Biomass-Derived Carbon and Carbon Nanofiber-Integrated Electrospun Janus Membranes: A New Frontier in Membrane Distillation

Membrane distillation (MD) is an emerging desalination technique that uses low-grade energy to extract water vapor from saline solutions. In a thermally driven MD system, achieving a lower heat transfer and a higher mass transportation rate is desirable. To balance the trade-off between heat transfer and mass transportation, we developed novel dual-layered electrospun Janus nanofibrous membranes in this study, showing asymmetric wettability on each layer. The developed Janus membrane was constructed with a bottom hydrophilic layer composed of PVDF-<i>co</i>-HFP/biomass-derived jute carbon (JC) particles, and the top hydrophobic layer was formed using PH/carbon nanofibers (PH/CNF). The effect of distinct carbon nanoparticles on the prepared membranes was investigated by analyzing their chemical structure, morphology, water contact angle (WCA), pore size, porosity, thickness, liquid entry pressure, and mechanical and thermal stability. The hydrophobic layer of the optimized Janus membrane exhibited a WCA of 138 ± 1°, and the hydrophilic surface showed 72 ± 4°. Additionally, the optimized Janus membrane composed of a hydrophobic PH/0.5 wt % CNF layer and PH/0.5 wt % JC hydrophilic layer experienced an outstanding improvement in water flux (with 70 g L^-1 of NaCl content), reaching to a value of 71.72 kg m^-2 h^-1 (∼162% improvement compared to the pristine PH membrane), while maintaining a salt rejection of >99.99% for 24 h of water gap membrane distillation. Notably, the optimum Janus PH-0.5CNF/PH-0.5JC membrane demonstrated an astonishing long-term stability with real seawater, exhibiting a remarkable flux of 78.42 kg m^-2 h^-1, which is ∼547% higher than commercially available PVDF membranes, while maintaining a salt rejection of 99.98% after 50 h. The proposed strategies provide a novel approach to fabricate an electrospun Janus membrane, and their performance highlights a strong potential candidate to be used in commercial water desalination plants.