Fouling- and chlorine- resistant bilayer heterostructured Janus charged nanofiltration membranes constructed via novel electrospray polymerization-based method

Janus charged nanofiltration (NF) membranes are appealing for efficient separation of both positively and negatively charged ions/molecules. Nevertheless, polyamide-based Janus charged membranes still face bottlenecks in engineering applications due to their poor fouling and chlorine resistance. To overcome this limitation, herein, bilayer heterostructured Janus charged NF membranes with a negatively charged non-polyamide outer selection layer and a positively charged polyamide inner selection layer were prepared via electrospray polymerization-based strategy for the first time. The evolutionary behavior of the mutually charge neutralization effect between two charged selection layers was explored. Results showed the membrane inner selection layer with denser cross-linked structures and lower positive charge densities exhibited a weak charge neutralization effect, leading to ∼90% rejection for both Na2SO4 and MgCl2 and >95% rejection for charged dyes. Impressively, the flux recovery rate of Janus NF membrane could reach 91.9% after three bovine serum albumin fouling cycles. More importantly, the non-polyamide outer selection layer could serve as an “armor” to safeguard polyamide inner selection layer, allowing Janus NF membranes to maintain a normalized salt rejection of 0.94 even under 12000 mg L−1 h chlorination conditions. Thus, this work provides an easy strategy for developing Janus NF membranes with high antifouling properties and chlorine resistance.