A new application for used reverse osmosis (RO) membranes as gas separation membranes was studied. In this regard, firstly, three pretreatment procedures were used to remove the foulants from the surface of used membrane and then they were coated with polydimethylsiloxane (PDMS). The results indicated that PDMS-coated used RO membranes were capable of separating O2/N2 and CO2/N2. The maximum O2/N2 and CO2/N2 selectivities of coated membranes were 5.9 and 32.5, respectively. The O2/N2 and CO2/N2 selectivities of PDMS membrane were reported in the range of 2.1e2.2 and 11e12, respectively. Finally, an economic assessment was carried out to compare prepared PDMS coated RO membranes with commercial PPO membrane. This showed that coated membranes are less expensive than PPO membrane for CO2/N2 gas separation. The outcome of the research was a simple method for converting used RO membranes to cost effective gas separation membranes.

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