Urea removal from dialysates in anion-transfer menbrane enzyme reactor

Abstract

Improved urea removal system utilizing Anion Transfer Membrane (A.T.M.) is investigated. The A.T.M. selectively passes the urea and anions but it prevents the passage of electrolytes essential for the body and toxic ammonium ion. The overall membrane resistances of A.T.M. are determined by a dual closed-loop technique. Using 0.2 M sodium phosphate citrate buffer, effects of urease enzyme concentration on urea removal and effects of activators such as DL-alanine and glycine on urea removal are investigated. Comparison with other urea removal systems are made by simulation using two compartment model. Experimental results showed that 1.5 unit/ml urease enzyme concentration is adequate for the system of 0.5 L. blood bath and 0.5 L. dialysate bath. Effects of activators was not observed probably owing to very low urea concentration in dialysate. The simulation has been shown that A.T.M. system is more efficient than other system in urea removal and toxic ammonium ion removal. Very low ammonium ion concentration (16$\mu$G/L) in extracellular fluid is obtained, but absolute prevention of ammonium ion passage is not achieved unless adsorbent for ammonium ion is not used. The results suggest further work for developments of A.T.M. for artificial kidney use.