Adsorption of bilirubin to magnetic multi-walled carbon nanotubes as a potential application in bound solute dialysis

Carbon nanotubes (CNTs) have excellent adsorption properties for a wide range of substances, but the leakage of CNTs into blood and the non-specific adsorption of plasma proteins are major issues in the application of CNTs in blood purification. To minimize these shortcomings, multi-walled carbon nanotubes (MWCNTs)/iron oxides magnetic composites were prepared and intended to be used in bound solute dialysis. Magnetic MWCNTs were characterized by FTIR, XRD, SEM, VSM and Boehm titration. Their adsorption characteristic for bilirubin (a prominent marker of liver failure disease) was measured in aqueous solutions. The magnetic MWCNTs that theoretically contained 50% of 4 h-pre-treated MWCNTs and 50% of magnetite could meet the requirements for good dispersion ability, high adsorption capacity for bilirubin, and the convenience of magnetic separation. The magnetic MWCNTs showed a rapid rate for the uptake of bilirubin, and maximum adsorption capacity could reach 263.16 mg/g at 30 degrees C. Besides, the adsorption isotherm was well described by Langmuir model, and the adsorption process was thermodynamically favorable. The binding constant for the adsorption of bilirubin to magnetic MWCNTs was 1.8 x 10(5) M-1 at 30 degrees C. In bound solute dialysis, 35% of bilirubin could be removed from a solution of albumin without significant effect on the concentration of albumin. This study demonstrated that magnetic MWCNTs could offer a new type of adsorbent for removal of albumin bound toxins in bound solute dialysis. (C) 2012 Published by Elsevier B.V.