Significantly improved pervaporation performance by relatively continuous and defect-free distribution of IL-modified ZIF-8 in PDMS membrane

Abstract

Organophilic pervaporation (PV) mixed matrix membranes (MMMs) possess huge potential in organic wastewater treatment with merits of environmentally friendly and high-efficiency. The filler dispersion structure inside MMMs is required to explore in depth to upgrade the PV performance. In this study, an ethoxysilyl functionalized ionic liquid (IL-PTES) modified ZIF-8 nanoparticles (IL-PTES@ZIF-8) were synthesized by one-pot method, and then incorporated into the PDMS matrix to prepare MMMs for PV separation of ethyl acetate (EtOAc) from its diluted aqueous solution. The preferential adsorption performances to EtOAc by IL-PTES, especially for the functions of specific chemical groups in IL-PTES, were researched via molecular dynamicssimulation approach. Furthermore, the IL-PTES covered on ZIF-8 surface could crosslink with PDMS chains, thereby enhancing the interfacial compatibility between ZIF-8 and PDMS. Importantly, the self-aggregated IL-PTES subtly “glued” the nanoparticles together to lead IL-PTES@ZIF-8 a relatively continuous and defect-free distribution state. This condition would lead to a high-efficiency molecular pathway with less polymer phase and much relatively continuous ZIF-8 phase with high selectivity. PV results suggested that the MMMs with 15% IL-PTES@ZIF-8 loading displayed an optimal separation performance with an ultra-high separation factor of 492 (158.7% more than that of pristine PDMS membrane) and normalized EtOAc flux of 4.98 ​kg ​μm ​m−2·h−1 (2 times as much as that of pristine PDMS membrane) for separating 1 ​wt% EtOAc aqueous solution at 30 ​°C. These findings offered significant advancement toward developing high-performance MMMs enabled by the synergy of MOFs and ionic liquid.

Keywords

• Mixed matrix membrane
• Modified ZIF-8
• Ionic liquid
• Pervaporation
• Ethyl acetate