Biopolymer-based reduced graphene oxide/functionalized CNTs with high separation efficiency: experimental investigation through density functional theory

Herein, we demonstrate a new design approach combining theoretical and practical frameworks in the development of biopolymer (chitosan)-based reduced graphene oxide (rGO) membranes with embedded functionalized carbon nanotubes (CNTs) via polymeric phase transformation. The crosslinked, highly porous biopolymer structure provides structural integrity to embed rGO laminates and CNTs, enabling them to have an ultra-water permeability of 9071.9 L m−2 h−1 bar−1 (1000-fold higher than GO) with a rejection of up to 99% for methylene blue, methyl orange, rhodamine B, and bromocresol green dyes. Further, the selectivity increased with the curing times of membranes, which negatively affected the permeability. The SEM image processing technique elucidated that the as-prepared composite membrane showed 300% higher surface porosity and pore sphericity compared to that of the conventional GO membranes. Additionally, we conducted density functional theory (DFT) adsorption and sorption analysis to examine the impact of individual constituents on the membrane's properties. Furthermore, the structural stability of GO has been improved to overcome several problems related to microstructural instability, low surface porosity, and erosion under crossflow conditions, which limits its application in membrane fabrication. We believe this study provides a novel method for designing and developing separation membranes.