Method for extracting lithium from high-salinity salt lake brine with assistance of sodium tripolyphosphate

Abstract

The invention belongs to the field of lithium resource extraction, and particularly discloses a method for extracting lithium from high-salinity salt lake brine with the assistance of sodium tripolyphosphate. The method comprises the following steps: 1, adding sodium tripolyphosphate into the lithium-containing salt lake brine, controlling the molar ratio of tripolyphosphate radicals in the sodium tripolyphosphate to Mg in the brine to be (1.1-1.2): 1, adding NH4Cl and ammonia gas, and adjusting the pH value of the brine to be 9-10 to obtain treated salt lake brine; 2, pretreating the salt lake lithium extraction nanofiltration membrane; step 3, adopting a nanofiltration device and a salt lake lithium extraction nanofiltration membrane to perform two-stage filtration process on the treated salt lake brine under the conditions of pressure of 2-4MPa and room temperature to obtain penetrating fluid, namely a lithium-rich solution and residual fluid, namely a [Mg (P3O10)] < 3->-rich solution; step 4, introducing the obtained penetrating fluid into an evaporator for evaporation and concentration, and filtering and separating to obtain a lithium concentrated solution; and adding sodium carbonate into the lithium concentrated solution for reaction, carrying out solid-liquid separation, and washing the precipitate to obtain Li2CO3 precipitate. The method is used for selectively and efficiently extracting lithium from salt lake brine and has efficient separation performance, high salinity adaptability and long-term stability.

Images