Research On The Extracting Of Li⁺by Precipitation Of Al（OH）₃

Lithium, a kind of the lightest metal elements, has its unique properties, which iswidely used in industrial production and every aspect of our daily life. Lithium iscalled as the energy metal which can move the world. Our country is a big countrywith lithium resources, lithium resources reserves ranks second in the world, and69%of the lithium reserves exists in salt lake brine. Because of the coexistence of lithiumand alkali metal or alkaline metal, while there have very similar chemical propertiesin both lithium and alkali metal or alkaline metal, so the difficulties which extractinglithium from salt lake are increased. So, how to extract lithium from salt lake becomea key technical problems which our lithium industry require immediately solve.Precipitation of Al（OH）₃is a prominent method of extracting lithium from brinedue to its excellent selectivity and high precipitation rate. However, previous studieshave not fundamentally solve the problem of the recycling of aluminum salt, thisgreatly increases the cost of the process. This article in view of this fundamentalproblem, has systematacially researched on the extracting of lithium and recycling ofaluminum. And first proposes a process route by acid-leaching method and alkalinefusion method to recycle aluminum completely. Compared with the traditionalmethod for aluminum no recovery or half a recovery, this method has an advantage onthe cost. The experiments have showed the best technological conditions ofprecipitation of lithium and separation of aluminum and lithium, as well as the key offactor of acid-leaching method and alkaline fusion method.In the precipitation reaction of lithium, the experiment results show that theoptimum technological conditions are: the temperature of the precipitation reaction is65℃, the brine need to be diluted with equal amount of water, the precipitationsystem need to be mixing and ageing for an hour after reaction, the additions ofNaOH is0.30mol, the Al/Li is2.45, the sodium hydroxide concentration is2mol/L,the dropping rate of the sodium hydroxide control in15ml/minutes, the charging method adopts with the aluminum trichloride and sodium hydrate parallel flow intothe brine. By this time the precipitation rate of lithium can reach up to about94%.In the separation of aluminum and lithium, it has been discussed four aspects,such as the calcination temperature, calcinations time, leaching time and leachingtemperature. The conclusion we obtained by experiments is that: the lithiumaluminum of sediment needed to calcine in400℃for50minutes, use tripleextractions which in70℃water bath. Through the above steps we can get the lithiumsolution which with single component. Lithium ion whether leaching rate andleaching concentration both are higher. The leaching rate can achieve97.69%, theconcentration of the lithium can achieve3.54g/L.In the experiments of dissolution of aluminum oxide and circular reaction, it hasbeen discussed four aspects, such as the dosage of sodium hydroxide, the dissolutiontime of sodium hydroxide, the dosage of concentrated hydrochloric acid and thecharging method. At last we come to a conclusion that: the dosage of sodiumhydroxide is0.24mol, the dissolution time of sodium hydroxide are30minutes, thedosage of concentrated hydrochloric acid are0.32mol. The circular reaction of theprecipitation rate for lithium can achieve92.65%. XRD shows that whether circularreaction or first reaction both have generated the lithium aluminum of sediment.