Dehydration and solvent separation are crucial processes for industries and research facilities. Distillation and extraction are energy-intensive processes that are not always effective.
Pervaporation (PV), which is based on the solution-diffusion transport mechanism, provides an alternative strategy. Polymer-based membranes such as those made of Polydimethylsiloxane (PDMS) have offered
good pervaporation performance.
PV is a highly efficient and low energy-consuming process as it is based on the solution-diffusion transport mechanism. It is a procedure for separating diluted liquid mixtures through partial vaporisation, with the chemical potential across a membrane acting as the driving force . Due to the separation of liquid mixes rather than gaseous mixtures, it differs from a basic vapour permeation. This method is a combination of both permeation and evaporation. Though PDMS membranes have always been the go-to membrane for this, their drawback performance was improved by incorporating nanofillers like Zeolitic imidazolate framework (ZIF) particles into the membrane.
TYPES: Membranes can be of two types depending upon the nature of the component to be separated: 1) hydrophilic membranes that allow the preferential transport of polar molecules and 2) hydrophobic membranes that allow the transport of the less polar or non-polar molecules
Membranes made of polymers other than PDMS have also shown to deliver good PV performance, covering the blending conditions, membrane characteristics as well as the separation performance. These polymers are generally obtained from sources like animals (e.g., poly(butylene succinate), poly(lactic acid), poly(hydroxyalcanoates)), vegetables (e.g., starch, cellulose-based polymers, alginate, polyisoprene), bacterial fermentation products (e.g., collagen, chitin, chitosan), and other specific production processes (e.g., sericin which is a by-product of the silk processing process). These polymers possess a high affinity towards polar compounds like water, can form films easily and can potentially be subject to chemical modification due to the large number of functional groups present. The only drawback is their low mechanical strength, which has nonetheless, been attempted to be improved by coating onto porous supports and crosslinking with other materials (i.e., glutaraldehyde and sulphuric acid), and physically merging with inorganic nanomaterials.
Thus, Mixed matrix membranes are the novel approach towards solvent separation and dehydration through the process of pervaporation. It improves the performance by incorporating different inorganic fillers into the PDMS matrix, in which metal-organic frameworks (MOFs) have proven to be the most efficient. Among the MOFs, Zeolitic imidazolate framework (ZIF) based membranes have shown an excellent performance, with high values for flux and separation factors.
As there are still many Factors Affecting Pervaporation Performance of ZIF-PDMS Membranes there is a need to to tailor the morphology and functional groups of the metal-organic frameworks (MOFs) to improve MOF polymer interactions and various other parameters.
Reference: A Review on Mixed Matrix Membranes for Solvent Dehydration and Recovery Process
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