Biochar from Andropogon grass (Andropogon gayanus cv. Planaltina) applications in dye removal by adsorption and slow filtration

Abstract

Dyes represent a class of contaminants with a high impact on aquatic ecosystems due to their toxicity. As these pollutants are difficult to degrade, studies on the treatment methods for these compounds are highly important to minimize damage to water bodies that receive these effluents. In this work, the adsorption and slow filtration processes using charcoal produced from the pyrolysis of Andropogon grass (Andropogon gayanus cv. Planaltina) were individually evaluated for removal of the methylene blue dye. The adsorption studies included the evaluation of kinetic behavior, evaluating pseudo-first-order and pseudo-second-order models and adsorption isotherms using the Langmuir, Freundlich, and Dubinin-Radushkevich models. According to the results, it was found that the adsorptive process had greater efficiency between pH 8 and 10. The pseudo-second-order model better described the adsorption kinetic behavior (R2 = 0.9722) and as for the adsorption isotherms, Freundlich's model best described the process. The maximum charcoal adsorption capacity of Andropogon grass for the removal of methylene blue was 17.63 mgg-1. In the filtration process, dye removal reached an efficiency above 99% at filtration rates of 1.5 and 2.1 m3m-2day-1.