Occurrence And Extraction Mechanwasm Of Lithium In Aluminous Rocks From Central Guizhou

Bauxite is distributed unevenly in the world.At present,the proved bauxite resources reserve in China is 3.95 billion tons.However,due to the large population base and the increasing consumption,with the continuous consumption of high-quality bauxite,the import of bauxite in China has increased year by year.It's an urgent problem to effectively utilize the low-grade bauxite resources with huge reserves and low utilization rate.The bauxite in Central Guizhou Province is an important bauxite mineral area in Guizhou Province.A large number of aluminite has been accumulated in the mining for a long time,among which valuable elements such as aluminum and lithium were enriched,and the most ideal development method is the efficient comprehensive utilization of resources.The study on the occurrence state and separation and enrichment mechanism of lithium in bauxite in Central Guizhou Province can provide valuable reference for the effective comprehensive utilization of bauxite resources.The paper taked the bauxite of the upper roof of Jiujialu of Lower Carboniferous in Guizhou as the research object.The occurrence of lithium,the leaching of aluminum and lithium with acid and the extraction of aluminum and lithium in the solution by chemical adsorption coprecipitation were studied.The mechanism of mixed acid leaching and adsorption of lithium by aluminum precipitation were analyzed,and the following conclusions were obtained.1.It is found that the comprehensive samples of aluminite are mainly composed of diaspore,boehmite,kaolinite,illite and anatase.The main chemical composition is Al₂O₃ and SiO₂,the ratio of aluminum to silicon is 1.19,and the Li content is 980ppm.The results showed that kaolinite and illite were mostly layered and lamellar by polarizing microscope,SEM and EPMA,while diaspore and boehmite were mostly colloidal and short columnar,and a small amount of them were fine scale.Anatase is scattered in granular form and scattered in the mineral junction and a diaspore.The grain size of mineral inlay is fine and the degree of dissociation is low.2.The existing state of lithium in aluminite was determined by using the modern instrument analysis method such as time of flight secondary ion mass spectrometry and chemical phase method.It was concluded that Li mainly existed in clay minerals,and a small amount of lithium was found in diaspore and boehmite.It is suggested that Li is mainly connected with the hydroxyl group of the octahedral aluminum oxide and the loss of the positive charge of the tetrahedron of silica in the crystal structure of kaolinite and illite by ion bond,and a small part of Li occupies the missing hydrogen ion position in a diaspore and boehmite crystal.Because of the high-grade silicon in the aluminite,the elements such as aluminum lithium can be recycled by roasting and acid leaching.3.The aluminum lithium elements were extracted from bauxite by direct leaching without roasting and acid leaching after roasting.The leaching effect of aluminum and lithium in aluminous rock can be obtained without pre activation.The optimum conditions of leaching were acid concentration 60%,liquid-solid ratio 4:1mg/l,reaction temperature 100?and reaction time 3 hours.At this time,the leaching rate of aluminum lithium elements reached 88.64%and 96.35%.The thermodynamics and kinetics of the mixed acid leaching process are analyzed.The main chemical reactions can be determined by calculating the thermodynamic constants.After the analysis of kinetics,the activation energy of mixed sulfuric acid leaching is calculated to be 50.97k J/mol,and it is determined that the process of mixed sulfuric acid leaching is controlled by chemical reaction.In the experiment of hydrochloric acid leaching after pre roasting,the results show that the microwave roasting has the characteristics of short useful time and low calcination temperature,and the highest leaching rate of lithium is 95%.4.By adjusting the p H of hydrochloric acid leaching solution after calcination,more than 99%of Al in the solution was separated and extracted from the solution by aluminum hydroxide precipitation.The optimum conditions were tested.The precipitation rates of aluminum and lithium were 99%and 95%at p H=7,reaction time for 10min and reaction temperature 25?.Different precipitation p H values have a significant influence on the crystal form of aluminum hydroxide precipitation.When p H=4,amorphous aluminum hydroxide is obtained,and the surface is densely distributed with a pore structure formed by particles with particle size less than 100 nm.Bayer is formed at p H=7,which is composed of plate,rod and granular crystals,and the crystal particles are uniform,and the single crystal size is about 50 nm.In the process of aluminum hydroxide precipitation,lithium in the solution will be adsorbed,and the lithium aluminum will be adsorbed and co precipitation will be made.The precipitation rate of lithium will be stable in the range of 90%to 95%.Compared with the original ore,the recovery of aluminum reaches 85%and lithium recovery reaches88%.Li⁺will not fail or desorption due to the change of precipitation crystal form of aluminum hydroxide.5.The prepared aluminum hydroxide precipitate can be washed by water after calcining at 1100?to obtain alumina and the more pure lithium containing solution.The results show the alumina has two crystal forms,one is about 100 nm in size,and is packed in plate and sheet.One crystal is hexagonal column,plate and cluster growing and gathering,and the particle size of the cluster reaches micron level.Lithium carbonate particles were obtained by Na₂CO₃ precipitation method.The particle size is uniform,the size is about 5?m,and it is tetragonal and hexagonal flakes,and the dispersion is good.It is composed of small grains clustered in clusters,and the crystal has good anisotropic growth.6.The adsorption of lithium by aluminum precipitation was studied by isothermal adsorption model,adsorption thermodynamics and kinetics.Langmuir isotherm adsorption equation and Temkin isotherm adsorption equation can describe the adsorption of lithium by aluminum precipitation well.The calculation results of adsorption thermodynamics constants show that the adsorption of lithium by aluminum precipitation can be carried out spontaneously,which is an exothermic process,and the temperature rise is not conducive to the reaction,and it is a process of decreasing the disorder.Through the analysis of adsorption kinetics,adsorption of lithium by aluminum precipitation can be described with the quasi second-order rate model.The adsorption of lithium on aluminum hydroxide may be controlled by external mass diffusion at first,and then controlled by the diffusion process in particles.7.The DFT of adsorption density of aluminum and lithium is calculated by using the Perdew Burke erzerhof(PBE)formula under the generalized gradient approximation(GGA)of DMol³.Through the analysis of state density,it is concluded that Li⁺can occupy the empty point of hexagon center composed of six aluminum atoms in aluminum hydroxide,bond with the adjacent oxygen atoms,and calculate the Li⁺entering the aluminum hydroxide structure The migration barrier shows that the migration process belongs to exothermic reaction.