A method of adsorption of potassium ions from a peritoneal dialysis fluid, which has been removed from the peritoneal cavity of a patient performing peritoneal dialysis for subsequent recirculation and introduction into the peritoneal cavity of the patient. The peritoneal dialysis fluid is passed through a potassium adsorbent, such as a zeolite, which has been pre-equilibrated with an equilibration fluid comprising Na+, Ca2+, Mg2+, Cl&minus, lactate, in substantially the same concentration as in the peritoneal dialysis fluid and which equilibration fluid lacks K+. The zeolite may be titrated with an acid. Alternatively, a zeolite having a Si:Al ratio which is larger than 5:1 is used. Alternatively, a cation exchange material, such as sodium polystyrene sulfonate, is used.
