Bioleaching is the extraction of specific metals from their ores through the use of bacteria. Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms positive ions (cations) and has metallic bonds. ... Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ...

Bioleaching is a technique used by the mining industry to extract minerals such as gold and copper from their ores. Traditional extractions involve many expensive steps such as roasting and smelting, which require sufficient concentrations of elements in ores. Low concentrations are not a problem for bacteria because they simply ignore the waste which surrounds the metals, attaining extraction yields of over 90% in some cases. These microorganisms actually gain energy by breaking down minerals into their constituent elements. The company simply collects the ions out of the solution after the bacteria have finished. This article is about mineral extraction. ... Minerals are natural compounds formed through geological processes. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Atomic mass 63. ... Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ... Roasting is cooking with dry heat, whether an open flame, oven, or other heat source. ... Electric phosphate smelting furnace in a TVA chemical plant (1942) Chemical reduction, or smelting, is a form of extractive metallurgy. ... The periodic table of the chemical elements (this version outdated on October 13, 2006) A chemical element, or element for short, is a pure substance that cannot be decomposed into any simpler substance. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... A cluster of Escherichia colibacteria magnified 10,000 times. ... Multivalent redirects here. ... Dissolving table salt in water This article is about a chemical solution; for other uses of the term solution, see solution (disambiguation). ...

Some advantages associated with bioleaching are:

• economical: bioleaching is generally simpler and therefore cheaper to operate and maintain than traditional processes, since fewer specialists are needed to operate complex chemical plants.

• environmental: The process is more environmentally friendly than traditional extraction methods. For the company this can translate into profit, since the necessary limiting of sulfur dioxide emissions during smelting is expensive. Less landscape damage occurs, since the bacteria involved grow naturally, and the mine and surrounding area can be left relatively untouched. As the bacteria breed in the conditions of the mine, they are easily cultivated and recycled.

Some disadvantages associated with bioleaching are: Profit, from Latin meaning to make progress, is defined in two different ways. ... For the Italian comics character with this name, see Lo Sconosciuto Most general, a specialist is a person which are able to solve some predefined class of problems. ... A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... A factory worker in 1940s Fort Worth, Texas. ... Pollution is the release of environmental contaminants. ... The phrase environmentally friendly is used to refer to goods or services considered to inflict little harm on the environment. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Before flue gas desulfurization was installed, the emissions from this power plant in New Mexico contained excessive amounts of sulfur dioxide. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Biological reproduction is the biological process by which new individual organisms are produced. ... The international recycling symbol. ...

• economical: the bacterial leaching process is very slow compared to smelting. This brings in less profit as well as introducing a significant delay in cash flow for new plants.

• environmental: Toxic chemicals are sometimes produced in the process. Sulfuric acid and H⁺ ions which have been formed can leak into the ground and surface water turning it acidic, causing environmental damage. Heavy ions such as iron, zinc, and arsenic leak during acid mine drainage. When the pH of this solution rises, as a result of dilution by fresh water, these ions precipitate, forming "Yellow Boy" pollution. For these reasons, a setup of bioleaching must be carefully planned, since the process can lead to a biosafety failure.

Currently it is more economical to smelt copper ore rather than to use bioleaching, since the concentration of copper in its ore is generally quite high. The profit obtained from the speed and yield of smelting justifies its cost. However, the concentration of gold in its ore is generally very low. The lower cost of bacterial leaching in this case outweighs the time it takes to extract the metal. In finance, cash flow refers to the amounts of cash being received and spent by a business during a defined period of time, sometimes tied to a specific project. ... // Toxic and Intoxicated redirect here – toxic has other uses, which can be found at Toxicity (disambiguation); for the state of being intoxicated by alcohol see Drunkenness. ... Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of geologic formations. ... Heavy-ion refers to ion of atom which is usually heavier than carbon. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... General Name, Symbol, Number arsenic, As, 33 Chemical series metalloids Group, Period, Block 15, 4, p Appearance metallic gray Atomic mass 74. ... Acid mine drainage (AMD), or acid rock drainage (ARD), refers to the outflow of acidic water from (usually) abandoned metal mines or coal mines. ... The correct title of this article is . ... In chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. ... Acid mine drainage (AMD), or acid rock drainage (ARD), refers to the outflow of acidic water from (usually) abandoned metal mines or coal mines. ... Biosafety: prevention of large-scale loss of biological integrity, focusing both on ecology and human health. ...

The process

The extraction of gold from its ore can involve numerous ferrous and sulfur oxidizing bacteria, including Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans (formerly known as Thiobacillus). In stage 1, bacteria catalyse the breakdown of the mineral arsenopyrite (FeAsS) by oxidising the sulfur and metal (in this case arsenic ions) to higher oxidation states whilst reducing dioxygen by H₂ and Fe³⁺. This allows the soluble products to dissolve. Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Species Acidithiobacillus albertensis Acidithiobacillus caldus Acidithiobacillus cuprithermicus Acidithiobacillus ferrooxidans Acidithiobacillus thiooxidans Acidithiobacillus is a genus of proteobacteria. ... It has been suggested that this article or section be merged into Catalysis. ... Arsenopyrite is an iron arsenic sulfide (FeAsS). ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Atomic mass 32. ... General Name, Symbol, Number arsenic, As, 33 Chemical series metalloids Group, Period, Block 15, 4, p Appearance metallic gray Atomic mass 74. ... Semi-accurate illustration of a redox reaction Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... It has been suggested that this article or section be merged with Solution. ... Solvation is the attraction and association of molecules of a solvent with molecules or ions of a solute. ...

FeAsS_(s) -> Fe²⁺_(aq) + As³⁺_(aq) + S⁶⁺_(aq)

This process actually occurs at the cell membrane of the bacteria. The electrons pass into the cells and are used in biochemical processes to produce energy for the bacteria to reduce oxygen molecules to water. Illustration of a cell membrane The cell membrane, also called the plasma membrane or plasmalemma, is a semipermeable lipid layer surrounding the cytoplasm of all living cells. ... e- redirects here. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ... Biochemistry is the chemistry of life. ... Impact of a drop of water. ...

In stage 2, bacteria oxidise Fe²⁺ to Fe³⁺ (whilst reducing O₂).

Fe²⁺ -> Fe³⁺

They then oxidise the metal to a higher positive oxidation state. With the electrons gained, they reduce Fe³⁺ to Fe²⁺ to continue the cycle.

M³⁺ -> M⁵⁺

The gold is now separated from the ore and in solution. General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ...

The process for copper is very similar. The mineral chalcopyrite (CuFeS₂) follows the two stages of being dissolved and then further oxidised, with Cu²⁺ ions being left. General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Atomic mass 63. ... Chalcopyrite (sometimes called peacock pyrite) is a copper iron sulfide mineral that crystallizes in the tetragonal system. ...

Extraction from mixture

Copper (Cu²⁺) ions are removed from the solution by ligand exchange solvent extraction which leaves other ions in the solution. The copper is removed by bonding to a ligand, which is a large molecule consisting of a number of smaller groups each possessing a lone pair. The ligand is dissolved in an organic solvent such as kerosene and shaken with the solution producing this reaction: In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a... In organic chemistry, functional groups are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... Benzene is the simplest of the arenes, a family of organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon and hydrogen; therefore, carbides, carbonates, carbon oxides and elementary carbon are not organic (see below for more on the definition controversy... It has been suggested that RP-1 be merged into this article or section. ...

Cu²⁺_(aq) + 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. Because the initial reaction is reversible, it is determined by pH. Adding concentrated acid reverses the equation, and the copper ions go back into an aqueous solution. Synthesis of copper(II)-tetraphenylporphine, a metal complex, from tetraphenylporphine and copper(II) acetate monohydrate. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms positive ions (cations) and has metallic bonds. ... Atomic redirects here. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... A commonly-used example of a polar compound is water (H2O). ... A chemical reaction occurs when vapours of hydrogen chloride in a beaker and ammonia in a test tube meet to form a cloud of a new substance, ammonium chloride A chemical reaction is a process that results in the interconversion of chemical substances [1]. The substance or substances initially involved... A reversible reaction is a chemical reaction that may proceed in both the forward and reverse directions. ...

Then the copper is passed through an electro-winning process to increase its purity: an electric current is passed through the resulting solution of copper ions. Because copper ions have a 2+ charge, they are attracted to the negative cathodes and collect there. In electricity, current refers to electric current, which is the flow of electric charge. ... Diagram of a copper cathode in a Daniells cell. ...

The copper can also be concentrated and separated by displacing the copper with Fe from scrap iron: A single-displacement reaction is when one element appears to move out of one compound and into another. ...

Cu²⁺_(aq) + 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. Treating the mixture with sodium cyanide in the presence of free oxygen dissolves the gold. The gold is removed from the solution by adsorbing (taking it up on the surface) to charcoal. Sodium cyanide is a highly toxic chemical compound, also known as sodium salt of hydrocyanic acid and cyanogran. ... Adsorption is a process that occurs when a gas or liquid or solute (called adsorbate) accumulates on the surface of a solid or more rarely a liquid (adsorbent), forming a molecular or atomic film (adsorbate). ... Charcoal is the blackish residue consisting of impure carbon obtained by removing water and other volatile constituents from animal and vegetation substances. ...

Bioleaching with fungi

Several species of fungi can be used for bioleaching. Fungi can be grown on many different strata, as with electronic scrap, catalytic converters, and fly ash from municipal waste incineration. Experiments have shown that two fungal strains (Aspergillus Niger, Penicillium simplicissimum) were able to mobilize Cu and Sn by 65%, and Al, Ni, Pb, and Zn by more than 95%. Abandoned monitor Electronic waste or e-waste is any broken or unwanted electrical or electronic appliance. ... Catalytic converter on a Saab 9-5. ... Fly ash (also known as a coal combustion product, or CCP) is the finely divided mineral residue resulting from the combustion of powdered coal in electric generating plants. ... This article or section is in need of attention from an expert on the subject. ... In the scientific method, an experiment (Latin: ex-+-periri, of (or from) trying), is a set of actions and observations, performed in the context of solving a particular problem or question, to support or falsify a hypothesis or research concerning phenomena. ... In biology, Strain can be used two ways. ...

 Aspergillus Niger can produce some organic acids such as citric acid. So it can be used for bioleaching sulfides . 

Further reading

• BHP Billiton - [1]
• Bactech - [2]
• T. A. Fowler and F. K. Crundwell - 'Leaching of zinc sulfide with Thiobacillus ferrooxidans'
• BioHeap
• Brandl H. (2001) Microbial leaching of metals. In: Rehm H.J. (ed.) Biotechnology, Vol. 10. Wiley-VCH, Weinheim, pp. 191-224