A Review on Lithium Extraction Processes from Spodumene and Resource Utilization of the Generated Lithium Slag

The booming new energy industry has fueled a surge in global lithium demand, with the annual demand for lithium carbonate (Li2CO3) equivalent (LCE) projected to reach 11.2 million tons by 2050. As a key raw material for lithium extraction, spodumene generates approximately 10–15 tons of lithium slag per ton of lithium carbonate (Li2CO3) produced. However, the comprehensive utilization rate of lithium slag in China remains below 30%, and most of it is disposed of through landfilling, posing soil pollution risks. This review summarizes the main lithium extraction processes from spodumene: the sulfuric acid method (with a lithium recovery rate of over 96% but high acid consumption); alkali processes (achieving 96%–99% lithium recovery and featuring low equipment corrosion, yet with untested applicability to low-grade ores); salt roasting (simplifying purification processes but only achieving ~60% sulfate recovery); and chlorination roasting (with a lithium recovery rate of over 95% but requiring strict safety controls). Additionally, this review covers the resource utilization of lithium slag: 8–10 million tons of gypsum can be recovered annually (filling 16%–20% of China’s industrial by-product gypsum supply gap); the silica–alumina micro-powder can enhance concrete strength and reduce glass fiber production costs; and over 94% of tantalum (Ta) and niobium (Nb) can be recovered from fine tantalite concentrate slag. Key research gaps and future development directions are also identified to support the low-carbon development of the lithium industry.