RESUMO
The endocarp of Wodyetia bifurcata was used to produce biochar by vacuum pyrolysis as an alternative adsorbent for methylene blue (MB) removal. The influence of different pyrolysis temperatures, particle diameters and activation agents in the adsorption process was studied. Kinetics and adsorption equilibrium were also evaluated. Biochar obtained at higher pyrolysis temperatures and activated with H3PO4 showed the best adsorptive capacities, achieving 83% of MB removal. The experimental data fitted better with pseudo-second order model. Isotherms performed at 25, 40, 50 and 60⯰C showed that the adsorption of MB onto the activated biochar had no concentration dependence in the range studied. Experimental isotherms fitted well with the Freundlich and Sips models and the thermodynamic parameters suggested a physical adsorption mechanism in a heterogeneous surface, spontaneous at all temperatures evaluated. In brief, the activated carbon obtained from Wodyetia bifurcata can be a promising material for MB removal from aqueous solutions.
Assuntos
Carvão Vegetal , Poluentes Químicos da Água , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Azul de MetilenoRESUMO
This work aims to produce activated carbon from the endocarp of Syagrus oleracea by vacuum pyrolysis and evaluate its potential as an adsorbent. The effects of pyrolysis temperature (400 °C, 500 °C, 600 °C, and 700 °C), particle diameter (0.467 mm, 0.267 mm, and lower than 0.234 mm), and activation agent (H2SO4, H2PO3, and KOH) on the potential for methylene blue adsorption were investigated. In addition, kinetics and adsorption equilibrium were evaluated. The best condition found was particle diameter < 0.234 mm, final pyrolysis temperature of 700 °C, and using KOH. Adsorption kinetics followed pseudo-second order, with equilibrium reached within 20 min. Isotherms followed the Freundlich model. Values of adsorption capacity were in the order of 30 mg/g. Thermodynamic parameters indicated that adsorption occurred spontaneously with a reduction in the heterogeneity of the solid interface/solution. The results obtained demonstrate the great adsorption capacity of the activated carbon prepared from endocarp of Syagrus oleracea via vacuum pyrolysis for the removal of up to 98% methylene blue from aqueous solutions.