Galena roasting

The principal ore of lead is galena, PbS. Although there are some galena deposits in Great Britain, much of this country s requirements must be imported. In the extraction of lead, the sulphide ore is first roasted together with quartz in a current of air ... 

Lead is obtained chiefly from galena (PbS) by a roasting process. Anglesite, cerussite, and minim are other common lead minerals. 

Lead The production of lead from lead sulphide minerals, principally galena, PbS, is considerably more complicated than the production of zinc because tire roasting of the sulphide to prepare the oxide for reduction produces PbO which is a relatively volatile oxide, and therefore the temperature of roasting is limited. The products of roasting also contain unoxidized galena as well as die oxide, some lead basic sulphate, and impurities such as zinc, iron, arsenic and antimony. 

Alternatively, the carbon reduction can be replaced by reduction of the roasted ore with fresh galena ... 

As noted above, the roasting of most metal sulfides yields either the oxide or sulfate. However, a few metals can be obtained directly by oxidation of their sulfides, and these all have the characteristic property that their oxides are much less stable than SO2. Examples are Cu, Ag, Hg and the platinum metals. In addition, metallic Pb can be extracted by partial oxidation of galena to form a sulfate (the Scotch hearth or Newnham process, p. 370). The oversimplified reaction is ... 

The principal lead ore is galena, PbS. It is roasted in air, which converts it into PbO, and this oxide is then reduced with coke ... 

When galena, a lead ore (composed of lead sulfide) is roasted in a well-ventilated, open furnace, part of the lead is oxidized by air oxygen to lead oxide and the sulfur to sulfur dioxide, which is released into the atmosphere (see Textbox 33) ... 

Lead (m.p. 328 °C, density 11.4g/cm3) has been used for thousands of years, and its chemical symbol is taken from its Latin name, plumbum. Some lead is found uncombined, but most is found as the sulfide, galena, from which it is obtained by roasting the ore to produce the oxide and then reducing the oxide with carbon. 

Flintshire An early lead-smelting process in which galena was roasted in a reverberatory furnace. 

Lead occurs in nature as the sulfide, galena, PbS. Lead is more electropositive than mercury, and roasting the sulfide in air forms lead oxide. 

Lead is commonly obtained by roasting galena (PbS) with carbon in an oxygen-rich environment to convert sulfide ores to oxides and by then reducing the oxide to metallic lead. Sulfur dioxide gas is produced as a waste product. Large amounts of lead are also recovered by recycling lead products, such as automobile lead-acid electric storage batteries. About one-third of all lead used in the United States has been recycled. 

The lead concentrate must he roasted for effective removal of sulfur and then smelted in a blast furnace. Sulfur is mostly removed hy a sinter process. The galena concentrate or the ore itself, if its impurity content is low, is mixed with silica and other slag-forming reagents and roasted in sinter machines to produce lead oxide, lead silicate, and some metallic lead. The principal reactions are ... 

Lead, plumbum nigrum, its occurrence in connection with silver, its uses in making certain bronzes, for making lead water pipes, and in sheet form, are described by Pliny. Its oxide (Pb 0) is described under the names of molyb-daena, lithargyros, and galena, as the product of roasting lead in the air, and as produced in the furnaces where silver and gold are smelted. White lead (cerussa) and our red lead were also known and described by Pliny, much as by authorities already quoted. 

On roasting lead sulphide (galena) with lime, sulphur dioxide is evolved. It is assumed that the reactions which take place are as follows ... 

In Cornwall and Devon the ores used contain arsenopyrite mixed with iron and copper pyrites, tin ore, zinc blende, galena, etc. Before roasting, the ores are separated as far as possible by hand, and tinstone is removed by washing the finely powdered material. The roasting is conducted in a reverberatory furnace having a revolving floor over which a number of scrapers are fixed. The ore, which contains 10 to 80 per cent. As, is introduced through a hopper on to the floor, which revolves once every 12 minutes or so. It is heated to dull redness for... 

Lead is obtained from its ore, galena (PbS), by roasting the sulfide in air and reducing the resulting PbO with carbon monoxide in a blast furnace ... 

The most important ore of lead is galena, (PbS). To recover the metal, this sulfide may be first roasted to PbO, to PbS04, or to a mixture of the two. However, both the sulfate and the oxide react with excess lead sulfide at high temperatures to yield lead metal and sulfur dioxide. PbO may also be reduced using carbon or carbon monoxide. 

Tin and lead have been known since ancient times. Cassiterite, Sn02, was mined in Britain and transported by sea to the Mediterranean area where copper was available. After reducing the Sn02 with charcoal to produce tin, the tin was alloyed with copper to make bronze as early as about 2500 BC. Consequently, tools and weapons made of bronze figured prominently in the period known as the Bronze Age (about 2500 to 1500 BC). At an early time, lead was found as native lead or as galena, PbS, that could be converted to the oxide by roasting the sulfide in air followed by reduction with carbon. As a result, tin and lead are among the elements known for many centuries. Of course, the reason that the metals Sn, Cu, Au,... 

The major ore of zinc (though it occurs in numerous other minerals) is sphalerite, a form of ZnS usually found to also contain iron and commonly associated with galena (PbS). Cadmium is mostly found isomorphously replacing zinc in zinc minerals. To obtain metallic zinc from its ore, the ore is first calcined to ZnO and this is then roasted at ca. 1000°C with charcoal in the absence of air, whence the metal distills out. Cadmium can be separated from sulfate solutions of both zinc and cadmium by addition of zinc dust ... 

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