Abstract: The minor actinides (MA, mainly Am, Cm and Np) are the largest contributors to the long term radiotoxicity of the waste. The removal of MA from the waste would reduce the necessary storage time from more than 10⁶ years to less than 10³ years. Diamides, namely the diglycolamides(containing ether linkage between two amide groups), have also been studied for their extraction ability towards minor actinides as they act as tridentate ligands to complex with the metal ions. Among diglycolamides, recently developed N,N,N′,N′-tetraoctyl diglycolamide (TODGA) has been identified as one of the most powerful extractant being considered for the partitioning of trivalent actinides and lanthanides from HLLW solutions. So, in the present paper,two extraction reagents, TODGA and N,N-dihexyl octamide (DHOA) have been used as extractants for extraction Np(Ⅳ,Ⅴ,Ⅵ) ions from aqueous nitric acid solutions. The effects of concentration of the nitric acid, salting-out agents in aqueous and the extractant in ordanic phase on distribution ratios are examined. The results show that TODGA and DHOA can well extraction Np(Ⅳ) and Np(Ⅵ), and the Np(Ⅴ) is hardly extractioned by TODGA and DHOA. The order of distribution ratios of Np(Ⅳ,Ⅴ,Ⅵ) ions by TODGA and DHOA is D(Np(Ⅳ))＞D(Np(Ⅵ))＞D(Np(Ⅴ)). DHOA can also restrain the extraction of Np(Ⅳ,Ⅴ,Ⅵ) by TODGA. The extraction equation of Np(Ⅳ,Ⅴ,Ⅵ) ions by TODGA have also been studied as followed:
JZ（Np4+（aq）+4NO-3（aq）+3TODGA（org）FY（FY）Np(NO3)4•3TODGA（org）
NpO+2（aq）+NO-3（aq）+TODGA（org）FY(FY)NpO2(NO3)•TODGA（org）
NpO2+2（aq）+2NO-3（aq）+2TODGA（org）FY(FY)NpO2(NO3)2•2TODGA（org）JZ）