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.