In view of the importance of resource recycling and the use of environmentally safe systems to extract the metals contained in wastes, the present study concerns the extraction/separation of lanthanum from spent Ni-MH batteries. Investigation was made of the extraction behavior of lanthanum using aqueous two-phase systems (ATPSs), and a new environmentally safe hydrometallurgical method was developed for the selective extraction of La from Ni-MH battery leachate. The extraction behavior of La was evaluated considering the influence of the following parameters: concentration of different extractant; pH; ATPS-forming electrolyte (Li2SO4, Na2SO4, MgSO4, Na2C4H4O6, or Na3C6H5O7); ATPS-forming polymer (L64 or PEO1500). The recovery efficiency was evaluated by analyzing the extraction percentage (%E), and the best conditions for analyte extraction were achieved using the ATPS formed by PEO1500 + Li2SO4, at pH 6.00, with 1,10-phenanthroline as the extractant agent (%E = 74.1%). The method was applied to a real Ni-MH battery leachate. After three successive extraction steps, high separation factor (S) values were obtained for the separation of lanthanum from concomitant metals (S-La,S-Ce = 180; S-La,S-Pr = 184; S-La,S-Nd = 185). A stripping assay was carried out, and after a single step, 88.5% of the lanthanum was available for a possible electrowinning step. (C) 2017 Elsevier B.V. All rights reserved.