The document provides an overview of bioleaching, the process of extracting metals from ore using microorganisms, detailing its history, methods, and the various microorganisms involved. It outlines the bioleaching process, including inputs, commercial techniques like slope, heap, and in-situ leaching, as well as the extraction processes for metals like copper and uranium. While bioleaching is environmentally friendly and suitable for low-grade ores, it has disadvantages such as being time-consuming and having inconsistent yields.

1. VIVEKANANDHA ARTS AND SCIENCE COLLEGE FOR WOMEN
VEERACHIPALAYAM, SANKAGIRI, SALEM, TAMILNADU.
DEPARTMENT OF MICROBIOLOGY
SUBJECT: MARINE MICROBIOLOGY
TOPIC : BIOLEACHING
SUBJECT INCHARGE:
Dr.R.Dineshkumar,
Assistant professor,
Department of Microbiology,
Vivekanandha Arts and Science
College For women ,
Sankagiri,Salem, Tamilnadu.
SUBMITTED BY:
M.Bowsiya,
II-M.Sc., Microbiology,
Vivekanandha Arts and Science
College for women,
Sankagiri, Salem, Tamilnadu.

2. Index
*Introduction
*Microorganisms Involved in bio leaching
*Bioleaching process
*Factors & parameters Influencing Bioleaching
*Benefits of Bio leaching
*Advantages of Bio leaching
*Disadvantages of Bio leaching

3. Introduction
Bioleaching:
. Bioleaching is the process by which metals are dissolved from ore
bearing rocks using microorganisms.
• Bioleaching is also called microbial leaching.
Microorganisms
Ore ----------------------------> pure metal

4. “Bioleaching” or “bio-oxidation” employs the use of naturally occurring bacteria,
harmless to both humans and the environment, to extract of metals from their ores.
• Conversion of insoluble metal sulfides into water-soluble metal sulfates.
• It is mainly used to recover certain metals from sulfide ores. This is much cleaner than
the traditional leaching.
• Started around the late 1940s in South Africa. Since then it has become a worldwide
phenomena.
• Bioleaching is used to recover copper, zinc, lead, arsenic, antimony, uranium, nickel,
molybdenum, gold, silver and cobalt.

5. Microorganisms Involved in Bioleaching.
The most commonly used microorganisms in bioleaching are:
• Thiobacillus thiooxidans
• Thiobacillus ferrooxidans
Other microorganism:
• Sulfolobus – Ca, As
• Saccharomyces cerevisiae – Cu, Pb, Sn
• Penicillium simplicissium - Cr

7. Bio leaching process
1. The Inputs of Bioleaching:
• Metal ore or concentrate to provide energy for microbes.
• Proper air is supplied based on whether they are aerobic or anaerobic.
• CO , because bioleaching microbes need the macro-nutrient C; N, P,
₂ Ka,
Mg nutrients needed for bioleaching microbes.
• pH control is needed, optimum: 2.3-2.5.
• Bioleaching microbes cultivation for inoculation.
• Temperature control mechanisms, optimum: 30°C-50°C.
• Distribution system, stirring, sprinklers, airflow, tubes allowing for the circulation of microbes.
• Reaction catalysts if needed.

11. Types of Bioleaching
There are three commercial process used in bioleaching:
• Slope leaching
• Heap leaching
• In situ leaching
Fig.: Commercial bioleaching processes-
A)Slope leaching,
B) Heap leaching ,
C) In-situ leaching.

13. Slope leaching
* Here the ores are first ground to get fine pieces and then dumped into large
leaching dump.
*Water containing inoculum of thiobacillus is continuously sprinkled over the ore.
*Water is collected from the bottom and used to extract metals and generate
bacteria in an oxidation pond.

14. Heap leaching
• Here the ore is dumped into large heaps called leach heaps.
• Water containing inoculum of thiobacillus is continuously sprinkled over the ore.
• Water is collected from the bottom and used to extract metal and generate bacteria
in an oxidation pond.

15. • In this process the ore remains in its original position in the earth.
• Surface blasting of earth is done to increase the permeability of water.
• Water containing thiobacillus is pumped through drilled passage the ores.
• Acidic water seeps through the rock and collects at the bottom.
• Again, water is pumped from bottom.
• Mineral is extracted and water is reused after generation of bacteria.
In- situ leaching

17. Copper leaching
• Ores of copper from which copper is recovered are:
• Chalcocite (Cu2S)
• Chalcopyrite (CuFeS2)
• Covellite (CuS)
• Copper leaching is operated as simple heap leaching and in situ leaching process.
• Dilute sulphuric acid is percolated down through the pile.
• Liquid coming out of bottom of pile reach in mineral.
• Liquid is collected and transported to precipitation plant.
• Metal is precipitated and purified.

18. • Chalcocite is oxidized to soluble form of copper
Cu 2S + O2 CuS + Cu2+ + H 2O
→
• Thereafter chemical reactions occur, i.e.
CuS + 8Fe3+ + 4H2O Cu + 8Fe + SO4 + 8H
→
• Copper is removed.
Fe + Cu2+ Cu + Fe2+
→
• Fe2+
is transferred to oxidation pond
Fe + ¼O2 + H+ Fe3+ + 1/2H2O
→
Reactions :

19. • Fe3+
ions produced by the oxidation of ore.
• It is pumped back to pile.
• Sulphuric acid is added to maintain pH.
15
Fig.: Copper recovery process using bio-
mining technology

21. Uranium leaching
• Uranium is extracted when insoluble tetravalent uranium is oxidized with a hot
H2SO4/FeSO4
solution to make hexavalent uranium sulphate.
• pH required for the reaction is 1.5-3.5
• Temperature: around 35 degree C
• Following reaction take place in the process
U2O + Fe2
(SO4)3 UO2SO4 + 2FeSO4
→

22. Uranium leaching is an indirect process.
• When T.ferroxidans are involved in uranium extraction, they do not directly attack
on ore but on the iron oxidants.
• The pyrite reaction is used for the initial production of Fe
Reactions:
2FeS + H2O + 7½(O2) Fe2
→
(SO4)3 + H2SO4

23. • Microbial leaching of refractory process metal ores to enhance gold and silver
recovery is one of the promising applications.
• Gold is obtained through bioleaching of arsenopyrite/ pyrite.
• Silver is also obtained by bioleaching of arsenopyrite but it is more readily
solubilized than gold during microbial leaching of iron sulphide.
Gold and Silver leaching

25. • Simple process.
• Inexpensive technique.
• No poisonous sulfur dioxide emission as in smelter.
• No need of high pressure and temperature.
• Ideal for low grade sulphide ores.
• Environment friendly process.
Benefits of Bio leaching

26. Advantages of Bio leaching
• Bioleaching is simpler, cheaper to operate and maintain.
• The process is more environmentally friendly than traditional extraction methods.
• Bioleaching if used for all processing could drastically reduce the amount of
greenhouse gases in our atmosphere.
• Bioleaching can be used extract metals from ores that are too poor for other
technologies.

27. Disadvantages of Bio leaching
• Time consuming (takes 6-24 months or longer).
• Have a very low yield of minerals.
• Requires a large open area for treatment
• May have no process control.
• High risk of contamination.
• Inconsistent yield because bacteria can not grow uniformly.