【摘要】 锂辉石是提锂的重要来源，常用浮选法分离富集，但由于长石类等脉石矿物具有相似的表面性质，致使最终产品难以达到理想纯度，为增大两者的表面性质差异，常采用表面预处理，尤其以氢氧化钠提供的弱碱处理方式最为简便。本文基于密度泛函理论，采用Materials Studio（MS）软件建立锂辉石晶体模型，先后进行收敛性测试、几何结构优化、表面能计算以及计算氢氧根离子在锂辉石（110）表面上的各原子位点上的吸附能；并且利用原子力显微镜（AFM）和X射线光电子能谱（XPS）技术检测分析，开展了锂辉石表面选择性碱溶蚀的机制研究。MS计算结果表明，锂辉石晶体几何优化适宜的平面波截断能(E_cut)值为662 eV, k点取样密度k-point为3×3×3，确定（110）面为锂辉石最常见的解理面，得出氢氧根离子在Li, Al和Si原子位点均可发生自发性吸附，并促进表面各原子键的断裂，其吸附结构的相对稳定性强弱为：Si>Al>Li，但整体稳定性较低，易产生脱附现象；AFM分析结果表明弱碱处理后的锂辉石表面粗糙度明显升高，通过选择性碱溶蚀作用导致部分区域出现溶蚀坑痕迹；XPS技术揭示锂辉石表面经过弱碱处理降低了Li 1s, Al 2p和Si 2p原子轨道的结合能，吸附一定量氢氧根离子的同时促进表面溶蚀部分Li-O,Al-O和Si-O键等，得出锂辉石表面碱溶蚀作用的选择性为：Li, Si和Al，从而暴露出更多或新鲜的Li, Al和Si原子位点。更多还原

【Abstract】 For the nation, lithium is a vital resource. The process of extracting lithium from ores is now the main way to obtain lithium metal. Flotation is the method most frequently used to extract lithium from lithium spodumene. During flotation, surface qualities are typically regulated by mechanical, ultrasonic, acidic, or alkaline treatments in order to enhance the difference in surface properties between spodumene and gangue minerals. In particular, sodium hydroxide’s weak alkaline treatment is the most practical and efficient. This article began with the crystal structure of spodumene. Using Materials Studio（MS） software, a crystal model of spodumene was built based on density functional theory. To start, a convergence test was run to figure out what value of plane wave truncation energy(E_cut) and k-point sampling density（k-point） is right. Second, using the CASTEP module in MS software, appropriate parameters were chosen to optimize the shape of the crystal model. Next, the usual spodumene cleavage planes（110） and（001） should be removed, and their respective surface energies should be ascertained. Ultimately, the most stable crystal plane model was chosen as a depiction of the spodumene surface by comparing the surface energies of the two crystal planes. With the use of the GGA-PBE basis set of the DMol3 module, the adsorption energy of the hydroxide ion adsorption model at the Li, Al, and Si atomic sites on the crystal plane was determined. In parallel, the mechanism of selective alkali corrosion on the surface of spodumene was found and examined using X-ray photoelectron spectroscopy（XPS） and atomic force microscopy（AFM） methods. According to the MS calculation results, it was discovered through convergence testing that the energy of the spodumene crystal model first fell and then progressively approached equilibrium when E_cut and k-point rise. When optimizing the shape of spodumene crystals, the estimated energy difference indicated that 662 eV was the appropriate E_cut value, with a k-point of 3×3×3. Out of the two primary cleavage planes of spodumene, the（110） surface was more likely to occur, as indicated by the computed surface energies of the spodumene（110） and（001） surfaces, which were 0.65 and 1.42 J·m^-2. In addition, the（110） plane was more stable than the（001） plane since it required less energy to create. Consequently, it was shown that the（110） plane was the most frequent cleavage plane for spodumene when grinding or natural conditions were met. The values of the adsorption energies were determined to be-1.61,-1.98, and-3.18 kJ·mol^-1 by creating an adsorption model for hydroxide ions on the top sites of Li, Al, and Si atoms on the（110） crystal plane of spodumene. As a result, it was determined that hydroxide ions could spontaneously adsorb at Li, Al, and Si atomic sites and encourage the dissolution of atoms’ bonds on the surface. The relative stability of their adsorption structures was Si>Al>Li, but overall stability was poor and desorption phenomena was likely to occur. According to the results of the AFM investigation, selective dissolving caused dissolution pits to form in some parts of the lithium spodumene surface, and weak alkaline treatment considerably increased the surface roughness of the material. There were numerous large or little projecting particles in the range of height variation, which had grown from-3.9～2.6 to-318.7～274.1 nm. It might be concluded that the distribution and composition of atomic sites on the surface of spodumene were changed by the selective dissolving of sodium hydroxide, based on the results of the quantum chemical calculation discussed previously in the article. Spodumene’s surface was weakly alkaline treated, as revealed by XPS technology, which resulted in changes to the binding energies of Li 1s（56.57 and 64.38 eV to 55.73 and 63.12 eV）, Al 2p（75.06 to 74.49 eV）, and Si 2p（102.90 to 102.75 and 101.95 eV）. This reduced the binding energies of Li, Al, and Si atoms collectively. Parallel to this, the median binding energies of related compounds in the 1s orbitals of Li atoms, the 2p orbitals of Al atoms, and the 2p orbitals of Si atoms were compared via the National Institute of Standards and Technology（NIST） website. It could be observed from this that certain Li-O, Al-O, and Si-O bonds on the surface were selectively dissolved by sodium hydroxide. On the surface of spodumene, it resulted in modifications to the relative atomic contents of Li, Al, and Si. In addition, it adsorbed some hydroxide ions concurrently, revealing more Li, Al, and Si atomic sites on the surface of spodumene. As a result, this would enable the activation of metal ions and the adsorption of traps. It was demonstrated that a specific quantity of hydroxide ions can be adsorbed on the surface of spodumene while also encouraging the surface corrosion of some Li-O, Al-O, and Si-O bonds, etc. This resulted in the selectivity of alkali corrosion for Li, Si, and Al, exposing one or more new Li, Al, and Si atomic sites, which was advantageous for the following metal ion activation and collector’s adsorption.更多还原