Polymeric pseudo-liquid membrane as a stable liquid membrane—Evidence for carrier-diffusion mechanism

Novel liquid membrane system, which has been named polymeric pseudo-liquid membrane, were constructed from poly(2-ethylhexyl acrylate) (P2EHA), which showed rubbery state under operating conditions, as a membrane matrix and dibenzo-18-crown-6 (DB18C6) as a model transporter. The membrane performance was studied, adopting KCl as a model substrate. The present polymeric pseudo-liquid membranes transported KCl. The transport rate of K+ was dependent on the concentration of transporter within the membrane and on the square of the concentration difference across the membrane. Those dependencies revealed that transport across the present polymeric pseudo-liquid membrane was attained by carrier-diffusion mechanism. In other words, the transporter and the transporter/substrate complex freely diffused within the membrane. The membrane transport ability was greatly affected by molecular weight of membrane matrix. The K+ flux was increased with the decrease in molecular weight of membrane matrix, P2EHA. The flux was also dependent on the operating temperature; the K+ flux was increased with rise in the operating temperature. The present study revealed that polymeric pseudo-liquid membranes are applicable to membrane separation as one of liquid membrane transport systems.