Wood-Inspired Filter with a Lignin-Reinforced Nanocomposite Layer for Enhanced Oil/Water Separation and Selective Dye Removal

Nanocomposite filter membranes have attracted a great deal of attention in water purification. However, the weak interaction between nanomaterials and filter matrices severely reduces the stability and causes secondary pollution. Herein, inspired by the structure and function of natural wood, we report a simple strategy for fabricating a filter that uses alkaline lignin as a multifunctional modifier to tailor graphene oxide (GO) and bridge from GO to the surface of the glass fiber (GF). The obtained lignin-GO-modified GF filter was covered by a thin nanocomposite layer (∼2 μm) and exhibited hydrophilic and underwater oleophobic properties. It performed well in separating different oil-in-water emulsions (>92% for n-hexadecane, n-dodecane, and engine oil) under gravity and in selectively removing cationic dyes due to interception and adsorption via electrostatic effects and π–π interactions. Moreover, the filter had good stability and could be regenerated by washing without a significant loss of removal efficiency of n-dodecane-in-water emulsions during five consecutive cycles (1.86% per cycle). Therefore, this study shows that the wood-inspired filter membrane holds considerable promise for wastewater treatment, especially for oil/water separation and selective dye removal.