ABSTRACT
While membrane technology continues to thrive in seawater desalination, it would defeat the very purpose of saving the environment if toxic solvents are involved in membrane manufacture. As a paradigm of green chemistry, nontoxic solvents, particularly triethyl phosphate (TEP), can be used to fabricate polyvinylidene fluoride (PVDF) hollow fiber membranes for membrane distillation. In this chapter, the phase inversion kinetics of the PVDF/TEP system has been closely investigated and compared with the conventional N-methyl-2-pyrrolidone (NMP)/PVDF system. The former shows a less abrupt phase inversion rate and produces a more porous sponge-like structure than the latter. The 12/88 wt% PVDF/TEP binary solution produces fibers with promising performance. They not only possess robust mechanical properties and a liquid entry pressure up to 2.0 bar but also exhibit an average flux of 20 kg/m2 h at 60 °C and a NaCl rejection of 99.99%. Since there are no additives or nonsolvents in the dope solutions and no post-treatments involved, the use of TEP as a green solvent will significantly reduce the complexity of membrane fabrication, scale up, and commercialization. Clearly, the much safer solvent TEP is able to replace toxic solvents commonly used in membrane manufacture and to produce membranes with highly competitive performance.
