kinetic models by non-linear regression, while the equilibrium experimental data were correlated to the Freundlich and Langmuir models. The monolayer adsorption capacities of this dye reached significant values, between 19.08 and 48.01 mg/g.

Las hojas de platanera, segundo residuo vegetal en orden de importancia del cultivo del plátano, se utilizaron como materia prima para la preparación de seis tipos de carbones activados diferentes. Los adsorbentes se fabricaron a partir de este precursor lignocelulósico mediante activación química con ácido fosfórico modificando durante el proceso de producción la concentración de activante y la temperatura de carbonización. Los diversos carbones activados obtenidos presentaron puntos de carga cero, ligeramente ácidos con considerables áreas superficiales específicas (798.51-1227.60 m2/g) y elevados volúmenes totales de poro (0.83-1.29 cm3/g) resultando predominantemente mesoporosos. Para determinar la capacidad adsorbente de estos tipos de carbones se realizaron pruebas batch utilizando Azul de Metileno. Los datos experimentales dinámicos fueron sometidos a los modelos cinéticos de pseudo-primer y pseudo-segundo orden mediante regresión no lineal, mientras que los datos experimentales de equilibrio se correlacionaron a los modelos de Freundlich y de Langmuir. Las capacidades de adsorción monocapa de este colorante alcanzaron valores importantes que oscilaron entre 19.08 y 48.01 mg/g.