Lignin-enriched cellulose membranes for efficient removal of synthetic dyes from aqueous environments

The study presents cellulose-based membranes derived from lignin-rich (unbleached high-kappa number softwood and hardwood) and lignin-free (fully bleached softwood) kraft pulps for the removal of cationic dyes from both simulated and real aqueous environmental systems. Characterization techniques revealed that the lignin-enriched cellulose-based membranes exhibited enhanced wet mechanical properties and a broader range of functional groups. The functional diversity inherent in lignin-containing membranes resulted in superior adsorption capacity for dyes such as Methylene Blue and Crystal Violet, compared to lignin-free counterparts. Detailed adsorption performance metrics—including kinetics, equilibrium studies, and the effects of pH and ionic strength—were thoroughly investigated. The adsorption capacity was 99–102 μmol g −1 for hardwood-derived membranes and 79–85 μmol g −1 for softwood-derived membranes at 25 °C. The process followed the pseudo-first-order kinetic model, likely due to the membranes' low porosity and energy homogeneity, which facilitated rapid adsorption. Electrostatic interactions played a pivotal role in dye attraction, while pH and ionic strength studies emphasized the importance of hydrogen bonding between cationic dyes and lignocellulose-based membranes. This research highlights the significance of utilizing cellulose-based membranes with enhanced lignin content in water purification, demonstrating their effective adsorption capabilities in both controlled and real-world environments. The approbation tests of these membranes showcased their substantial potential for practical water purification applications, contributing to the development of sustainable and efficient water treatment solutions. • Cellulose-based membranes derived from lignin-rich pulps were synthesized. • Membranes exhibit enhanced wet mechanical properties and diverse functional groups. • The presence of lignin facilitates H-bonding with dyes, enhancing the adsorption compared to lignin-free membranes. • High-lignin content cellulose membranes provide an environmentally friendly, scalable option for water treatment. • Practical applicability confirmed in both controlled and real-world environments.