Clearance of low molecular-weight uremic toxins p-cresol, creatinine, and urea from simulated serum by adsorption

In this study, five adsorbents including activated carbon (AC), three zeolites ZSM-5 with a molar ratio of SiO₂ to Al₂O₃ of 23–400, and graphene oxide (GO) were selected to investigate their abilities for the clearance of three low molecular-weight uremic toxins (p-cresol, creatinine, and urea) from simulated serum at 37 °C. The physicochemical properties of the adsorbents were characterized using the X-ray powder diffractometer and porosimeter. It was found that the adsorption can be followed by the pseudo-second-order kinetic model and the Langmuir equation better fits all adsorption isotherms than the Freundlich equation under the conditions studied. Of the three adsorbents, ZSM5-400 (ZSM-5 with Si/Al = 400) has a maximum adsorption capacity for urea (0.70 mmol/g) and GO has a maximum adsorption capacity for p-cresol (4.01 mmol/g) and creatinine (1.01 mmol/g). To efficiently treat chronic kidney disease patients case by case, the adsorption isotherms of p-cresol and creatinine on the mixed adsorbents was experimentally and theoretically studied to evaluate the possibility of using “tailor-made” adsorbents. The cell viability of the selected adsorbents at different doses for fibroblast NIH/3T3 cells was finally examined.