• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The extraction of metals from their ores using micro-organisms.

Extracts from this document...

Introduction

The extraction of metals from their ores using micro-organisms. New processes for mining. The extraction of Copper. Copper mining has been a main source of copper for many thousands of years. The most common form that copper is found in is in its ores, copper oxides and copper sulphides. Copper can be extracted from its ores by using bacteria this process is called biohydro-metallurgy. The bacteria that are used to extract pure copper are 'Thiobacillus ferro-oxidans and Thiobacillus thio-oxidans these bacteria live by oxidising Fe2+ and S2- ions, these ions are present in insoluble minerals of copper, zinc and lead and the oxidation releases the ions into solution where they can be extracted as metals.'1 Bacteria at work. The waste left over from previous ore crushing, (tailings), are heaped up on ground that is impermeable and the ground is sprayed with a leaching solution which contains Thiobacillus ferro-oxidans and Thiobacillus thio-oxidans, 'this leaching solution is ideal as bacteria thrive in acidic conditions. ...read more.

Middle

The problems that result from roasting and cyanidation mean that only a fraction of the gold is extracted from the sample. 3 Bacteria at work. If the refractory sulphide concentrate is treated with a thermophilic bacterium, Sulpholobus acidocalderius, it helps catalyse the oxidation of sulphide ions and then this resulting mixture, when treated with sodium cyanide, produces a total extraction of the gold. More research lead to the discovery of a mixture of different thermophilic bacterium that worked over a range of temperatures, PHs, and arsenic conditions making it ideal for gold extraction in other countries and increasing the extraction process even more. The bio-oxidation process works in two stages, taking arsenopyrite as an example, the bacteria catalyses the formation of iron(II), arsenic(III) and sulphur(VI): FeAsS Fe(II) + As(III) + S(VI) During the second stage two of the products are oxidised: Fe(II) Fe(III) As(III) As(V) All the products from the oxidation of arsenopyrite are soluble in water, so after the process has taken place the water is treated with hydrated calcium hydroxide, this neutralises sulphuric acid and helps form a layer of iron(III) ...read more.

Conclusion

Bio-oxidation is cost effective, efficient, safe, and environmentally friendly. Compared to roasting, bio-oxidation reduces capital costs by 12-20%, operating costs by 10% and construction time by 25%. The yield of gold is also increased, the process doesn't take months and the process is extremely profitable. By using the bacterial process primarily it eliminates the emissions produced by roasting, large amounts of SO2, As2 and O3, and also the costs of disposing of arsenic. The operation is simple and a skilled workforce isn't required, the plants are also healthier and safer. Only 20% of all the refractory gold treatment plants use bio-oxidation, for this to increase the governments would need to provide funding. Political powers would also need to approve and regulate new processes, checking it is safe and not very environmentally damaging. 5 Sources: 1 Article one - by John Merson, Mining with microbes 2 Article two - extracting copper ions from leaching solutions 3 Article three - by Jack Barrett and Martin Hughes, A Golden Opportunity 4 http://e-mj.com/ar/mining_copper_extraction.htm, 5 http://e-mj.com/ar/mining_bacterial_oxidation.htm, articles from the engineering and mining journal from 1999. 1 Rachel Jeffreys. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Living Things in their Environment section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Living Things in their Environment essays

  1. Marked by a teacher

    Research question - Is using dogs for work ethical?

    5 star(s)

    The European Union attempted to ban all cosmetics tested on animals to be sold in Europe, but France (the country which L'Or´┐Żal is based) is protesting against the ban. This could be because animal testing can give people reassurance that the product is safe and possibly sales would fall on the cosmetics by this company.

  2. Marked by a teacher

    Taxonomy is the branch of biology that deals with the identification and naming of ...

    5 star(s)

    Bacteria that depend on oxygen to live are known as aerobic bacteria. Those that do not require oxygen are know as anaerobic bacteria. Aerobic bacteria are more advanced. They can oxidize things such as glucose and nitrates to obtain their energy.

  1. Marked by a teacher

    Bacterial Leaching of Copper and Gold

    3 star(s)

    + Fe(s) -> Cu(s) + Fe2+(aq) The electrons lost by the iron are taken up by the copper. Copper is the oxidising agent (it accepts electrons), and iron is the reducing agent (it loses electrons). Traces of precious metals such as gold may be left in the original solution.

  2. Investigating the effect of four antibiotic agents on gram positive and gram negative bacteria.

    Pestle and mortar This is the best piece of equipment to use besides a garlic crusher to squeeze enough juice out of the garlic to cover the small discs of filter paper. Scalpel This is metal so it can be flamed before and after using it to cut the fresh

  1. The comparison of bacterial content in a range of milks.

    Most of the kinds of bacteria commonly found in milk and others cause it to curdle. However clean the cows and the dairy are kept it is not possible to exclude all bacteria from the milk. Some come from within the mammary glands or udder of the cow.

  2. Investigation - Examination of bacterial sensitivity on antibiotics.

    The amount of bacteria that I inoculated in my method was 1ml as opposed to the 0.5ml I used in my planning I made this change because0.5ml is too little to have enough bacteria growth on the agar. (ii) I incubated the sealed dish for one week ( 7days), instead

  1. An Investigation into the water quality of the River Banwell in

    In the above diagram it shows inorganic phosphates being leached from the mountain. Plants then absorb these phosphate compounds. Animals gain their phosphorus by consuming plants or trophic levels that feed on the plants. Inorganic phosphate is lost through excretion.

  2. Mining for Gold and Copper using Biohydrometallurgy.

    + 2LH(organic) -> CuL2(organic) + 2H+(aq) The ligand donates electrons to the copper, producing a complex - a central metal atom (copper) bonded to 2 molecules of the ligand. Because this complex has no charge, it is no longer attracted to polar water molecules and dissolves in the kerosene, which is then easily separated from the solution.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work