Preparation and assessment of polyvinylidene fluoride hollow fiber membrane for desalination by membrane distillation

Membrane distillation is an emerging thermally driven separation processes in which vapors pass through a hydrophobic microporous membrane due to temperature difference. This work is concerned with the fabrication and characterization of polyvinylidene fluoride (PVDF) hollow fiber membrane fabricated on a pilot scale spinning system using different spinnerets (D-o/D-i mm: 1.2/0.5, 1.12/0.36, 0.96/0.28, 1.25/0.36) to provide fibers of different thicknesses. Several batches have been prepared using N-methyl pyrrolidone or dimethyl formamide as solvents. Further, the effect of different additives on characteristics including polyvinylpyrrolidone (PVP 40K), polyethylene glycol, polyvinylidene fluoride-co-hexafluropropylene (PVDF-co-HFP) and nano-silica has been explored. Prepared fibers have been post treated before drying. The fibers have been characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy (AFM), porosity and contact angle to determine internal structure, composition, morphology and surface properties. AFM results indicated average surface roughness for the raw sample ranging between 34 and 38 nm, water contact angle about 85-95 degrees and porosity about 85%-95% Further, mechanical properties have been investigated to determine tensile properties including break force, stress, strain and Young???s modulus. The later varied widely between 30 and 60 MPa. The article has been terminated with conclusions and recommendations regarding further work.