Highly selective PDMS membranes embedded with ILs-decorated halloysite nanotubes for ethyl acetate pervaporation separation

Abstract

The development of high-performance polydimethylsiloxane (PDMS)-based mixed matrix membranes (MMMs) for the recovery of ethyl acetate (EtAc) from low-concentration aqueous solutions remains a challenge in the pervaporation field. In this study, ionic-liquids-decorated halloysite nanotubes (ILs@HNTs) composites, which were precisely designed and prepared using a tandem modification strategy, were embedded into PDMS matrix to fabricate MMMs for the permselective pervaporation of EtAc. The results revealed that the ILs incorporated within the lumens and onto the external surfaces of HNTs not only exhibited excellent compatibility with PDMS, but also created permselective diffusion channels for EtAc. Benefit from the synergistic effect of highly permeable HNTs lumens and highly selective ILs, the resultant MMM loaded with 15 wt% ILs@HNTs presented a remarkable separation factor (341) and high flux (925 g m−2 h−1) for the separation of 1 wt% EtAc aqueous solutions at 30 °C. These values were 2.10 and 1.45 times higher, respectively, than those of pristine PDMS membranes. Furthermore, the molecular simulations conducted to analyze the permeation behavior of guest molecules in the HNTs lumens provided theoretical support for the pervaporation experimental results. Moreover, the effects of ILs grafting degree, filler loading, feed temperature, and feed concentration on the pervaporation performance of the fabricated MMMs were systematically investigated. The unique modification method developed in this study can be expanded to other tubular materials and provide valuable guidelines for designing high-performance membrane structures.