EXTRACTION SYSTEM AND EXTRACTION METHOD FOR SEPARATING MAGNESIUM AND EXTRACTING LITHIUM FROM MAGNESIUM-CONTAINING BRINE USING SECONDARY AMIDE SOLVENT, AND APPLICATION THEREOF

摘要

Provided are an extraction system and an extraction method for separating magnesium and extracting lithium from magnesium-containing brine using secondary amide solvent, and application thereof. The extraction system comprises secondary amide consisting of a single compound or a mixture of two or more compounds, wherein R₁ is selected from C2-C12 alkyl or C3-C12 cycloalkyl comprising a single-ring structure, R₂ is selected from C1-C11 alkyl or C3-C11 cycloalkyl comprising a single-ring structure, the total number of carbon atoms in the molecules is 12-18, and the solidifying point of the extraction system is lower than 0℃. Performing single-stage or multi-stage counter-current extraction under the condition that the volume ratio of the organic phase to the brine phase is 1-10:1, the density of the brine is 1.25-1.38 g/cm³ and the temperature is 0-50℃, performing re-extraction to obtain the low-magnesium-lithium-ratio water phase, obtaining lithium chloride, lithium carbonate and lithium hydroxide respectively after concentration, impurity removal and preparation. The molecular structure of the secondary amide in the present invention is simple, the multi-stage extraction rate of Li⁺ is high, the lithium and magnesium separation coefficient is large; water is used for re-extraction, the consumption of acid and alkaline is greatly reduced; the technological process for extraction and separation is short, the extraction system is small in solution loss.