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On a weight basis lead is the fifth most used metal in the world. As a metal, lead is prized for properties such as high density, ease of fabrication, chemical stability in air and water, ability to absorb high energy radiation, and for its electrochemistry, especially the reaction with sulfuric acid. The lead–acid storage battery is used worldwide. Lead also forms alloys and compounds. Lead is generally recovered from ores containing 2–6% lead sulfide. After concentration, the sulfide is smelted to metal, refined to remove impurities, and the valuable by-products such as silver and gold recovered. Refining and by-product recovery are achieved by traditional pyrometallurgical and electrolytic methods. These primary production methods are described. Recycling of the lead in scrap lead–acid batteries is steadily increasing and, in the United States, accounts for two-thirds of the lead consumed annually. Secondary production methods are described, including technologies under development to improve recycling capabilities. The principal metals alloyed with lead are antimony, arsenic, calcium, copper, tin, tellurium, and silver. Minor alloying elements are cadmium, bismuth, selenium, indium, aluminum, and strontium. Lead alloys are generally melted and cast into molds to produce useful shapes. The alloys are also rolled, extruded, and forged. The primary use for lead alloys is in the production of battery parts for lead–acid batteries. Smaller but significant uses are ammunition, cable sheathing, sheet for roofing and construction, insoluble anodes, solders, and special low melting point materials. Lead is toxic to the kidney, cardiovascular system, developing red blood cells, peripheral and central nervous systems, testes, and fetus. Exposure to lead may occur from a variety of occupational and nonoccupational sources. Exposure, toxicity, and detection of lead in humans is discussed as is the treatment of lead poisoning. Keywords: lead; ores; smelting; lead emissions; refining; secondary lead; recycling; lead-antimony; lead-calcium; lead-acid batteries; lead-copper; lead-silver; lead-tin; solders; corrosion protection; bearings; sound abatement; radiation shielding; nonoccupational exposure; occupational exposure; toxicity; lead poisoning |
