Construction of a gelatin scaffold with water channels for preparing a high performance nanofiltration membrane

Abstract

In order to realize energy saving and resource recovery in desalination and waste-water treatment, it is urgent to develop nanofiltration (NF) membranes with high permeability and selectivity. Therefore, many researchers devote to designing different hydrophilic polymer-interlayers for the thin-film composite (TFC) membranes, targeting to prepare NF membranes with outstanding separation performance. However, the thin polymer-interlayer (<10 nm) can only slow down the diffusion rate of aqueous monomer and affect the interfacial polymerization (IP) process, forming a thin and defect-free polyamide (PA) layer. Herein, we constructed a hydrophilic and homogeneous gelatin (GT) scaffold with a thickness of over 100 nm on polysulfone (PSF) substrate and prepared a PA separation layer by IP process to obtain a high-performance TFC based NF membrane. The scaffold can not only affect the diffusion rate of piperazing (PIP) in IP process to form a thin PA layer, but also provide additional channels for water diffusion, which would significantly improve the permeability of NF membranes. Moreover, the fabricated PA layer has a high cross-linking degree and a negative surface potential, endowing the NF membrane with a high salts rejection rate, especially for divalent anions. Hence the permeability of the resulting NF membrane (up to 16.95 ± 1.18 L m−2 h−1 bar−1) is about 2.5 times as compared with the controlled membrane, while achieving a high Na2SO4 rejection of 99.3% ± 0.2%. In addition, the coefficient of selectivity for NF membrane are 97.73 for αNaCl/Na2SO4 and 45.66 for αNaCl/MgSO4 respectively, which are several times higher than those of the controlled NF membrane. This work provides a low-cost and facile method to prepare a TFC based NF membrane with a high permeability and selectivity.