Enhanced Desalination Polyamide Membranes Incorporating Pillar[5]arene through in-Situ Aggregation-Interfacial Polymerization-isAGRIP

Graphical Abstract

Inspired by biological models, artificial water channels can be used to overcome the permeability/selectivity trade-off of traditional desalination membranes. This work demonstrates that rational incorporation of pillar[5]arene artificial water channels in composite polyamide membranes synthesized via interfacial polymerization, provide defect free biomimetic membranes. Intrinsic water-to-salt permeability on the operational BWRO desalination pressure and medium salinity conditions are: 2.76±0.5 L m⁻² h⁻¹ bar⁻¹ and high 99.5 % NaCl rejection.

Abstract

Membrane-based desalination have an important role in water purification. Inspired by highly performant biological proteins, artificial water channels (AWC) have been proposed as active components to overcome the permeability/selectivity trade-off of desalination processes. Promising performances have been reported with Pillararene crystalline phases revealing impressive molecular-scale separation performances, when used as selective porous materials. Herein, we demonstrate that Pillar[5]arene PA[5] aggregates are in-situ generated and incorporated during the interfacial polymerization, within industrially relevant reverse osmosis polyamide-PA membranes. In particular, we explore the best combination between PA[5] aggregates and m-phenylenediamine (MPD) and trimesoylchloride (TMC) monomers to achieve their seamless incorporation in a defect-free hybrid polyamide PA[5]-PA membranes for enhanced desalination. The performances of the reference and hybrid membranes are evaluated by cross-flow filtration under real reverse osmosis conditions (15.5 bar of applied pressure) by filtration of brackish feed streams. The optimized membranes achieve a ∼40 % improvement, in water permeance of ∼2.76±0.5 L m⁻² h⁻¹ bar⁻¹ and high 99.5 % NaCl rejection with respect to the reference TFC membrane and a similar water permeance compared to one of the best commercial BW30 membranes (3.0 L m⁻² h⁻¹ bar⁻¹ and 99.5 % NaCl rejection).