Biochar from sugarcane bagasse for reactive dye adsorption considering a circular economy approach

Abstract

Ethanol from sugarcane has advantages over fossil fuel in reducing greenhouse gas emissions and improving the air quality in cities. However, ~280kg of sugarcane bagasse, an agro-industrial waste, are still generated during the processing of 1 ton of sugarcane. In this paper, the sugarcane bagasse, was converted into activated biochar (AB) and the physicochemical properties and morphology of the AB were determined. The potential absorbent for reactive blue 19 dye (RB19) onto AB under different conditions was studied, considering the pH influence, adsorption isotherms, kinetic studies and thermodynamic parameters. Finally, a preliminary circular economic analysis was also performed. The characterization of AB showed microtubes of up to 1µm diameter and cavities lower than 0.5µm, with a specific surface area of 687m2/g and an iodine number of 656mg I2/g. The Freundlich adsorption isotherm resulted in the best fit for the experimental data, with maximum adsorption of 58.1 mg/g at pH 2 and 31.4mg/g at pH 5. The adsorption took place in the first 2h, following a pseudo-second-order kinetic model. The thermodynamic experiments showed that higher temperatures improved the removal efficiency by ~10% and that the process is endothermic. The preliminary circular economic analysis for AB preparation revealed a cost of 2.18USD/Kg of adsorbent. This study indicates that AB is an economical material for large-scale wastewater treatment in textile industries, offering an alternative pathway for the agro-industrial waste generated during the ethanol production.