Liquid–liquid extraction of uranium from nitric acid solution using di-n-butylsulfoxide in petroleum ether as extractant

Abstract

A simple, efficient and economical liquid–liquid extraction method has been developed for quantitative extraction of uranium from 2 M HNO3using di-n-butyl sulfoxide in petroleum ether. The dependence of the partition reaction of U(VI) on the concentration of HNO3, extractant and temperature was studied. The reaction was found to be inversely dependent upon the temperature and the values for related thermodynamics functions (ΔH, ΔS, ΔG) for extraction equilibrium were determined to be -33.6 kJ/mol, -1.29 kJ/mol/degree and -0.11 kJ/mol/degree, respectively. The effect of Al(NO3)3as salting-out agent and diverse ions on the extraction was examined. The salting-out agent slightly enhanced the extraction. All cations studied have showed negligible effect on the extraction, whereas phosphate and fluoride interfered seriously. Among others, oxalate, citrate and sulphide ions affect the extraction to a lesser extent. Uranium was successfully extracted from a synthetic mixture of Ti+4, Zr+4, Hf+4and Th+4using EDTA as masking agent. Among strippants, deionized water was found most suitable, and the recovery of uranium was noted to be ≥96%. The stoichiometric composition of the extracted species was found to be UO2(NO3)2·2DBSO. The extraction mechanism is discussed on the basis of the results obtained. The extractant has high loading as well as recycling capacity without any degradation. The method was also applied to the Standard Reference Material (NBL-49) and the measured value was found to be in agreement with the reported value within ±2% deviation.