Effect of anions on thermodynamics of extraction of Am(III) and Eu(III) with octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide

The extraction of Arn(III) and Eu(III) by octyl(phenyl)-N,N-diisobutylcarba moylmethylphosphine oxide (CMPO) in xylene from aqueous media containing 1. 0 M NH4NO3, NH4SCN, NH4ClO4 or a mixture of 0.3 M NH4NO3 + 0.7 M NH4ClO4 at pH 2.70 and at the temperatures of 15, 25, 35 and 45 +/- 0.1 degreesC has been studied. At all the temperatures, the species extracted were ML3. 3CMP O (M = Am(III) or Eu(III), L = NO3-, SCN- or ClO4-) and M(NO3)(ClO4)(2). 3C MPO. The thermodynamic parameters of the extraction reactions have been eva luated using the temperature coefficient method. The -DeltaG values follow the order SCN- > NO3- + ClO4- > NO3- ClO4-, whereas the -DeltaH values an o rder NO3- + ClO4- > SCN- > NO3- approximate to ClO4-. The effect of these a nions on the thermodynamic parameters have been discussed employing compens ation effects and also on the basis of the energy associated with the trans fer of these anions from aqueous to the extractant phase.