Method for producing lithium carbonate from low-lithium brine by separating magnesium and enriching lithium

A method for producing lithium carbonate from low-lithium brine by separating magnesium and enriching lithium, comprising:

• a. heating, evaporating and condensing a salt-lake brine to separate halide salts;
• b. extracting the separated halide salts with trialkyl phosphate or a mixture of trialkyl phosphate and monohydric alcohol as an organic phase;
• wherein a ratio of weight (kg) of the separated halide salts to a volume (L) of the organic phase is 1.0:0.5˜5.0;
• c. filtering a mixture from step b to produce an organic phase and remaining halide salts after a two-phase separation;
• d. reverse extracting the organic phase from step c with water as a reverse extraction agent at a volume ratio of water to organic phase of 1.0:0.5˜10.0 in 1-5 stages of reverse extraction;
• e. separating the organic phase from the water of step d after liquid layers are formed and then evaporating and concentrating the separated water to obtain a concentrated water phase;
• f. adding sodium carbonate or sodium hydroxide into the concentrated water phase from step e to precipitate magnesium carbonate or magnesium hydroxide, and then filtering the precipitated magnesium carbonate or magnesium hydroxide to remove Mg2+, wherein the water phase has a pH of more than 10 to completely precipitate Mg2+;
• and
• g. adding sodium carbonate into the water phase with Mg2+ removed from step f to precipitate lithium carbonate, and then filtering and drying the precipitated lithium carbonate to produce a final product.