Alginate hydrogel interlayer assisted interfacial polymerization for enhancing the separation performance of reverse osmosis membrane

Reverse osmosis (RO) is widely used in water purification process. However, most commercial RO membranes have low water permeance, and encounter a "trade-off" effect between permeance and rejection. In this work, a kind of RO membrane with an in-situ formed film of sodium alginate (SA) hydrogel as an interlayer on the surface of a polysulfone (PSf) substrate has been extensively investigated. The SA hydrogel interlayer significantly controls and reduces the diffusion rate of the aqueous monomer, m-phenylenediamine (MPD) during the interfacial polymerization (IP), leading to the formation of a relatively smooth (−58 nm) polyamide (PA) separation skin layer with more unreacted acryl chloride groups remaining thereon, which makes it more hydrophilic after the hydrolysis of these groups. Under the optimal fabrication conditions, the water permeance achieves 27.8 L m−2 h−1 MPa−1 with a salt rejection maintaining at 99.2 % for 2000 mg L−1 NaCl solution, indicating that the prepared RO membrane has a broad prospect for the application in brackish water desalination, which is beneficial for the future development of RO membranes with high performance.