Performance of organo-clay-PDMS membranes in pervaporation processes.

Abstract

The objective of this work is to improve the pervaporation separation characteristics of polydimethylsiloxane (PDMS) membranes by imbedding organo-clay particles in the polymer structure. Montmorillonite is a clay mineral with a 2:1 layered structure. The negative charges on its layers due to the compositional inhomogeneities are counterbalanced with inorganic cations. Organo-montmorillonite is formed when the inorganic cations are exchanged with organic cations. The nature, type and structure of exchangeable cations on montmorillonite strongly influence their sorptive characteristics. Different combinations of these factors will produce very different interlayer environments. Tetraphenylphosphonium (TPP) and tetraalkylammonium cations (TAAn; where n is the number of carbon of the chain) were intercalated into montmorillonite to form a series of organo-clays (TPP-M; TAAn-M). The organo-clay-PDMS composite membranes (TPP-M-PDMS: TAAn-M-PDMS) were prepared by adding the organo-clays into the PDMS solution. Pervaporation experiments of dilute 1,2-DCE and benzene solutions were performed using organo-clay-PDMS composite membranes. The effects of the nature of organo-clays, of the organo-clay content, and of the temperature and downstream pressure as operating variables on the membrane performance were investigated. (Abstract shortened by UMI.)