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Abstract
The extraction behaviour of Mo(VI) from nitric acid medium was investigated employing di(octyl-phenyl) phosphoric acid (DOPPA) in different diluents. Dodecane was found to give higher DMo value as compared to other diluents investigated (under similar conditions). DMo decreases with HNO3 concentration up to 3 M and increases thereafter up to 10 M, suggesting that two different mechanisms are involved in this extraction system. Speciation studies show that HMoO3.(HA2) and MoO2.2(HA2) are the predominant species at 0.1 M HNO3, whereas at 6 M HNO3 the predominant species is MoO2(NO3)2.2(HA). Selectivity of DOPPA for Mo with respect to U increases with HNO3 concentration up to 10 M. Thermodynamic studies show that at lower acidity (<3M), extraction is enthalpy as well as entropy favoured, while at higher acidity (>3M) the extraction process is enthalpy stabilised and entropy destabilised. Conditions for quantitative recovery (>99%) of Mo(VI) were arrived at and selectivity with respect to other fission products was evaluated.
ACKNOWLEDGMENTS
The authors thank Dr. S.B. Manohar, Head, Radiochemistry Division, B.A.R.C., Mumbai for his keen interest in this work. They are grateful to Mr. S.D. Mishra, Chief Design Engineer and Mr. P.M. Gandhi, Chief System Engineer (Process), Waste Management Projects Programme, B.A.R.C., Mumbai, for their constant encouragement.