Green glycerol tailored composite membranes with boosted nanofiltration performance

Bio-coating processes have been recognized as an effective way to advance loose nanofiltration membrane synthesis. A great challenge still remains that the high permeability is difficult to achieve in the bio-coated membrane, especially after thermal cross-linking for optimizing the membrane comprehensive performance. Herein, for the first time, glycerol as a green additive was utilized to not only regulate the structure of the chitosan-polyphenol layer by mitigating crosslinking but also prevent the pore structure of the support from shrinking during the heat treatment process. Based on the comprehensive physicochemical characterizations, the synthesized chitosan-polyphenol membrane with glycerol-intermediated fabrication exhibits more hydrophilic and smoother selective layer and preserved porous support, endowing the membranes with outstanding nanofiltration performance. Glycerol improves the membrane permeability by 300%, reaching 25 L m−2h−1bar−1, while the rejection of the membrane can almost be maintained. Most importantly, the over-70 h filtration results indicate that the nanofiltration membrane coated with glycerol exhibited excellent stability and anti-fouling ability. This strategy provides a simple and effective way to improve the permeability of nanofiltration membranes that need heat treatment.