Al-MCM-41 sorbents for bovine serum albumin: relation between Al content and performance

Abstract

The adsorption of bovine serum albumin (BSA) onto Al-MCM-41 samples with different Si/Al ratio and pore width about 36 Å was studied. It is shown that the adsorption capacity of Al-MCM-41 increased with decreasing of the Si/Al ratio, probably due to the increased affinity of BSA for the external surface of the adsorbents. The materials synthesized are agglomerates of primary particles, with high external surface area. The external area plays a predominant role in BSA adsorption on Al-MCM-41. The effect of pH on the adsorption of BSA has been studied at four pHs, namely 5, 6.1, 7.2 and 7.6. All pH values are above the isoelectric points of BSA. The adsorption capacity for BSA was found to be highest at pH 5, among those tested in this work, and decreased with increasing pH. This is postulated to be due to electrostatic repulsion between BSA and the surface of the adsorbents, as both are negatively charged when the pH is above 5. In addition, increasing repulsion between adsorbed BSA molecules with the increase of pH from 6.1 to 7.6 was found to reduce the adsorption capacity. The acid sites of the Al-MCM-41 seem to have no significant influence on the BSA adsorption.