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Transcript of Zinc
Melting point: 419.5° C
Atomic number: 30
Boiling point: 906.8° C
Atomic mass: 65.409
Ore: zinc pyrite / zinc blende
Electrons per shell: 2, 8, 18, 2
Zinc is the 24th most abundant element in the Earth's crust and has five stable isotopes.The most common zinc ore is sphalerite (zinc blende). The largest mineable amounts are found in Australia, Asia, and the United States. Background Information Physical properties:
Phase - solid
Color - pale bluish-grey
Density - 7.14 g.cm-3
Liquid density - 6.57 g.cm-3
Melting point - 692.68 K (419.53°C, 787.15°F)
Boiling point - 1180 K (907°C, 1665°F)
Density-7.11 g/cm3 at 20 degrees centigrade.
Statement- Zinc burns in air with a red heat with evolution of white clouds of Zinc Oxide Properties of Zinc Zinc + Copper (with some Tin)--> Brass & Bronze
Galvanization: the process of applying a protective zinc coating to steel or iron, in order to prevent rusting.
It is used as an anode material in batteries.
In US, it's used to create money.
Zinc oxide is used as a white pigment in paints and photocopy inks.
Zinc oxide is used in rubber to protect it from UV radiation.
Zinc is also used in dietary supplements. It is helpful in healing injuries, reducing the length and severity of colds and has antimicrobial properties which help in the relief of gastroenteritis.
It is also used in sunscreens and baby diaper rash products as a barrier protector.
It is used in toothpaste to prevent bad breath and in shampoos to stop dandruff. Uses of Zinc Production of Zinc MINING:
Zinc ores are dug from underground mines using conventional blasting, drilling, and hauling techniques. The ores occur as zinc sulfide, zinc carbonate, zinc silicate and in compounds of manganese and iron.
In addition to the ore itself, oil and sulfuric acid are required for the breakdown of the ores; and electricity, coke, or natural gas are needed to provide the heat energy.
Keeping the zinc molten and undisturbed for several hours can make further metal improvement. Zinc has to be cooled down. It has to be cooled down in order to be shaped properly or molded.
Zinc does not react with water.
Reaction of zinc with the halogens:
Zn(s) + Br2(g) ZnBr2(s) [white]
Zn(s) + I2(g) ZnI2(s) [white]
Reaction of zinc with acids:
Zinc metal dissolves slowly in dilute sulphuric acid to form solutions containing the aquated Zn(II) ion together with hydrogen gas;
Zn(s) + H2SO4(aq) --> Zn2+(aq) + SO42-(aq) + H2(g)
Zinc with hydrochloric acid: Zn + 2 HCl -----> ZnCl2 + H2
Reaction of zinc with bases:
Zinc metal dissolves in aqueous alkalis such as potassium hydroxide, KOH, to form zincates such as [Zn(OH)4]2-. The resulting solutions contain other species as well. Zinc Reactions Zinc was first processed during the heating of the ores.
The raw material used for the production of zinc is zinc concentrate, which is the result of a flotation process after the ore has been mined and milled. The zinc ore contains 1-15% zinc whereas the concentrate typically contains approx. 55% zinc, 6.5% iron and 32% sulphur together with other elements at much lower levels. Zinc Zinc Extraction Process (continued in the next few slides)
Facts: The most important raw material for production of Zinc is Zinc Sulphide (ZnS) ore commonly known as Sphalerite. Next in the importance are Zinc Carbonates (Calamine/Smithsonite) and Zinc Silicate. Most of the zinc production worldwide originates from sulphide ores. Zinc is the fourth most common metal in use, trailing only iron, aluminium, and copper with an annual production of about 12 million tonnes. Z inc is a moderately reactive metal that displaces hydrogen from steam or a dilute acid. THANK YOU FOR WATCHING!
NOW GO SLEEP... Continued...
The final process takes place in the foundry where the zinc takes its final form, either as a metal with a purity of 99.95% or as an alloy together with copper, aluminium or magnesium. The zinc is cast into various forms (normally ingots or plates)with weights from 9 kg to 4 tons. Zinc is an essential mineral that stimulates the activity of about 100 enzymes in the body. It also:
supports your healthy immune system
is necessary to synthesize DNA
is essential for wound healing.
supports the healthy growth and development of the body during adolescence, childhood and pregnancy.
Though the actual amount of zinc necessary to support the human body is quite small, its effects on the body are astronomical.
Sources of Zinc
Zinc is present in a variety of foods that many people consume daily. The food with the most zinc per serving is oysters, but most Americans receive the greatest portion of their zinc intake from red meat and poultry. Some other food sources that contain zinc are some seafood, whole grains, fortified cereals, beans, nuts and dairy products. Importance of Zinc 80% of zinc mines are underground, 8% are of the open pit type and the remainder is a combination of both. However, in terms of production volume, open pit mines account for as much as 15%, underground mines produce 64% and 21% of mine production comes from the combined underground and open pit mining.
Rarely is the ore, as mined, rich enough to be used directly by smelters; it needs to be concentrated. Zinc ores contain 5-15% zinc. To concentrate the ore it is first crushed and then ground to enable optimal separation from the other minerals. Typically, a zinc concentrate contains about 55% of zinc with some copper, lead and iron. Zinc concentration is usually done at the mine site to keep transport costs to smelters as low as possible. Zinc Mining Smelting is a metal extraction process in which an ore (usually mixed with purifying and/or heat generating substances such as limestone and coke) is heated at high temperature in an enclosed furnace. After a reducing reaction (see reduction), lighter ore-components (impurities called slag or tailing) rise to the top and float on the molten metal. Smelting is opposite of roasting which involves an oxidizing reaction (see oxidation). Smelting (definition) Over 95% of the world’s zinc is produced from zinc blende (ZnS). Apart from zinc the concentrate contains some 25-30% or more sulphur as well as different amounts of iron, lead and silver and other minerals. Before metallic zinc can be recovered, by using either hydrometallurgical or pyrometallurgical techniques, sulphur in the concentrate must be removed. This is done by roasting or sintering. Roasting & Sintering 2 1.5 1 The Hydrometallurgical Process In a leaching stage, the zinc oxide is separated from the other calcines. Sulphuric acid is used to do this.
The zinc content dissolves whereas iron precipitates and lead and silver remain undissolved. However, the dissolved solution contains some impurities which need to be eliminated in order to obtain a high-purity zinc product at the end of the production process. Purification is mainly done by adding zinc dust to the solution.
The thus obtained purified solution passes an electrolytic process where the purified solution is electrolyzed between lead alloy anodes and aluminium cathodes. An electrical current is circulated through the electrolyte by applying an electrical difference of 3.3-3.5 volts between the anode and cathode causing the zinc to deposit on the aluminium cathodes in high purity. The deposited zinc is stripped off, dried, melted and cast into ingots. 3 The Imperial Smelting process is based on the reduction of zinc and lead into metal with carbon in a specially designed Imperial Smelting furnace.
The IS process is an energy-intensive process and thus became very expensive following the rise of energy prices.
Today, Imperial Smelting furnaces are only in operation in China, India, Japan and Poland. The Pyrometallurgical Process 4