Process And Mechanism Of Lithium Extraction From Lepidolite In Yichun

Yichun lepidolite is the mine tailings of niobium-tantalum mineral after being floated. Exploitation and utilization of lepidolite could not only create significantly economic benefit and decrease the dependence of carbonate lithium on foreign companies but also prevent the idle of waste resources.The methods and techniques for the treatment of Yichun lepidolite from Jiangxi were studied by chloridizing roasting as well as by autoclaving leaching using mixed agents to extract lithium and potassium.In the experiments of chloridizing roasting, the effects of roasting temperature, time, and the addition of calcium oxide on the chloridizing efficiency were studied. X-ray diffraction (XRD) was employed to characterize the residues. The results show that the extraction efficiency of lithium and potassium are92.4%and71.06%by chloridizing roasting at850℃for3hours. The main phases of the residues are LiAl(SiO3)2, SiO2, KCl, accompanied with NaCl and K(Si3Al)O8. When the mass ratio of calcium oxide to lepidolite was0.7, the melting point was increased obviously. The extraction efficiency of potassium was increased to96.7%at900℃for30min. The main phases of residues are Ca0.6sNa0.35(Al1.65Si2.35O8),CaF2,and SiO2The autoclaving leaching was designed by even experiments. The influence on the leaching rate of litium of factors such as the mass ratio of sodium sulfate to lepidolite(X1), the mass ratio of sodium hydroxide to lepidolite(X2), the mass ratio of calcium hydroxide to lepidolite(X3), the mass ratio of distilled water to lepidolite, autoclaving leaching time(T),temperature(t) were studied. A regression mathematical model regarding these factors has established. The model showed that the mass ratio of sodium hydroxide to lepidolite and temperature are the main fators. Based on experimental results, the best experimental conditions were obtained. The extraction efficiency of lithium is more than98%when the autoclaving leaching proceeds at120℃for T=2～3hrs with the mass ratio of lepidolite:distilled wate:sodium sulfate:sodium hydroxide:calcium hydroxider=1:6:1.2:0.2:0.4.The autoclaving leaching kinetics of lepidolite was studied. The results show that the process is controlled by diffusion. The activation energies of the reaction are from4.135kJ/mol to0.768kJ/mol with the increase of temperature from100℃to140℃.