Separation and Recovery Properties of Rare Earth Elements Using a pH-sensitive Polymer Having Benzoic Acid Substituent Group

The separation of metal ions was examined using a poly{4-[2-(vinyloxy)-ethoxyl]-benzoic acid} [Poly(VEBA)s] as a pH-sensitive polymer. It showed phase separation at around pH 6.5. As a result, several specific characteristics of scavenging metals were confirmed. Among them, a specific result for rare earth elements was obtained. A separation and recovery system of rare earth elements was developed by using pH change and filtration. The recovery for 16 kinds of rare earth elements was approximately 100%. It was possible to separate the metal from Poly(VEBA)s by remelting Poly(VEBA)s with sodium hydroxide solution. Poly(VEBA)s could be recycled by recovery of polymer. This system has high safety to the environment and organism because of an all-water system without-using any organic solvent.