Preparation of Aminated Sodium Lignosulfonate and Efficient Adsorption of Methyl Blue Dye

The aminated sodium lignosulfonate (AELS) was prepared through a Mannich reaction and characterized via FT-IR, TG, SEM and XPS in this study. Subsequently, the adsorption capacity of AELS for methyl blue (MB) was evaluated under various conditions such as pH, adsorbent dosage, contact time, initial concentration and temperature. The adsorption kinetics, isotherms and thermodynamics of AELS for methyl blue were investigated and analyzed. The results were found to closely adhere to the pseudo-second-order kinetic model and Langmuir isotherm model, suggesting a single-molecular-layer adsorption process. Notably, the maximum adsorption capacity of AELS for methyl blue (153.42 mg g^-1) was achieved under the specified conditions (T = 298 K, M = 0.01 g, pH = 6, V = 25 mL, C₀ = 300 mg L^-1). The adsorption process was determined to be spontaneous and endothermic. Following five adsorption cycles, the adsorption capacity exhibited a minimal reduction from 118.99 mg g^-1 to 114.33 mg g^-1, indicating good stability. This study contributes to the advancement of utilizing natural resources effectively and sustainably.