Rod-coated PVA interlayer induced nanofiltration membrane: Method development and application for separation of dye/NaCl with greater performance

The textile industry consumes large quantities of freshwater and discharges large quantities of dye/salt wastewater, causing serious environmental problems. Nanofiltration (NF) has proven to be able to achieve efficient dye/salt separation. However, conventional polyamide (PA) NF membranes are often constrained by the trade-off between selectivity and permeability. Herein, we developed a highly dye/NaCl selective nanofiltration membrane with a rod-coated PVA interlayer. The rod-coating approach allows better control of PVA dosage to create a perfect PVA interlayer. The formation and effect of rod-coated PVA interlayer significantly improved the permeability. With an optimal PVA dosage of approximately 0.32 g/m2, the permeance of the iTFC membrane (>30.0 L/(m2 h bar)) was almost 3 times that of the control membrane. Moreover, the iTFC-PVA membrane had an outstanding Rhodamine B rejection (99.8 %), low sodium chloride (NaCl) rejection, and maximum dye/NaCl selective ratio as high as 428. It is anticipated that the iTFC membrane has great potential in the field of dyehouse wastewater treatment. Furthermore, our study proves that the Mayer rod-coating approach is suited to fabricating high-performance PA-NF membranes with PVA interlayers. It is anticipated that organic-containing wastewater can better be treated by the developed membrane to achieve a better water environment and resource recovery.