Davier- Researching on how to extract zinc from zinc blende and reorganizing points.
Eugene- Researching on the problems of extracting zinc from zinc blende on environment and commenting on other group's writeup.
Xin Yang- Researching on the ways to solve the problems and improve on the writeup after the critique is made.
Saturday, September 1, 2012
Chemistry E learining
Zinc Blende is a mineral that is the main ore of zinc. We will now introduce the methods to obtain zinc metal from zinc blende through extraction and the impact on production of zinc.
Zinc Blende structure.
Extraction of the two immiscible phases, separating a solute from one phase into the other. A simple example is the tea leaves. When the leaves are being boiled, caffeine, tannins and theobromine that gives the tea the flavoring and coloring. This is just like a representation of the process extraction where chemicals are involved.
Methods to extract zinc from zinc blende:
Concentration: 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.
1. Powdered Zinc Blende is concentrated by froth floatation process.
2. Roasting: This is to remove the sulfur in the zinc blende. To convert into zinc oxide which is more reactive than zinc blende. Since zinc oxide is much reactive compared to zinc blende, therefore it will be easier to obtain zinc metal from zinc oxide than zinc blende.
2ZnS + 3O2 ---> 2ZnO + 2SO2
3. Reduction: To remove the oxygen atom from the zinc oxide to obtain zinc metal. Carbon acts as the reducing agent to reduce zinc oxide and get oxidized itself.
ZnO + C ---> Zn + CO
4. Purification:
Impure Zinc obtained above contain impurities of Pb, Fe, Cd, As etc. This impure Zinc is known as spelter. Firstly, Cd is distilled off at 800 C and then electrolytic purification is done using impure Zn as anode and cathode consists of sheets of pure Al. Pure Zn is scrapped off from Al-sheets.
Impacts on environment:
1. Production of sulfur dioxide. Sulfur dioxide will result in acid rain, and thus causing much corrosion on buildings. Moreover, when acid rain comes in contact with the lakes, will kill the living organisms that cannot withstand the acidified water in the lake.
2. Smelter slag and other residues of the process contain significant amounts of metals which mostly are metal will cause water pollution. This will in turn kill many aquatic plants and aquatic animals.
Ways to solve the problem:
1. To reduce sulfur dioxide, we can react calcium oxide (CaO) with sulfur dioxide to form calcium sulfite. (CaSO3) Thus this will reduce the emission of sulfur dioxide and reducing air pollution.
http://wiki.answers.com/Q/How_can_sulfur_dioxide_be_removed_using_calcium_oxide
http://www.writing.engr.psu.edu/speaking/figure4_21.pdf
http://en.wikipedia.org/wiki/Sphalerite
http://en.wikipedia.org/wiki/Zinc_sulfide
http://en.wikipedia.org/wiki/Zinc
http://www.2classnotes.com/digital_notes.asp?p=Extraction_of_Zinc
http://www.zinc.org/basics/zinc_production
Zinc Blende structure.
Extraction of the two immiscible phases, separating a solute from one phase into the other. A simple example is the tea leaves. When the leaves are being boiled, caffeine, tannins and theobromine that gives the tea the flavoring and coloring. This is just like a representation of the process extraction where chemicals are involved.
Methods to extract zinc from zinc blende:
Concentration: 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.
1. Powdered Zinc Blende is concentrated by froth floatation process.
2. Roasting: This is to remove the sulfur in the zinc blende. To convert into zinc oxide which is more reactive than zinc blende. Since zinc oxide is much reactive compared to zinc blende, therefore it will be easier to obtain zinc metal from zinc oxide than zinc blende.
2ZnS + 3O2 ---> 2ZnO + 2SO2
3. Reduction: To remove the oxygen atom from the zinc oxide to obtain zinc metal. Carbon acts as the reducing agent to reduce zinc oxide and get oxidized itself.
ZnO + C ---> Zn + CO
4. Purification:
Impure Zinc obtained above contain impurities of Pb, Fe, Cd, As etc. This impure Zinc is known as spelter. Firstly, Cd is distilled off at 800 C and then electrolytic purification is done using impure Zn as anode and cathode consists of sheets of pure Al. Pure Zn is scrapped off from Al-sheets.
Impacts on environment:
1. Production of sulfur dioxide. Sulfur dioxide will result in acid rain, and thus causing much corrosion on buildings. Moreover, when acid rain comes in contact with the lakes, will kill the living organisms that cannot withstand the acidified water in the lake.
2. Smelter slag and other residues of the process contain significant amounts of metals which mostly are metal will cause water pollution. This will in turn kill many aquatic plants and aquatic animals.
Ways to solve the problem:
1. To reduce sulfur dioxide, we can react calcium oxide (CaO) with sulfur dioxide to form calcium sulfite. (CaSO3) Thus this will reduce the emission of sulfur dioxide and reducing air pollution.
http://wiki.answers.com/Q/How_can_sulfur_dioxide_be_removed_using_calcium_oxide
http://www.writing.engr.psu.edu/speaking/figure4_21.pdf
http://en.wikipedia.org/wiki/Sphalerite
http://en.wikipedia.org/wiki/Zinc_sulfide
http://en.wikipedia.org/wiki/Zinc
http://www.2classnotes.com/digital_notes.asp?p=Extraction_of_Zinc
http://www.zinc.org/basics/zinc_production
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