Adsorption of the uremic toxin p-cresol onto hemodialysis membranes and microporous adsorbent zeolite silicalite.

Para-cresol CH3C6H4OH is a protein-bound solute which is not eliminated efficiently by hemodialysis systems. In this study, we present adsorption of p-cresol as a complementary process to hemodialysis. The kinetics and isotherms of adsorption onto cellulose-based membranes (cellulose diacetate and triacetate), synthetic membranes (polyamide, polysulfone, polyacrylonitrile and polymethylmethacrylate) and microporous zeolite silicalite (MFI), have been evaluated in static conditions. The results indicate that p-cresol has a low affinity to all membranes but polysulfone and polyamide and that the times to reach equilibrium conditions are slow. In contrast, equilibration time on silicalite is fast (2 min to eliminate 90%) while adsorption levels are high (maximum adsorption about 106 mg g(-1)). Adsorption onto microporous adsorbents could be a novel way to eliminate uremic toxins from blood.