In-situ lignin assembly on aramid nanofibers: fibrous hybrids for stable and efficient Pb²⁺ removal

Constructing lignin-based nano-adsorbents with modulated surface polarity demonstrates promising efficiency, sustainability and biocompatibility in the application of Pb²⁺ removal, nevertheless, which is hard to achieve. Here, a delicately designed assembly process of amphiphilic lignin was performed on the surfaces of aramid nanofibers (ANF), and a fibrous nano-hybrid (ANF@L_x) with uniform sheet-like lignin aggregations on ANF was obtained. Ascribing to the dominated π-π stacking between benzene rings on ANF and lignin, the H-bond between them weakened relatively, and more oxygen containing polar groups on lignin were exposed. Combining the advantages of fibrous morphology and active surfaces, the ANF@L_x exhibited favorable processibility that can be molded into membranes and aerogels with different scales and shapes, and conducive adsorption capacity (∼587.8 mg/g), kinetic (achieve equilibrium within 1 min) and selectivity toward Pb²⁺ in contaminated water resources. Thus, this work paved a green, simple and energy efficient way to modulate the assembly of lignin in micro-nano interfaces, and construct lignin-based nano-adsorbents with both of high Pb²⁺ removal efficiency and promising industrial application potential.