Life cycle assessment of ore-based lithium carbonate production using sulfuric acid roasting and soda leaching: Impact of sodium sulfate electrodialysis

Abstract

The environmental footprints of batteries and battery chemicals play an important role in the transition towards decarbonized transportation. Lithium carbonate is a conventional lithium salt that is used in manufacturing lithium-ion batteries for electric vehicles and other applications. It is mainly produced either from lithium rich brines or from spodumene ores, the latter being generally more energy intensive due to minerals processing steps and high temperature operations. Finding the process routes for lithium carbonate with the lowest possible environmental impacts is crucial for minimizing the whole battery life cycle environmental footprints. In this work, a simulation-based life cycle assessment was conducted for producing lithium carbonate from spodumene concentrate using two different hydrometallurgical process routes: Sulfuric acid roasting and soda leaching. In the sulfuric acid roasting process, the treatment of generated sodium sulfate was also investigated, as sodium sulfate is a common and hard-to-abate waste from many industrial processes. An electrodialysis method described in the literature was used to convert sodium sulfate into sodium hydroxide and sulfuric acid, which were re-used in the process, or allocated as marketable products in the life cycle assessment. The life cycle impact assessment shows that the soda leaching process exhibits reduced environmental impacts in all chosen impact categories, often reaching a reduction of 40–50 % compared to the sulfuric acid roasting process. The largest sources of environmental impacts in both processes were energy generation and sodium carbonate production. The sodium sulfate treatment scenario in the sulfuric acid roasting process showed lowered environmental impacts when compared to the baseline scenario, except in water use, which was significantly higher. If the level of water use can be curtailed through process optimization and reaction efficiency, electrodialysis could be seen as an environmentally feasible method for sodium sulfate waste treatment in existing sulfuric acid roasting processes. Nevertheless, it can be suggested that in lithium refining from spodumene ore a preferred processing strategy would be to avoid sulfate generating unit processes altogether if technologically possible.