大洋多金属结核合成锂离子筛与吸附基础研究

【作者】 冯林永；

【导师】 杨显万； 蒋训雄；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2009， 博士

【摘要】 本论文系统地研究了以大洋多金属结核矿物和氢氧化锂为原料制备锂离子筛、合成的离子筛直接从低锂复杂溶液体系中提取锂的技术工艺和基础理论。文中总结了国内外研究大洋多金属结核的成就,诸如形成机理、主要矿物相及利用现状。介绍了世界锂资源开发现状、盐湖卤水提锂工艺技术及存在的问题。从而明确提出了本论文的研究背景与意义：利用大洋多金属结核矿物特有的性质制备离子筛,实现直接从低锂复杂溶液体系中提取锂,达到深海固体矿物资源与盐湖卤水化学资源协同开发的目的。为我国资源安全的战略提供一个全新的视角,具有重大意义。论文中实验分为五大块,分别为深海多金属结核中元素赋存状态研究、合成前驱体的研究、结核中元素热力学行为与前驱体合成反应研究、前驱体中锂脱出的研究、离子筛吸附锂的研究。元素赋存状态研究部分：借助矿物显微镜、XRD、SEM、能谱等仪器及化学抽提方法,得到了元素的赋存状态信息。锰、铁、铜、钻、镍等元素主要富集在中间层和外壳层中。(1)锰的存在形式有四种,分别是δ-MnO2、含铁较低的富锰水合物相、含铁量约为10%的锰铁水合物相、含铁在15%以上富铁的锰铁水合物杂相。(2)铁主要以非晶态的针铁矿胶体存在,约30%的铁呈胶体浸染在锰的水合物中,但浸染很不均匀,外壳层多为低铁的富锰水合物相,中间层多为富铁的锰铁水合物杂相。(3)铜、钴、镍或呈类质同象或呈胶体吸附态存在。大部分铜与锰相关,少量与铁及黏土矿物有关,10～20%的铜与锰、铁均无关,呈吸附态存在。钴主要赋存在富铁的锰铁水合物杂相中,少数钴浸染在水针铁矿胶体中而与铁相关。几乎全部的镍赋存在锰的水合物中而与锰有关。(4)多金属结核中元素赋存的特点,使合成的离子筛具有天然掺杂特性。前驱体的合成研究部分：(1)用TG-DTG-DSC检测分析了多金属结核与LiCl·H2O、LiNO3·3H2O、LiOH合成前驱体的过程,合适的锂化合物为LiOH。(2)借助XRD技术和X Pert HighScore软件,从生产工艺角度研究了温度、时间、锂锰摩尔比、升温速率等因素对合成前驱体的影响。获得了合理的焙烧工艺条件：温度600～700℃、焙烧时间6～10 h、升温速率5～10℃/min、锂锰摩尔比0.5～0.8。(3)SEM观察到前驱体表面形貌不规整且呈团聚态,粒度在50～150μm之间。TEM观察到前驱体主体为锂锰尖晶石,晶包大小100-200 nm。XPS检测也表明形成了尖晶石,铁进入尖晶石晶格中。元素热力学行为与合成前驱体反应研究部分：(1)从热力学上说明前驱体中存在MnFe2O4、CoFe2O4、NiFe2O4及CuFe2O4四种复合氧化物。(2)绘制了复合氧化物的ΔfGθ—T图,在0-413℃内复合氧化物的生成顺序依次为CoFe2O4→NiFe2O4→CuFe2O4→MnFe2O4,413-520℃内生成顺序为CoFe2O4→NiFe2O4→MnFe2O4→CuFe2O4,高于520℃后生成顺序为CoFe2O4→MnFe2O4→NiFe2O4→CuFe2O4。(3)前驱体形成的化学反应：在温度低于413℃时主要为结核中元素形成复合氧化物阶段,在413-520℃时氢氧化锂熔融进入复合氧化物晶格中,主要为形成前驱体阶段。前驱体中锂脱出的研究部分：(1)从理论上分析了LiCl-HCl-H2O体系的热力学性质。绘制了298 K下的LiMn2O4-H2O系Eh-pH图,从热力学上说明了前驱体脱锂的可行性。(2)从工艺角度研究了锂锰比、时间、温度、酸浓度、粒度、液固比及搅拌速率等因素对锂脱出率和锰溶损率的影响。获得了合理的脱锂工艺条件：酸洗时间210 min、酸洗温度60℃、酸浓度1.0mol/L、粒度-400目、液固比50：1、锂锰比0.7、搅拌速度350 r/min。在此条件下锂的洗脱率为82.9%,锰的溶损率为5.7%。酸洗后的前驱体经XRD检测仍呈尖晶石结构,但晶格常数变小。(3)在确定的条件下,进行了锂脱出过程动力学研究,确定锂脱出过程符合有固态产物层生成的“区域浸出模型”。锂脱出过程受离子在尖晶石晶格中的扩散控制,反应活化能为40.3 kJ/mol,表观反应级数为0.758。建立了锂脱出率的动力学数学模型：离子筛吸附锂的研究部分：(1)从工艺角度研究了时间、初始锂浓度、pH值、温度、粒度及液固比等因素对吸附锂的影响。得到了合理的吸附锂条件：室温、时间240 min、pH值8.0左右、粒度-300目、液固比100：1。在此条件下锂的吸附量为10.5 mg/g,锰的溶损率小于0.02%。(2)pH滴定曲线表明,酸洗时进入离子筛晶格中的H+,吸附时与Li+发生交换反应。离子筛静态饱和吸附容量为15.8 mg/g,动态饱和吸附容量为17.8 mg/g。(3)锂的吸附等温曲线具有与L2型相似的特点,可以用Langmuir方程和Freundlich方程来描述。Langmuir方程计算的饱和吸附量为11.4 mg/g,与实验值极为相近。吸附过程中吉布斯自由能变化-1.08kJ/mol,吸附过程可以自发进行。(4)离子筛对锂的吸附遵循准二级动力学方程,属于化学吸附反应过程。在21℃、40℃、50℃时理论吸附量分别为11.2mg/g、13.3 mg/g、14.6 mg/g,与实验值基本一致。吸附锂的活化能为6.92kJ/mol。(5)合成的离子筛具有良好的循环使用性能。15次循环吸附锂的总量为90.1 mg/g,35次循环吸附锂的总量可达200 mg/g。(6)在低锂复杂溶液体系中,离子筛对锂具有高度的选择性,各离子分配系数大小排序为Li+>>Ca2+>Na+> Sr+> Rb+> B2+>K+>Mg2+,表明离子筛适合用于从低锂复杂溶液体系中提取锂。(7)吸附后离子筛经XRD检测仍呈尖晶石结构,说明吸附的锂离子又进入了锰矿物晶格内。SEM观察到离子筛表面形貌仍呈团聚状态。TEM观察到尖晶石晶面间距约4.69A,与XRD图中主峰的晶面间距值一致,验证了XRD检测结果。这是离子筛循环吸附锂的基础。更多还原

【Abstract】 This paper studies the technology and theory of preparing of ion sieve from ocean polymetallic nodule and lithium hydroxide, and recovering of lithium by the ion sieve from complex lithium-low solution systemFirst, the studying achievement is summarized about ocean polymetallic nodule, such as formative mechanism, ore phase and application situation. At the same time, it is introduced such as development situation of lithium resource, technology of recovering lithium from Brine Lake and other unsolved-problems. After that, the research background is lodged. For the peculiar feature of ocean polymetallic nodule, it is suitable to prepare ion sieve and to recovery of lithium directly from complex lithium-low solution, which can fulfill coexploiting of ocean solid resource and brine lake resource. That has great signification for supplying a new view for resource security strategy.The paper is divided into five departments, and they are element morpha, preparing precursore, thermodynamic behaviour of elements, mechanism of forming precursore, extraction lithium from precursore and lithium absorbed by ion sieve respectively.Element morpha in ocean polymetallic nodule:By XRD, SEM, EDS, microscope and chemical extraction, the element morpha is obtained such as Mn, Fe, Cu, Co and Ni. Those elements are mainly concentrated in intermediate layer and crust layer. (1) There are four kinds of manganese compounds, which areδ-MnO2, manganese-high hydrate, manganese-iron hydrate (about 10% Fe) and impurity of manganese-iron hydrate (more than 15% Fe). Most iron is at the form of amorphous goethite. About 30% iron is dip-dyed in manganese hydrate and its distribution is not average. The manganese-high hydrate is always concentrated in crust layer and impurity of manganese-iron hydrate is concentrated in intermediate layer. (3) The elements such as Cu, Co and Ni are in the form of isomorphism or colloid. Most Cu has relation with Mn, few with iron and clay,10%-20% Cu is in the form of absorption and has not relation with Mn and Fe. The element Co is mainly distributed in impurity of manganese-iron hydrate, and few Co is dip-dyed in goethite and has utter relation with iron. Almost all of Ni is enriched in manganese hydrate and has relation with manganese. (4) The element distribution feature shows that the preparing ion sieve has nature adulterated performance.Formation of precursor:(1) From the reaction between polymetallic nodule and different lithium compose and the result characterized by TG-DTG-DSC, it is shown that lithium hydroxide is suitable for preparing ion sieve. (2) By XRD technology and X Pert HighScore software, the factors is studied such as temperature, time, ratio of lithium-manganese and calefactive velocity. The suitable roasting condition is that temperature 600～700℃, time 6～10 h, calefactive velocity 5～10℃/min and ratio of lithium-manganese 0.5～0.8. (3) Characterized by SEM, the surface of precursor is irregular and reveals aggregate structure, and its granularity is 50～150μm. Characterized by TEM, the precursor is cubic spinel crystal, ans its cell dimension is 100～200nm. Characterized by XPS, lithium manganese spinel is also formed, and iron element enters crystal lattice.Thermodynamic of elements and mechanism of preparing precursor:(1) By thermodynamic analysis, it is possible to form the composite oxides such as MnFe2O4、CoFe2O4、NiFe2O4 and CuFe2O4. (2) The oxygen potential graph is drawn. The forming order of composite oxides is CoFe2O4→NiFe2O4→CuFe2O4→MnFe2O4 from 0℃to 413℃, CoFe2O4→NiFe2O4→MnFe2O4→CuFe2O4 from 413℃to 520℃and CoFe2O4→MnFe2O4→NiFe2O4→CuFe2O4 above 520℃. (3) The mechanism of forming precursor is that when temperature is below 413℃, the elements in polymetallic nodule will form composite oxides. When temperature increases to 520℃, lithium hydroxide becomes liquid, gets into composite oxide cells and forms precursor.Extraction lithium from precursor:(1) The property of LiCl-HCl-H2O system is analyzed. The Eh-pH graph is drawn at 298K. The thermodynamic analysis shows that it is possible for lithium extraction. (2) The effects on the extractive lithium and resolutive manganese are examined respectively from the technological angle, such as lithium-to-manganese ratio, time, temperature, acid concentration, particle size, liquid-to-solid ratio and agitation rate. The reasonable technological condition is that time 210 min, temperature 60℃, acid concentration 1.0 mol/L, particle size -400 mesh, liquid-to-solid ratio 50:1, lithium-to-manganese ratio 0.7 and agitation rate 350r/min. Under this condition, the extractive rate of lithium is up to 82.9% and the rate of resolutive manganese is equal to 5.7%. By XRD characterizing, after lithium extraction, the ion sieve still shows spinel structure, but the cell becomes small. (3) The kinetics of extractive lithium is studied and the result shows that extractive lithium process is controlled by ion diffusion and follows the "zone leaching model". The reaction activation energy is 40.3 kJ/mol. The apparent reaction order is 0.758. The kinetic mathematical model for extractive lithium process isAdsorption lithium by ion sieve:(1) The effects of time, initial lithium concentration, pH value, temperature, particle size and liquid-to-solid ratio on the lithium ion adsorbing are examined from the technological aspect. The reasonable technological conditions obtained by experiment are:room temperature, time 240 min, pH value 8.0, particle size -300 mesh, liquid-to-solid ratio 100:1. At those experiment conditions, the capacity of adsorbed lithium is up to 10.5 mg/g, and the percentage of dissolved manganese is below 0.02%. (2) The pH titration curve shows that H+ will enter the cell of ion sieve in acid washing process, and then is exchanged by Li+ in adsorption process. The static saturation adsorptive capacity is equal to 15.8 mg/g, and the dynamic saturation adsorptive capacity is equal to 17.8 mg/g. (3) The isothermal adsorption curve is similar with L2, and can be described by Langmuir equation and Freundlich equation. Calculating by Langmuir equation, the saturation adsorptive capacity is 11.4 mg/g, which is very closed to the experiment value. TheΔG of adsorbing process is equal to -1.08 kJ/mol, which indicates that the adsorbing process can start automatically. (4) In dynamic aspect, the adsorbing lithium process is fitted for quasi-second dynamics equation and belongs to chemical adsorption. The theory adsorption capacities are 11.2 mg/g,13.3 mg/g and 14.6 mg/g respectively at 21℃,40℃and 50℃, which are very closed to experiment values. The activation energy is 6.92 kJ/mol. (5) The ion sieve prepared has good reusing performance. The capacity of lithium adsorbed is up to 90.1 mg/g in 15 recursions, and 200 mg/g in 30 recursions. (6) The ion sieve has great selectivity for Li+ in complex lithium-low solution system. The order of ion distribution coefficient fellows Li+>>Ca2+>Na+> Sr+> Rb+> B2+>K+>Mg2+, and it is suitable to recovery of lithium from complex solution system. (7) By XRD characterizing, after lithium adsorbed, the ion sieve still shows spinel structure, which shows the Li+ enters the lattice of manganese ores. Characterized by SEM, the surface of ion sieve is still aggregate structure. Characterized by TEM, the interplanar crystal spacing is equal to 4.69 A, which fits with the crystal spacing of first diffraction peak in XRD diagram. That is the reusing base of ion sieve.更多还原