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High-pressure reverse osmosis (HPRO) holds promise as a technology for the energy-efficient desalination of hypersaline brine (≥70 g/L total dissolved solids). In this work, we examined the effects of membrane compaction for four types of thin-film composite (TFC) RO membranes from DuPont Water Solutions (XLE, BW30, SW30HR, and XUS180808) using a crossflow filtration setup. The membranes were tested at a maximum applied pressure (ΔP) of 200 bar using a seawater desalination brine feed solution (70 g/L NaCl) to simulate conditions encountered in HPRO processes. Post-compaction membrane characterization revealed the densification of the support and selective layers of the TFC membranes (42–61% decrease in thicknesses and 15–22% reduction in polyamide heights, respectively) with respect to their pristine analogues. We also performed a mechanical strength analysis of the support layers that revealed the inverse relationship between the Young's modulus and magnitude of support layer compression. Our results suggest that support layers with a tensile strength ≥7 MPa and a Young's modulus ≥130 MPa are necessary to fabricate mechanically robust TFC membranes for HPRO application. In terms of desalination performance, the least compact-resistant membrane, XLE, displayed a drastic drop in water permeability and salt rejection from 1.63 L m−2 h−1 bar−1 and 97.5% in seawater RO test (ΔP: 55 bar, 35 g/L NaCl feed solution) to 0.39 L m−2 h−1 bar−1 and 95.0% in HPRO test (ΔP: 200 bar, 70 g/L NaCl feed solution). On the other hand, the most compact-resistant membrane, XUS180808, showed the least decline from 0.60 L m−2 h−1 bar−1 and 99.4% in seawater RO test to 0.35 L m−2 h−1 bar−1 and 99.2% in HPRO test. Overall, all four membranes showed irreversible decline in performance after HPRO tests whereby they could not regain their original permeability values at lower pressures (<200 bar). [Display omitted] • TFC membranes were tested in HPRO for brine desalination (ΔP: 200 bar; feed: 70 g/L NaCl). • Best-performing membrane showed a permeability of 0.35 L m−2 h−1 bar−1 (99.2 % rejection). • Compacted membranes displayed a densified support layer (42–61 % decrease in thickness). • Support layers with tensile strength ≥7 MPa and modulus ≥130 MPa are suitable for HPRO. • Nanovoids were preserved in the compacted polyamide layers (∼20 % decrease in height). [ABSTRACT FROM AUTHOR]

[Display omitted] • Reverse IP strategy was proposed to fabricate TFC PA membranes. • Defect-free PA skin layer was constructed on hydrophobic PVDF/PTFE substrates. • The membranes exhibit excellent performance in aqueous and organic solutions. • Pure water permeances are over 11 LMH/bar with MgCl 2 rejections of over 95%. • Methanol permeances are over 3.3 LMH/bar with Congo red rejections of over 98.5%. Polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) porous membranes are ideal substrates for preparing thin-film composite (TFC) polyamide (PA) membranes with improved solvent resistance. However, it remains difficult to construct PA skin layers on PVDF and PTFE substrates via conventional interfacial polymerization (IP) due to the hydrophobic nature of these materials. To address this challenge, a reverse IP process was proposed to construct a defect-free PA skin layer on PVDF and PTFE substrates, in which the hydrophobic PVDF and PTFE substrates were soaked with the organic phase to ensure uniform coverage of reacted solution on the substrates. This novel strategy can effectively tackle the issue of uneven wetting of the aqueous phase on hydrophobic substrates in the conventional IP process. The resultant TFC membranes (i.e. M rev-PVDF and M rev-PTFE) exhibit excellent nanofiltration (NF) performance in both aqueous and organic solutions. M rev-PVDF and M rev-PTFE have MgCl 2 rejections of 96.12% and 95.17%, alongside the water permeances of 12.8 LMH/bar and 11.2 LMH/bar, respectively (M rev-PTFE was activated with DMF). It is further shown that M rev-PVDF and M rev-PTFE could also reject 99.4% and 98.5% of Congo red in methanol solution at solvent permeances of over 3.3 LMH/bar, while they also perform excellently in other polar protic solvents. Consequently, this work opens a new window for constructing high-performance TFC PA membranes on hydrophobic substrates and expands the application of the TFC PA NF membrane. [ABSTRACT FROM AUTHOR]