Solvent dependent membrane-solute sensitivity of OSN membranes

Organic solvent nanofiltration (OSN) offers great potential as a versatile tool for process intensification in the chemical industry. Nevertheless, the mass transfer mechanism through OSN membranes is not fully understood. The complex interactions between membrane, solvent and solute make it difficult to predict the separation performance of the membrane. In order to increase the fundamental understanding of the underlying transport phenomena systematic experimental investigations were carried out. A matrix of solvents, solutes and membranes was defined, covering a wide range of properties. The selection of the solutes was based on their industrial relevance to cover representative solute properties. Another criterion was their molecular weights, which should be rather low in order to obtain rejection less than 100%, to evaluate potential solute specific impact factors. The separation characteristics of 17 polar to apolar solutes with molecular weights from 114 g/mol to 339 g/mol were investigated. Moreover, five solvents and two membranes were included in the systematic investigation. On the basis of the results different solvent dependent solute sensitivity regions were identified for each membrane which differ by the impact of solute properties on the rejection. Different transport mechanisms seem to dominate within the different solute sensitivity regions. A correlation of the hydrogen bonding capacity of the solvents with the impact of solute properties on the rejection was found. This new insight offers new perspectives for the prediction of membrane rejection behavior in OSN.