The Extraction Of Alkali Metal Compounds From The Lepidolite

The lepidolite, which is a mainly material for producing lithium carbonate, contains large amounts of alkali element. It can be also used to prepare potassium compound. The preparation of lithium carbonate from the lepidolite by sulfuric acid process is studied in this paper. This part of the experiment consists of leaching, purification and precipitation steps. The factors which may influence the yield of lithium carbonate is studied and the optimizing conditions are as follows:In the leaching process, the deionized water is used to leach the baked material at room temperature for three times, the ratio of the deionized water and the baked material is1:1, the yield of the leaching solution is85.7%. In the purification process,30%NaOH solution is added into the leaching solution by three steps which are controlled by pH value. The loss of lithium in this process is about20%. After that, the purified solution is concentrated through distillation until the concentration of lithium sulfate get28g/L, then30%Na2CO3solution is added into the concentrated solution at90℃, the mole ratio of Na2CO3and Li2SO4is1.1:1. The raw lithium carbonate is washed with boiled water, the yield and purity of lithium carbonate can be62.0%and98.0%respectively.The preparation of potassium sulfate by adsorption-desorption with5A molecular sieve and methanol salting-out method is also studied. It show that the5A molecular sieve has an effective adsorptive capacity of K+, it’s available in the basic puritied solution and the K+adsorption rate can be80.7%, the loss rate of Li+is about20%. When25%NH4C1is used as the desorbent, the K+desorption rate can be84.8%. The methanol salting-out is an effective method of extracting K2SO4from K2SO4and Na2SO4mixture solution. Especially the KC1is used as a precipitator to remove some Na2SO4from the mixture solution, then methanol is added into the solution, the yield and purity of K2SO4can be93.8%and76.1%respectively. Cooling-crystallization process is used to promote the purity of K2SO4, the final purity can get99.9%, which exceed the industry standard of K2SO4.