Uses of Lead

From 50 to 60% of the Mexican lead production is used as oxides which enter into several industrial processes, in particular, battery manufacturing and production of tetraethyl lead. The remainder is used in the production of solder, cables, ammunition, pigments, paints, ceramics, enamels, and other products (Cortinas 1988). Another important use of lead in Mexico is in the manufacturing of metal parts that require lead alloys (Molina 1977) some relevant data are presented in Table 3 (IMZPC 1986, 1987). 

Recovered lead has a major role in the Mexican market of lead for example, in 1986 it constituted 26%, considering both primary and secondary lead. In spite of the important production of lead, with the exception of 1985, its reported uses decreased in Mexico from 1982 to 1987 also, most of the sales of lead registered for the internal market were exported after the industrialization process. Exports of lead have increased continuously in recent years (Table 4) (IMZPC 1986, 1987). In 1986, Mexico was the third world exporter of lead after Australia and Canada (IMZPC 1987). 

Several Mexican industries use this metal in their processes. Besides those already mentioned, they include the sectors of iron and steel, oil, petrochemistry, textiles, cellulose and paper, and metallurgy. 

The importance of recovered lead in the battery industry is growing most of the manufacturers use this type of lead and have their own recovering facilities. As a result, the market for primary lead for this industry has decreased steadily, especially during the last 5 yr. 

Sources World Bureau of Metal Statistics (WBMS) 1989 Camara Minera Mexicana 1988 CRM  

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The use of lead nitrate in place of silver nitrate is to be avoided, for the precipitated lead sulphide occludes most of the free acid. 

The metal is very effective as a sound absorber, is used as a radiation shield around X-ray equipment and nuclear reactors, and is used to absorb vibration. White lead, the basic carbonate, sublimed white lead, chrome yellow, and other lead compounds are used extensively in paints, although in recent years the use of lead in paints has been drastically curtailed to eliminate or reduce health hazards. 

Rigid Applications. The use of the lead stabilizers is very limited in the United States but, they are stiU used in several rigid PVC appHcations in Europe and Asia. The highest use of lead stabilizers in rigid PVC is for pipe and conduit appHcations. Tribasic lead sulfate is the primary heat stabilizer with lead stearates included to provide lubrication. The lead products are typically fully formulated, usually including lubricants and pigments for pipe extmsion appHcations. These lead one-packs, when used at about 1.8—2.5 phr, provide all of the stabilizer and lubrication needed to process the polymer. A lead one-pack contains tribasic lead sulfate, dibasic lead stearate calcium stearate, polyethylene wax, paraffin wax, ester wax, and pigments. 

Use of lead ia modem iadusttial society results from its unique physical and chemical properties. By the middle of the nineteenth century, world production of lead had risen to 1 x 10 metric tons per year, passed 1 x 10 t /yr early in the twentieth century, and reached 1.5 x 10 t /yr by midcentury. Lead production is expected to reach 5.6 x 10 t/yr by the year 2000. 

The future use of lead may be decided by the resolution of an environmental paradox. Some markets for lead are being phased out because of environmental concerns, eg, the use of tetraethyllead as a gasoline additive. However, a 1990 State of California law and similar laws in nine eastern U.S. states require that 2% of new cars meet 2ero-emission standards in 1998. By 2003 this requirement rises to 10% of new vehicles. Zero emission vehicles are generally accepted to mean electric, ie, battery powered cars, and there is considerable research effort to bring suitable electric vehicles to market by 1998. 

Most uses of lead in chemical compounds other than in storage batteries are dissipative. The greater part of the lead used in other forms is recoverable. 

The main use of lead metaborate is in glazes on pottery, porcelain, and chinaware, as weU as in enamels for cast iron. Other appHcations include as radiation-shielding plastics, as a gelatinous thermal insulator containing asbestos fibers for neutron shielding, and as an additive to improve the properties of semiconducting materials used in thermistors (137). 

The most common white pigments are titanium dioxide, 2inc oxide, leaded 2inc oxide, 2inc sulfide [1314-98-3], and Hthopone, a mixture of 2inc sulfide and barium sulfate [7727-43-7]. The use of lead whites and antimony oxides has been decreasing steadily for environmental reasons. 

Lead Whites. Basic lead carbonate, sulfate, siHcosulfate, and dibasic lead phosphite are commonly referred to as lead whites. Usage is limited because of environmental restrictions placed on the use of lead-containing compounds. 

Bismuth V n d te. The use of lead chromate pigments has been slowly phased out of many appHcations. Thus a search for more environmentally acceptable relatively inexpensive yeHow pigments having exceHent coloristic properties has been ongoing. 

Serious attempts to use LB films in commercial appHcations include the use of lead stearate as a diffraction grating for soft x-rays (64). Detailed discussion on appHcations of LB films are available (4,65). From the materials point of view, the abiHty to build noncentro symmetric films having a precise control on film thickness, suggests that one of the first appHcations of LB films may be in the area of second-order nonlinear optics. Whereas a waveguide based on LB films of fatty acid salts was reported in 1977, a waveguide based on polymeric LB films has not yet been commercialized. 

Minor quantities of arsenic trioxide have been obtained from the roasting of arsenopyrite, but the presence of copious amounts of SO2 iu the gas and vapor stream requires the use of lead-lined kitchens (9). 

Monosodium methanearsonate (MSMA) [2163-80-6] CH AsONaOOH, disodium methanearsonate (DSMA) [144-21-8], CH2AsO(NaO)2, cacodyhc acid [75-60-5], (CH2)2AsOOH, and arsenic acid [7778-39-4], H AsO, are used ia agriculture appHcations (11,12). MSMA, DMSA, and cacodyUc acid are used as herbicides (qv) especially ia cotton (qv) fields for the control of Johnson and nutsedge grass and other weeds. Arsenic acid (13) and cacodyhc acid may be used as a desiccant for the defoHation of the cotton boU prior to harvesting. Calcium arsenate [7778-44-1], Ca2(As0 2> once an important chemical for the control of the boU weevil and cotton worm, has disappeared from appHcation and the use of lead arsenate [7784-40-9], Pb AsO, for fmit crops is currentiy restricted. 

Because of the toxicity associated with lead compounds, governmental rulings have severely limited the use of lead drier in coatings. From a performance viewpoint the use of lead in aluminum paint will destroy the leafing characteristics of the film. Coatings containing lead that are exposed to sulfur fumes will discolor. 

Other approaches to the generation of the azallyl cation have been found. One of the most useful involves the use of lead tetraacetate (73TL2143). The anodic oxidation of aziridines also leads to the azallyl cation intermediate (75JA1600). 

Alloys of antimony, tin, and arsenic offer hmited improvement in mechanical properties, but the usefulness of lead is limited primarily because of its poor structural qualities. It has a low melting point and a high coefficient of expansion, and it is a veiy ductile material that will creep under a tensile stress as low as 1 MPa (145 IbFin"). 

Pf-Br, K3PO4, CH3NO2. This method avoids the use of lead nitrate. ... 

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