Protein ultrafiltration concentration polarization layer flux resistance .1. Importance of protein layer morphology on flux decline with gelatin

The effect of added ethanol and (NH4)(2)SO4 an the morphology of the gelatin concentration polarization (CP) layer during ultrafiltration (UF) was analyzed using protein ternary phase diagrams, as well as turbidity and intrinsic viscosity measurements. CP layer resistance was characterized by measuring the flux decline index (FDI) of a 0.10 wt% gelatin solution in a dead-end UF system at 40 degrees C. Ethanol concentrations up to 30 wt% produced an aggregated CP layer morphology with a moderate FDI. However, above 30 wt%, a swollen macromolecular gel formed on the membrane surface, resulting in a lower FDI. Low salt levels led to the formation of compact protein particles in the CP layer that had a moderate FDI. In contrast, a concentration of 8 wt% produced a high FDI coacervate structure. The highest FDI was observed at salt concentrations above 12 wt%, where the surface morphology consisted of a dense particulate gel. Overall, the FDI could be altered by a factor of similar to 3 by manipulating the concentration of solute in the solution.