Recovery and application of magnetic nanosized sorbents from waste lithium-ion batteries

Secondary pollution from hydrometallurgical recycling of lithium ion batteries (LIBs) may affect the sustainability of the overall process. This study explores the valorisation of two LIB processing streams, namely iron-sludge and Mn-stripping effluent, as magnetic nanosized sorbents. A surfactant-autoclave synthesis route was developed to obtain CuFe2O4 from synthetic precursors. This same process was then applied to synthesise a quinary ferrite, CuCoMnNiFe2O4, from iron-sludge. Both products exhibited crystallite sizes below 20 nm. The obtained materials, given the elevated specific surface (>160 m2/g) and mesoporous structure, were tested for sorption of cations from synthetic solutions and pre-treated Mn-stripping effluent. Both materials showed preferential sorption behaviour for Mn (≈16 mg/g) versus Co, Li and Na. Mn and Co removal from the pre-treated effluent was more efficient when using the recycled material (Mn 100%, Co 70%) rather than CuFe2O4 (Mn 91%, Co 59%). Furthermore, single-phase nanocrystalline MnCoNiFe2O4 ferrites were synthesized from the two LIB streams by an ultrasound-surfactant-microwave treatment. FESEM profile width measured particle sizes of about 57 nm when the material was dried at 100 °C after synthesis and 98 nm when sintered at 700 °C. The physical and chemical properties (i.e. magnetization, porosity, sizes) of the synthesized materials were studied to assess the effects of the advanced hydrothermal routes and the starting materials on the final products.