| This study examines the fouling of polymeric membranes with albumin using four membranes with different hydrophilic/hydrophobic characteristics and pore structures. A radioactive tracer technique was used to study adsorption of albumin on these membranes. In the aqueous phase protein concentration range of 0-40 mg/ml, the adsorption isotherms were linear for polyvinylidene fluoride, nylon and polycarbonate membranes. Only for polypropylene membranes, was a nonlinear adsorption isotherm observed. For an aqueous phase concentration of 1 mg/ml, the most adsorption occurred on polypropylene (19.9 mg/m{dollar}sp2){dollar} and polycarbonate (20.6 mg/m{dollar}sp2){dollar}; adsorption on PVDF and nylon were considerable less (1.44 mg/m{dollar}sp2{dollar} and 3.26 mg/m{dollar}sp2,{dollar} respectively). No effect of pore size was found in the adsorption isotherms.; Fouling was characterized by the permeability of water and albumin solutions through membranes. The effect of adsorption on fouling was also quantified; a direct relation was found between the relative permeability of albumin solution and protein adsorption. A high adsorptive membrane had low relative permeability of albumin solution and a low adsorptive membrane had high relative permeability of albumin solution. For hydrophobic membranes, the high protein adsorption was responsible for low permeability of albumin solution. On the other hand, protein aggregation played a more dominant role for hydrophilic membranes.; Low temperature plasma was used to modify the adsorption on the membranes. Tortuosity and thickness of membranes were important parameters for the surface modification to be effective. Protein adsorption decreased with increasing oxygen content in the feed gas for the n-butane/oxygen treatment, indicating the importance of hydrophobic interactions for albumin. For the oxygen plasma and the n-butane/oxygen plasma treatments, the protein adsorption was reduced by 96% and 73%, respectively. Correspondingly, the permeability of albumin solution increased by 91% and 89%, respectively. For practical use, the n-butane/oxygen plasma treatment may be a better alternative than oxygen plasma treatment because of the rotation of hydrophilic groups into the bulk polymer for the latter treatment. For the nitrogen and n-butane/nitrogen treatments, protein adsorption increased with increasing nitrogen content in the feedgas despite a decreasing contact angle, indicating that electrostatic interaction influenced the adsorption. The higher adsorption on the aminated membranes resulted in a reduction in relative permeability. |
