A novel water-soluble ligand of N,N,N"',N"'-tetraethyl-N',N"-ethidene bisdiglycolamide (TEE-BisDGA) was synthesized and used as a masking agent for selective extraction of Am(III) over Eu(III) from HNO3 solution by N,N,N',N',N",N"-hexaoctylnitrilotriacetamide (NTAamide(C8)) in kerosene. Influences of acidity, concentration of water-soluble ligands and extractant as well as nitrate ions on the distribution ratios (D) and separation factors (SF) of Am(III) and Eu(III) were investigated. In the range of examined acidity from 0.001 to 0.20 mol/L, D-Am and D-Eu, decreased with the increase of HNO3 concentration. Using 0.10 mol/L NTAamide(C8) as an extractant, the maximum SFAm/Eu. of 26 can be obtained in the presence of 0.01 mol/L TEE-BisDGA in aqueous phase with pH of 3.0, which was significantly higher than that case with no TEE-BisDGA. Job's method and mole ratio method were employed for extraction mechanism research. It has been shown that Am(III) and Eu(III) formed di-solvated species with TEE-BisDGA and mono-solvated species with NTAamide(C8), respectively. Moreover, the stability constants log beta values were obtained from UV-vis adsorption spectroscopic titration for Nd(III) complexes with TEE-BisDGA and N,N,N',N'-tetraethyldiglycolamide (TEDGA), which indicated that TEDGA had a stronger complex ability than TEE-BisDGA. (C) 2017 Elsevier B.V. All rights reserved.