Mixtures of organic solvents are generated as intermediate products in many chemical industries. Separation of these mixtures and recycling of these solvents is an important stage leading to close the production cycle and reduce the generation of waste streams. Comparing all available separation methods, membrane separation techniques, especially pervaporation (organic-organic pervaporation), appears to be a good alternative to the classical separation methods.

Simultaneously, organic-organic pervaporation is the most challenging mode of pervaporation, owing to the lack of the suitable membranes, low selectivity and stability of available membranes. Another limiting facor in the organic-organic pervaporation is the possible presence of water in organic solvents [1-4]. The understanding the influence of water presence on membrane transport and separation is necessary for the further development of organic-organic pervaporation.

This work is focused on the properties of pristine and Mixed Matrix Membranes based on PDMS used in the separation of dimethyl carbonate/methanol mixtures containing trace amount of water (ca. 0.1 wt%). Additonal experiments were done for organic solvents mixtures with increasing content of water from 0.1 to 6 wt% [4].

The influence of water presence in organic solvents on the overall efficiency of organic-organic pervaporation was investigated using the enrichment factor of water (EF_water) and rejection of water (R_PV,W) as metrics. The obtained results indicated the presence of a coupling effect between methanol and water molecules. It was found that despite the hydrophobic character of both pristine and modified PDMS membranes, water was preferentially transported from the feed to th e permeate side if water content was below 0.1 wt%. However, for the higher amount of water in the feed solution, it was found that both membranes partially suppressed the transport of water molecules.

Comparison with methanol/MTBE/water, ethanol/ethyl acetate/water, isopropanol/ethyl acetate/water, and ethanol/ETBE/water systems were also performed [1-3].

References:

[1] R. Kopeć, M. Meller, W. Kujawski, J. Kujawa, Polyamide-6 based Pervaporation Membranes for Organic-Organic Separation, Separation and Purification Technology, 110 (2013) 63-73.

[2] K. Knozowska, G. Li, W. Kujawski, J. Kujawa, Novel heterogeneous membranes for enhanced separation in organic-organic pervaporation, Journal of Membrane Science 599 (2020) 117814.

[3] K. Knozowska, R. Thür, J. Kujawa, I. Kolesnyk, I. Vankelecom, W. Kujawski, Fluorinated MOF-808 to create high-performance hybrid membranes with enhanced hydrophobicity for organic-organic pervaporation, Separation and Purification Technology 264 (2021) 118315

[4] K. Knozowska, J. Kujawa, T. M. Muzioł, A. Szymczyk, W. Kujawski, 3D structure enhancers based on functionalized MIL-53(Al) for improved dimethyl carbonate/methanol pervaporative separation, Journal of Membrane Science 695 (2024) 122442.