The invention discloses an extraction
system and method for separating
magnesium and extracting
lithium from
magnesium containing brine with a secondary
amide /
tertiary amide complex
solvent and application of the extraction method. The extraction
system contains secondary
amide and
tertiary amide, and each of the secondary amide and the
tertiary amide is composed of a single compound or a mixtureof two or more compounds. The total number of carbon atoms in a molecule of the secondary amide ranges from 12 to 18, the total number of carbon atoms in a molecule of the tertiary amide ranges from 18 to 32, and the solidifying point of the extraction
system is lower than 0 DEG C. Single-stage or multi-stage counter-current extraction is carried out under the condition that the volume ratio of anorganic phase to a brine phase is (1-10):1, the density of the brine is 1.25-1.38 g / cm<3>, and the temperature ranges from 0 DEG C to 50 DEG C; and a water phase low in
magnesium-
lithium ratio is obtained through reextraction, and
lithium chloride,
lithium carbonate and
lithium hydroxide products are obtained through concentration, purification and preparation. The extraction system and method for separating magnesium and extracting lithium from the magnesium containing brine with the secondary amide / tertiary amide composite
solvent and the application of the extraction method have the excellent effects that a secondary amide extraction agent is simple in molecular structure and easy to produce, and the
viscosity and other physical characters of the complex
solvent are improved through the tertiary amide; the multi-stage extraction rate of Li+ is high, the magnesium-lithium
separation coefficient is large, water is used for reextraction, and acid-base consumption is greatly reduced; and the extraction separation technological process is short, the extraction system is small in
dissolution loss, and high industrial application value is achieved.