Biocarvões de bagaço de cana-de-açúcar pirolisados em diferentes atmosferas de aquecimento para adsorção de Mn(II) de solução aquosa

Abstract

Toxic metals such as manganese are contaminants discharged into water resources from various pollution sources, including effluents from activities like mining. This contamination renders the use of such water resources impractical. Therefore, water treatment methods such as adsorption are necessary to ensure water quality. Currently, several adsorbent materials are proposed for removing toxic metals from aqueous effluents. Among these, biochars obtained from agro-industrial waste offer a low-cost, high-performance option. Sugarcane, considered one of the world's most efficient agricultural crops, produces waste that can be transformed into sugarcane bagasse, one of the most reused agricultural biomasses. Sugarcane bagasse has significant potential for biochar production. This study aims to produce biochars from alkali- modified sugarcane bagasse under different pyrolysis atmospheres for the removal of Mn(II) from aqueous media. Pyrolysis was conducted using a muffle furnace and in tunnel-type furnaces with nitrogen or argon atmospheres. The produced materials were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and zero point of charge (pHPCZ) to assess the effect of the pyrolytic atmosphere on the morphology, thermal stability, and composition of the materials. Adsorption equilibrium studies were conducted under different conditions to evaluate the performance of the produced biochars in removing manganese from aqueous effluents. The different types of pyrolysis atmosphere and biomass pretreatment influenced the yield of the biochars and the functional groups on the material surface. Meanwhile, pHPCZ values were practically independent of the pyrolysis atmosphere, with a slight decreasing trend for materials obtained in N2 and Ar atmospheres. The biochar obtained in an argon atmosphere exhibited the highest number of basic and acidic groups among the biochars produced and showed higher adsorption capacity at lower concentrations of the metal ion. The highest maximum removal capacity was achieved by the biochar produced in the muffle furnace.