Alkali-resistant polyethyleneimine/triglycidyl isocyanurate nanofiltration membrane for treating lignin lye

Abstract Lignin is a widely used biomass material and has great application potential in papermaking, textile, petrochemical industry, etc. However, the traditional separation and extraction method for the lignin system has some disadvantages in energy consumption and separation effect, which greatly limited the application of lignin. The rapid development of nanofiltration (NF) membranes provides new ideas for solving this problem. The PEI/TGIC membrane with great alkali resistance (pH 7–14) by cross-linking polyethyleneimine (PEI) and triglycidyl isocyanurate (TGIC) was developed in this work. The influencing factors of membrane surface characteristics were discussed and membrane preparation parameters were optimized. The optimized PEI/TGIC membrane (prepared with 0.02% TGIC and 0.8% PEI) had the characteristics of high permeability and selectivity under low pressure (2 bar). The PEI/TGIC membrane was stable to the removal of PEG 1500 in an alkaline environment (pH 7–14). For lignin lye, the PEI/TGIC membrane could intercept the lignin (rejection>95%) while allowing the sodium hydroxide to almost completely penetrate. Under the operating pressure of 2 bar, the lye permeation flux could be maintained at 22 L m−2 h−1. This work provided new ideas for the application of nanofiltration membranes and the treatment of lignin lye.