Enhancing interfacial interaction of PDMS matrix with ZIF-8 via embedding TiO2@ZIF-8 composites for phenol extraction in aqueous-aqueous membrane extractive process

The presence of phenol as an organic pollutant in industrial effluents is the biggest threat to the aquatic environment and human health. The aqueous-aqueous extraction process is an attractive method to treat saline phenolic wastewater (feed solution) via diffusion through a semi-permeable polydimethylsiloxane (PDMS) to the receiving solution. To improve the value of mass transfer coefficient, thinning the PDMS layer and embedding it with nanoparticles/metal-organic frameworks (MOFs) can lead to membrane defects or weakened mechanical strength, which is not promising for large-scale practical applications. Therefore, herein, an interfacial design strategy is demonstrated to disperse TiO2@ZIF-8 composites as hybrid particles into the top selective layer (PDMS) of TFC (thin-film composite) membrane to enhance polymer-filler compatibility and mass transfer coefficient. The TiO2@ZIF-8 composites enhanced the affinity to the polymer matrix, thereby increasing the mechanical stability and preventing interfacial voids and agglomeration. Moreover, the TiO2@ZIF-8 incorporated TFC membranes exhibited an enhanced mass transfer coefficient (ko) of (25.28 ± 0.5) × 10−7 and a reduced reverse salt flux of 9.5 mg/m2.h. The enhanced mechanical stability and mass transfer coefficient were attributed to the synergistic effect provided by TiO2@ZIF-8 composites, as ZIF-8 particles provided continuous pathways (pore-flow mode) and TiO2 nanoparticles provided compactivity with PDMS. The synergistic effects of hybrid particles could provide a new strategy to develop PDMS for the extraction of various organic compounds.