Preparation and properties of lignin-based composite membranes

Composite membranes were prepared from lignin alkali (LA), polyvinyl alcohol (PVA), and cellulose nanofibrils (CNF) using a simple, low-cost, and environmentally friendly method. The deodorization performances and structures of these membranes were also characterized. The sample referred to as L3C3P5 prepared with a solution containing 35.7 wt% LA, 53.6 wt% PVA, and 10.7 wt% CNF showed the best deodorization properties, and the H₂S adsorption time reached 36 min. The adsorption performance was further improved by adding nano-CuO to the membrane, and the H₂S adsorption time of the doped membrane L3C3P5C4 reached 60 min. While the H₂S adsorption performance improved, structural analysis revealed that the addition of nano-CuO reduced the crystallinity in the membrane, caused the membrane to crack, and led to a decrease in the mechanical properties. The surface oxygens in the L3C3P5C4 membrane were primarily C-O bonds and lattice oxygens in CuO. After the H₂S adsorption reaction, the lattice oxygen disappeared, and CuS products appeared.