Cellulose and its cationic derivative obtained from soybean hull as a tool for the remediation of textile dyes in wastewater: Physicochemical characterization and molecular mechanism interaction

Textile industries represents one of the most pollutants industries due to the discharge of contaminated water into waterways. Around 20% of industrial water pollution arise from textile manufacture. Among the current remediation techniques, adsorption using agro-industrial wastes is emerging as an efficient tool. In this work, chemical semi-crystalline cellulose and its derivative functionalized with quaternary ammonium groups were assayed as adsorption beds. These adsorbents were physically characterized by Fourier transform infrared spectroscopy, X-ray diffraction, nitrogen adsorption to determine total surface area and differential scanning calorimetry. Applicability and efficiency of these biosorbers were assayed using Congo Red as a model textile dye which is an organic pollutant compound. Adsorption of this dye induced disorder onto the surface of cellulose modifying its morphology. The adsorption kinetics were studied, showing that the adsorption of the dye followed a pseudo-second order rate expression on both adsorbents. Different adsorption isotherm models were applied to describe the equilibrium isotherms. The empirical Freundlich model was found to be more suitable for both adsorbents. Adsorption capacities of the extracted and the cationized cellulose were 112 and 314 mg/g, respectively, therefore maximum adsorption capacity values (similar to 55 mg/g) were found to be much higher and adsorption times (20-90 min) were found to be much lower than the average of various Congo Red adsorbents produced from agro-industrial waste. A thermodynamic study showed that the adsorption of Congo Red onto cellulose and its cationic derivative was endothermic in nature (20.03 and 8.58 kJ/mol, respectively) with a positive entropic change.