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

'Bacterial leaching.'

Extracts from this document...

Introduction

Copper and gold can successfully be extracted from their ores by the process of 'bacterial leaching.' It allows heavy metals to be extracted from low-grade ores and leftover tailings. The addition of bacteria such as Thiobacillus thio-oxidans and Thiobacillus thioferro-oxidans, oxidise Fe2+ ions and S2- ions, these metal ions are released into a solution where the metallic elements can be extracted. Copper is produced firstly by making a heap of the low-grade copper and leftover tailings from previous mining, onto an area of ground that is impermeable, allowing the copper ion solution to be drained away further on in the process. Acidic-leaching solution is then sprayed over the heap, the leaching solution containing the bacteria Thiobacillus thio-oxidans and Thiobacillus thioferro-oxidans of which thrive in acidic conditions. They therefore require a supply of Fe2+ ions or S2- ions, oxygen, carbon dioxide and bacterial nutrients. By obtaining the energy needed to survive, the bacteria oxidise Fe2+ and S2- ions. As a result the bacteria convert the insoluble mineral into a solution containing copper. ...read more.

Middle

Any unwanted gaungue falls to the bottom of the concentrator and is removed. 397 words The slurry then passes through a pre-leach thickened to remove some of the water, the thickened slurry moves into the leaching circuit. The slurry contains the gold particles encapsulated inside a matrix of minerals, therefore to extract the gold, the minerals need to be oxidised and made in-soluble so that the minerals can be dissolved in water leaving behind the gold. Having been thickened the concentrate is then treated with the necessary bacteria, catalysing oxidation, increasing the amount of gold recovery. Below is an example of the oxidation of Arsenopyrite, with the addition of the bacterium Sulpholobus acidocalderius: The first reaction of the oxidation occurs at the cell membrane of the bacteria, to form soluble compounds of iron(II), arsenic(III) and sulphur(VI): FeAsS Fe(II) + As(III) +S(VI) Stage two involves the iron and arsenic to be oxidised separately, sulphur is already oxidised: Fe(II) Fe(III) and As(III) As(V) The overall reaction is: 2FeAsS(s) ...read more.

Conclusion

Traditional methods also allow for a lot more copper to be obtained from the ore. Therefore, conventional methods have proved more cost effective suggesting why it is the primary process. However, for gold, bacterial leaching has concluded a success. Due to the fast development in research and technology, a 90% increase in gold recovery is apparent with the addition of bacteria. More gold means more money, which is evidently why it is the preferred process. There is more money to be made from the base metals alone, such as; nickel, cobalt and zinc, of which not less than 89% is recovered. Finally the low running costs of the plants have differentiated the process of bacterial leaching from traditional methods, as it costs as little as $30 to produce a tonne of concentrate. For a new mining process such as bacterial leaching to be approved before operating commercially, it must prove to be worthwhile and cost effective. Environmental factors must also be taken into account to make sure the process is not damaging. Location is important for transport of materials, but also to avoid noise pollution. The process will also need to be approved by the government before any further developments can be made. ...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 Aqueous Chemistry 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 Aqueous Chemistry essays

  1. Autobiography of Gold

    Now a little bit of more about my family background. We have been known since prehistoric times when we were used as a coins exchanged for trading. We are a fairly weak group of people with a solidity of only 2.5 on moh's scale.

  2. How much Iron (II) in 100 grams of Spinach Oleracea?

    M AS 6.7 Colour CD A2 6.9 Chemistry of Colour CD A2 9.1 Oxidation and Reduction M AS 9.2 Electrode Potentials SS A2 11.6 d-block Complexes SS A2 Risk Assessments Substance Sulphuric Acid Hazard Reacts violently with water and many metals.

  1. Investigating Membrane Permeability.

    This writing from www.coursework.info Test tubes 6,7,8: Looking at the results of these test tubes, it is clear that the permeability of the cell membrane decreases as the temperature increases. This is because of the nature of the cell membrane and its protein pores.

  2. Water Pollution & Sewage Disposal

    damage of trees at high elevations (for example, red spruce trees above 2,000 feet) and many sensitive forest soils. In addition, acid rain accelerates the decay of building materials and paints, including irreplaceable buildings, statues, and sculptures that are part of our nation's cultural heritage.

  1. Bacterial Leaching.

    A ligand is a compound with a lone pair of electrons that binds to metal ions. The central metal ion is surrounded by a number of ligands. A compound that is a suitable ligand for copper ions is dissolved in an organic solvent that will is immiscible with water.

  2. Mining With Microbes

    The overall result is that the bacteria convert the insoluble sulphide minerals into a solution containing Cu2+, Fe2+ Fe3+ & and SO42- ions. Because the piles sit on an impermeable base layer, it is easy to drain off the solution carrying the copper ions.

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