Sulfate precipitation from lithium brine

The worldwide production of lithium in aU forms was 21,1001 in 2006 (see Ref 27, p. 96). Lithium sulfate solutions are obtained by treating certain ores with sulfuric acid. Lithium is also produced from certain brines that have a low magnesium content. In both cases, adding carbonate precipitates lithium carbonate. Mixing a lithium carbonate slurry with calcium hydroxide produces lithium hydroxide, and lithium hydroxide monohydrate is crystallized from the supernatant solution. Lithium hydroxide is the least soluble alkali metal hydroxide, with a maximum concentration of... 

From the final pond the concentrated brine (Table 1.3) with a density of about 1.25 g/cc was pumped nearly 4.8 km (3 mi 1.5 mi in 1967, Gadsby, 1967) to the processing plant in the town of Silver Peak. The plant had been converted from a silver ore cyanide-leach plant that had operated there from 1864-1961. In the conversion all of the tanks and settlers were rubber lined to reduce iron contamination in the product, and considerable new equipment was added. The solar pond brine was first reacted with lime to remove most of the residual magnesium and some of the sulfate and borate ions, and then a small amount of soda ash was added to precipitate most of the calcium from the lime reactions. The slurry from these operations was settled and filtered, and the overflow solution sent to storage tanks. From there the brine was pumped through filter presses to be totally clarified, and then heated to 93°C (200°F lithium carbonate has an inverse solubility) and reacted with dry soda ash and hot wash and make-up waters to precipitate the lithium carbonate product. Extra water was added to prevent salt from crystallizing, since the pond brine was samrated with salt. The lithium carbonate slurry was thickened in a bank of cyclones, and the underflow fed to a vacuum belt filter where it was washed and dewatered. The cyclone overflow and filtrate were... 

Lithium may be recovered from natural chloride brines. Such recovery processes may require additional steps depending on the magnesium and calcium content of the brine. The process involves evaporation of brine, followed by removal of sodium chloride and interferring ions such as calcium and magnesium. Calcium is removed by precipitation as sulfate while magnesium is removed by treating the solution with lime upon which insoluble magnesium hydroxide separates out. Addition of sodium carbonate to the filtrate solution precipitates hthium carbonate. 

C to precipitate lithium carbonate. The end-liquor was next treated with a small amount of phosphoric acid and evaporated to nearly sodium sulfate s crystallization point, precipitating trisodium phosphate that was recycled to the licons leach step. The final solution then only contained <0.07% Li instead of its original 0.28% Li, and it was sent to the soda products plant. The operation produced about 900 mt/yr of lithium carbonate, with an overall recovery from the lithium in the brine entering the evaporators of about 30% (Rykken, 1976 Williams, 1976). The operation was terminated in 1978 after 40 years of production when the soda products plant was closed. 

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