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Lead

Lead (pronounced /ˈlɛd/) is a main-group element with symbol Pb (Latin: plumbum) and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metals. Lead has a bluish-white color when freshly cut, but tarnishes to a dull grayish color when exposed to air. It has a shiny chrome-silver luster when melted into a liquid.

Lead is used in building construction, lead-acid batteries, bullets and shot, weights, and is part of solder, pewter, fusible alloys and radiation shields. Lead has the highest atomic number of all stable elements, although the next element, bismuth, has a half-life so long (longer than the estimated age of the universe) it can be considered stable. Like mercury, another heavy metal, lead is a potent neurotoxin that accumulates in soft tissues and bone over time. Lead poisoning was documented in ancient Rome, Greece, and China.

Characteristics

Lead has a dull luster and is a dense, ductile, very soft, highly malleable, bluish-white metal that has poor electrical conductivity. This true metal is highly resistant to corrosion, and because of this property, it is used to contain corrosive liquids (e.g., sulfuric acid). Because lead is very malleable and resistant to corrosion it is extensively used in building construction, e.g., external coverings of roofing joints. Lead can be toughened by adding a small amount of antimony or other metals to it. It is a common misconception[citation needed] that lead has a zero Thomson effect. All lead, except 204Pb, is the end product of a complex radioactive decay. Lead is also poisonous, as are its compounds, and therefore is dangerous to human health and use as a food containment device is not recommended.

History
Lead has been commonly used for thousands of years because it is widespread, easy to extract and easy to work with. It is highly malleable and ductile as well as easy to smelt. Metallic lead beads dating back to 6400 B.C. have been found in Çatalhöyük in modern-day Turkey.[1] In the early Bronze Age, lead was used with antimony and arsenic. Lead is mentioned in the Book of Exodus (15:10).

In alchemy, lead was thought to be the oldest metal and was associated with the planet Saturn. Lead pipes that bear the insignia of Roman emperors are still in service[citation needed] and many Roman "pigs" (ingots) of lead figure in Derbyshire lead mining history and in the history of the industry in other English centres. The Romans also used lead in molten form to secure iron pins that held together large limestone blocks in certain monumental buildings. Lead's symbol Pb is an abbreviation of its Latin name plumbum for soft metals; originally it was plumbum nigrum (literally, "black plumbum"), where plumbum candidum (literally, "bright plumbum") was tin. The English words "plumbing", "plumber", "plumb", and "plumb-bob" also derive from this Latin root.

Occurrence
Metallic lead does occur in nature, but it is rare. Lead is usually found in ore with zinc, silver and (most abundantly) copper, and is extracted together with these metals. The main lead mineral is galena (PbS), which contains 86.6% lead.
Most ores contain less than 10% lead, and ores containing as little as 3% lead can be economically exploited. Ores are crushed and concentrated by froth flotation typically to 70% or more. Sulfide ores are roasted, producing primarily lead oxide and a mixture of sulfates and silicates of lead and other metals contained in the ore.

Lead oxide from the roasting process is reduced in a coke-fired blast furnace.[3] This converts most of the lead to its metallic form. Three additional layers separate in the process and float to the top of the metallic lead. These are slag (silicates containing 1.5% lead), matte (sulfides containing 15% lead), and speiss (arsenides of iron and copper). These wastes contain concentrations of copper, zinc, cadmium, and bismuth that can be recovered economically, as can their content of unreduced lead.[2]

Metallic lead that results from the roasting and blast furnace processes still contains significant contaminants of arsenic, antimony, bismuth, zinc, copper, silver, and gold. The melt is treated in a reverberatory furnace with air, steam, and sulfur, which oxidizes the contaminants except silver, gold, and bismuth. The oxidized contaminants are removed by drossing, where they float to the top and are skimmed off.

Most lead ores contain significant concentrations of silver, resulting in the smelted metal also containing silver as a contaminant. Metallic silver as well as gold is removed and recovered economically by means of the Parkes process.

Desilvered lead is freed of bismuth according to the Betterton-Kroll process by treating it with metallic calcium and magnesium, which forms a bismuth dross that can be skimmed off.

Very pure lead can be obtained by processing smelted lead electrolytically by means of the Betts process. The process uses anodes of impure lead and cathodes of pure lead in an electrolyte of silica fluoride.

Production and recycling
Production and consumption of lead is increasing worldwide. Total annual production is about 8 million tonnes; about half is produced from recycled scrap. Top lead producing countries, as of 2008, are Australia, China, USA, Peru, Canada, Mexico, Sweden, Morocco, South Africa and North Korea.Australia, China and the United States account for more than half of primary production.

2008 mine production: 3,886,000 tones
2008 metal production: 8,725,000 tones
2008 metal consumption: 8,706,000 tones
At current use rates, the supply of lead is estimated to run out in 42 years. Environmental analyst, Lester Brown, however, has suggested lead could run out within 18 years based on an extrapolation of 2% growth per year.This may need to be reviewed to take account of renewed interest in recycling, and rapid progress in fuel cell technology.

概述
　　【元素名称】铅【元素符号】Pb
　　【晶体结构】晶胞为面心立方晶胞。
　　【相对原子质量】207.2
　　【元素类型】金属元素
　　【物理性质】带蓝色的银白色重金属，熔点327.502°C，沸点1740°C，密度11.3437克/立方厘米，硬度1.5，质地柔软，抗张强度小。
　　【原子体积】18.17立方厘米/摩尔

应急处理处置方法及防护
　　泄漏应急处理
　　切断火源。戴好防毒面具，穿好一般消防防护服。用洁净的铲子收集于干燥净洁有盖的容器中，用水泥、沥青或适当的热塑性材料固化处理再废弃。如大量泄漏，收集回收或无害处理后废弃。
　　①对于泄漏的PbCl4和Pb(ClO4)2，应戴好防毒面具等全部防护用品。用干砂土混合，分小批倒至大量水中，经稀释的污水放入废水系统。
　　②对于泄漏的PbO、四甲(乙)基铅和Pb3O4，应戴好防毒面具等全部防护用品。用干砂土混合后倒至空旷地掩埋；污染地面用肥皂或洗涤剂刷洗，经稀释的污水放入废水系统。
　　③对于泄漏的PbF2，应戴好防毒面具等全部防护用品。在泄漏物上撒上纯碱；被污染的地面用水冲洗，经稀释的污水放入废水系统。
　　④对于泄漏的Pb(BrO3)2、PbO2和Pb(NO3)2，应戴好防毒面具等全部防护用品。被污染的要面用水冲洗，经稀释的污水放入废水系统。
　　⑤对于泄漏的烷基铅，用不燃性分散剂制成乳液刷洗。如无分散剂可用砂土吸收，倒至空旷地方掩埋；被污染的地面用肥皂或洗涤剂刷洗，经稀释的污水放入废水系统。
　　处理方法：当水体受到污染时，可采用中和法处理，即投加石灰乳调节pH到7.5，使铅以氢氧化铅形式沉淀而从水中转入污泥中。用机械搅拌可加速澄清，净化效果为80%～96%，处理后的水铅浓度为0.37～0.40mg/L。而污泥再做进一步的无害化处理。对于受铅污染的土壤，可加石灰、磷肥等改良剂，降低土壤中铅的活性，减少作物对铅的吸收。
　　防护措施
　　呼吸系统防护：作业工人应该佩戴防尘口罩。
　　眼睛防护：必要时可采用安全面罩。
　　防护服：穿工作服。
　　手防护：必要时戴防护手套。
　　其它：工作现场禁止吸烟、进食和饮水。工作后，淋浴更衣。实行就业前和定期的体检。保持良好的卫生习惯。
　　急救措施
　　皮肤接触：脱去污染的衣着，用肥皂水及流动清水彻底冲洗。
　　眼睛接触：立即翻开上下眼睑，用流动清水或生理盐水冲洗。就医。
　　吸入：迅速脱离现场至空气新鲜处。保持呼吸道通畅。呼吸困难时给输氧。呼吸停止时，立即进行人工呼吸。就医。
　　食入：给饮足量温水，催吐，就医。
　　灭火方法
　　干粉、砂土。

国内铅锌生产基地
　　中国铅锌业生产布局，依据铅锌矿产地的分布和建设条件，经 40多年来的发展、建设，现已形成东北、湖南、两广、滇川、西北等五大铅锌采选冶和加工配套的生产基地，其铅产量占全国总产量的85%以上，锌产量占全国总产量的95%。
　　1.东北铅锌生产基地。东北地区是我国开发较早的铅锌生产基地之一。早在 50年代初期，其铅产量占全国铅产量的80%以上，在中国铅锌生产居于重要地位。东北基地以七矿两厂为主，即青城子铅锌矿、八家子铅锌矿、柴河铅锌矿(现已闭坑)、桓仁铜锌矿、红透山铜锌矿、西林铅锌矿、天宝山铅锌矿和沈阳冶炼厂、葫芦岛锌厂。七矿两厂不仅是东北铅锌生产基地的支柱厂矿，也是培养造就科技人才的基地。六七十年代曾向全国新建的铅锌企业输送大批具有实践经验的科技和管理人才以及生产技术工人，为中国铅锌业的发展做出了积极贡献。
　　2.湖南铅锌生产基地。湖南铅锌矿产资源丰富，而且富矿多，大部分矿产地可开发利用。该基地铅锌厂矿是五六十年代建成的，由水口山矿务局、桃林铅锌矿、黄沙坪铅锌矿、东坡铅锌矿和株洲冶炼厂等组成的湖南铅锌生产基地，是当时全国自产原料的全国最大的铅锌生产基地，在全国产量占有重要地位。
　　3.两广铅锌生产基地。广东、广西两省区的铅锌资源丰富，两省区是 70年代形成的我国大型铅锌生产基地之一。广东以凡口铅锌矿和韶关冶炼厂为主，其次是丙村铅锌矿、昌化铅锌矿、大尖山铅锌矿。广西有泗顶铅锌矿、大新铅锌矿、河三铅锌矿、柳州锌品厂和大厂矿务局等。
　　4.滇川铅锌生产基地。云南铅锌矿产资源十分丰富，现铅锌保有储量均居全国之首。该基地铅锌企业也是五六十年代建成的，主要是会泽铅锌矿、澜沧老厂铅锌矿和昆明冶炼厂、个旧鸡街冶炼厂。云南铅锌矿产资源具有广阔的开发前景， 90年代开始兴建超大型铅锌矿床金顶矿山。四川有会东铅锌矿、会理铅锌矿两个主要矿山以及一批中小型矿山，近年来铅锌精矿产量猛增。
　　5.西北铅锌生产基地。西北地区铅锌矿产资源也很丰富，主要分布在甘陕青三省，而且西成矿带经近年来勘查储量又有大幅度的增长，资源前景十分可观。该基地铅锌生产以白银有色金属公司为主，有白银厂小铁山铅锌矿、第三冶炼厂和西北铅锌冶炼厂，陕西有铅硐山铅锌矿、二里河铅锌矿、银洞梁铅锌矿等和青海锡铁山矿务局。目前，西北铅锌产量较少，但开发前景可观。一是有丰富的铅锌矿产资源，位于甘陕交界的西成 -凤太矿带，经近20余年勘查出10多个大中型铅锌银金矿床，其中厂坝-李家沟铅锌达到超大型规模，银达到大型。二是厂坝正在抓紧建设一座大型矿山，将成为西北冶炼厂主要矿物原料供给基地，是全国大型铅锌矿山之一。
　　除上述五大铅锌生产基地外，内蒙古、江西、贵州等省区也建设了一批中小型矿山。其中内蒙古梧桐花铅锌矿、白音诺铅锌矿、翁牛特旗硐子铅锌矿等矿山。内蒙古是全国生产铅锌精矿主要省区之一，开发前景巨大。江西有银山铅锌矿等。贵州有赫章铅锌矿、杉树林铅锌矿等。

中国铅产业发展分析
　　中国在全球铅锌产业链中处于重要地位。但与铅锌生产、消费大国不相适应的是中国在全球竞争中的优势并不明显，特别是当前国内铅锌矿产资源保证程度下降、产业结构不合理、冶炼企业利润空间缩小以及环境污染严重等问题，产业可持续发展能力严重削弱。因此，尽快调整铅锌产业发展政策，积极谋求国际定价权已成为当务之急。
　　铅的主要消费领域是蓄电池、电缆护套、氧化铅和铅材，其中汽车蓄电池是铅消费的最大领域。中国是世界上金属铅储量较为丰富的国家，同时中国也是全球最大的精铅生产国和仅次于美国的第二大精铅消费国。
　　近年国内铅锌市场整体供求依然保持供不应求的局面，变化最大的是进出口量的波动。而从产销对比情况看，消费需求呈现出逐步放大迹象的同时，产量增长速度开始放缓。
　　2006年全国规模以上铅锌矿采选行业全年实现累计工业总产值41,312,690千元，累计产品销售收入49,692,399千元；铅锌冶炼行业全年实现累计工业总产值118,308,121千元，累计产品销售收入114,788,191千元。
　　2007年1-11月全国规模以上铅锌矿采选行业全年实现累计工业总产值57,601,704千元，累计产品销售收入63,564,719千元；铅锌冶炼行业全年实现累计工业总产值143,969,471千元，累计产品销售收入134,295,417千元。
　　2008年1-8月全国规模以上铅锌矿采选行业全年实现累计工业总产值39,811,272千元，累计产品销售收入36,855,392千元；铅锌冶炼行业全年实现累计工业总产值103,245,184千元，累计产品销售收入100,921,076千元。
　　2005年精炼铅产量237.84万吨，再生精炼铅产量54万吨；精炼铅消费量193.97万吨，其中蓄电池耗铅比例在继续增大；2006年铅产量275.92万吨。2005年国内锌产量为265万吨，同比下降0.66％，2006年国内锌产量为312万吨。