Polyoxometalates decoration combining with solvent activation for enhanced separation performance of nanofiltration membrane

Abstract

Nanofiltraion (NF) membranes are promising candidates for overcoming critical global issues of access to clean water. However, current NF membranes are hampered by the trade-off between the water permeability and selectivity as well as the fouling propensity. In this work, a facile surface decoration simultaneously combined with solvent activation strategy was adopted for the NF membrane modification via simply immersing membrane into the polyoxometalates (POMs) ethanol solution. The introduction of POMs by coordination assembly increases the membrane hydrophilic and electronegativity, and the ethanol loosens the membrane selective layer, leading to the enhanced membrane perm-selectivity and anti-organic fouling property. The permeance and Na₂SO₄ rejection of the optimized modified NF membrane are 14.90 ± 0.21 LMH/bar and 99.20 ± 0.38 %, which are ∼20 % and more than 3 % increments compared with those of the control membrane, respectively. The modified NF also reveals a lower permeance decline as well as a higher flux recovery toward both positive and negative charged foulants. In addition, benefiting from the biocidal activity of the POMs, the membrane anti-biofouling property is also significantly improved under an extremely low loading of POMs. More importantly, the chemical stability of the modified NF membrane is reinforced due to the protection from the introduced POMs. Our work contributes to revitalizing the prospect of developing NF membranes with excellent filtration performance and antifouling property.