Ferrioxalate photolysis-assisted green recovery of valuable resources from spent lithium iron phosphate batteries.

The photolysis can separate the lithium and iron leached by oxalic acid and H 2 O 2 from spent lithium iron phosphate cathode. The process free the addition of precipitant and no hazardous waste is generated. [Display omitted] • Photolysis instead of additional precipitants for metal separation and recovery. • Rapid and selective leaching of active material elements from spent LFP cathode. • No wastewater or hazardous emissions generated from the process. Recovering valuable resources from spent cathodes while minimizing secondary waste generation is emerging as an important objective for the future recycling of spent lithium-ion batteries, including lithium iron phosphate (LFP) batteries. This study proposes the use of oxalic acid leaching followed by ferrioxalate photolysis to separate and recover cathode active material elements from spent LFP batteries. The cathode active material can be rapidly dissolved at room temperature using appropriate quantities of oxalic acid and hydrogen peroxide, as determined through thermodynamic calculations. The dissolved ferrioxalate complex ion (Fe(C 2 O 4) 3 3−) is selectively precipitated through subsequent photolysis at room temperature. Depending on the initial concentration, the decomposition ratio can exceed 95 % within 1–4 h. Molecular mechanism analysis reveals that the decomposition of the Fe(C 2 O 4) 3 3− complex ion into water-insoluble FeC 2 O 4 ·2H 2 O results in the precipitation of iron and the separation of metal elements. Lithium can be recovered as dihydrogen phosphates through filtration and water evaporation. No additional precipitant is needed and no other side products are generated during the process. Oxalic acid leaching followed by photolysis offers an environmentally friendly and efficient method for metal recovery from spent LFP cathodes. The photochemical process is a promising approach for reducing secondary waste generation in battery recycling. [ABSTRACT FROM AUTHOR]