Solute permeability and reflection coefficients (sigma) through hollow
-fiber membranes were measured for cellulose and poly (methyl methacry
late) (PMMA) membranes. The dialysis apparatus used was a U-type hollo
w fiber unit which was loosely bundled and set in a perfectly mixed re
servoir with dialyzate flowing perpendicularly to the hollow fibers. M
ass transfer resistance across the boundary layer outside the fibers w
as small at low How velocity, so solute permeability could be measured
accurately. The mass transfer correlation obtained was Sh=0.38Re(out)
0.72Sc1/3 Ultrafiltration experiments were performed for the case of f
low within the fibers, in order to determine actual rejections and sig
ma values. The relationship between sigma and the molecular weights of
polyethylene glycols (PEGs) in the cellulose membrane approached that
of inulin and other solutes when the amount of hydrated molecules of
water to PEG units was taken into account. Negative sigma values were
observed in PMMA membrane for PEGs #1000-#6000.