Chemistry Assignment Essay
Metals are mined from ores, considering yield to see if it is economically viable for a business to mine at a particular site. However, due to environmental damage and global warming, recycling has increased globally to create a sustainable future. By examining the cost and energy expenditure of recycling and extracting aluminium we can understand why recycling is a better choice than extracting metal from its ore.
Discuss the importance of predicting yield in the identification, mining and extraction of commercial ore deposits Yield is the amount of product obtained or in mining terms how much (amount) a particular metal can be extracted from an ore (a deposit of minerals in which a commercial metal can be extracted from). Predicting yield in the processes of identification, mining and extraction is vital to the success of a business. For a business to compete with the global markets, the investment must be profitable and in some cases sustainable to last year’s into the future.
Percentage composition is used widely in the mining industries to calculate and measure the yield of particular metal from an ore. For example, haematite (Fe2O3), a compound consisting only of iron and oxygen, can theoretically produce around 70% iron while chalcopyrite (CuFeS2), consisting only of copper, iron and sulphur can produce theoretically 35% copper. However if we express yield as a percentage of the ore dug out, an iron ore would only contain about 16% iron and for a copper ore only contain 1-5% copper.
This is because an ore dug out of the ground contains unwanted minerals like dirt, rocks and other waste products which add to the mass of the required mineral ;giving a low yield percentage. Since compounds like chalcopyrite and haematite have uniform composition, ores are mixtures of useful minerals and other waste products which have variable composition (different location will yield different amounts of metals). This will affect if it is economical to mine the ore at a particular location and hence demonstrate that predicting yield is important.
Predicting yield in the process of mining and extraction is important, whether extracting the metal from the ore or actually mining it, because it can determine if it is profitable or not. Extraction techniques must be efficient and sustainable. Copper is extracted through roasting it with oxygen before smelting it to form liquid copper. It is then reduced by bubbling air into the liquid copper to reduce copper sulphide to copper metal. Since this sulphur dioxide doesn’t escape fast enough, it forms blister copper with is 98% copper. Electrolysis is used to refine it.
Due the significant amount of energy required and the cost involved it may seem copper is unprofitable. Yet if the copper price is high, the consumption is high, location is not far from refinery plants and factories that use copper, if there is a steady sustainable source(abundance) of copper ore and the extraction technique is efficient plus cost effective then a profit can be gained from the high cost of extraction, transport and the money needed to pay for the energy consumption. For a copper ore site to be economical it must contain at least 5% of copper or more.
Haematite is extracted through reducing it with carbon monoxide to form iron (metal) which falls to the bottom of the blast furnace. Limestone is also heated in the blast furnace which decomposes and reacts with silica to form a slag that floats on the liquid iron, hence stopping iron from reacting with oxygen. High heat is needed to separate iron from oxygen since iron is reactive to oxygen and sand and limestone is needed to prevent the union of these two elements. Hence for haematite to be economically viable an ore must contain at least 20% iron as the energy needed to extract the metal is large and the world’s demand for iron is great.
Since iron ore price is relatively high, a profit can be obtained from deposits of iron ore that contain more than 20% of iron. Hence predicting the yield of ore deposits is important to determine if it is profitable to mine. Justify the increased recycling of metals in our society and across the World Recycling is a process that changes waste materials into new products. In recent years, recycling of metals has increased dramatically in Australia and across the world. This is because we are more aware that recycling metals saves money, energy and causes far less pollution compared to extracting metals from ores.
This is also spurred on by the fact that our metal ore deposits are depleting (going to run out) if we mine and extract metals at this rate. Hence recycling has been encouraged by organisation like Planet Ark and this has helped spread the message of the benefits of recycling instead of putting money into extracting and mining ores. ‘Reusing and recycling’ metals allow us to conserve these precious commodities so it would be available for the future generation. Demand for metals will increase as new technology will be discovered. Hence recycling is needed to return back old and useless appliance so it can be made it new useful products.
Figure 1: It shows froth floatation Note: The vast amount of water used during the process Generally recycling metals use less energy (melting material requires the breaking of weak intermolecular bonds), water and cost less (less energy is needed to break the intermolecular bonds hence the cost will be minimised and new products with recycled material would be cheaper). Energy used in metal extraction comes from coal, oil or gas (as high temperatures are needed to break strong Intramolecular bonds). These fuels are non-renewable and are limited. It also releases large amounts of greenhouse gases when burnt which can cause global warming.
Water is used extensively in mining during froth floatation (figure 1). This water can be better spent for human consumption as some countries are experiencing drought and this can cause famine (Africa). Also, harmful chemicals used in the extraction of some metals can seep into the soil and water making it toxic to fauna, flora and humans (figure 1. 1). Figure 1. 1: Acid mine water pollution For example, Bauxite (aluminium ore) is mined near tropical forest. This can cause irreversible damage to the environment as natural vegetation is destroyed, leaving soil bare and subjected to erosion.
It can scar the land(figure 2)(removing so much soil and rock that leaves a gigantic hole in the landscape) and since many chemical process need to take place before aluminium is extracted, slag (unwanted metals) are left behind and pollutants are released into the atmosphere adding to global warming. Figure 2: Shows a mine that is extracting metals Note: The extensive invasion of the land and that it is irreversible. But recycling aluminium on the other hand doesn’t scar the land. Little to no pollution occurs and natural vegetation and fauna are not disrupted.
Large amounts of rubbish are no produced and water is not needed. For every 1 tonne of aluminium that is recycled, 5 tonne of bauxite is conserved. Metals make up a small percentage of the ore. A large percentage of the ore is the gangue (consisting of dirt, sand and other material) which ends up in landfills. This reduces the space for cities to expand, limiting the number of farms and communities that can be developed and cause overcrowding. Recycling metals doesn’t take up space; hence reduces landfill, as scrap metals are mostly recycled back to make new products.
Since ores are non-renewable resources (created by the Big bang and there is no way of returning it to Earth’s crust) it is conserved, reducing the amount of mines opened and environmental impacts that it is associated with. As ores high in metal concentration decrease, the cost of processing ever less pure ores increase. To compensate for the increase in less pure ores, more must be mined. This increases the price of ores making it a valuable resource which is expensive to the consumer. Recycling metals helps to lower the prices of these ores, as the metal is reused without having to mine for new ores.
Metals are used worldwide for a variety of purposes from soft drink cans to aircraft bodies. Australia has recycled 63% of aluminium cans; nearly two billion cans a year with a total value estimated to be 33 million dollars. America has recycled in excess of 62. 6 billion cans in the year 2004, worth more than one billion dollars back into the economy. Since recycled aluminium is exported to other countries, Australia benefits as it generate large amounts of money; positively impacting on Australia economy and its benefit flowing into society.
However, recycling can only be done if used material is collected from scattered location. The ore on the other hand is confined to one location (the mining site); where factories are often close by to produce products from the freshly extracted metals. But once the product hits the shelves it is scattered across many different countries and throughout communities. It is hard to keep track of all these products as some end up in landfill, waterways or in the people’s backyard.
Collecting used material for recycling would cost money as trucks are needed to transport scrap metal to recycling centres. Hence energy (fuel) is needed to operate this machinery. In recent years (figure3), the media has focused on recycling aluminium drink cans because they are widely used and commonly dispersed inappropriately throughout the community. E. g. In waterways, storm drains and in the ocean. Recycling of others metal like iron, steel, copper and lead have always been significant but never reported as it is mainly used at an industrial/commercial level rather than by consumers.
However since iron rust, it can be returned to the environment, but aluminium doesn’t corrode (if it does, it forms an oxide layer that actually protects it from further oxidation) it ends up in landfill; taking up space. The only way to ‘get rid of it’ is to recycle it so it can be made into new products. Notice that recycling of lead and ferrous materials have decreased Figure 3: Shows recycling metals Notice that when metals are recycled they can be reused to make different products.
Recycling is a sustainable process, saving the environment from pollution, money, conserving natural resources and reduces landfill. Energy is also reduced as recycling requires less energy than extracting a metal from its ore. This will ensure that future generations will be able to enjoy a better standard of living. Analyse information to compare the cost and energy expenditure involved in the extraction of aluminium from its ore and the recycling of aluminium The recycling of aluminium is cost-effective and uses less energy compared to extraction of aluminium from bauxite.
To extract bauxite, land must be cleared for mining. Heavy equipment like bulldozers, hydraulic excavators and explosives are used to clear and mine the ore. These equipment cost considerable amount of money and use vast amount of energy (fuel) to operate. Transporting trucks, ships, railway cars are used to transport ores to extracting facilities or shipped to other countries; cost money and again energy (fuel) is needed to power these machines. Notice the size of the person compared to the truck.
University/College: University of California
Type of paper: Thesis/Dissertation Chapter
Date: 4 November 2016
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