Recovery of lithium from salt lake brine of high Mg/Li ratio using Na[FeCl4 ∗ 2TBP] as extractant: Thermodynamics, kinetics and processes

- Novel extractant, Na[FeCl4 ∗ 2TBP], was used for lithium extraction from salt lake brine.
- Extraction thermodynamics and kinetics were investigated using a single-drop method.
- Separation factor of Li/Mg using this extractant was high up to 180.
- New extractant was stable after several extraction/stripping cycles for extracting lithium from East Taijinaier salt lake brine.

A systematic investigation on the extraction of lithium from salt lake brine with high Mg/Li using a novel extractant, Na[FeCl4 ∗ 2TBP]org, is reported with an emphasis on the extraction thermodynamics, kinetics and process. In liquid-liquid extraction, this extractant shows high separation factor of lithium/magnesium up to 178.4. Thermodynamic analysis indicated that the extraction is an exothermic process. However, when integrated with the kinetic effect, the lithium mass transfer increases at elevated temperature. The kinetics of lithium extraction by this extractant was investigated via a single drop column method. The magnesium, lithium concentration in brine, sodium, ferric concentration in organic extractant were studied, and a linear relationship was found between the rate of lithium transfer and the concentration of each component. The contribution of the formation/coalescence of organic extractant droplets, end-effect, to the lithium mass transfer was investigated. Perturbation at the brine/organic phases was found to promote lithium mass transfer during the rising step of droplets, mainly due to the low interfacial tension. Finally, a process was proposed to extract lithium ions from East Taijinaier salt lake brine and the stability of the new extractant was demonstrated by four extraction/stripping/saponification cycles. These results indicate that the present extractant was suitable for extracting lithium from brines with a high Mg/Li ratio.