【作者】 朱新锋；

【导师】 杨家宽；

【作者基本信息】 华中科技大学 ， 环境工程， 2012， 博士

【摘要】 废铅酸蓄电池是危险废物,不合理的处置会对生态环境和人类健康造成严重危害。传统火法回收废铅酸蓄电池工艺中二氧化硫、铅尘污染严重。因此,开发清洁的铅回收技术是再生铅工业可持续发展的迫切要求。铅膏是废铅酸蓄电池最难回收处理的部分。本文采用有机酸湿法浸出工艺处理铅膏,转化为前驱体柠檬酸铅,然后低温焙烧制备超细铅粉,对该工艺的相关理论进行了初步研究。研究成果主要包括以下几方面的内容：1、废铅酸蓄电池铅膏的表征废铅酸蓄电池铅膏样品来源于湖北金洋冶金股份有限公司破碎分选系统分离获得的废铅膏。废铅膏首先洗涤至中性后,经过烘干、破碎筛分,小于120μm的细铅膏样品用于进行后续的湿法回收工艺。铅膏粒径小于120μm的细铅膏约占铅膏总重量的80%,比重约6.95 g/cm3。铅膏主要矿物组分有PbSO4、PbO2、PbO和金属Pb,其中PbSO4的含量约56.5%-64.5%,Pb02约29.5-32.5%,PbO约4-5%,金属Pb约为0.5-5.5%,此外还有微量杂质Sb、Fe等。2、铅膏在柠檬酸-柠檬酸钠体系中湿法转化规律以PbO、PbO2、PbSO4铅膏单组份为研究对象,考察了在两种不同比例的柠檬酸-柠檬酸钠体系中的湿法浸出转化规律。经过化学计量的推算以及XRD、FT-IR、TG等手段表征,结果表明形成了两种不同配位数的前驱体柠檬酸铅：pH为3-4条件下,柠檬酸铅的化学式为Pb(C6H6O7)-H2O,粒径为10-50μm,板片状形貌；pH为5-6的条件下,柠檬酸铅化学式为Pb3(C6H5O7)2·3H2O,粒径为1-10μm,薄鳞片状形貌。采用PbO、PbO2、PbSO4及Pb四种单组份混合组成的模拟铅膏,在柠檬酸-柠檬酸钠体系中显示了与单组份浸出实验相同的浸出转化规律。在此基础上,以实际铅膏为研究对象,考察了浸出剂的投加量、反应温度、浸出反应时间对铅膏的转化率与回收率的影响。研究表明,合适的浸出工艺条件为：柠檬酸与总铅的摩尔比为3：1,柠檬酸钠与总铅的摩尔比为9：5,双氧水与二氧化铅摩尔比为2：1,固液比为1：5,反应时间8 h。采用SEM/EDX技术研究了铅膏浸出前后以及浸出过程中形貌及成分的变化过程,结果显示,在浸出转化过程中二氧化铅与氧化铅反应很快,而硫酸铅反应相对较慢。反应过程中硫酸铅颗粒不断变小,因此硫酸铅生成柠檬酸铅的反应是一个缩核反应。铅膏中硫酸铅在柠檬酸-柠檬酸钠溶液浸出动力学方程可用1-(1-a)1/3=Kt+B描述,反应的表观活化能为67·82 kJ·mol-1,浸出过程受化学反应步骤控制。对铅膏中杂质在柠檬酸／柠檬酸钠-双氧水体系中转化规律进行了初步的探讨,结果表明铁元素只有40%左右进入溶液,锑杂质元素进入到液相比例最高只能达到80%左右。3、铅膏在乙酸-柠檬酸钠体系中湿法转化规律PbO、PbO2和PbSO4在乙酸-柠檬酸钠体系脱硫转化生成柠檬酸铅的分子式为Pb3(C6H5O7)2·3H20。合适的浸出条件为柠檬酸钠与铅的摩尔比为4：3,乙酸与铅的摩尔比为8：3,固液比为1/5,反应时间为2 h。温度升高可以促进铅膏脱硫反应,同时对柠檬酸铅形貌有较大影响。浸出生成柠檬酸铅颗粒粒径在5μm以下,过滤困难。可以通过柠檬酸铅的重结晶进行调控,温度是结晶再生长过程的一个重要因素,改变结晶温度与时间可以调控结晶物质的粒径,同时结晶过程可以将部分杂质分离到滤液中,净化最终产物柠檬酸铅。4、柠檬酸铅热分解制备超细铅粉的初步探讨热重与红外联用对柠檬酸铅的热分解研究结果表明：柠檬酸铅在空气中热分解过程可大致分为脱水、热分解及燃烧三个阶段。在热分解初始反应均为结晶水的失去,在200-280℃范围内部分有机物产生,而此后主要产物为二氧化碳。两种柠檬酸铅在空气中产物为氧化铅与金属铅。焙烧温度对两种柠檬酸铅在空气中分解起到关键性的作用。柠檬酸铅前驱物Pb(C6H6O7)-H2O在低温时主要焙烧产物是a-PbO、β-PbO与金属铅,温度较高时焙烧产物为β-PbO。在400-450℃范围内延长反应时间可以得到Pb304。柠檬酸铅前驱物Pb3(C6H5O7)2·3H2O在不同温度下产物与柠檬酸铅Pb(C6H6O7)·H2O的焙烧产物相似,但是延长焙烧时间没有Pb304的产生,这可能是由于前驱物中配位数的差异造成的。通过微电极电化学实验表明：两种前驱体制备的超细铅粉循环伏安扫描曲线可逆性较好、循环稳定性较优,证明该自制铅粉有一定的应用前景。本论文的研究成果为废铅膏有机酸湿法回收利用提供了实验依据；将传统的湿法冶金与金属配合物理论有机结合,丰富了有机酸为浸出剂的金属提取与回收的湿法冶金体系；同时对于其他电子废弃物的湿法回收具有一定的参考价值。更多还原

【Abstract】 Discarded and spent lead acid batteries are hazardous wastes which could cause serious damages to both eco-environment and human health if treated and pilled improperly. Since the noxious lead dust and SO2 emission in the traditional pyrometallurgy, it is urgent to develop clean lead recovery technology for the sustainable development of secondary lead industry, among which lead paste is the most difficult part for recovery and disposal. In this thesis, lead paste was leached with organic acid to produce lead citrate precursor which would prepare ultra-fine lead oxide when calcinated at relatively low temperature. And there are also some efforts attached on systematical research on the theories and principles related to this technology. The main researches include the following contents:1. Characterization of lead paste in spent batteriesThe lead paste studied in this thesis comes from the crushing and separation device of Hubei Jin Yang Co., LTD. Before leaching experiments lead paste would be first pre-treated such as neutralizing, drying, crushing and further separation. Then chemical analysis and hydrometallurgy leaching was conducted by using part of the paste whose particle size is less than 120μm, which accounts for 80% by mass, and its specific gravity is 6.95 g/cm3. The major mineral constituents of lead paste are PbO, PbO2, and PbSO4. And the main components are PbSO4 (56.5-64.5%), PbO2 (29.5-32.5%), PbO (4-5%) and Pb (0.5-5%) by mass. In addition, there are trace impurities as Sb and Fe.2. The conversion of lead paste in the citric acid-sodium citrate systemThe hydrometallurgical converting law of PbO, PbO2, or PbSO4 leaching with the mixture of citric acid and sodium citrate in the different proportions respectively has been studied. Calculating by stoichiometry method and characeriation of XRD, FT-IR SEM and TG, it was found that the leaching product is Pb(C6H6O7)H2O at pH=3-4 who has board flake shape with particle size of 10-50μm, while the precipitate is Pb3(C6H5O7)2·3H2O at pH=5-6 which is thin scales shape with particle size of 1-10μm. And the converting law of simulative paste consisting of PbO, PbO2, PbSO4 and Pb in the citric acid-sodium citrate system is nearly the same with that of the single component. Having accomplished the leaching study of simulative paste, experiments were conducted to study the effect of the dosage of leaching reagent, temperature and time on both desulphurization rate of lead paste and recovery rate of lead paste by using the real lead paste. The optimal condition was found to be:3:1 of mol ratio of citric acid to total lead,9:5 of mol ratio of sodium citrate to total lead,2:1 of mol ratio of hydrogen peroxide to lead dioxide,1/5 as the starting paste/water mass ratio,8h of leaching time.The results of SEM/EDX showed that in leaching process, PbO2 and PbO reacted quickly, while PbSO4 reacted relative slowly. And since during the reacting process the particle size of PbSO4 reduced continuously, the reaction of generating lead citrate from PbSO4 fited well with the core-shrinking model. The leaching of PbSO4 in the citric acid and sodium citrate solution fited the kinetic equation:1-(1-a)1/3=Kt+B. The apparent activation energy was 67.82 kJ-mol"1 and the leaching process was controlled by chemical reaction procedure. Initial study indicates that about 40% of Fe entered in solution, while Sb can reach to 80% to the utmost extent.3. The conversion of lead paste in the acetic acid-sodium citrate systemThe product prepared by leaching of PbO, PbO2 and PbSO4 in acetic acid and sodium citrate solution was deduced to be Pb3(C6H5O7)2·3H2O by stoichiometry method. The optimal condition for leaching real lead paste was found to be:8:3 of mol ratio of acetic acid to total lead,4:3 of mol ratio of sodium citrate to total lead,2:1 of mol ratio of hydrogen peroxide to lead dioxide,1/5 as the starting paste/water ratio,2h of leaching time. The temperature increase had a positive impact on both desulphurization rate of lead paste and the morphology of the crystallized lead citrate. The smaller size of lead citrate particles (<5μm) was formed at room temperature, thus resulting on the difficulty in the filtration process. However recrystallization of the precursor could deal with the filtration difficulty by appropriately changing the particle size of the precursor resulting from optimizing the crystallizing duration and temperature. Moreover, the crystallizing process could remove the impurities into the filtrate which would lead to cleaner lead citrate precursor.4. Preparation of ultra-fine Lead oxide from lead citrateTG-FTIR analysis of the lead citrate precursor revealed that the thermal decomposition process of lead citrate in air was approximately divided into dewatering stage, main organic constituent decomposing stage and burning stage. TG-FTIR data of two kinds of lead citrate showed that dehydrating crystal water was the initial reaction of thermal decomposition, and subsequently organic matters were produccd within 200-280℃, the main products were CO2 thereafter. The final products from two kinds of lead citrate were mainly both PbO and Pb. Calcination temperature played a crucial role in the decomposition of lead citrate in air. The main product of Pb(C6H6O7)-H2O at relatively low temperature was a-PbO, (3-PbO and Pb, while at relatively higher temperature it was P-PbO. And if prolonging the calcination duration at the temperature of 400-450℃, Pb3O4 would be produced. And the calcinating products of Pb3(C6H5O7)2·3H2O at different temperature was similar with those of the Pb(C6H6O7)·H2O, except that no PbsO4 could be formed by prolonging the duration. Through electrochemical test by self-made micro-electrode, ultra-fine lead oxide has shown regular redox mechanism, good reversible property and cycle stability, which promised certain application prospect.The result of this study could guide the utilization of hydrometallurgy method on recycling of spent lead-acid battery; combining the traditional hydrometallurgy and the metal complexes theory would enrich the extraction and recovery of metal by using organic acid, it also could direct the hydrometallurgical recovery of other E-waste.更多还原