Hui Ping - Explanation on how the metal is extracted.
Yuan Lin - Impacts on the environment.
Rachel - Solutions to address the problems.
Monday, 3 September 2012
Saturday, 1 September 2012
Solutions to extraction of aluminium from bauxite
1. Aluminium recycling.
4 The problem of water pollution
- Since the Clean Water Act, other legislation has been enacted as well. Now, eleven different federal government agencies and 21 federal government programs all monitor the quality of water and regulate pollution.
http://en.wikipedia.org/wiki/Soil_erosion#Prevention_and_remediation
http://library.thinkquest.org/26026/Environmental_Problems/water_pollution_-_solutions.html
- It is the process by which scrap aluminium can be reused in products after its initial production.
- The process involves simply re-melting the metal, which is far less expensive and energy intensive than creating new aluminium through the electrolysis
- Recycling scrap aluminium requires only 5% of the energy used to make new aluminium and releases a mere 5% of greenhouse gases.
- The process involves simply re-melting the metal, which is far less expensive and energy intensive than creating new aluminium through the electrolysis
- Recycling scrap aluminium requires only 5% of the energy used to make new aluminium and releases a mere 5% of greenhouse gases.
 |
| Shredded aluminium beverage cans |
2. Solutions to tackle problem of habitat destruction.
Areas like the Marine Protected Areas (MPAs) and Marine Reserves are established to protect habitats by prohibiting mineral extraction, fishing, etc in certain areas. One example of MPA is the NOAA National Marine Sanctuaries in USA. Marine Reserves are also found in countries like New Zealand.
3. Problem of soil erosion.
One way is to maintain a vegetation cover as the roots are able to hold on to the soil firmly.
Terracing is an extremely effective means of erosion control as the soil will not get washed down the slope easily. It is practiced in places like Sa Pa, Vietnam.
Areas like the Marine Protected Areas (MPAs) and Marine Reserves are established to protect habitats by prohibiting mineral extraction, fishing, etc in certain areas. One example of MPA is the NOAA National Marine Sanctuaries in USA. Marine Reserves are also found in countries like New Zealand.
3. Problem of soil erosion.
One way is to maintain a vegetation cover as the roots are able to hold on to the soil firmly.
Terracing is an extremely effective means of erosion control as the soil will not get washed down the slope easily. It is practiced in places like Sa Pa, Vietnam.
 |
| Terraces |
4 The problem of water pollution
- Many laws have been created to restrict industries from dumping materials into the water.
- For example, in the United States, the Clean Water Act was written to completely put an end to all dumping of pollutants into water.
- The law has not been that effective in many areas, but in other locations, it has achieved its goals.
- For example, in the United States, the Clean Water Act was written to completely put an end to all dumping of pollutants into water.
- The law has not been that effective in many areas, but in other locations, it has achieved its goals.
http://library.thinkquest.org/26026/Environmental_Problems/water_pollution_-_solutions.html
-Rachel.
Environmental Impact of extraction of aluminium from bauxite
Bauxite is generally mined by open cast or strip mining. Rather than tunneling into the earth, these methods include extracting minerals from an open pit. Heavy machinery is used to remove all the earth covering the mineral. This will cause an immediate impact on the environment.
The exact effects of bauxite mining are related to the site. It almost always involves some habitat destruction, soil erosion, loss of biodiversity, or water pollution. These effects can be short term, and followed by regrowth, or severe and permanent.
Habitat destruction, especially of rainforests, may be the most noticeable impact of bauxite mining but it is not the only one.
Open cast mining involves removing the top layer of soil in order to get at the ores underneath. The resultant soil erosion results in the difficultly for vegetation, be it natural or crops, to re-establish itself. This is especially true if the removed soil is not replaced soon after the mining operation is finished. Some mining companies have a better record of reducing soil erosion than others.
The deforestation and soil erosion can lead to problems linked to flooding, including wastewater being swept into the drinking supply. Associated aluminium refineries, which produce the end product, can cause the drinking water supply to be hazardous. Sometimes, usually in colder regions such as Hungary, the mining may be deep enough to hinder with the water table. It also causes land pollution as some of the by products such as scrap metals are unrecyclable and thus they will be dumped in the dump sites.
In addition,
the extraction results in air pollution and worsening of greenhouse effect. Carbon
dioxide is produced as a by-product from the burning of anodes and carbon
monoxide and fluorine compounds that have toxicity are left as remnant gases
after electrolysis from the molten croylite, polluting the atmosphere.
How destructive bauxite mining will be, depends a lot on the location and how responsible the company is. In the worst cases it can harm the environment and affect the lives of the local people. In the best cases the land can recover quite well afterwards.
http://1800recycling.com/2010/11/aluminum-extraction-recycling-environment/
http://www.worldal.com/news/others/2010-07-03/127812172829282.shtml
http://www.chemguide.co.uk/inorganic/extraction/aluminium.html
- Yuanlin
Explaination for extraction of Aluminium from Bauxite
The extraction of aluminium from bauxite invloves the following steps:
1.Purification of bauxite
2.Electrolysis of aluminium oxide
3.Refining
As aluminium is placed relatively high up in the reactivity series, it cannot be extracted from its ore using carbon reduction. Thus it can only be extracted by electrolysis, which is a process of using electricity to break down or decompose a compound. The ore is first converted into pure aluminium oxide by the Bayer Process(the principal industrial means of refining bauxite to produce aluminium oxide) as bauxite is essentially an impure aluminium oxide. It is then electrolysed in molten cryolite(another aluminium ore) as the aluminium oxide has too high a meting point to electrolyse on its own.
Thereafter, crushed bauxite is treated with moderately concentrated sodium hydroxide solution which is hot, reacting to give a solution of sodium tetrahydroxoaluminate.
The impurities in the bauxite remain as solids which are separated out from the solution by filtration.The aluminium oxide is dissolved in a mixture of molten cryolite and fluorspar which lowers the melting point. It is then electrolysed in a rectangular steel tank with carbon lining, which serves as cathode.
Aluminium formed at the cathode gets collected at the bottom of the electrolytic cell, where it is removed periodically. As the metal obtained by this metal is only about 99% pure, further purification can be carried out by Hoop's electrolytic method.
http://www.chemguide.co.uk/inorganic/extraction/aluminium.html
http://entrancechemistry.blogspot.sg/2011/05/extraction-of-aluminium-from-bauxite.html
1.Purification of bauxite
2.Electrolysis of aluminium oxide
3.Refining
As aluminium is placed relatively high up in the reactivity series, it cannot be extracted from its ore using carbon reduction. Thus it can only be extracted by electrolysis, which is a process of using electricity to break down or decompose a compound. The ore is first converted into pure aluminium oxide by the Bayer Process(the principal industrial means of refining bauxite to produce aluminium oxide) as bauxite is essentially an impure aluminium oxide. It is then electrolysed in molten cryolite(another aluminium ore) as the aluminium oxide has too high a meting point to electrolyse on its own.
Thereafter, crushed bauxite is treated with moderately concentrated sodium hydroxide solution which is hot, reacting to give a solution of sodium tetrahydroxoaluminate.
The impurities in the bauxite remain as solids which are separated out from the solution by filtration.The aluminium oxide is dissolved in a mixture of molten cryolite and fluorspar which lowers the melting point. It is then electrolysed in a rectangular steel tank with carbon lining, which serves as cathode.
Aluminium formed at the cathode gets collected at the bottom of the electrolytic cell, where it is removed periodically. As the metal obtained by this metal is only about 99% pure, further purification can be carried out by Hoop's electrolytic method.
http://www.chemguide.co.uk/inorganic/extraction/aluminium.html
http://entrancechemistry.blogspot.sg/2011/05/extraction-of-aluminium-from-bauxite.html
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