Lysine-attached anodic aluminum oxide (AAO)–silica affinity membrane for bilirubin removal

Anodic aluminum oxide (AAO)–silica composite membrane was prepared by depositing silica onto the AAO membrane through sol–gel method. The obtained composite membrane exhibited excellent uniformities, low nonspecific adsorption and good hydraulic permeability. Lysine (Lys) as ligand was immobilized onto the AAO–silica composite membranes by activating with glutaraldehyde. The content of Lys of Lys-attached affinity membranes was ∼5.6 mg/g membrane. Such Lys-attached affinity membranes were used to adsorb bilirubin from the bilirubin–phosphate solution and bilirubin–albumin solution. The adsorption mechanism of bilirubin and the effects of temperature, initial concentration of bilirubin, albumin concentration and ionic strength on adsorption were investigated by batch experiments. The results showed that the adsorption capacity increased with increasing the temperature while decreased with increasing the NaCl concentration and albumin concentration, and the adsorption isotherm fitted the Langmuir model well. The result of dynamic experiment showed Lys-attached affinity membranes can well remove the bilirubin from the bilirubin–albumin solution.