Enhanced water/dimethyl ether separation by surface modified PEBAX 1657 membranes containing a nanocomposite layer

Dimethyl ether (DME) is a vital precursor chemical and potential hydrogen-carrier, that is currently separated from water through energy intensive distillation. Membrane gas separation is an alternative separation technology, but requires a H 2 O/DME selectivity high enough to retain purified DME in the retentate stream. Here, a conventional polymeric membrane (PEBAX 1657) was converted into a composite state by spray-coating a nanocomposite layer consisting of core-shell cobalt nanoparticles covered in polyaniline modified with sulfonic groups. The hybrid membrane enhanced water permeability through strong hydrogen bonding with the nanocomposite layer, while restricting DME due to unfavorable interactions. The DME diffusivity was significantly reduced after applying a 10 % w /w nanocomposite layer, leading to a 45 % decrease in DME permeability. At low water activity, the hybrid membrane enhanced water vapour permeability by up to 95 %, achieving 14,645 ± 191 barrer along with a H 2 O/DME selectivity of 80. At high water activity, the hybrid membrane reached a H 2 O/DME selectivity of up to 95, with a water vapour permeability of 17,107 ± 147 barrer. In comparison, the neat PEBAX 1657 membrane had a H 2 O/DME selectivity of only 24–40. Comparable improvements in hybrid membranes' H 2 O/DME selectivity also occurred at lower water vapour activity. The improvement of separation performance in this hybrid membrane demonstrated how a nanocomposite layer can successfully enhance or hinder vapour permeabilities and significantly improve the separation performance, advancing membrane technology for the separation of DME. • Fabrication of a nanocomposite layer consisting of cobalt nanoparticles with polyaniline binder. • Nanoparticle and polyaniline functionalized to reduce dimethyl ether intermolecular interactions. • Nanocomposite layer coated on PEBAX to form a non-porous membrane. • Dimethyl ether permeability was reduced by 45 % within the nanocomposite membrane. • Water/dimethyl ether selectivity achieved 95 within the nanocomposite membrane.