Polyelectrolyte-assisted interfacial polymerization for polyamide nanofiltration membrane with enhanced separation and anti-biofouling properties in groundwater treatment

We proposed a facile method of using polyelectrolyte additive to tune interfacial polymerization reaction and tailor polyamide NF membrane with better separation performance and lower bio-fouling potential for groundwater treatment. A moderate concentration of negatively charged poly(4-styrene sulfonate) (PSS) was introduced to the aqueous phase solution during the interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC). The presence of PSS hindered the diffusion of PIP, leading to the formation of polyamide layer with a looser structure, increased thickness, and additional negative charges on the membrane surface. The fabricated TFC-P₆ membrane possessed enhanced water permeance (21.8 ± 0.7 L m⁻² h⁻¹ bar⁻¹) and better selectivity (α = 11.5 ± 1.0) of calcium chloride over sodium sulfate which can be beneficial to achieve higher water recovery compared to the control TFC membrane. In addition, the TFC-P₆ membrane demonstrated enhanced rejection of perfluorooctane sulfonate (~95 %) and the biofouling was inhibited by its additional negative charge and smoother surface. Our results introduced a robust and scalable strategy of polyelectrolyte-assisted interfacial polymerization for designing high performance NF membranes in groundwater treatment.