Polyamide membrane with an ultrathin GO interlayer on macroporous substrate for minimizing internal concentration polarization in forward osmosis

The conventional polyamide membranes composed of a polyamide active layer on an ultrafiltration (UF) substrate hold a dominant position in forward osmosis (FO). However, the membrane permeation is currently restricted by severe internal concentration polarization (ICP) due to the high resistance of the UF substrate with hierarchical pore structures. Herein, an ultrathin graphene oxide (GO) interlayer on polyethersulfone (PES) macroporous substrate is intentionally constructed to tailor the structure of composite membrane, and thus improve the separation performance. The ultrathin GO interlayer not only inhibits the penetration of polyamide into substrate, but also provides a smooth surface for interfacial polymerization (IP). Besides, it can significantly decrease membrane resistance due to its thickness of only 10 nm. Consequently, a uniform, continuous and defect-free polyamide active layer was formed due to the confined IP reaction upon the PES substrate. It was found that the polyamide membrane with GO interlayer exhibited a favorable water flux of 22 L m−2 h−1 at AL-FS mode with deionized water and 2 mol/L NaCl as feed and draw solutions, respectively, 144% higher than that of the control membrane without GO interlayer. Meanwhile, it achieved a moderate ICP over GO interlayer modified macroporous support. Moreover, it exhibited an excellent stability during 120 h test. The research provides a promising approach to fabricate high-performance polyamide membrane on macroporous substrate for forward osmosis.