Membrane fouling mechanisms by BSA in aqueous-organic solvent mixtures.

[Display omitted] • Membrane fouling by BSA worsened by the presence of IPA or DMSO. • FESEM, EP, fouling model, and interaction energy used to reveal fouling mechanisms. • Worst fouling in 30% v/v DMSO due to significant external and some internal fouling. • Fouling in presence of IPA was dominated by internal fouling and less than DMSO. • DLVO- and XDLVO-based interaction energy poorly tied to relative flux trends. To exploit the benefits of membrane-based separation for the pharmaceutical and chemical industries, the understanding of membrane fouling in organic solvents is crucial. Specifically for the separation of biocatalysts in the manufacture of pharmaceuticals, this study investigated membrane fouling by bovine serum albumin (BSA) in 10% v/v isopropanol (IPA), 10% v/v dimethyl sulfoxide (DMSO), 30% v/v IPA, and 30% v/v DMSO, benchmarked against that in water. The presence of either IPA or DMSO worsened fouling, with the latter comparatively worse. To understand the fouling mechanisms, Field Emission Scanning Electron Microscopy (FESEM) images were taken to assess external fouling, Evapoporometry (EP) was used to measure the pore-size distributions of the fouled membranes to examine internal fouling, a fouling model was applied to extract the fouling parameters, and the interfacial interaction energies were derived. Results indicate that the worst fouling in 30% v/v DMSO was due to both significant external fouling and internal fouling, whereas the second-worst fouling by 30% v/v IPA was caused predominantly by internal fouling. The magnitudes of the total DLVO- and XDLVO-based interaction energies were found to be poorly related to the relative flux declines. This study provides valuable insights into membrane fouling in different solvent environments. [ABSTRACT FROM AUTHOR]