In this study, a hydro-metallurgical process has been proposed to separate and recover valuable metals from citric acid leach solution of waste lithium nickel cobalt manganese oxide based cathodes. Nickel, cobalt, manganese and lithium were effectively separated and recycled by a combined method of selective precipitation and solvent extraction. First, about 98% of nickel was selectively precipitated by dimethylglyoxime reagent under conditions of equilibrium pH of 6 and molar ratio of Ni2+ to dimethylglyoxime of 0.5, with little loss of other metals. Then about 97% of cobalt was precipitated by ammonium oxalate and recovered as CoC2O4 center dot 2H(2)O under conditions of equilibrium pH of 6, reaction temperature of 55 degrees C and molar ratio of C2O42+ to Co2+ of 1.2. The recovery of manganese was conducted by solvent extraction method using D2EHPA with 70-75% saponification rate. About 97% of manganese was extracted under optimal experimental conditions and recovered as MnSO4 after stripped with sulfuric acid solution. The McCabe-Thiele isotherm indicated that three extraction stages were needed for complete extraction of manganese at specific extraction condition. Finally, about 89% of lithium was precipitated and recovered as Li3PO4 by 0.5 mol L-1 Na3PO4 solution. This combined hydrometallurgical recovery process is a relatively simple and environment-friendly route, which all metal values in the leach liquor can be effectively separated and recovered and both dimethylglyoxime and D2EHPA can be recycled and re-used. (C) 2014 Elsevier B.V. All rights reserved.