Zinc concentrate
Encyclopedia
Zinc concentrate is a semi-processed intermediate product used in the production of zinc
metal and zinc alloy
s, which is the result of a flotation process after the zinc ore
has been mined and milled. The zinc ore contains 1-15% zinc whereas the concentrate typically contains approximately 55% zinc
, 6.5% iron
and 32% sulfur
together with other elements at much lower levels.
By percentage, zinc concentrate normally contains zinc sulfide
(80% to 85%), iron sulfide
(7.0% to 12%), lead sulfide
(3.0% to 5.0%) silica
(2.5% to 3.5%), and cadmium sulfide
(0.35% to 0.41%).
The zinc production process involves roasting the concentrate at approximately 950 °C. When the right temperature is reached oxidation of the zinc, iron and sulfur occurs. The sulfur can be collected and turned into commercial grade sulfuric acid
(H2SO4).
The iron and zinc then oxidises, and having been reduced to a powdered form is diluted with sulfuric acid, neutralised, and then filtered to remove contaminants.
The refined solution is then electrolysed
in a cell
fitted with a lead
anode
and an aluminium
cathode
. In this process the zinc is deposited on the cathode from which it is later stripped off. It is then sent to a foundry
where it takes its final form as either zinc metal (99.95% pure zinc), or zinc 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
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
metal and zinc alloy
Zinc alloy
Electroplated Zinc alloys have been developed for meeting the most challenging specifications in terms of corrosion protection, temperature and wear resistance.-History:...
s, which is the result of a flotation process after the zinc ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
has been mined and milled. The zinc ore contains 1-15% zinc whereas the concentrate typically contains approximately 55% zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
, 6.5% iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
and 32% sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
together with other elements at much lower levels.
By percentage, zinc concentrate normally contains zinc sulfide
Zinc sulfide
Zinc sulfide is a inorganic compound with the formula ZnS. ZnS is the main form of zinc in nature, where it mainly occurs as the mineral sphalerite...
(80% to 85%), iron sulfide
Iron(II) sulfide
Iron sulfide or ferrous sulfide is a chemical compound with the formula . In practice, iron sulfides are often non-stoichiometric. Powdered iron sulfide is pyrophoric Iron(II) sulfide or ferrous sulfide (Br.E. sulphide) is a chemical compound with the formula . In practice, iron sulfides are...
(7.0% to 12%), lead sulfide
Lead sulfide
Lead sulfide is an ionic compound of lead and sulfur, having two possible proportions:*Lead sulfide, the ionic compound containing lead in the +2 oxidation state*Lead sulfide, the ionic compound containing lead in the +4 oxidation state...
(3.0% to 5.0%) silica
Silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
(2.5% to 3.5%), and cadmium sulfide
Cadmium sulfide
Cadmium sulfide is the inorganic compound with the formula CdS. Cadmium sulfide is a yellow solid. It occurs in nature with two different crystal structures as the rare minerals greenockite and hawleyite, but is more prevalent as an impurity substituent in the similarly structured zinc ores...
(0.35% to 0.41%).
The zinc production process involves roasting the concentrate at approximately 950 °C. When the right temperature is reached oxidation of the zinc, iron and sulfur occurs. The sulfur can be collected and turned into commercial grade sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
(H2SO4).
The iron and zinc then oxidises, and having been reduced to a powdered form is diluted with sulfuric acid, neutralised, and then filtered to remove contaminants.
The refined solution is then electrolysed
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...
in a cell
Electrochemical cell
An electrochemical cell is a device capable of either deriving electrical energy from chemical reactions, or facilitating chemical reactions through the introduction of electrical energy. A common example of an electrochemical cell is a standard 1.5-volt "battery"...
fitted with a lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
anode
Anode
An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....
and an aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
cathode
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
. In this process the zinc is deposited on the cathode from which it is later stripped off. It is then sent to a foundry
Foundry
A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal in a mold, and removing the mold material or casting after the metal has solidified as it cools. The most common metals processed are aluminum and cast iron...
where it takes its final form as either zinc metal (99.95% pure zinc), or zinc alloy together with copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
, aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
or magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
. The zinc is cast into various forms, normally ingots or plates, with weights from 9 kg to 4 tons.