How the Carbonization Time of Sugarcane Biomass Affects the Microstructure of Biochar and the Adsorption Process?

Biochars (BCs) are very versatile adsorbents, mainly, in the effectiveness of adsorption of organic and inorganic compounds in aqueous solutions. Here, the sugarcane biomass (SCB) was used to produce biochar at different carbonization times: 1, 2, 3, 4, and 5 h, denominated as BC1, BC2, BC3, BC4, and BC5, respectively. The superficial reactivity was studied with adsorption equilibrium experiments and kinetics models; Methylene Blue (MB) was used as adsorbate at different pH values, concentrations, and temperatures. In summary, the carbonization time provides the increase of superficial area, with exception of BC4, which decreased. Equilibrium studies showed inflection points and fluctuations with different initial dye concentration and temperature; SCB showed the best adsorption capacity compared to the BCs at the three temperatures tested, varying with the increase of MB concentration, suggesting the dependence of these two main factors on the adsorption process. The proposed adsorption mechanism suggests the major influence of Coulomb interactions, H-bonding, and π-interactions on the adsorption of MB onto adsorbents, evidencing that the adsorption is led by physical adsorption. Therefore, the results led to the use of the SCB without carbonization at 200 °C, saving energy and more adsorbent mass, considering that the carbonization influences weight loss. This study has provided insights of the use of SCB in MB dye adsorption as a low-cost and eco-friendly adsorbent.