Extraction chemistry of palladium(II).Mechanism of antagonistic synergistic extraction of palladium by a 4-aroyl derivative of l-phenyl-3-methyl-pyrazolone-5-one and trialkylamine of high molecular weight

摘要

The synergistic extraction behavior of Pd~(II),one of the main radioactive fission products in the reprocessing process,from HNO_3 solutions with a 4-aroyl derivative of l-phenyl-3-methyl-pyrazolone-5-one(PMP),a weakly acidic chelating extractant l-phenyl-3-methyl-4-(2-methoxybenzoyl)-pyrazolone-5-one(HPMMBP),and a trialkylamine of high molecular weight,tri-iso-octylamine(TiOA),has been studied.An obviously antagonistic extraction effect was observed in the extraction system under the given conditions.To understand this phenomenon,a preliminary investigation was performed to explain the mechanism of this reaction.According to the theory of the corresponding solutions(TCS),the association between HPMMBP and TiOA is presented and discussed in the organic phase.An associated species HPMMBP-TiOA formed through hydrogen bonding in a CHC1_3 medium might be the main reason why an antagonistic extraction effect occurred.The association constant between HPMMBP and TiOA was calculated to be 0.212+-0.03.