Leaching kinetics of fluorine during the aluminum removal from spent Li-ion battery cathode materials

The high content of aluminum(Al)impurity in the recycled cathode powder seriously affects the extraction efficiency of Nickel,Cobalt,Manganese,and Lithium resources and the actual commercial value of recycled materials,so Al removal is crucially important to conform to the industrial standard of spent Li-ion battery cathode materials.In this work,we systematically investigated the leaching process and optimum conditions associated with Al removal from the cathode powder materials collected in a wet cathode-powder peeling and recycling production line of spent Li-ion batteries(LIBs).Moreover,we specifically studied the leaching of fluorine(F)synergistically happened along with the removal process of Al,which was not concerned about in other studies,but one of the key factors affecting pollution prevention in the recovery process.The mechanism of the whole process including the leaching of Al and F from the cathode powder was indicated by using NMR,FTIR,and XPS,and a defluoridation process was preliminarily investigated in this study.The leaching kinetics of Al could be successfully described by the shrinking core model,controlled by the diffusion process and the activation energy was 11.14 kJ/mol.While,the leaching of F was attributed to the dissolution of LiPF6and decomposition of PVDF,and the kinetics associated was described by Avrami model.The interaction of Al and F is advantageous to realize the defluoridation to some degree.It is expected that our investigation will provide theoretical support for the large-scale recycling of spent LIBs.

An Innovative Approach to Separate Iron Oxide Concentrate from High-sulfur and Low-grade Pyrite Cinders

High-sulfur and low-grade pyrite cinders are the waste products of sulfuric acid manufacturing plants.Many valuable components,such as iron oxide,are contained in pyrite cinders and difficult to be separated and purified just via the high temperature roasting process.Considering this,an innovative method including water-washing,aqua regia leaching,hydrothermal alkali activation and acid-washing was developed.And the effects of different parameters on recovery efficiency of iron oxide were systematically investigated.The optimum parameters were proposed as follows：water rinse-leaching at room temperature for 5-20 min,and melting at 160 ℃ for 2.0h with NaOH（concentration of 30mass%）,followed by leaching with aqua regia solution（3.0vol.%）for 1.0h.After the treatment,the content of iron oxides increased from 54.3to 96.0mass% with the recovery rate exceeding 85%.Meanwhile,calcium sulphate was recovered as the high value-added products by alkali extraction liquid.Furthermore,the phase transformation and microstructure of the samples in the process were studied by physicochemical methods to reveal the separation mechanisms of different components in the pyrite cinders.