Effect of trimethyl, triethyl, tripropyl, and tributyl amine functional groups in strong-base anion exchange resin on the sorption of Pu(IV) from nitric acid

摘要

Four macroporous, strong-base anion exchange resins of similar crosslinkage and porosity, which differed only in their trialkyl amine functional groups, were compared for sorbing PU(IV) from nitric acid. Resins with trimethyl, triethyl or tripropyl amine functional groups exhibited generally similar behavior over the range of 1 to 12 M nitric acid. The distribution coefficients of these three resins for PU(IV) peaked near 7 M nitric acid, as expected. However, the resin with a tributyl amine functional group sorbed PU(IV) only from >7 M nitric acid, in a pattern different from that seen with any other anion exchange resin. We believe this behavior indicates two independent sorption mechanisms for Pu(IV). For the first three resins, a hydrophilic Pu(HNO(sub 3))(sub 4)(center dot)5H(sub 2) complex approaches the exchange site, where it is converted to HPu(NO(sub 3))(sub 6)(sup (minus)) during sorption. The other process, which has been observed only with the tributyl amine resin, may involve the direct sorption of a hydrophobic hexanitratoplutonate complex. This possibility is supported by absorption spectrophotometric data.