Abstract
Highly permeable dialysis membranes of asymmetrical structure were developed to mitigate amyloidosis which patients undergoing long-term dialysis treatment caught. Filtration and backfiltration through the membranes play an important part in solute transport. The rejections of the asymmetrical membranes are different between transport directions. To design high performance membranes, it is important to clarify the effects of the difference in rejection between directions of solute transport. Rejection and overall mass transfer coefficient of dextran were determined by filtration and counter-current dialysis experiments to compare transport characteristics of gradient structure membranes having a skin layer inside the wall of hollow fibers with those of the reverse gradient structure membranes having a skin layer outside. Overall mass transfer resistance and rejection of the gradient structure membranes are lower for transport from outside to inside than for that from inside to outside, indicating that solutes are easy to move from outside to inside. On the other hand, those of the reverse gradient structure membranes are lower for transport from inside to outside than for that from outside to inside, indicating that solutes are easy to move from inside to outside. The solute transport characteristics of the reverse gradient structure membranes are suitable for dialysis treatment. We conclude that thee overall mass transfer coefficient of the asymmetrical dialysis membrane increases by providing them with differences in rejection between transport directions.
