Zinc smelting

The ancient process for smelting zinc has not yet been fully understood. The available evidence about the way zinc smelting was conducted has been interpreted in different ways (Craddock 1998 Morgan 1985). One explanation suggests that before zinc was smelted from an ore as calamine (composed of zinc carbonate), for example, the ore was first calcinated to produce zinc dioxide while carbon dioxide evolved  

Zinc dioxide is a friable material that could then readily be reduced to metallic zinc by carbon, the main component of the fuel  

Zinc melts at a fairly low temperature, 419°C, and boils at 918°C, below the temperature at which zinc oxide is reduced to zinc. If zinc had been smelted in the way described, the metal would have distilled when formed. To prevent its reoxidation when in the gaseous condition, the atmosphere of the furnace would have had to be kept free of oxygen so that the metal could cool and condense. The earliest available information on zinc distillation, however, is from as late as the twelfth century c.e. in India the suggested explanation advanced here does not, therefore, provide an answer as to how zinc was smelt before that time. 

Mercury (chemical symbol Hg, from the Latin name of the metal, hydrar-gyrium, liquid silver), previously also known as quicksilver is, at ordinary temperatures, a silvery white liquid metal that boils at 360°C. The metal is occasionally fmmd in nature in the native state. Most mercury has been derived, however, from the red mineral cinnabar (composed of mercuric sulfide) that was also used in the past as a red pigment known as vermilion (see Textbox 41). The Greek philosopher Aristotle, writing in the fourth 

Further heating results in decomposition of the oxide formed and the release of mercury vapor  

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The abundance of indium in the earth s cmst is probably about 0.1 ppm, similat to that of silver. It is found in trace amounts in many minerals, particulady in the sulfide ores of zinc and to a lesser extent in association with sulfides of copper, tin, and lead. Indium follows zinc through flotation concentration, and commercial recovery of the metal is achieved by treating residues, flue dusts, slags, and metallic intermediates in zinc smelting and associated lead (qv) and copper (qv) smelting (see Metallurgy, EXTRACTIVE Zinc and zinc alloys). 

Production. Indium is recovered from fumes, dusts, slags, residues, and alloys from zinc or lead—zinc smelting. The source material itself, a reduction bullion, flue dust, or electrolytic slime intermediate, is leached with sulfuric or hydrochloric acid, the solutions are concentrated, if necessary, and cmde indium is recovered as 99+% metal. This impure indium is then refined to 99.99%, 99.999%, 99.9999%, or higher grades by a variety of classical chemical and electrochemical processes. 

In addition to domestic production of Frasch and recovered elemental sulfur, U.S. requirements for sulfur are met with by-product sulfuric acid from copper, lead, molybdenum, and zinc smelting operations as well as imports from Canada and Mexico. By-product sulfur is also recovered as sulfur dioxide and hydrogen sulfide (see Sulfurremoval and recovery). 

E/ectrothermlc Process. Electrothermic zinc smelting is described in refs. 29—30. The oxide furnaces in the one U.S. plant are 11-m high, three are 1.75-m dia. 

S / S than ores of zinc (ZnS) have. Thus, the value of S / S in atmospheric SO2 can identify whether the source of pollutant was an iron or zinc smelting operation. 

Zhou, W. (1996), Chinese traditional zinc smelting technology and the history of zinc production in China, Bull. Metals Museum 25, 36-47. 

Plants readily accumulate lead from soils of low pH or low organic content however, uptake is significantly reduced after the application of lime or phosphate, which converts lead to hydroxides, carbonates, or phosphates of relatively low solubility (Demayo et al. 1982). Lead persists for lengthy periods in forest litter the estimated Tb 1/2 is 220 years (Turner et al. 1985). High levels of lead persisted for at least 6 years in litter, soil, amphibians, and mammals after zinc smelting was discontinued in Palmerton, Pennsylvania (Storm et al. 1994). Lead seems to be tightly bound by... 

Beyer, W.N., G.W. Miller, and E.J. Cromartie. 1984. Contamination of the 02 soil horizon by zinc smelting and its effect on woodlouse survival. Jour. Environ. Qual. 18 247-251. 

Beyer, W.N. 1988. Damage to the forest ecosystem on Blue Mountain from zinc smelting. Pages 249-262 in D.D. Hemphill (ed.) Trace Substances in Environmental Health — XXII. A Symposium. Univ. Missouri Press, Columbia, MO. 

Cocks, E. J. and Walters, B., A History of the Zinc Smelting Industry in Britain, George G. Harrap, London, 1968, 7. 

Electrothermic process, for zinc, 26 577 Electrothermic zinc smelting, 26 612 Electrotransport technique, for purifying vanadium, 25 522... 

Zinc smelters, 26 584 Zinc smelting, 26 554 electrothermic, 26 612 Zinc sodium chromate... 

Xu Li (1990). Traditional zinc-smelting technology in the Guma district of Hezhang County. In 2000 Years of Zinc and Brass, ed. Craddock, P.T., British Museum Occasional Paper No. 50, British Museum, London, pp. 103-121. 

Worked Example 3.10. Here, we will consider a real situation. There is thought to be contamination from a zinc smelting plant, so a sample of soil from near the smelter is collected and digested in sulfuric acid (of concentration 0.01 mol dm in order to leach out the soluble zinc as the sulfate salt. 

Indium may be recovered from zinc ores by several patented processes. Usually it is recovered from residues obtained from zinc extraction. The residues, slags, fume, or dusts from zinc smelting or lead-zinc smelting are treated with a mineral acid. Other steps involved in recovery often vary, but mostly use solvent extraction and precipitation steps. In some processes, treatment with caustic soda yields indium hydroxide. The hydroxide is calcined to obtain oxide, which then is reduced with hydrogen at elevated temperatures to obtain the metal. Distillation or electrolysis are the final steps to... 

Sidenko, N. V., Giere, R., Bortnikova, S. B., Pal CHIK, N. A. Cottard, F. 2001. Mobility of heavy metals in self-burning waste heaps of the zinc smelting plant in Belovo (Kemerovo Region, Russia). Journal of Geochemical Exploration, 74, 109-125. 

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