Lithium Extraction from Brine using Coated Ion Exchange Particles

Example 10

Lithium is extracted from a brine using coated ion exchange particles. The brine is an aqueous chloride solution containing 100,000 mg/L Na, 200 ppm Li, and other species including Ca, Mg, and B. The coated ion exchange particles are comprised of an ion exchange material and a coating material. The ion exchange material is Li₂MnO₃ and the coating material is titanium dioxide. The particles are comprised of 95 wt. % active material and 5 wt. % of coating material. The particles have a mean diameter of 200 microns. The particles are created by first synthesizing Li₂MnO₃ via a solid state method and then the coating is deposited from a Ti-propoxide precursor onto the surface of the Li₂MnO₃ material.

The ion exchange particles are loaded into an ion exchange reactor shown in FIG. 10. The ion exchange reactor comprises a cone-bottom tank with a thinner cylindrical column connected and mounted at the bottom of the cone-bottom tank (1001), a polypropylene 100 um mesh mounted at the bottom of the column (1002) to allow fluid to be pumped into and out of the tank through the mesh while the ion exchange particles are retained inside the tank, an overhead stirrer (1003), a pH controller (1004), an internal filter comprising a polypropylene 100 micron pore size mesh (1005), and a spraying system (not shown) at the top of the tank with one or more nozzles positioned to spray water to wash ion exchange particles off the sides of the tank and down to the bottom of the tank.

The particles are loaded into the tank as a dry material. 1.5 N sulfuric acid is pumped into the tank and stirred with the ion exchange particle to yield a lithium sulfate eluate solution. During acid treatment, the particles absorb hydrogen while releasing lithium. The coating allows diffusion of hydrogen and lithium respectively to and from the active material while providing a protective barrier that protects the active material. After 40 minutes, the eluate solution is collected from the tank through the mesh, dewatered, purified using sodium carbonate precipitation and resin ion exchange beads to remove trace Mg/Ca, and processed into lithium carbonate through addition of sodium carbonate solution at 90 degrees Celsius.

After treatment in acid, the protonated particles are treated with brine wherein the particles absorb lithium while releasing hydrogen. The brine is pumped into the tank and stirred with the ion exchange particles, and the particles are converted from a protonated state to a lithiated state with a lithium-enriched composition. An aqueous solution of NaOH is added to the tank to maintain the pH of the brine at 6. After 4 hours, the spent brine is removed from the tank through the meshes. The ion exchange particles form a settled bed in the column. The ion exchange particles are washed continuously with water, which flows through the column to efficiently remove residual brine from the ion exchange particles. After washing, the residual wash water is drained from the bottom of the column through the mesh, leaving a moist bed of the ion exchange particles at the bottom of the column with minimal entrainment of brine and minimal entrainment of water.

The lithiated material is then treated again with acid to yield lithium in solution as described previously. The cycle of protonation and lithiation is repeated to extract lithium from the brine and yield a lithium sulfate solution. Degradation of the ion exchange particles is limited due to the coating providing a protective barrier.