Adsorption properties of zeolites for artificial kidney applications

A method of elimination of uremic toxins such as urea, uric acid, creatinine, p-cresol and indoxyl sulfate from solutions by adsorption onto zeolites is introduced. The physical and chemical properties of microporous materials are varied systematically (pore size, acidity, hydrophobicity, grain size, charge compensating cations, stabilization by high pressure hydrothermal treatment). Initial uremic toxins concentrations of solutions applied are close to the concentrations measured in blood of healthy persons and of patients having renal failure. The adsorption results obtained at 37 degrees C show that adsorption of uremic toxins onto zeolites is specific and not only depended on the size of the channels but also on the interactions between the substances and the zeolite lattices. For initial concentrations close to that of persons having renal failure, it is possible to eliminate 75% creatinine by adsorption onto an acidic mordenite (MOR) and 60% p-cresol by adsorption onto a hydrophobic silicalite (MFI). These results are comparable or better than conventional dialysis systems where the elimination is about 67% for creatinine and about 29% for p-cresol. Adsorption of uremic toxins onto active carbon is equal or better than onto zeolites, however, the application of this adsorbent has to be rejected as adsorption is non-specific. (c) 2005 Elsevier Inc. All rights reserved.