COUPLING OF UREA HYDROLYSIS AND AMMONIUM REMOVAL IN AN ELECTRODIALYZER WITH IMMOBILIZED UREASE

A five-compartment electrodialyzer with immobilized urease was developed for the removal of urea from aqueous solution. The immobilized urease supported on polyurethane foam was placed in the central (dilute) compartment, where urea was hydrolyzed and the products were transported simultaneously into the concentrate compartments on its both sides by electrodialysis. The effect of the kinds of buffer salts on the product distribution of urea hydrolysis between two concentrate compartments was investigated under phosphate and citrate buffer systems. It was found that no ammonium-nitrogen was present in the concentrate compartment on the anodic side for both buffer systems. This result could be due to the half-life of carbamate ions was too short to transport into anodic concentrate compartment before they decomposed to ammonium carbonate. The removal of urea from buffer-free aqueous solution was also studied. It was shown that urea and its hydrolysis product could be removed by the electrodialyzer with immobilized urease.