Gas separation and water desalination performance of defect-free interfacially polymerized para-linked polyamide thin-film composite membranes

The introduction of interfacially polymerized (IP) polyamide thin-film composite (TFC) membranes in the 1980s revolutionized reverse osmosis desalination industry. However, IP-derived TFCs have not achieved industrial success for gas separation applications due to presence membrane defects their dry state. In this work, we report defect-free crosslinked prepared from para-substituted aromatic and cycloaliphatic diamines, p-phenylenediamine (PPD) piperazine (PIP), reacted with trimesoyl chloride (TMC). key parameters our modified IP process mitigate are long reaction time (~5 min) high organic solution temperature (100 °C). properties para-linked were compared previously reported made meta-phenylenediamine (MPD) TMC. gas- water permeances increased order: MPD-TMC < PPD-TMC PIP-TMC, whereas gas-pair selectivities salt rejections followed opposite sequential trend: > ? PIP-TMC. Elimination allowed exploitation ultra-selective nature TFCs, specifically hydrogen helium separations. At 23 °C, exhibited H2/CH4 312, 362 1290, respectively, moderate H2 37.4, 32.6 25.8 GPU (1 = 10?6 cm3(STP) cm?2 s?1 cmHg?1). Furthermore, demonstrated excellent performance H2/CO2 pure-gas 10–14 at °C. strong size-sieving capability originated tight interchain packing induced by bonding. Wide-angle X-ray diffraction confirmed a dominant fraction submicropores less than ~4 Å within PIP-TMC networks.