Highly permeable polyamide nanofiltration membrane incorporated with phosphorylated nanocellulose for enhanced desalination

Nanofiltration (NF) membranes with excellent permeability and selectivity are highly desirable for the efficient separation but still remain a great challenge. Herein, a novel thin-film nanocomposite (TFN) membrane with excellent permeability and enhanced desalination was prepared by in-situ incorporating phosphorylated cellulose nanofibers (P-CNF) during interfacial polymerization. The unique attributes of P-CNF, especially the well dispersibility in water, excellent hydrophilicity and highly negative charges, were propitious to the formation of defect-free separation layer with hydrophilic nanochannels and high surface charge density. The composite membrane obtained thereby exhibited not only enhanced permeance of up to 17.0 L m(-2) h(-1) bar(-1) but a high rejection of 95.4% for Na2SO4, successfully overcoming the trade-off effect between permeability and selectivity. Importantly, a low rejection of down to 5.3% for NaCl was achieved for the membrane due to a slight increase in effective pore size. Therefore, this composite membrane demonstrated elevated separation factor of up to 18.0 towards mono/divalent salts, 3-6 times higher than those of the reported TFN membranes and commercial NF membranes. Additionally, this membrane displayed highly efficient antibiotic desalination, suggesting its promising potential in pharmaceutical fields. As a result, the incorporation of P-CNF yielded a great enhancement to the water permeance and desalination ability of the polyamide membranes by tuning the microstructure. This work provided a novel biobased green nanomaterial for the fabrication of advanced NF membrane with outstanding perm-selectivity. The developed highly selective and permeable NF membrane has huge potentials in the efficient separation of divalentsalt/antibiotic and monovalent salt.

Automated summary

In this study, a novel thin-film nanocomposite (TFN) membrane with excellent permeability and enhanced desalination was prepared by incorporating phosphorylated cellulose nanofibers (P-CNF) during interfacial polymerization. The presence of P-CNF in the membrane resulted in a defect-free separation layer with hydrophilic nanochannels and high surface charge density, leading to enhanced permeability and rejection performance. The developed membrane showed 3-6 times higher separation factor than reported TFN membranes and commercial NF membranes, indicating its potential in efficient separation and antibiotic desalination.