In this work, a method for leaching black mass from spent Li batteries using oxalic acid was developed and experimentally verified with the objective of selectively separating lithium and cobalt. Oxalic acid proved to be an efficient and selective leaching agent. Under 1 M C₂H₂O₄, 120 min, L:S = 20, 80 °C and 300 rpm, a lithium yield of 90% was achieved, while cobalt dissolution remained low at 1.57%. Subsequently, cobalt spontaneously precipitated from the leachate within several hours, and the solid phase was fully separated after 24 h. The leachate contained minor amounts of accompanying metals, with dissolution yields of 0.5% Mn, 8% Fe and 1.4% Cu. These impurities were removed from the leachate by controlled pH adjustment using NaOH at ambient temperature and 450 rpm, with complete precipitation at pH 12. This procedure generated a purified lithium-rich leachate, which was converted into lithium oxalate by crystallisation at 105 °C. Subsequent calcination of the resulting solid at 450 °C for 30 min produced Li₂CO₃ with a purity of 91%. Based on the experimental findings, a conceptual technological process for selective lithium leaching using oxalic acid was proposed, demonstrating the potential of this method for sustainable lithium recovery.

One of the environmental aspects of processing electronic waste using hydrometallurgical methods is the generation of waste solutions. Solutions after leaching and recovery of target metals are destined for disposal and contain valuable non-ferrous metals such as Cu, Sn, Ni, and others. Their disposal leads to wasting their material potential. The aim of this work is to propose a method by which selected non-ferrous metals can be selectively recovered from these solutions prior to disposal. The results of the experimental work show that the combination of pH adjustment with sodium hydroxide followed by cementation with iron is a suitable procedure for copper displacement from the solution. The cemented copper contains impurities. Removal of these impurities is possible by washing in sulfuric acid. pH adjustment can also be achieved using waste material containing copper. The results confirm that copper can be selectively recovered from waste solutions.