Cation exchange membranes were prepared with 2,3-epithiopropyl methacrylate (ETMA) -2-acrylamide-2-methylpropane sulfonic acid (AMPS ) copolymers. Transport of uranyl ion against its concentration gradient through the membranes was investigated by using a system containing carbonate solution (left side) and uranyl ion (and other metal ion) solution (right side). ETMA-AMPS copolymer membranes transported UO;+ against its concentration gradient. Na2C03 solution was most effective as receiving solution for the uphill transport of UOi+. The transport was greatly affected by the composition of the copolymer membranes. Highly selective transport of UOz+ from the solution containing U O F and other metal ions was observed by using Na2C03 solution in the left side. The main driving force for this transport of UO;+ is the high complex-formation ability of UOi+ with CO!-.
In the previous article,' we reported that alkali and alkaline earth metal ions could be transported against their concentration gradient through membranes made of 2,3-epithiopropyl methacrylate (ETMA) -2-acrylamide-2-methylpropane sulfonic acid (AMPS) copolymers. We have also reported that uranium in seawater could be selectively adsorbed with macroreticular resins containing amidoxime groups and then uranium adsorbed on the resins was concentrated in the eluate.2 The development of membranes which can transport uranyl ion against its concentration gradient is expected to recover uranyl ions in the eluate. So far transport of uranyl ion against its concentration gradient through polymer membranes has not been reported.
In this article, the uphill and selective transport of uranyl ions through ETMA-AMPS copolymer membranes were investigated.
EXPERIMENTAL Synthesis of ETMA-AMPS Copolymers
ETMA was prepared by the method reported earlier.3 AMPS was provided by Nitto Riken Kogyo