Blackmass flotation of end-of-life batteries: How to do without pre-treatment?

The study is part of the European Batraw project, which aims to develop new ways of recycling end-of-life batteries. In recent years, mineral processing techniques have been applied to the treatment of secondary materials. In battery recycling, the black mass, a mixture of graphite and metal oxides such as NMC, contains most of the economic value of batteries. At present, all black mass is processed by hydrometallurgy, resulting in process oversizing and poor graphite recovery. In order to overcome these problems, flotation could be adapted thanks to the difference in hydrophobicity between graphite and metal oxides. As each black mass is different, particularly in terms of particle size and ageing conditions, this technique is currently not very robust without costly pretreatments such as pyrolysis. The aim of this study is to understand the major obstacles to the use of this technique, in order to better adapt the operating conditions or possible pre-treatments. The results show that, while the presence of binder is an obstacle to the use of flotation, other parameters, such as particle size or the proportion of graphite in the black mass, which can be anticipated upstream or when adjusting operating parameters, could make pyrolysis unnecessary.