Improving the pervaporation performance of PDMS membranes for n-butanol by incorporating silane-modified ZIF-8 particles

The hydrophobicity of porous particles is important for the performance of mixed-matrix membranes for pervaporation separation of n-butanol aqueous solution. Here, a strategy was proposed to further enhance the hydrophobicity of ZIF-8. ZIF-8 particles were first coated by polydopamine (PDA) to create chemically reactive surface and then modified with silane coupling agents n-propyltrimethoxysilane and n-octyltriethoxysilane. The water contact angles of the obtained P-ZIE-8@PDA and O-ZIF-8@PDA separately increased from 132.8 degrees to 137.3 degrees and 151.5 degrees, which demonstrated a remarkable enhancement in hydrophobicity. The silane-modified ZIF-8 particles were subsequently incorporated into PDMS to fabricate mixed-matrix membranes, which exhibited an improved adsorption selectivity for butanol. The best membrane with 1 wt% loading (O-ZIF-8@PDA) exhibited a separation factor of 56 and butanol flux of 480.6 gm(-2) h(-1) for a 1.5 wt% butanol solution at 55 degrees C. The separation factor increased by 23% compared with that of a ZIF-8/PDMS membrane. Moreover, compared with those of a pure PDMS membrane, the separation factor and butanol flux increased by 34% and 85%, respectively. Thus, the strategy is an effective method to improve the PV performance of PDMS membranes for butanol separation.