Fenton modified flotation is one of the effective ways to separate and recycle the electrode materials, LiCoO2 and graphite, from spent lithium-ion batteries (LiBs). However, a satisfactory LiCoO2 grade of flotation concentrate still could not be achieved after the Fenton modification. Comparison of its flotation results with the direct flotation and roasting modified flotation indicates the concentrate grade of LiCoO2 after Fenton treatment only increased by 5%, reaching 60%, while that of the roasting flotation could be up to 90%. Analyses of surface morphology and chemical composition indicate that the newborn surface of the electrode particles are wrapped with an inorganic compound layer composed of Fe(OH)(3), which is the secondary product of semi-solid phase Fenton. The inorganic film results in a similar hydrophobicity and finally leads to the poor flotation results. Deducing from the reaction mechanism of Fenton, the enhancement of alkaline environment is a main reason for the precipitation of Fe3+ on the surface of particles. Therefore, an appropriate amount of hydrochloric acid (HCI) was added to react with precipitation, and the final concentrate grade reached 75%. (C) 2017 Elsevier B.V. All rights reserved.