Study On Dissolution And Extraction Of Aluminum And Lithium From Coal Gangue

Aluminum and lithium products are important chemical materials,which are widely used in all walks of life.The demand for aluminium and lithium in China’s market is increasing year by year.The problems of insufficient production capacity and less reserves of existing ore sources are prominent.It is particularly necessary to explore new ore sources.It is found that there are more aluminium and lithium resources in coal gangue produced in Pingshuo coalfield.Stepwise extraction of aluminium and lithium from low-grade coal gangue can not only supplement the large demand for aluminium and lithium resources in the market,but also realize high-value utilization of coal gangue waste.The H-type ion sieve of spinel LiMn₂O₄ ion sieve after acid elution of lithium can efficiently and selectively recover lithium ion from dilute solution.It is the most promising lithium ion adsorbent at present.Taking coal gangue in Pingshuo coalfield as raw material,the leaching rule of aluminium and lithium in coal gangue clinker activated by sodium carbonate was studied by single factor controlled variable method.At the same time,the self-made LiMn₂O₄ precursor was used to recover ions from acid leaching solution.The samples were characterized by XRF,XRD,IR,SEM and TG.The main conclusions of the experiment are as follows:（1）The crystal form of coal gangue activated by sodium carbonate at high temperature changes greatly.The optimum activation conditions for coal gangue are activation ratio of 0.8 and activation temperature of 800^oC.The leaching rate of Al and Li reached 71%and 79%respectively after heating in 80 ^oC water bath for 4 hours with 150 mL 6 mol/L hydrochloric acid,and the content of Li in solution reached 11.946 mg/L.Aluminum trioxide was prepared by removing iron and adjusting pH.The extraction of aluminium from coal gangue was realized.By adjusting the pH to 14,the final solution containing Li⁺can be obtained.At this time,the concentration of Li ion in the solution is 11.528 mg/L.（2）The leaching characteristics of aluminium and lithium in alkaline solution were investigated by alkali leaching of coal gangue clinker activated by sodium carbonate in sodium hydroxide solution.Through investigating the technological conditions of alkali leaching,it can be seen that the activated coal gangue clinker after alkali leaching with sodium carbonate can not achieve the separation of Al Li and Si in coal gangue,which is not conducive to the subsequent extraction of alumina and lithium.This may be due to the conversion of aluminium and lithium in coal gangue activated by sodium carbonate into salts insoluble in alkali solution or the re-occurrence of aluminium and lithium in sodium silicate crystalline phase insoluble in alkali solution.（3）LiMn₂O₄ spinel was synthesized by solid-state sintering using LiOH·H₂O and C₄H₁₄MnO₈ as raw materials.The experimental results show that the ionic sieve precursors with complete crystal form can be synthesized by calcining lithium-manganese molar ratio at 0.5 and 800 ^oC for 15 H.The maximum adsorption capacity of H-type ion sieve for lithium ion after acid elution reaches 24.25 mg/g.The self-made H-type ion sieve is used to adsorb and recover lithium from aluminium extraction solution.The recovery rate can reach more than 99%.The recovery of lithium from coal gangue can be realized.However,there are some problems such as failure to recycle,loss of manganese element and difficult formation of ion sieve.