Abstract
To reduce the volume of the dialysate used in a hemodialyser two methods are now considered to be possible. One is to purify the dialysate by adsorbing BUN, but presently no adsorbent is possible to adsorb urea selectively. The other is to recover water from the dialysate by the reverse osmosis process, which has been developed for purifying various kinds of waste water. In the latter process membranes made of cellulose acetate butyrate (CAB) is reported to reject urea effectively.
In this experiment the reverse osmosis module, made by De Danske Sukkerfabrikker (DDS) and equipped with CAB membranes made in our laboratory, is combined with a Lollow fiber dialyser and with a dialysate supplier. As a simulation experiment urea is removed using this system from aqueous urea solution or dialysate solution containing urea, which are used in place of blood.
Results shows that rejection of urea by CAB membranes is 80-90%, that of electrolytes is 99%, water recovery is 40-60%, and thus this system works good for the purpose. Further developments are necessary to improve CAB membrane to prevent degradation, and to increase water recovery, all of which are now under progress.
