Development of polydimethylsiloxane composite membrane for organic solvent separation

Membrane processes have proven to be energy-efficient technologies for separation of various substances, including organic solvents. In this study, crosslinked polydimethylsiloxane (PDMS) composite membranes were developed for organic solvent separation. Precursor solutions containing double-ended vinyl PDMS with four different molecular weights were spin-coated onto a polyethersulfone membrane substrate, and the crosslinking reaction was accelerated by heat treatment to produce PDMS composite membranes. The influence of the PDMS molecular weight and crosslinking on the membrane properties and performance was tested. It was shown that less swelling, more selective hexane absorption, and increased separation coefficient was observed with decreasing PDMS molecular weight. The trade-off relationship between the permeance and the separation coefficient was observed as the membranes prepared with lower molecular weights of PDMS showed lower permeability and higher separation coefficient. The separation coefficient showed a maximum value at a supplied ethanol concentration of 50 wt%. In addition, various solvent mixtures containing hexane and alcohols were used for organic solvent separation performance test using the PDMS composite membranes. A correlation was observed between the separation coefficient and the difference of χ parameters between alcohol/PDMS and hexane/PDMS. The mechanisms for solvent permeation and separation were discussed based on the interaction parameters, membrane swelling and solvent dissolution. The results of this study could be used as guidelines for the development of solvent-resistant PDMS composite membranes.