Fabrication of high-performance nanofiltration membranes by using sulfated cellulose nanofibril as the intermediate support layer

The preparation of high-performance nanofiltration membranes with high permeability and selectivity is a big challenge. Herein, we proposed a novel composite nanofiltration membrane used sulfated cellulose nanofibril (SCNF) to prepare the intermediate support layer. Three SCNFs with different amounts of surface charge was prepared by deep eutectic solvent pretreatment and mechanical treatment. The composite nanofiltration membrane was fabricated with three layers, and physicochemical properties and separation performance of composite nanofiltration were analyzed. The results showed that with the increase of the amount of surface charge of the intermediate support layer of SCNF, the roughness and absolute value of surface zeta potential of the composite nanofiltration membrane all increased, the maximum roughness value was 112 nm, while the absolute value of surface zeta potential was 85 mV. The decreasing of water contact angle indicated that hydrophilicity of composite nanofiltration membrane enhanced. The membrane exhibited high Na2SO4 rejection above 98% and water permeability above 30 L/m2/h under 2 bars. Moreover, the optimal membrane of PES/H-SCNF/PIP-TMC showed the rejection order was Na2SO4 (98.91%) > Mg2SO4 (78.42%) > MgCI2 (49.80%) > NaCI (21.23%) > CaCI2 (12.31%). These outstanding separation characters endowed the membranes with a great prospect in the process of desalination for future application.