METHODS AND APPARATUSES USING UREA PERMSELECTIVE DIFFUSION THROUGH CHARGED MEMBRANES

Methods and apparatuses for regenerating used dialysis fluid are described herein. In an embodiment, a regenerative dialysis fluid system includes a dialysis unit configured to generate used dialysis fluid including urea, a urea separation unit configured to separate at least a portion of the urea from the used dialysis fluid into a secondary fluid, and a urea removal unit configured to remove at least a portion of the urea from the secondary fluid and return the secondary fluid to the urea separation unit. In an embodiment, the urea separation unit includes a membrane separating a dialysis fluid chamber from a urea chamber, the membrane including at least one of: (i) a positive charge to prevent positive ions from transporting across the membrane; and (ii) a negative charge to prevent negative ions from transporting across the membrane.