The key factors and mechanism study on lithium extraction by TBP-FeCl3 extraction system

Solvent extraction of lithium from brines with high magnesium/lithium ratios: investigation on parameter interactions

Solvent extraction of lithium from brine with a high Mg/Li ratio was investigated. Tributyl phosphate (TBP), ferric chloride (FeCl3), and kerosene were used as the extractant, co-extractant, and diluent, respectively. The mechanism of the extraction process was studied by LC-MS, UV-VIS, and FT-IR analyses. Effects of organic to aqueous phase volume ratio (O/A) on the extraction efficiency and separation factor were optimized. The effects of major parameters including Fe/Li molar ratio, hydrochloric acid concentration, and TBP volume percent as well as their interactions on the lithium extraction efficiency were evaluated using central composite design. These major parameters represent interactions within their selected ranges. While the lithium extraction efficiency as the response value in the experimental design showed the most sensitivity to the acid concentration, the separation factors were more affected by alteration in the TBP volume percent with the fixed optimum values of the other major parameters. The highest one-stage extraction efficiency of 76.3% and Li/Mg separation factor of 304 were obtained at the optimum conditions of Fe/Li = 2.99, HCl = 0.01 M, and TBP = 55%. The Mg/Li mass ratio could be significantly reduced from 192 in the feed to 1.5 in the stripping solution. Based on the findings, a schematic diagram of the process including extraction, stripping, and saponification steps was proposed.

Lithium Extraction from Salt Lake Brine with High Mass Ratio of Mg/Li Using TBP-DIBK Extraction System

Lithium extraction from salt lake brine with a high mass ratio of Mg/Li by counter-current method using TBP-DIBK extraction system was investigated in this study. In the extraction process, TBP and DIBK acted as extractant, kerosene was used as diluent, and FeCl3 was used as co-extractant. The operation conditions of extraction, scrubbing, stripping, and regeneration were investigated. In this study, 5.5 mol/L LiCl + 0.5 mol/L HCl was used as a scrubbing solution for purifying products, and 6 mol/L HCl solution was used as a stripping agent to transfer Li+ from organic phase to aqueous phase. Furthermore, 2 mol/L NaOH and saturated MgCl2 were used as the regeneration agent to remove H+ from organic phase. The counter-current extraction experiments of 3-1-1-3 stages were carried out. After 10 cycles, the lithium extraction efficiency reached 99.90%; the separation factor of Li/Mg, Li/K, Li/Na, and Li/Ca was 5.215 × 104, 2.159 × 103, 3.659 × 102, and 3.104 × 102, respectively. The results indicated that the TBP-DIBK extraction system was effective at extracting lithium from salt lake brine with a high mass ratio of Mg/Li. Furthermore, the study of extraction thermodynamics suggested that lithium extraction was an exothermic process and that lower temperature promoted lithium extraction.

A New Extraction System Based on Isopropyl Salicylate and Trioctylphosphine Oxide for Separating Alkali Metals

It was established that isopropyl salicylate can be used similarly to 1,3-diketones as a key component for a new efficient extraction system for selective separation of alkali metal cations. According to DFT modeling of complexes of isopropyl salicylate and 1,3-diketone with alkali metal cations (Li+, Na+, K+), six-membered metallacycles are formed whose stability decreases along the series Li > Na > K, which results in the observed enhanced affinity to lithium. The extraction ability of isopropyl salicylate is manifested in the presence of trioctylphosphine oxide (TOPO). The newly obtained complexes of isopropyl salicylate with alkali metal cations as well as their extracts in a mixture with TOPO are characterized by means of FT-IR, Raman, and NMR spectroscopy. The probable structure of the extracted lithium complex is presumed and the role of TOPO in the extraction process is investigated in detail. Extraction experiments showed extremely high separation coefficients for Li/Na and Li/K pairs in the extraction from a model multi-component solution.