STANDARDIZATION IN THE PRODUCTION AND TESTING PROCEDURES FOR POLYETHERSULFONE HOLLOW-FIBER ULTRAFILTRATION MEMBRANES

Several hollow fiber ultrafiltration membranes have been produced from polyethersulfone-polyvinyl pyrrolidone-N-methyl-2-pyrrolidone solutio ns and tested. The effects of feed flow velocity through the fiber bor e on pressure drop in the test fiber bundle, membrane separations for PEG solutes, and the obtainable mass transfer coefficients under the t est conditions have been experimentally determined and discussed. Furt her, the effects of storage time and prefiltration of the fiber castin g polymer solution on the performance characteristics of the resulting membranes have been studied. The viscosity of the fiber casting solut ion increased upon storage for a few weeks, and it decreased after the solution was filtered prior to use in fiber production. Storage time and filtration treatment of the fiber casting solution had significant effects on the morphology of the resulting membranes. Casting solutio n of longer storage time and without filtration pretreatment produced smaller size pores on the membrane bore-side skin layer, and a larger number of such pores and/or a thinner skin layer in the resulting memb rane. On the basis of these results, the need for standardizing the fi ber producing conditions and fiber testing procedure is pointed out, a nd a few suggestions are made for such standardization.