Lithium extraction technology of spodumene concentrate by sulfuric acid roasting

Spodumene mining has a long history and mature technology. Currently, more than half of the lithium metal on the market is produced by spodumene. The cost of lithium extraction from spodumene is high, but the product has fewer impurities and relatively stable quality. Spodumene has become the main force in lithium production because of its large mineral grains and is easy to be enriched through ore dressing. Among the current resources, the grade of raw lithium oxide (Li2O) is above 1%, which is worth mining.

Lithium extraction from hard rock minerals was once the main source of lithium salt production in the world. After more than 100 years of development, the lithium extraction process of hard rock minerals has become very mature, and this process can produce high-quality lithium salt products. There are four main methods for lithium extraction from ore: sulfuric acid roasting, lime sintering, soda pressure cooking and chlorination roasting. The commonly used method in industry is sulfuric acid roasting.

Lithium (spodumene) extraction by sulfuric acid roasting After the original ore is mined, spodumene is enriched by crushing, gravity separation, flotation and other beneficiation methods, and the concentrate is filtered and dried to obtain lithium concentrate. At present, lithium concentrate is extracted by sulfuric acid roasting. The process of this method is as follows:

1) Spodumene is roasted at 950-1100℃ to change its crystal form from α to β-type spodumene with loose structure;

2) The ball-milled mineral is mixed with concentrated sulfuric acid and then roasted at 250-300℃ for sulfuric acid to convert lithium into soluble lithium sulfate, and then leached to obtain lithium sulfate solution.

3) Lime powder is added to neutralize excess H2SO4, and the pH is adjusted to neutral to remove impurities such as Fe, Ca and Mg in the leachate.

4) The purified solution of lithium sulfate is obtained by evaporation and concentration, and then sodium carbonate is added to undergo double decomposition reaction to generate lithium carbonate.