Hybrid Membranes Fabricated By Incorporating 2D Materials For Pervaporation Process Intensification

The development of high-performance membrane materials is crucial to intensify the pervaporation process. Polymer-inorganic hybrid membranes can combine the advantages of polymeric membranes and inorganic membranes, which are expected to achieve high permeability, high selectivity, and strong stability. This study faces the national significant demands of clean fules production. In order to intensify the pervaporation process for ethanol dehydration, a series of hybrid membranes incorporated with two-dimentional(2D) materials have been fabricated by the rational design of membrane materials and optimal regulation of membrane structures. The as-prepared hybrid membranes have appropriate structures and excellent performances, which offers a new strategy for the membrane fabrication and process intensification of pervaporation.To reveal the potentials of 2D materials as the fillers of pervaporation membranes, two kinds of zeolite imidazolate framework-8(ZIF-8), ZIF-8 particles(ZIF-8P) and ZIF-8 sheets(ZIF-8S), were synthesized and blended into sodium alginate(SA) to fabricate hybrid membranes. The membrane structures were systematically characterized, and the membrane performance were evaluated. The isotropic morphology of ZIF-8P and weak interfacial interactions damaged the molecular sieving function in the SA-ZIF-8P hybrid membranes, while the 2D morphology and ordered alignment of ZIF-8S could enhance the molecular sieving function. Therefore, the diffusion process was intensified for the SA-ZIF-8S membranes, and when the content of ZIF-8S was 4 wt.%, optimum separation performance with a permeation flux of 1218 g/(m2h) and a separation factor of 1840 and was achieved.To simultaneously intensify the solution and diffusion processes, novel hybrid membranes were fabricated by incorporating GO into SA matrix. The SA-GO membranes exhibited brick-and-mortar morphology, unusual crystallinity change, and increased free volume. By manipulating the physical and chemical structures of GO, the interfacial morpholy, free volume property, and hydrophilic-hydrophobic nature of hybrid membranes were optimized. Thus, more water channles were constructed and the molecular sieving function of GO was enhanced. The separation performance of the hybrid membranes were improved, and optimum separation performance with a permeation flux of 1699 g/(m2h) and a separation factor of 1566 and was achieved. Moreover, the hybrid membrane exhibited superior long-term operation stability.To develop pervaporation membranes with higher performance, the 2D nanoporous g-C3N4 nanosheets(CNs) were synthesized and blended into sodium alginate(SA) to fabricate hybrid membranes. The ultrathin structure and high porosity of CNs could further reduce the transport resistances, while the uniform pore size distribution can provide more precise molecular sieving function. Additionaly, the high aspect ratio and ordered alignment of CNs could further enhance the molecular sieving ability. By further optimizing the interfacial morphology, free volume property, and hydrophilic-hydrophobic nature of the hybrid membranes, higher separation performance was achieved. When the content of CNs was 3 wt.%, the permeation flux of the hybrid membrane was as high as 2469 g/(m2h) and the separation factor could reach 1653. The as-prepared hybrid membranes exhibited higher thermal stability, mechanical stability, anti-swelling ability, and superior long-term operation stability.