Preparation of molecular selective GO/DTiO2-PDA-PEI composite nanofiltration membrane for highly pure dye separation

The state-of-the-art graphene oxide (GO) has been wildly used in water purification due to its tunable nanoscale interlayer between the two-dimensional nanosheets . However, the structural instability and flux decline performances significantly limit the practical application of GO-based membranes. Herein, a novel GO/DTiO 2 -PDA-PEI (dopamine modified TiO 2 ) composite nanofiltration membrane has been prepared via a multi-coupled strategy, combining with the self-assembly, copolymerization and surface grafting. Tuning the nanoscale interspace between the GO nanosheets , and constructing the membrane with positively charged surface and negatively charged subsurface, the loose GO/DTiO 2 -PDA-PEI composite nanofiltration membrane (GDP 1 P 2 -0.6 membrane with a mean pore size = 0.87 nm) show the filtration performance with water permeance as high as 41.6 L m −2 h −1 bar −1 and dye rejection around 99.9%, and the molecular selective factor (Eriochrome black T/Na 2 SO 4 ) of α = 47.6. Long-term performance and stimulation have been investigated to further analyze the dye concentration and salt removing. The investigations demonstrate that the GO/DTiO 2 -PDA-PEI composite nanofiltration membrane enriches 14.9-fold Eriochrome black T (ET) and reduces Na 2 SO 4 to 0.36% in the term of the concentration factor 15 and batch diafiltration factor 5.