Biosorption of the red 4B dye was evaluated using non-colonized sugarcane bagasse and colonized by Pleurotus ostreatus. The fungal colonization caused an increase in the acid and phenolic groups, making the biosorbent surface more positive, with lower thermal stability due to decomposition of lignocellulosic compounds, lower pHpcz, and smaller pores. The biosorbents showed better adsorption at pH 2.0 and required 260 min to reach equilibrium. The kinetic data fit the pseudo-second order mathematical model, which predicts strong chemical interaction between adsorbent and adsorbate. The mathematical models that best fit the isothermal data were the combination of Langmuir for low dye concentrations and Freundlich for high dye concentrations in the solution for the non-colonized biosorbent, which predict that adsorption occurs in monolayer and multilayer, respectively. For the colonized biosorbent, the model that best fits the isothermal data (25°C and 40°C) was the Freundlich model, showing that the adsorption for this case occurs in multilayers. Thermodynamic studies (25°C, 40°C and 50°C) show that increasing temperature decreases the biosorption capacity (exothermic process for both biosorbents), and the system shows low spontaneity with increasing concentration. Also, the entropy for non-colonized sugarcane bagasse increases at low concentrations, however after fungal colonization, it decreases for both. In industrial effluent, the non-colonized biosorbent presented a higher biosorption capacity, but fungal colonization demonstrates greater sustainability by initially allowing the production of mushrooms.
Keywords: Textile industry; adsorption; agroindustrial waste; bagasse; dye.