Tailoring the CH4/CO2/N2 separation performance of ultrapermeable polymeric composite membranes by altering the concentration of Pd/g-C3N4

Abstract

Effectively tailoring the interfacial interaction between the nanoadditives and polymer matrix to develop defect-free membrane is the key parameter to fabricate mixed matrix membranes (MMMs) with improved gas separation performance. Here, MMMs were successfully fabricated by using Pd/g-C3N4 as a nanoadditive for the separation of CO2/CH4 and CO2/N2 gas mixtures. The g-C3N4 with palladium provides more compatible structure to the MMMs. The addition of Pd/g-C3N4 nanoadditive introduces additional functional groups into the membrane matrix which induces the permeability of the molecules. The Pd/g-C3N4:PSf MMMs exhibited better thermal, mechanical stability and gas permeability than the bare polysulfone (PSf) membrane. The MMM loaded with 300 mg of the nanoadditive exhibited greater permeability than unfilled membrane which is nearly 5 times for CH4, 4 times for N2 and 10 times for CO2 at 2 bar pressure with selectivity of 5.25 for CO2/CH4 and 2.15 for CO2/N2 mixtures. The permeability of the CO2 molecules is higher than the N2 and CH4 molecules because of its smaller kinetic diameter. The Pd/g-C3N4 nanoadditive exhibited microporous nature with presence of nitrogen-rich functional groups which develops CO2-philic functional groups in MMMs. These findings emphasize the unique properties of Pd/g-C3N4 nanoadditive in MMMs towards pure and mixed gas permeability and separation. This simplistic approach to modulate PSf membrane via Pd/g-C3N4 addition promotes the practical design of highly effective gas separation membranes.