【作者】 郭翠香；

【导师】 赵由才；

【作者基本信息】 同济大学 ， 环境工程， 2008， 博士

【摘要】 在有色金属冶炼等工业过程中产生大量的含铅危险废物，不当堆存于环境中将会对生态环境和人类健康造成严重危害，但同时这些废物也是可回收再生金属的重要的二次资源，对其进行无害化与资源化处理，对我国经济实现可持续发展作用重大。另外，我国氧化铅矿储量丰富，但结构复杂，品位低，其选冶过程回收率较低，且使用大量的化学药剂，由此带来复杂严重的环境问题。同时，传统火法炼铅过程中也存在铅尘污染严重、对原料含铅品位要求高的缺点。本文以含铅废物和贫杂氧化铅矿为原料，提出碱浸——溶液净化——电解的湿法冶炼清洁生产工艺提取金属铅，并对该工艺的相关理论基础进行了系统研究。铅在NaOH溶液中选择性浸出的可行性是该工艺的基础，通过热力学分析和溶解度实验，并绘制Pb-H₂O系、PbS-H₂O系、Pb-SO₄^2--H₂O系、Pb-CO₃^2-H₂O系的E-pH图，得出结论：常温下在5 mol·L^-1NaOH溶液中，铅的溶解度为25．56 g·L^-1。PbO、PbSO₄和PbCO₃均可自发溶于强碱溶液中，但PbS却不溶。在热力学分析的基础上，研究了氧化铅矿和含铅废物在NaOH溶液中的浸出动力学。氧化铅矿的浸出速率，在铅浸出率较低的条件下，受NaOH溶液通过固体残留物层的扩散控制，而在浸出率较高的条件下，受表面化学反应控制。含铅烟尘比氧化铅的浸出过程更加容易进行，速率较快。确定了含铅烟尘和氧化铅矿在NaOH溶液中浸出的最佳工艺条件，并分析了杂质金属的浸出行为。采用循环伏安法研究了铅在NaOH溶液中的电极反应动力学过程，碱液中铅在阴极上为配合物直接得电子析出金属铅，电极反应为准可逆过程，铅的析出受扩散控制，扩散系数为：1．15×10^-6cm²．s^-1。铅在阴极上的析出电位随铅浓度的降低，扫描速度、NaOH浓度和温度的增加而负移。阳极反应主要为析氧的反应，但电解液中的铅会在阳极被氧化生成PbO₂、Pb₃O₄和PbO₃^2-，氧化速率随铅浓度和温度的降低，NaOH浓度的增加而降低。研究了铅电积各工艺参数，包括铅浓度、温度、电流密度、NaOH浓度、极距、电极材料等对电流效率和能耗的影响，得出了最佳的工艺条件：电解液中铅初始浓度20 g·L^-1，电解结束时溶液中剩余铅浓度5 g·L^-1，温度50℃，电流密度400 A·m^-2，NaOH浓度5 mol·L^-1，电极材料为不锈钢。计算了Zn、As、Sb、W、Cu和Sn在碱液中析出的平衡电位，并采用循环伏安和整体电解的方法系统研究了溶液中存在的离子对铅电积过程和工艺的影响，发现：溶液中即使存在较高浓度的锌也不会对铅电积过程造成影响，然而铜却可优先于铅在阴极上首先析出，因此在电积铅之前必须予以净化处理。溶液中锡的存在会影响铅在阴极上沉积的电流效率，As、Sb、W等的影响则不大。PO₄^3-，SO₄^2-，SO₃^2-，SiO₃^2-，SCN^-，CO₃^2-，Cl^-和AC^-对电流效率和能耗基本上没有影响，但C₄H₄O₆^2-，C₂O₄^2-和明胶的存在会降低电流效率、增加能耗。对强碱浸出液中铜的净化采用铅粉置换的方法去除，研究了该方法的可行性并得到了最佳的置换净化工艺条件：Pb／Cu摩尔比2：1，净化时间15 min，反应温度30℃。采用Na₂S和CaO作为净化剂去除溶液中的杂质离子，结果表明Na₂S可有效沉淀浸出液中的Cu和Cd，并可部分沉淀Mn，Zn，W，Sb，Sn等杂质，但同时也使溶液中的铅发生沉淀，加入CaO可共沉淀部分的Sb和Sn。在以上理论研究的基础上，提出了利用氧化铅矿和含铅烟尘（渣）生产金属铅以及从含铅锌烟尘中综合回收铅和锌的工艺流程。采用碱浸-净化-电解工艺，利用氧化铅矿和含铅烟尘两种原料进行的提取铅的实验均取得了较好的结果，铅的纯度>97％，能耗≤0．7kWh·kg^-1铅，同时设计了中试方案。更多还原

【Abstract】 A huge quantity of lead-bearing wastes，which is classified as hazardous wastein most countries，has been generated in the industries such as hydrometallurgicalprocess of zinc，batteries manufacture，and chemical process．In general，the contentsof lead in the wastes may be quite low and usually are disposed of at dumping sites．In addition，thousands of millions of tailings containing low grade lead are also beingstored at the dumping sites in the mining plants．The concentration of lead from thesesecondary resources may be quite difficult and their recycling as raw materials hasbeen limited due to the unavailability of cost-effective technologies．Pyrometallurgical process may be one option for the lead extraction from the wastes，but its lead dust pollution has caused environmental constraints．Considering thedissolution of lead in the alkaline solution，a cleaner hydrometallurgical process usingalkaline leaching and electrowinning had been developed for the extraction of leadfrom the wastes and low-grade lead ores in this work．Thermodynamics of alkaline leaching of lead was calculated．The solubility oflead in 5 mol·L^-1 NaOH solution at 25℃was observed to be 25．56 g·L^-1．Meanwhile，the E-pH diagrams of Pb-H₂O，PbS-H₂O，Pb-SO₄^-2--H₂O and Pb-CO₃^2--H₂O systemswere calculated and plotted．It was found that PbO，PbSO₄ and PbCO₃ can bedissolved in concentrated NaOH solutions while the dissolution of PbS may benegligible．Leaching kinetics of lead oxide ore and lead bearing wastes in NaOHsolution were also investigated．The leaching of lead oxide may be controlled bydiffusion of NaOH solution passing through the solid phase layer at lowertemperature and less NaOH concentration，and by surface chemical reaction at hightemperature and high NaOH concentration．Generally；lead bearing wastes can bemore easily and quickly leached than lead oxide ores did．Electrode reaction kinetics of lead electrodeposition from NaOH solution wasstudied by cyclic voltammetry．The reduction of lead occurs entirely through thecomplex species Pb（OH）₃^- but not Pb²⁺．The catholic reaction is a quasi-reversible process controlled by mass transfer with a diffusion coefficients of 1．15×10^-6 cm²·s^-1．Lead electrodeposition potential shifts towards negative values as the decrease of Pbconcentration and the increase of scanning rate，NaOH concentration and temperature．Anodic process is mainly the oxygen evolution reaction，but lead complex in thesolution will be oxidized to PbO₂、Pb₃O₄ and PbO₃^2- in the anode．The oxidizationrate decreases as the increase of NaOH concentration and the decrease of Pbconcentration and the temperature．The effects of several parameters including lead concentration，temperature，current density，NaOH concentration，electrode distance and electrode material oncurrent efficiency and energy consumption of lead electrodeposition wereinvestigated．The optimum conditions were 20 g·L^-1 of lead concentration，5 g·L^-1 oflead concentration left in the electrolyte，50℃of temperature，400 A·m^-2 of currentdensity,5 mol·L^-1of NaOH concentration，and stainless steel of electrode material．Equilibrium potential of Zn、As、Sb、W、Cu and Sn electrodeposition fromNaOH solution is calculated．The effects of impurities in the solution on leadelectrodeposition process were studied by cyclic voltammetry and electrowinningmethods．The results show that relatively high zinc concentration in the solution hasno effect on the lead electrodeposition process．Copper in the solution must bepurified before lead electrodeposition because it will be electrodeposited prior to leadin the cathode．Tin，C₄H₄O₆^2-，C₂O₄^2- and glutin in the solution decrease the currentefficiency of the lead electrodeposition process，while As，Sb and W，as well asPO₄^3-，SO₄^2-，SO₃^2-，SiO₃^2-，SCN^-，CO₃^2-，Cl^- and AC^- have no influence．Cu can be removed from the leaching solution by Pb power replacement．Theoptimum condition is Pb／Cu ratio of 2：1，reaction time of 15 min，temperature of：30℃．Na₂S and CaO were used to remove impurities，and found all the Cu，Cd，Pb andmost Mn，Zn，W，Sb，and Sn in the leaching solution can be removed．Addition ofCaO can co-deposit part of Sb and Sn．The lead production flowsheet using lead oxide ore and lead bearing wastes andthe process of comprehensive recovery of lead and zinc from lead and zinc bearingwastes were put forward based on the bench-scale results．The purity of lead thusprepared can be over 97％，with an energy consumption below 0．7 kWh·kg^-1． Pilot-scale project was also designed．It has been concluded that the processdeveloped in this work is cost-effective．更多还原