Selective transport and removal of Cd from chloride solutions by polymer inclusion membranes

The transport of Cd ions from chloride media high in salinity and acidity through a polymer inclusion membrane has been investigated. The membrane consisted of cellulose triacetate as the polymeric support, o-nitrophenyl octyl ether (NPOE) as the plasticizer and Aliquat 336 as the carrier. The influence of aqueous and membrane components on the metal flux has been evaluated. The transport system designed here is shown to be effective for the transport of Cd in both highly saline and highly acidic media, with similar flux values being reached for both in the range studied. The effect of carrier and plasticizer content in the membrane has been investigated; the maximum flux value was achieved with a carrier content of 3 mg cm−2 and 0.3 mL of NPOE. The results showed that the absence of plasticizer inhibited the transport of the metal at low carrier content, but when dealing with membranes containing a high amount of carrier, the transport of Cd was possible. This highlights the ability of this carrier to create intramembrane pathways in which the complex formed by metal species and a carrier can be transported. Finally, the separation system developed has been successfully applied to the removal of this toxic metallic pollutant from different aqueous samples, such as spiked seawater and a Ni–Cd battery leaching.