Superior Interfacial Thermal Efficiency and Membrane Distillation using Conductive PANi/PVDF Membrane under Induction Heating

Abstract:

Abstract: Membrane Distillation (MD) has proven to be a promising alternative water production and reclamation technique to alleviate the global water scarcity. However, conventional MD suffers from low thermal efficiency mainly due to inefficient bulk heating method, which unfavorably causes severe interfacial temperature polarization and large thermal energy input for bulk feed heating. Herein, we reported a conductive PANi/Fe₃O₄@PVDF membrane as an in-situ electromagnetic induction heater for high thermal efficient direct-contact MD (DCMD) desalination. In specific, a conductive layer with induction-responsive Fe₃O₄ dispersed in conductive PANi polymer matrix was coated on a hydrophobic porous PVDF membrane by phase inversion technique. Localized interfacial heating on membrane surface was achieved under a high-frequency electromagnetic field, which excited the surface-coated conductive layer and heats up interfacial water molecules for superior water transportation. We show that composite membrane efficiently heated water droplet deposited on the membrane surface. In addition, we demonstrate that dispersing Fe₃O₄ nanoparticles in conductive PANi polymer matrix enabled better heating efficiency than using only Fe₃O₄ nanoparticles, which can be attributed to enhanced joule heating by formation of larger closed loops of eddy currents. Moreover, we determined unique water flux and salt rejection behaviors of the composite conductive membrane in DCMD desalination through a systematical parametric and simulation study, and demonstrated that in-situ induction heating of the PANi/Fe₃O₄@PVDF membrane significantly promoted the thermal efficiency of the DCMD to over 85%. Our study provides important insights into highly efficient and sustainable MD processes for household or community scale water production and reclamation using non-traditional water sources such as brackish water, seawater and brines.

Keywords: Membrane distillation; Seawater desalination; Conductive membrane; Electromagnetic induction; Superhydrophobic membrane