Woody biomass derived nano lignin-enabled membrane with high structural stability for efficient wastewater treatment

The application of renewable and functional group-enriched lignin has recently gained massive popularity in wastewater treatment applications. Herein, woody biomass-derived organosolv lignin nanoparticles (LNPs) with uniform colloidal spherical morphology and average particle size (⁓150 nm) were synthesized via a simple and facile anti-solvent nanoprecipitation technique and used for the fabrication of ultrafiltration nanocomposite membrane. Upon the addition of LNPs to polyether sulfone (PES) matrix, the LNPs-impregnated membrane exhibited a thinner surface layer that induced low resistance to water flow, high pore density (83.2 ± 0.9%) with uniformly distributed pores, wider and well-connected internal macrovoids with higher sub-layer porosity, and a higher negative surface charge (−29.8 mV). These structural features hence contributed to high stable permeation flux (92.3 L m⁻² h⁻¹) and higher removal efficiencies (> 95%) for treating cationic (methylene blue) and anionic (methylene orange) dyes over a wide range of environmentally relevant pH conditions. The electrostatic interactions between the charged membrane surface and dye species revealed the underlying mechanism for higher dye rejection through the PES-LNP membrane. Finally, the structural stability analysis confirmed the complete incorporation/immobilization of LNPs within the PES matrix, making it ready for real-world applications in wastewater treatment. © 2023 The Institution of Chemical Engineers