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

Describe the processes used to extract copper and gold from their ores using bacterial leaching - In each case, explain how the micro-organisms liberate the metal from its ores and describe how the metal is then extracted from the mixture.

Extracts from this document...

Introduction

Q1:- Describe the processes used to extract copper and gold from their ores using bacterial leaching. In each case, explain how the micro-organisms liberate the metal from its ores and describe how the metal is then extracted from the mixture. Bacterial Leaching of ores and other Materials Bacterial leaching is a process in which bacteria is used to extract heavy metals from low grade ores and tailings (left from an earlier traditional mining). In mining industry, bioleaching is a new technique used to extract minerals such copper and Gold from their low grade ores. The main agents used in bioleaching process are micro organisms such as Chemolithoautotrophs; they capture carbon for the synthesis of cellular components not from organic nutrients but from carbon dioxide (CO2) in the atmosphere. These bacteria are Thiobacillus Ferrooxidans and Thiobacillus Thiooxidans. Thiobacilli grow in acidic environment because they are acidophilic (acid loving). They drive energy by the oxidation of the Ferrous iron and Sulphur part of the mineral for their survival. They grow at PH value from 1 to 4 and strictly under aerobic conditions. Bacterial Leaching has been divided into two mechanisms:- * Direct Mechanism: - Direct mechanism is that in which bacteria is physically attached to the mineral surface. In this reaction, the electron passes into the bacterial cell which produces ATP (Adenotriphosphate), is the energy currency of the cell which reduces oxygen molecules to water. ...read more.

Middle

Thiooxidans S2O3-2(aq) + 2OH-(aq) 2S2O3-2(aq) not stable in alkaline solution S4O6-2(aq) +2e- S4O6-2(aq) + 2H+ (g) Thiooxidans H2S4O6 (400 words) Oxidation of Arsenic metal (III) to arsenic metal (V). Arsenic metal (V) is present in complex forms. As+3(aq) Fe+3 / FeS2 As+5 (aq) Thiobacillus bacteria The overall reaction for Arsenopyrite is:- 2FeAsS (s) + 7O2 (g) + 4H+ (g) + H2O (aq) 2Fe+3 (aq) +2HSO-4(aq) +2H3AsO4 (aq) Now, the Gold metal is left in the original solution which can be obtained by treating the solution with sodium cyanide (NaCN). Cynidation process increases the gold recovery from 10% to 100%. Extraction from Mixture:- Pure solid Gold metal can be extracted by Cynidation reaction in the presence of free oxygen. Au (aq) + 2NaCN (aq) + 1/4O2 + 1/2 O2 (g) Na [Au (CN) 2] (aq) + NaOH- (s) 2Na [Au (CN) 2] (aq) +Zn(s) 2NaCN (aq) + Zn (CN) 2 + Au (s) Extraction of copper Copper can be extracted from their low grade ores like chalcopyrite (CuFeS2), Pyrite (FeS2), Covellite and others. It is similar to the extraction process of gold. The process Stage 1:- The acid leaching solution (contains H2SO4, Thiobacillus thiooxidans and thioferrooxidans) is sprayed on mineral chalcopyrite (CuFeS2) which is then oxidised into copper (II) ions, ferrous ions (Fe+2), ferric ions (Fe+3), sulphate (II). ...read more.

Conclusion

Bioleaching is a slow process as it takes decades rather than years to extract metals but as traditional method is expensive but it is faster. As facts had revealed that bacterial leaching is the cause of acid mine drainage. Secondary extraction process for copper but as a primary extraction process for Gold:- (800 words) Bacterial leaching is considered as secondary process for copper for the fact that it is not able to perform on a large scale and copper is present in large amounts in their ores. It is also an extremely slow process and uneconomic. For gold however it proved to be cost effective as it recovered almost all the gold. Q3:-Summarise the development stages that a new mining process (such as bacterial leaching) must pass through before it can operate commercially? * It must be safe not damaging the environment. * Able to meet the demand of the trade market. * The process should be cost effective to produce the metal. * Funding should be provided by government and political powers to regulate a new process. * Tests should be carried out in labs to make sure the process works well. * The location used for bacterial leaching should be suitable to the favourable conditions of the process, * A large scale plant should be built for industrial use. (950 words) Summary:- Basically microbiological research focuses on the biochemistry, physiology and genetics of the involved micro-organisms and on the complex interrelationship in the community of the leaching species. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Microbiology 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 University Degree Microbiology essays

  1. Free essay

    Identifying microorganisms using differential staining techniques

    This stain removes the crystal violet colour from the gram negative cells turning them clear and traps the crystal violet colour in the gram positive cells (Kelleher, 2004). Finally, a stain known as safranin is used to stain the walls of the cell.

  2. Introduction to Spectrophotometric Analysis - By using spectrophotometric analysis or spectrophotometry, one can determine ...

    to excite its electron to a more stable state (Olson, 1976). Where else, oxyhaemoglobin has an oxygen atom attached to the haemoglobin and is already quite stable and is low in affinity, thus absorbing less energy (Olson, 1976). Furthermore, the different wavelength values is due to the colour of the

  1. The aim of this investigation is to make a series of dilutions using the ...

    sample. Dilution 200�l (Reverse Pipetting): Standard Deviation: Neat (undiluted) 0.075 1:2 0.131 1:5 0.015 1:10 0.004 1:20 0.007 1:100 0.003 Table 9 Discussion: Explanation of the Raw Data and Results: Table 2 shows that the neat (undiluted) dilution had the highest mean; also it was the highest for the 100�l reverse pipetting, 200�l sample and the 200�l reverse pipetting.

  2. Distinguishing Species of Bacteria

    (Davidson, 2010) Another endoenzyme is oxidase. In the oxidase test, a drop of tetramethyl-p-phenylenediamine reagent is placed on a piece of filter paper. Using a toothpick rub a small amount of bacterial growth from a culture plate into the drop and observe for the development of a purple colour.

  1. This review looks at how silicification of bacteria allows preservation of the bacteria through ...

    there is no direct proof of the bacteria role in silica biomineralization. Studying the bacterial metabolism however, did create evident chemical / physical changes at the cell surface. Some of the changes include excretion of complexing ligand by-products, [24] ultra-structural growths of different mineral reactivity, [25] and changes in H- in the cell interfacial region.

  2. Write an essay in up to 2000 words on the following topics, describing the ...

    The problem we face with these infections is to keep the premises clean and free from germs which lead to the infections. Patients who have a long stay at the hospital tend to be victims to these infections as they are around them more often.

  1. Nucleic acid hybridization

    Helix destabilising agents 1. Formamide reduces the Tm of poly (dA:dT) by 0.75�C per 1% (v/v) formamide of poly (dG:dC) by 0.5�C per 1% (v/v) formamide. 2. For random DNA sequences is approximately 0.6�C per 1% formamide. 3. Effects on Tm of RNA-RNA or RNA-DNA duplexes are less clear and may vary considerably between different sequences.

  2. The biology of Fusarium oxysporum f. sp. gladioli, causal agent of corm rot of ...

    availability ( Woltz and Jones 1981).Fusarium oxysporum is an autotroph, requiring only a carbon source for structure and energy, and inorganic compounds to synthesized organic compounds such as sugars, lipids and amino acids ( Woltz and Jones 1981). Increasing nitrogen levels in the soil generally lead to an increase in Fusarium wilt development (Woltz and Jones 1973)

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