Abstract: STUDY ON THE SOLVENT EXTRACTION OF Tc(Ⅶ)WITH TRIALKYL PHOSPHINE OXIDEFeng Xiaogui Liang Junfu Song Chongli Jiao Rongzhou(Institute of Nuclear Energy Technology,Tsinghua University,P.O.Box 1021,Beijing 102201)ABSTRACTThe extraction behavior of Tc(Ⅶ) by TRPOkerosene from nitric acid solution is studied.The extraction reaction is H＋＋TcO－4＋2TRPOHTcO4·2TRPO.The possible reaction mechanism is discussed,and the ΔG，ΔH,ΔS and the apparent equilibrium constant for the extraction reaction are given.The effects of HNO3,UO2(NO3)2 and Zr(NO3)4 concentrations on the extraction of Tc(Ⅶ) are studied respectively.It is found that the distribution ratio of Tc(Ⅶ) increased with the increase of the acidity until a maximum is reached at 0.35 mol/L HNO3,then the distribution ratio of Tc(Ⅶ) decreased with the increase of the acidity.The extraction of Tc(Ⅶ) is slightly enhanced in the presence of UO2＋2 or Zr4＋,and the coextraction of Tc(Ⅶ) with UO2＋2 and Zr4＋ is found.Key words TRPO Extraction Tc(Ⅶ)