• 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

Kayleigh Innes Open Book Paper - Bacterial Leaching. Water running out of copper mines contains dissolved copper ions that have been leached from copper minerals by bacteria. Some mines make use of bacterial leaching as a means of extracting copper from low-grade ore and tailings from conventional mining. The bacteria thiobacillus ferro-oxidants and thiobacillus thio-oxidants get the energy they need to survive by oxidising Fe2+ ions and S2- ions. The S2- ions are present in insoluble copper minerals, zinc and lead. The action of the bacteria releases the metal ions into solution where they can be extracted. When this process is applied to industry, the low-grade ore, and tailings are piled up on an impermeable base layer, and sprayed with an acidic leaching solution containing thiobacillus ferro-oxidants and thiobacillus thio-oxidants. The bacteria do not need any organic materials to feed off, just Fe2+ ions, S2- ions carbon dioxide, and oxygen. ...read more.

Middle

The following reaction occurs: Cu2+(aq)+2LH(organic) = CuL2(organic)+2H+(aq) (L= Ligand.) This removes the copper ions from the water and places them in a solution where they are in higher concentration. The copper ions are removed from the solution through an 'electro-winning' process, in which an electric current is passed through the solution, and the metal collects at the negative electrode. The metal can then be removed in sheets. A similar process can be used for mining gold. Extracting gold from the ground is difficult. Up to 30% of the world's gold occurs as refractory minerals - microscopic particles of gold trapped within other minerals. Treating the refractory sulphides with the bacterium 'sulpholobus acidocalderius'. The bacteria catalyse the oxidation of the sulphide minerals encasing the gold. The extract is then cyanised, and the gold recovery can be up to 100%. ...read more.

Conclusion

This produces a sulphide concentrate, which is then roasted to liberate the gold. The resulting mixture is then treated with aerated sodium cyanide to extract the gold. This final process is called cyanidation. The traditional method of extracting gold used a lot of energy, and produces a lot of pollution in the form of sulphur dioxide and arsenic (III) oxide, which causes environmental damage. Roasting the gold does not always liberate all the metal, so it yields only a fraction of contained gold. Bacterial leaching yields at least 92% of the contained gold, is much cheaper, and produces no gasses. Bacterial leaching is usually used for secondary extraction of copper because the traditional methods produce the copper faster, and produce a higher yield than bacterial leaching, which is more useful for extracting the remaining copper from the tailings and low-grade ore. It is, however, more suitable for the primary extraction of gold, as it produces a much higher yield of gold than traditional methods, and causes little pollution. ...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

    How ever I do dissolve in a mixture of hydrochloric acid and concentrated nitric acid in a 3:1 ratio. Oh, one more thing about my self... I do not like visiting my friend oxygen a lot but however I do sometimes form oxides indirectly.

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

    present in 100 grams of Spinach. Although this is not the expected answer of 4 mg's, it is closer to the expected result than Experiment A. This could be due to the smaller volume of spinach extract solution that I used in Experiment B's titrations.

  1. 'Bacterial leaching.'

    to a high concentration (in the organic solvent). Adding concentrated acid reverses the reaction, allowing the copper ions to go back into an aqueous solution. Then the copper is passed through an 'Electro-winning' process in which an electric current runs through the solution of copper ions, and as copper ions

  2. Water Pollution & Sewage Disposal

    Its brown coloration obscures the sky with a yellow haze that lowers the visibility. This drives away tourists from coming. Ozone layer in the stratosphere filters out 99% of dangerous ultraviolet radiation from the sun.

  1. Extraction of copper from its ore by using bacterial leaching

    kerosene), but it must be immiscible with water. Picture of kerosene structure: After shaking this solution with the water containing the copper ions, these are removed from there where they are in low concentration ( in water) and transferred to the organic solvent ( high concentration). Equation: (some words to the reaction!)

  2. Chemistry Open Book Paper - Extracting Copper From Its Ore.

    This has the effect of sending the lighter particles to float to the top. The lighter particles are the gold containing particles. This concentrate can be separated from the remaining mixture, as the concentrate will float. The water can now be removed and recycled.

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