Lithium Extraction from Salt Lakes

With the rapid advancement of the electronic technology industry, the global demand for lithium resources is growing at an annual rate of about 10%. As a major lithium resource country, China has rich lithium deposits, especially in the salt lakes of Qinghai and Tibet, where lithium resource reserves occupy an important position in the world.

In Qinghai, the lithium resources in the salt lakes are mainly divided into sulfate and chloride types according to the differences in anions in their brines. Sulfate-type salt lakes usually have a high magnesium-lithium ratio, while chloride-type salt lakes have a relatively low ratio. Although the total amount of lithium resources in Qinghai Salt Lake is considerable, the high magnesium-lithium ratio and high impurity content result in a relatively low lithium grade, which poses a challenge to the mining of lithium resources. In order to effectively extract lithium resources, it is necessary to continuously improve and optimize the lithium extraction technology of salt lake brine.

Overview of Lithium Extraction from Qinghai Salt Lakes

In Qinghai Salt Lakes, the high magnesium-lithium ratio is the main obstacle to the development of lithium resources. Therefore, achieving efficient separation of magnesium and lithium has become the key to the development of lithium resources. At present, there are several relatively mature lithium extraction technologies, including:

Adsorption method: using materials that selectively adsorb lithium ions as adsorbents to adsorb lithium ions in brine, and then using eluent to elute lithium ions, and through further separation and concentration processes, obtain lithium resources that can be used for conversion.

Calcination method: For brine with a high magnesium-lithium ratio, calcination at high temperature decomposes bischofite, and the generated magnesium oxide solid and hydrogen chloride gas are separated, and then lithium carbonate is extracted through soaking, filtration, purification, evaporation and precipitation.

Membrane separation method: Through a selectively permeable membrane, under the impetus of external forces, the separation, purification and concentration of multi-component solutes or solvents are achieved. In the extraction of lithium from Qinghai Salt Lake, membrane separation is mainly used for the separation of magnesium and lithium and the concentration of lithium solutions.

Solvent extraction method: Using tributyl phosphate as an extractant, ferric chloride as a complexing agent, and hydrochloric acid as a stripping agent, lithium is extracted from low-grade brine through multi-stage countercurrent extraction and subsequent washing, stripping, pickling and other steps, and finally lithium carbonate or lithium chloride is produced through spray drying and other processes.

At present, among the lithium extraction technologies of Qinghai Salt Lake, adsorption method and ion selective membrane method are relatively mature and gradually become industry benchmarks. Although there are some challenges in the actual application of adsorption method, such as high loss rate of adsorbent and unsatisfactory adsorption effect, the technology has successfully achieved large-scale production.

Overall, with the continuous advancement and innovation of technology, the development of lithium resources in Qinghai Salt Lake will be more efficient and environmentally friendly, providing solid support for meeting the growing global demand for lithium resources.