This script adresses the general principles and processes of the isolation of elements. The script contains a flow sheet for the extraction of iron, a flow sheet for the extraction of copper, a flow sheet for the extraction of aluminium and a short answer to important questions concerning the issue.
General Principles & Process of Isolation of Elements
Important Points :
1. The chemical substances in the earth’s crust obtained by mining are called Minerals.
2. Minerals, which act as source for metal, are called Ore. From ore metal can be obtained economically.
3. The unwanted impurities present in ore are called Gangue.
4. The entire process of extraction of metal from its ore is called Metallurgy.
5. Removal of gangue from ore is called Concentration, Dressing or Benefaction of ore.
6. Concentration by Hydraulic washing is based on the difference in gravities of ore and gangue particles.
7. Concentration by Magnetic separation is based on differences in magnetic properties of ore components. If either of ore or gangue is capable of attracted by a magnet field, then such separation is carried out.
8. Concentration by Froth Flotation Process is based on the facts that sulphide ore is wetted by oil & gangue particles are wetted by water.
9. Concentration by Leaching is based on the facts that ore is soluble in some suitable reagent & gangue is insoluble in same reagent. e.g. Bauxite ore contains impurities of silica, iron oxide & TiO2 .The powdered ore is treated with NaOH which dissolve Al & impurities remains insoluble in it.
Al2O3 +2NaOH + 3H2O → 2Na [Al(OH)4].
10. Calcination involves heating of ore in absence of air below melting point of metal. In this process volatile impurities escapes leaving behind metal oxide.
Fe2O3.xH2O → Fe 2O3 + xH2O
ZnCO3 → ZnO + CO2
CaCO3.MgCO3 → CaO + MgO + 2CO 2
11. Roasting involves heating of ore in presence of air below melting point of metal in reverberatory furnace. In this process volatile impurities escapes leaving behind metal oxide and metal sulphide converts to metal oxide.
2 ZnS + 3O2 → 2ZnO +2 SO2
2 PbS + 3O2 → 2 PbO +2 SO2
2 Cu2S + 3O2 → 2Cu2O + 2 SO2
12. Reduction of metal oxide involves heating of metal in presence of suitable reagent Coke or CO2.
13. Reactions taking place at different zones of blast furnace in extraction of iron:-
(i) Zone of reduction:- Temperature range 250oC-700oC
3Fe2O3 + CO → 2Fe3O 4 + CO2
Fe3O4 + CO → 3FeO + CO2
FeO + CO → Fe + CO2
(ii) Zone of slag formation:- Temperature range 800oC-1000 oC
CaCO3 → CaO+CO2
CaO + SiO2 → CaSiO3, P4O 10 + 10C → 4P + 10CO,
SiO2 + 2C → Si + 2CO, MnO2 + 2C → Mn + 2CO
(iii) Zone of fusion: - Temperature range 1150oC-1350 oC
CO2 + C → 2CO
(iv) Zone of fusion: - Temperature range 1450oC-1950o C
C + O2 → CO2
14. Vapour phase refining is used for extraction of Nickel (MOND PROCESS) and Zirconium &Titanium
(VAN ARKEL PROCESS).
15. Zone refining is used for extraction of Si, Ge, Ga, etc.
16. Chromatography method is based on selective distribution of various constituents of a mixture between
two phases, a stationary phase and a moving phase. The stationary phase can be either solid or liquid on
solid support.
17. Column chromatography is based on adsorption phenomenon. This method is useful for those elements,
which are available in small amounts and the impurities are not much different in chemical properties from
the element to be purified
FLOW SHEET FOR EXTRACTION OF IRON:-
[Figures and tables are omitted from this preview.]
Pig Iron: - It contains Fe 93-95%, Carbon 2.5-5%, and Impurities 3%.
Cast Iron: - It contains Fe 99.5-99.8%, Carbon 0.1-0.2% Impurities 0.3%.
Spongy iron: - Iron formed in the zone of reduction of blast furnace is called spongy iron. It contains impurities of C, Mn , Si, etc.
[...]
Frequently Asked Questions
What are minerals and ores according to the "General Principles & Process of Isolation of Elements" language preview?
Minerals are chemical substances obtained by mining from the earth's crust. Ores are minerals that act as a source for metals, allowing metals to be extracted economically.
What is gangue in the context of metallurgy?
Gangue refers to the unwanted impurities present in an ore.
What is metallurgy, and what does concentration/dressing/benefaction of ore refer to?
Metallurgy is the entire process of extracting a metal from its ore. Concentration, dressing, or benefaction of ore refers to the removal of gangue from the ore.
How does hydraulic washing work for ore concentration?
Concentration by hydraulic washing is based on the difference in gravities of ore and gangue particles.
On what principle is concentration by magnetic separation based?
Magnetic separation relies on the differences in magnetic properties of ore components. If either the ore or the gangue is attracted by a magnetic field, this separation method can be used.
What is the principle behind froth flotation in ore concentration?
Froth flotation is based on the principle that sulfide ores are wetted by oil, while gangue particles are wetted by water.
How does leaching work for concentrating ores, providing an example?
Leaching is based on the ore being soluble in a suitable reagent while the gangue is insoluble in the same reagent. For example, bauxite ore, containing silica, iron oxide, and TiO2 impurities, is treated with NaOH to dissolve the aluminum component, leaving the impurities undissolved.
What is calcination, and what happens during this process?
Calcination involves heating the ore in the absence of air, below the melting point of the metal. During this process, volatile impurities escape, leaving behind the metal oxide.
What is roasting, and how does it differ from calcination?
Roasting involves heating the ore in the presence of air, below the metal's melting point, usually in a reverberatory furnace. During roasting, volatile impurities escape, and metal sulfides are converted to metal oxides.
What is involved in the reduction of metal oxides?
Reduction of metal oxide involves heating the metal oxide in the presence of a suitable reducing agent like Coke or CO2.
What are the different zones in a blast furnace during iron extraction, and what reactions occur in each zone?
The different zones and reactions in a blast furnace are:
- Zone of Reduction (250oC-700oC): 3Fe2O3 + CO → 2Fe3O4 + CO2; Fe3O4 + CO → 3FeO + CO2; FeO + CO → Fe + CO2
- Zone of Slag Formation (800oC-1000oC): CaCO3 → CaO + CO2; CaO + SiO2 → CaSiO3; P4O10 + 10C → 4P + 10CO; SiO2 + 2C → Si + 2CO; MnO2 + 2C → Mn + 2CO
- Zone of Fusion (1150oC-1350oC): CO2 + C → 2CO
- Zone of Fusion (1450oC-1950oC): C + O2 → CO2
What metals are extracted using vapour phase refining, and what are the processes involved?
Vapor phase refining is used for nickel extraction (Mond Process) and zirconium & titanium extraction (Van Arkel Process).
What is zone refining used for?
Zone refining is used for extracting high purity Si, Ge, Ga, etc.
What is the principle behind chromatography methods?
Chromatography methods are based on the selective distribution of various constituents of a mixture between two phases: a stationary phase and a moving phase. The stationary phase can be solid or liquid on a solid support.
What is column chromatography based on?
Column chromatography is based on adsorption phenomenon and is useful for elements available in small amounts where impurities don't differ much in chemical properties from the element being purified.
What is pig iron, cast iron, and spongy iron?
Pig iron contains Fe 93-95%, Carbon 2.5-5%, and Impurities 3%. Cast iron contains Fe 99.5-99.8%, Carbon 0.1-0.2%, and Impurities 0.3%. Spongy iron is formed in the zone of reduction in a blast furnace and contains impurities like C, Mn, and Si.
- Quote paper
- Ph.D Rajeev Oberai (Author), 2018, General Principles and Processes of the Isolation of Elements, Munich, GRIN Verlag, https://www.grin.com/document/416230
