Ultrafast Graphene Oxide-Lignin Biopolymer Nanocomposite Membranes for Separation of Biomolecules, Dyes, and Salts

Graphene oxide offers a promising opportunity to fabricate highly efficient and pressure-endurable membranes in terms of water permeability while demonstrating a high level of solute rejection. However, achieving higher permeance with an excellent separation capability is still challenging. Herein, we report a class of graphene oxide-lignin biopolymer (GOLB) membranes for the first time prepared by functionalizing GO nanosheets with lignin biopolymer extracted from plant pulp. Lignin biopolymer is the most abundant, green, low-cost, and environmentally friendly material with a variety of oxygen functional groups. The as-prepared GOLB membranes have a unique laminated structure that provides an excellent rejection (>99%) for several organic dyes, proteins, and biomolecules with variable molecular weight and exhibits ultrawater permeance similar to 1300 L m(-2) h(-1) bar(-1), more than that of reported GO-based membranes. It is interesting that due to larger interlayer spacing, such membranes show less rejection (<10%) for salts, i.e., NaCl, MgCl2, Na2SO4, etc. Furthermore, these membranes are highly stable up to 37 days in an aqueous environment and 28 days in acidic and basic solutions compared to pristine GO-based membranes.