Design and function of lignin/silk fibroin-based multilayer water purification membranes for dye adsorption

The treatment of dye wastewater poses a significant challenge to the sewage recycling industries. However, the reduction of secondary pollution resulting from the membrane residues, to maintain high performance, remains a considerable obstacle. A novel approach for the fabrication of multilayer nanofiber structures using a layer-by-layer electrostatic spinning technique with biological materials was reported in this study. Incorporating the chemical adsorption advantages of lignin nanofiber and the physical adsorption advantages of silk fibroin (SF) nanofiber enabled the full realization of excellent dye interception performance. A comparative analysis was conducted on the lignin derived from eucalyptus, pine, and straw to determine the most suitable option. Notably, eucalyptus lignin exhibited superior antimicrobial properties. The adsorption of crystal violet by eucalyptus lignin/SF membrane was consistent with the Freundlich isotherm model and the pseudo-second-order kinetic model, revealing a chemisorption mechanism involving Π-Π conjugation, hydrogen bonding, and the binding of anions and cations. The lignin/SF membrane exhibited a retention rate exceeding 99.5 % for crystal violet, methylene blue, and brilliant green dyes. Furthermore, it demonstrated efficacy in retaining heavy metal ions, including cadmium and copper. The original biomass material imparts the property of rapid degradation to a multilayer membrane that can be used as an effective and eco-friendly water purification material.