Impact of support pore properties on the performance of layer-by-layer self-assembly nanofiltration membrane

This paper investigates the impact of the porous structure of the support on the permselectivity and backwash resistance of Layer-by-Layer (LBL) nanofiltration (NF) membranes. Four different polyethersulfone (PES) hollow fiber membranes with varying pore sizes were coated with poly(allylamine hydrochloride)/poly(sodium-4-styrenesulfonate) (PAH/PSS) polyelectrolyte pairs. The study found that adjusting the number of bilayers in the coating process enabled the production of LBL membranes with similar molecular weight cut-off (MWCO) around 250 Da and high Mg2+ rejection of 95 %. However, Na2SO4 rejection decreased as the number of bilayers increased, as the positively charged PAH overcompensated. The study also found that the pore size of the support did not significantly impact the backwash resistance of the LBL membranes, indicating that the polyelectrolyte chains can penetrate through the pores of the supports regardless of pore size. This finding can guide the design of suitable supports for LBL NF membranes with tailored performances.