Microemulsion breakdown by pervaporation technique: the cyclohexane/water/ n-butanol/sodium dodecylsulfate system

Abstract

Preliminary results obtained on destabilizing microemulsions made up of cyclohexane, water, n-butanol, and sodium dodecylsulfate (SDS) using pervaporation membranes are promising. The hydrophobic/hydrophilic character of the membrane employed makes preferential removal of one of the microemulsion components possible. This leads to microemulsion breakdown. While cyclohexane permeates through hydrophobic polydimethylsiloxane membranes, water permeates through polyvinyl alcohol membranes. Removal of either component leads to microemulsion collapse. For instance, when 13.8 vol.% of cyclohexane is removed from the cyclohexane-rich microemulsion: 1:87:8:4 (water: cyclohexane: n-butanol: SDS, respectively (in wt.%), destabilization occurs. The flux rate and the enrichment factor of the component removed through the membrane were found to be concentration dependent. The variations of both parameters with time for two microemulsions, one rich in cyclohexane and the other rich in water, were examined as function of temperature. The pervaporation permeation rate goes up at elevated temperature, but enrichment factor diminishes. The optimum volume of the pervaporate required to produce the destabilization of the microemulsion changes with temperature according to a linear Arrhenius relationship with an activation energy of 4.56 kcal mol −1.