Stepwise extraction of lithium and potassium and recovery of fluoride from aluminum electrolyte wastes through calcification roasting-two-stage leaching.

Aluminum electrolyte is a necessity for aluminum reduction cells; however, its stock is rising every year due to several factors, resulting in the accumulation of solid waste. Currently, it has become a favorable material for the resources of lithium, potassium, and fluoride. In this study, the calcification roasting-two-stage leaching process was introduced to extract lithium and potassium separately from aluminum electrolyte wastes, and the fluoride in the form of CaF2 was recycled. The separation behaviors of lithium and potassium under different conditions were investigated systematically. XRD and SEM-EDS were used to elucidate the phase evolution of the whole process. During calcification roasting-water leaching, the extraction efficiency of potassium was 98.7% under the most suitable roasting parameters, at which the lithium extraction efficiency was 6.6%. The mechanism analysis indicates that CaO combines with fluoride to form CaF2, while Li-containing and K-containing fluorides were transformed into water-insoluble LiAlO2 phase and water-soluble KAlO2 phase, respectively, thereby achieving the separation of two elements by water leaching. In the second acid-leaching stage, the extraction efficiency of lithium was 98.8% from water-leached residue under the most suitable leaching conditions, and CaF2 was obtained with a purity of 98.1%. The present process can provide an environmentally friendly and promising method to recycle aluminum electrolyte wastes and achieve resource utilization.

Leaching valuable metals from spent lithium-ion batteries using the reducing agent methanol.

When considering resource shortages and environmental pressures, salvaging valuable metals from the cathode materials of spent lithium-ion batteries (LIBs) is a very promising strategy to realize the green and sustainable development of batteries. The reductive acid leaching of valuable metals from cathode materials using methanol as a reducing agent was studied. The results show that the leaching efficiencies of Co and Li are 99% under optimal leaching conditions. The leaching kinetics of cathode materials in a H2SO4-methanol system indicate that the leaching of Co and Li is controlled by diffusion, with activation energies of 69.98 and 10.78 kJ/mol, respectively. Detailed analysis of the leaching reaction mechanism indicates that methanol is ultimately transformed into formic acid through a two-step process to further enhance leaching. No side reactions occur during leaching. Methanol can be a sustainable alternative for the reductive acid leaching of valuable metals from spent LIBs due to its high efficiency, application maturity, environmental friendliness, and low cost.

A novel approach for lithium recovery from waste lithium-containing aluminum electrolyte by a roasting-leaching process.

With the development of secondary resources, development of suitable methods for the recovery of high value metals from solid waste is crucial for sustainable development. Aluminum electrolysis of China, solid waste, such as waste aluminum electrolyte, has been largely idled and caused serious environmental pollution. In this paper, a novel approach is developed for achieving the separation/recovery of lithium from spent lithium-containing aluminum electrolyte by a sodium carbonate roasting-acid leaching process. The effect on the extraction behavior of lithium under different roasting and leaching conditions was systematically studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to elucidate the phase evolution. The results indicated that 73.1% of the lithium was obtained under the optimized conditions: a m(actual)/m(theory) ratio of 1.10 with roasting at 850 °C for 2.5 h; a HNO3 solution concentration of 2 mol/L, and a liquid to solid ratio of 10 at 60 °C for 180 min. Through the analysis of the roasting sample, it was found that the addition of Na2CO3 promoted the conversion of Na2LiAlF6 to LiF. The content of lithium in electrolyte significantly reduced from 2.20% to 0.71% after leaching, which made it possible for the residue to be reused as the raw material for the aluminum reduction cell. The leachate was neutralized and purified with CaO and Na2CO3 solution, respectively, and then lithium be recovered in the form of Li2CO3. Overall, this study highlights an effectively and environmentally feasible plan for the treatment of spent aluminum electrolyte and to recycle lithium.