Advancing Sustainable Direct Contact Membrane Distillation: Performance and Stability of Novel Polymer Inclusion Membranes

Abstract

Novel hydrophobic membranes for direct contact membrane distillation (DCMD) were developed using poly(1,1-difluoroethylene) (PVDF) loaded with the ionic liquid methyltrioctylammonium bis(2-ethylhexyl) phosphate (MTOA-DEHP). These polymer inclusion membranes (PIMs) were fabricated via non-solvent induced phase separation (NIPS). Detailed characterization revealed that MTOA-DEHP significantly enhances the morphological and physicochemical properties of the PIMs. Through a series of DCMD experiments, the membrane’s flux, salt rejection, and stability under varying conditions, including different feed solutions (i.e., synthetic NaCl solution and real seawater from the Atlantic Ocean), were assessed. Our results demonstrate that the PVDF/20 %MTOA-DEHP membrane exhibits superior performance, maintaining consistent transmembrane flux values (8.98 ± 0.61 kg·m−2·h−1) over multiple cycles and achieving high salt rejection rates (>99.9 %). Furthermore, the membrane demonstrates excellent stability, with minimal degradation observed even after prolonged operation. The results affirm the viability of PIMs as a promising avenue for achieving sustainable and efficient desalination via DCMD, particularly in real-world operational scenarios.