A Study On The Regeneration And Utilization Of Lithium Hydroxide Used As Gas Purificant

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.