A clean and efficient technology for lithium, rubidium, and cesium recovery from lepidolite using alkaline pressure leaching and alkaline solvent extraction with LIX 54 and TRPO
Lepidolite is one of the important resources containing Li, Rb, and Cs. Currently, sulfate roasting is the predominant industrial method for processing lepidolite. However, this approach faces challenges including low comprehensive recovery, high energy consumption, and significant reagent usage. This study introduces a clean and efficient technology for recovering Li, Rb, and Cs from lepidolite, based on alkali and water cycles. The process encompasses collaborative leaching with a mixture of sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH) 2 ), selective impurity removal using Ca(OH) 2 , and alkaline extraction for lithium recovery. Experimental results demonstrated that the leachate could be recycled 2 times to enrich Li, Rb, and Cs. The average leaching efficiencies after 2 cycles were: 92.7 % Li, 94.3 % Rb, 94.5 % Cs, and 94.6 % K, under the leaching conditions of 400 g/L NaOH, 0.6 of mass ratio of Ca(OH) 2 /ore, <106 μm particle size, 5 h reaction time and 250 °C. The XRD and SEM-EDS analyses revealed that the leach residue comprised the phases Ca 0.63 Fe 2.37 Fe 2 (SiO 4 ) 3 , NaCaHSiO 4 , CaF 2 , and Fe 3 O 4 . Furthermore, Ca(OH)₂ was employed for selective impurity removal from the solution, achieving a valuable metal loss of only 0.67 %. Subsequently, Li was efficiently recovered via synergistic solvent extraction using dodecyl phenyl methyl-β-diketone (LIX 54) and trialkylphosphine oxide (TRPO). The 85 % volume fractions of raffinate of Li could be returned to pressure leaching to reuse H 2 O and NaOH. The process developed in this study features environmental friendliness, high comprehensive recovery, and low reagent consumption, providing a promising approach for the clean and efficient utilization of lepidolite.
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