Investigation of the carrier saturation in facilitated transport of unsaturated hydrocarbons

Single-component facilitated transports of ethylbenzene, styrene, cyclohexene and 1-hexene were carried out using the feed concentrations ranging from 0.5 M to pure. Equilibrium constants of the Ag⁺-solute complex formation, determined by distribution method, were 0.7, 2.2, 32.0, 129.1 M⁻¹, respectively. Carrier saturation was not found with the membrane incorporated with 2.67 M Ag⁺-ion. As the carrier concentration was reduced to 0.51 M, increase in the feed concentration beyond 4.5 M had very little effect on ethylbenzene flux, suggesting the onset of carrier saturation. Styrene and cyclohexene underwent the carrier saturation when the carrier loading was 0.25 M, while a complete saturation was not observed with 1-hexene. Extraction of solute from the membranes revealed that less than 50% of Ag⁺-ions were occupied when the carrier saturation occurred. It was also found that the ability of solute to use available Ag⁺-ions in the membrane was dependent on the equilibrium constant.