The intercalation of nanoscale lattices into micro-sized graphene oxide sheets for enhancing pressure-driven desalination performances

Graphene oxide based nanofiltration membranes (GONMs) have attracted tremendous attention for water purification applications given their excellent mechanical properties and tunable inter-layer distance spacing (D-spacing). However, the desalination performance is significantly degraded in the pressure-driven filtration. In this work, we find that the pressure-driven water desalination properties are nanochannel spacing and length dependent, in which the cation-π interaction possibly plays a critical factor in the desalination procedure. Through the demonstration of surface weak-reduction and membrane thickness tuning, the D-spacing and molecule transport route length of GONMs are identified to affect the quality and quantity of cation-π interaction, respectively, which are innovatively regulated by the intercalation of nano-sized lattices into large GO sheets. As a result, the regulated membrane improves the rejection rates of MgCl2, NaCl, MgSO4 and Na2SO4 up to 41.10%, 64.14%, 84.62% and 93.19%, respectively, compared to unregulated counterparts of 13.72%, 15.93%, 34.58% and 40.99%, respectively. In addition, the regulated membrane also exhibits excellent removal efficiency of >93% against tested dyes with different molecular weight and surface charge properties. We consider that our approach could lead to the development of a powerful GONMs based platform for future water treatment.