Development of novel multichannel rectangular membranes with grooved outer selective surface for membrane distillation

In this study, poly(vinylidene fluoride) (PVDF) multichannel rectangular membranes were spun through the non-solvent-induced phase separation method with the aid of a specially designed spinneret. This unique spinneret has an outer rectangular slit and seven inner needles arranged in series. The newly designed membranes have the combined advantages offered by (1) hollow fiber (i.e., high membrane area per volume ratio and easy assembly into membrane modules); (2) flat sheet membranes (i.e., greater mechanical durability and compressibility); and (3) woven or nonwoven spacers used in flat sheet modules (as mechanical supports). Microscopic views and scanning electron microscopy (SEM) microphotographs show an irregular inner contour align symmetrically in the hydrophobic PVDF membrane. Multichannel rectangular membranes with a grooved pattern have the following advantages: (1) easy handling, (2) can be acted as spacers to discrete membrane from attaching together, and (3) creating eddies flow at the membrane outer selective layer. Attempts are also made to understand the deformation of grooved outer surface and irregular inner contour. Apart from interesting membrane geometry, this study also explores the prospect of utilizing aforementioned membranes for seawater desalination via direct contact membrane distillation (DCMD). A promising distillated flux of 54.7 kg m ^-2 s ^-1, using a hot feed brine solution of 80 °C, is obtained through these newly spun multichannel rectangular membranes.