Influence of nanobubbles on flotation behavior of electrode materials from spent lithium ions batteries

The electrode materials of spent lithium ions batteries mainly consist of graphite and lithium cobalt oxide，the separation of which with flotation is a key step in the recycling and utilization process of secondary re⁃ sources.The efficient separation of them with the conventional flotation technique is hard to be achieved due to the smaller size of electrode materials than that of common flotation particles.In the present study，the interface nanobub⁃ bles were imaged with the tapping mode atomic force microscope(AFM)，then the influence of nanobubbles on the in⁃ ter particles interaction and the size of agglomeration of graphite were quantified with colloidal probe technique and size analyzer respectively.At last，the flotation experiment for electrode materials with nanobubbles was designed.The results show that nanobubbles can be generated with cold water by increasing temperature and the graphite probe was subjected to a weak electrostatic repulsive force during approach.Meanwhile，a high adhesion force was shown be⁃ tween graphite and substrate during retrace in the presence of nanobubbles. The D50 of graphite agglomerations increases from 23 μm to 29 μm in the presence of nanobubbles.The flotation results show that the combustible recovery increases from 34% to 66% in room temperature water while from 44% to 74% in the case of cold water as the flota⁃ tion time increases from 2 min to 8 min.The higher combustible recovery and the better flotation selectivity was ob⁃ tained in flotation with cold water compared with room temperature water.