Study On Lithium Extraction From Lepidolite By Alkali-solid Phase Sintering Activation

Known as"energy metal",lithium and its compounds with excellent and special properties have been widely used in energy,chemical,electronics,metallurgy,aerospace and other fields..Recently,with the development of the new energy industry,lithium metal and high purity lithium salt demand is increasingly urgent.Lepidolite is an important lithium mineral resource and the green and low cost lithium technology has attracted wide attention.In view of the high energy consumption,severe corrosion to equipment and serious environmental pollution of the traditional sulfuric acid（salt）roasting method,chlorination,lime roasting method,pressure boiling process.The lower temperature calcination activation lithium mica used the basic have been put forward in this study.The lepidolite crystal structure have been damage and change into the easy decomposition of inorganic salt through the calcination activation.Then,the valuable metals such as Li and Al are leached in dilute acid solution.Firstly,on the basis of fully analyzing the mineral composition and chemical composition of lepidolite,according to the mineral characteristics of the main mineral lepidolite(K{Li_2-xAl_1+x[Al_2xSi_4-2xO₁₀]（F,OH）₂}（x=0-0.5）),the solid phase sintering activation of lepidolite was carried out under certain conditions by using KOH.so as to transform the stable crystal structure of lithium mica into feldspar which was easy to be decomposed in the acid.Through the activation reaction thermodynamics analysis,deduce the possible reaction paths,then research the effects of the change of lepidolite crystal type were studied at different of the mass ratio of lepidolite to potassium hydroxide,sintering time and sintering temperature.The results showed that the characteristic peaks of lepidolite disappeared and lepidolite was transformed leucite（K（Al Si₂O₆））and kaliophilite（KAl Si O₄）at the mass ratio of lepidolite to potassium hydroxide 10:3,sintering temperature 750℃ and the sintering time3 h.Through the analyses of XRD pattern and SEM morphology of lepidolite before and after activation,combined with the principle of chemical reaction kinetics,the reaction mechanism between lithium mica and alkali has been discussed.Secondly,the Li and Al leaching efficiencies of activated lepidolite were studied at different of the concentration of HCl,leaching time,leaching temperature and liquid-solid ratio and the results showed that leaching efficiencies of Li and Al were 99.30%and 42.10%when the concentration of HCl 7.50 wt%,leaching temperature 55℃,leaching time 1 h and liquid-solid mass ratio 5 m L:1 g.Finally,the mechanism of Li release was discussed in this paper by XRD and SEM characterization of activated lepidolite before and after leaching.Through the method of activated lepidolite in this paper,the Li leaching effect of lepidolite was obvious.