【作者】 刘冬雪；

【导师】 毕彩丰；

【作者基本信息】 中国海洋大学 ， 分析化学， 2007， 硕士

【摘要】 锂是最轻的金属元素,在地壳中的丰度仅为0.0065 %,由于在能源、航天、军事等领域的广泛应用,是重要的战略物质,对其回收处理再生,有重要意义。氢氧化锂是最主要的锂化合物之一,广泛应用于化工原料、锂离子电池、石油、冶金、玻璃、陶瓷等行业,同时也是国防工业、原子能工业和航天工业不可或缺的原料。在军事潜艇中将氢氧化锂制成“生命保障隔板”,这些隔板起到空气净化的作用,能吸收二氧化碳气体,以防止失事潜艇内空气中的二氧化碳气体达到威胁人员生命的水平,提高人员在等待救援时的生存能力。这种隔板在吸收二氧化碳时还能产生大量的热,使艇内温度达到华氏140度左右,给艇员创造一个温暖的空间。军用空气净化剂耗量大,若将其用后废弃物回收,作为原料重新制备出空气净化剂或其他锂盐,可以重复使用,节约大量资源。本课题对空气净化用氢氧化锂的再生利用进行了研究,主要内容有两部分。第一部分:对孤立作业体系使用的氢氧化锂的再生进行研究。第二部分:以氢氧化锂作为锂源制备纳米LiCoO2。对孤立作业体系使用后的氢氧化锂的主要成分进行了分析,根据原料的组成及含量,选择用苛化法生产氢氧化锂。讨论了苛化温度、苛化液浓度、苛化时间和浓缩方式等反应条件对生产过程及产品的影响,确定了最佳生产工艺,锂回收率在83⁹3 %之间。对产品中氢氧化锂的含量及钙、钠、钾、盐酸不溶物等杂质的含量进行分析,氢氧化锂的含量符合GB/T 8766-2002工业级标准要求。以氢氧化锂、柠檬酸和醋酸钴为原料,通过低温固相配位化学反应法合成了前驱体配合物,反应机理如下:通过元素分析、红外光谱分析和热重/差热分析对前驱体的组成、结构及热分解过程进行了研究,推断出前驱体的结构式如下:该前驱体进一步经过热处理即可制得超细纳米LiCoO2材料,此材料具有单一的α–NaFeO2型层状结构。前驱体的热分解大致分为两步进行,醋酸根先分解,再脱去柠檬酸根的碳得到纳米LiCoO2。对前驱体进行了非等温热分解动力学处理,得出了前驱体的热分解反应机理、热分解动力学方程、相应的动力学参数及活化熵⊿S≠和活化吉布斯函数⊿G≠,结果如下:前驱体的第3步热分解过程的反应动力学函数为:f（α）=1/3（1-α）[-ln（1-α）]^-2;热分解的动力学方程为:dα/dt=A·e-E/RT·f（α）= A·e-E/RT·1/3（1-α）[-ln（1-α）]^-2, E = 292.6 kJ/mol,LnA=53.06, r=0.9676,⊿S≠= 0.6118 kJ/mol·K,⊿G≠= -65.67 kJ/mol。利用XRD衍射分析和扫描电镜分析,系统地研究了合成条件对LiCoO2产品的物相结构及形貌的影响。研究表明,前驱体在一定压力下压片后,于600℃煅烧6h,随炉冷却即可形成层状结构的LiCoO2,产品物相纯净,结晶性好。SEM图可以看出产品的晶粒尺寸在100³00 nm之间,晶体形貌规整,边缘清晰,但存在一定程度的团聚现象。结合所观察到的实验现象,讨论了低温固相反应的监测手段、影响因素及反应机理。更多还原

【Abstract】 Lithium is the lightest metal element in the world and it’s abundance ratio in the crust is only 0.0065 %. It has an important significance on the regeneration and utilization of lithium because of it’s role in the field of energy, cosmonautics and military.Lithium hydroxide is one of the most important source of lithium salts, which are widely applied in chemical raw materials, lithium ion batteries, petroleum, metallurgy, glass, ceramic industries, as well as the defense industry, nuclear industry and the aerospace industry.“Life support baffles”in the military submarine are made of lithium hydroxide. These partitions can clean up the air, absorbing carbon dioxide gas, to prevent the concentration of carbon dioxide in the air from threatening the human life. These baffles release a large amount of heat as absorpting carbon dioxide, so that the temperature inside reached 140 degrees Fahrenheit to create a warm space for the crew. Because of large consumption of military air purifying agent, massive resources can be saved if we use the regenerant as raw materials to reproduce air purification or other lithium salts.The regeneration and utilization of lithium hydroxide used as gas purificant in special environment has been studied in the paper which included two parts. Part one: study on the regeneration of lithium hydroxide used in isolated system. Part two: syntheses, reaction condition and mechanism in preparaing nanophase LiCoO2 using LiOH as lithium resource.In the chapter 2, the primary components of spent lithium hydroxide in isolated system were determined first and causticization method was adopted to prepare LiOH·H2O according to the raw material. Effects on the properities of samples were studied from causticization temperature, concentration of causticization solution, causticization time, the optical synthesis technicss were found. The recovery rates of lithium were between 83 percent and 93 percent. The contents of LiOH and impurities such as sodium, kalium were determined and the content of LiOH measured up to the GB/T 8766-2002.In the chapter 3, nanophase LiCoO2 has been studied. The precursors were prepared by the method of the low-heating solid-state coordination using lithium hydroxide, citric acid and cobalt acetate as raw materials. The reaction mechanism is as follows:The composition, microstructure, reaction mechanism and thermo-decomposing process of the precursors have been studied using element analysis, IR spectrum, and TG/DTA analysis. The structural formula of the precursors was inferred as follows:Nanophase LiCoO2 material with pure layered structure ofα–NaFeO2 type were obtained by sintering the precursors. The thermo-decomposing process of the precursors approximately has two steps: the acetate decomposed first and then carbon of the citrate eliminated. The kinetic equations of thermal decomposition for precursors and the corresponding kinetic parameters were gained. The kinetic parameters include E, A, order of reaction and correlation coefficient etc. The activation entropy⊿S≠and activation free-energy⊿G≠were also gained. The thermal decomposition kinetic function of precursor in step(3) can be expressed as f(α)=1/3(1-α)[-ln(1-α)]-2, and the kinetic equation thermal decomposition may be expressed as dα/dt=A·e-E/RT·f(α)= A·e-E/RT·1/3(1-α)[-ln(1-α)]-2, E=292.6 kJ/mol,LnA=53.06, r=0.9676,⊿S≠= 0.6118 kJ/mol·K,⊿G≠= -65.67 kJ/mol。The effections of the systheses condition on the structures and morphologies of LiCoO2 were investigated systematically by the powder XRD and TEM techniques. The results of reaserch indicated that the optimization of synthses condition of nanophase LiCoO2 with layered structure were pressing pellets, sintereing for 6h at 600℃and natural cooling in the fumace. The particle morphology of LiCoO2 is distinct , the phase is pure, but the nanophase particles reunited at a certain extent between 100 nm and 300 nm.In the chapter 4, compined with the phenomena of the experiment, the paper presents the detection methods, effectiv factors on reaction and mechanism of the low-heating solid-state reaction.更多还原