Research On The Extracting Of Li⁺ By Precipitation Of Al(OH)₃ And The Recycling Of Aluminum

Lithium and its compounds are widely used in kinds of industrial fields for their unique nature. Because salt lakes bear very rich lithium resources, and extracting of lithium from brine is of a low cost, extracting of Li⁺ from brine has become an overwhelming trend.The main methods of extracting of Li⁺ from brine include precipitation, solvent extraction , adsorption and so on. But the classical precipitation has the disadvantage of a large evaporation and high cost and needing a lot of reagent to remove magnesium and so on; solvent extraction system is very expensive, the extraction itself of toxic agents such problems; adsorption has the disadvantage of itself loss in the solution, swelling and a few adsorption capacity snd so on, so it has not been industrialized; because of their own limitations and adverse factors other methods are not widely used.As early as in 1963 Koplnaeo used the precipitation of aluminum hydroxide in water to extract lithium from the Dead Sea. This method of high lithium selectivity and precipitation rate and being easy to achieve industrialization, is an effective separation of Mg-Li. However, this precipitation is not carried out on aluminum recycling, and is of the lithium concentration of leaching solution and large reagent needed, so large evaporation, high energy and high cost. Thererfor to these fundamental issues making the concentrated brine of the Sichuan Basin, Pingluoba marine sedimentation deep underground brine as the research object, this article has researched extracting of Li⁺ by precipitation of Al(OH)₃ and recycling of aluminum systematicly, got the optimized conditions in,the second time adsorption,calcining, dissolution of alumina, recycling precipitation and the choosing of precipitation reagents and identified the key factor that greatly increase the precipitation rate of lithium, with alkali fusion of aluminum to achieve the cycle and reduced the amount of alkali. The leaching solution composition under the the optimal conditions is single, multi-level access to the dip of lithium solution is up to 12.43g / l, to the several hundred milligrams per liter literature reported have great improve, developing a new technology of extracting lithium from the marine brine.The optimized conditions in precipitation experiments are as follows: the temperature of reaction is 65℃; the time of reaction is 2.5h; the value of Na/Al is 2.85; the concentration of NaOH is 2mol/L; the adding time of NaOH solution is 12min; the value of Al/Li is 2.67; the feeding mode is infiltration of feeding mode. The experiments showed that this method has the same effect in the chloride, sulfuric acid and nitric acid type brine.The second adsorption of Li⁺ content in unit mass of aluminum hydroxide (g) is up to 5.54mg.Taking leaching rate and energy consumption into account the optimized conditions in calcining and leaching experiments are as follows: the calcination temperature is 400℃; the time of calcination is 20min. Almost single-component solution of lithium was got. It can increase the concentration of lithium ion concentration up to 12.43g / l or higher by multistage elution.The higher reaction temperature, the shorter reaction time and the higher the dissolution rate of solid alumina within the equilibrium time. In a certain range the smaller concentration of NaOH solution, the higher dissolution rate.The optimal partial molar ratio of sodium aluminum is accounted for 50% in the recycling precipitation and the precipitation rate of Li⁺ is 92.89% in this time.Sodium carbonate and sodium hydroxide solution as the precipitating agents had the same effect. The final pH value is 6.75 corresponds to the best dosage of sodium carbonate. Recycling reaction of precipitation used CO₂ and the sodium aluminate solution for dual partial hydrolysis, the precipitation rate of Li⁺ is up to 94.54%.