Bioleaching/Biocorrosion
Metals/Biomining
Presented to: Dr. Michael Broaders
Presented by: Ms. Lisa Smith
Ms. Marian Cummins
Ms. Deborah Mc Auliffe
Presented on: 16th December 2005
1
Table of Contents
1. Introduction………………………………………………………………………3
2. Biocorrosion………………………………………………………………...........6
3. Biooxidation…...………………………………………………………………....7
4. Bioleaching…...……………………………………………………………..……8
4.1 History of Bioleaching………………………………………………………..8
4.2 Why Bioleaching has Bioleaching become such an attractive alternative?.....10
4.3 General Properties of the
Microorganisms…………………………………...11
4.4 Specific Microorganisms…………………………………………………….11
4.5 Bioleaching Processes……………………………………………………….12
4.6 The Process…………………………………………………………………..13
4.7 Methods to increase biomining efficiencies and the impacts of Genetic
Engineering on Biomining…………………………………………………..16
4.8 Metal extraction operations………………………………………………….17
4.9 Examples of current Industrial Bioleaching Operations…………………….20
5. Case Studies……………………………………………………………………...22
6. Economics of Biomining………………………………………………………...30
7. Remediation of Metal-Contaminated Soil………………………………………33
8. Conclusion…………………………………………………………………….…35
References…………………………………………………………………….....37
Glossary…………………………………………………………………………40
2
1. Introduction
By Lisa Smith
Metal contamination of soil environments and the assessment of its potential risk to
terrestrial and aquatic environments and human health is one of the most challenging
tasks confronting scientists today.
While not all metals in soil, plant systems are inherently toxic, particularly in low
concentrations, there is an increasing incidence of metal pollution from aerial fallout,
spills, wastes and agricultural amendments including sewage sludge. Metal solubility and
availability in soil is influenced by fundamental chemical reactions between metal
constituents and soil components.
Heavy metal contamination of soil is a common problem encountered at many hazardous
waste sites. Lead ,chromium, cadmium, copper, zinc, and mercury are among the most
frequently observed metal contaminants. They are present at elevated concentrations at
many National Priorty List sites, are toxic to people, and threaten ground water supplies.
Gortmore, west of Silvermines in Co. Tipperary is an instance of how mining can affect a
community and the surroundings environment. In January 1999 the Environmental
Protection Agency (EPA) reported that a large tailings pond at Gortmore was “a
perpetual risk to human health and the (local) environment”. Firstly, it was an artificial
lake almost 150 acres covering nine million tonnes of tailings or ore waste (including
lead) piped into it from a nearby zinc mine. Once operations ceased after 25 years the
lake dried out and was covered to prevent any further dust blow and to control the escape
of possible contaminants. But local people could see could see discharges flowing into
the waterway. The area was officially termed a “tailings management facility”, few
agreed. Cattle died from lead poisoning, there is no significant evidence of transfer of
lead to humans, lead poisoning is not widespread and food production is generally safe in
the area. Nevertheless further evidence suggests the Gortmore tailings management
facility is not the only toxic site in the area. Urgent action was needed to resort
contaminated sites (ireland.com, 2000). In August 2005 the Minster for Communications,
3
Marine and Natural Resources, Noel Dempsey announced funding by the state of €10.6
million for the remediation of toxic mining waste sites. Public consultation of proposed
remediation is to take place before the end of 2005 (ireland.com, 2005).
The sustainable development challenge facing the mineral and mining industry is to
provide the supply of minerals, metals and material required to sustain social and
economic growth without causing long term degradation of the environment.
Mining companies have become increasingly aware of the potential of microbiological
approaches for recovering base and precious metals from low-grade ores.
The mining industry uses microorganisms and their natural ability to digest, absorb and
change the quality of different chemicals and metals, to refine ores.
Biomining is the use of microorganisms to extract metals and minerals from ores in the
mining process. Ores of high quality are rapidly being depleted and biomining allows
environmentally friendly ways of extracting metals from low-grade ores.
Biomining uses naturally existing microorganisms to leach and oxidate. Biomining
includes two different processes biooxidation and bioleaching.
Biomining processes are usually done in heaps of ground ore. The low-grade ores are
ground into powder and piled in an irrigated outdoor facility. The heaps are then treated
with an acidic liquid that contains a fraction of the bacterial population required (some
naturally existing within the ore). The liquid with the metals extracted are then pumped
into another section where metal is recovered.
Bioleaching is a new technique used by the mining industry to extract minerals and
metals with the use of microorganisms. The process involves removing a soluble
substance from a solid structure by making it into a liquid form easy for extraction. In
this process low concentration of metals does not pose a problem for the bacteria as they
just ignore the waste which surrounds the metals, whereas with traditional extraction
that of roasting and smelting these processes require sufficient concentration of elements
in the ores. So bacterial leaching is a process by which the metal of interest is extracted
from the ore by bacterial action, as in the case of bacterial leaching of copper
4
Biooxidation also uses microorganisms, not to extract metals, but to make the metals
ready for extraction. Oxidation is the chemical reaction in which an element is changed
by the addition of oxygen and is mainly used for gold mining.
5
2. Biocorrosion
By Lisa Smith
Physicochemical interactions between a metallic material and its environment can lead to
corrosion.
Corrosion is a “naturally occurring process by which materials fabricated of pure metals
and/or other mixtures undergo chemical oxidation from ground state to an ionized
species” (Beech, 2003). The process proceeds through a series of oxidation (anodic) and
reduction (cathodic) reactions of chemical species in direct contact with, or in close
proximity to, the metallic surface.
In natural habitats and man-made systems, surface-associated microbial growth, i.e.
biofilms, influence the physico-chemical interactions between metals and the
environment, frequently leading to deterioration of the metal. For example in a marine
environment the presence of a biofilm can accelerate corrosion rates of carbon steel by
several orders of magnitude. However, in contrast, certain types of biofilms produce a
protective barrier effect resulting in a significant decrease in corrosion rates of metals.
Deterioration of metal under a biological influence is termed biocorrosion or
microbiologically influenced corrosion (MIC).
“Biocorrosion is a result of interactions between metal surfaces and bacterial cells and
their metabolites” (Beech, Sunner, 2004).
The main types of bacteria associated with metals in terrestrial (and aquatic)
environments are sulfate-reducing bacteria (SRB), sulfur-oxidising bacteria, ironoxidising/reducing bacteria, manganese –oxidising bacteria and bacteria secreting organic
acids and slime. These organisms coexist in naturally occurring biofilms.
SRB are the main group of microorganisms and are generally anaerobic, however some
genra tolerate oxygen and even grow in its presence. They are distributed within two
domains: Archaea and Bacteria.
There is increasing recognition that microbes such as bacteria play an even larger role in
all forms of corrosion than previously thought. It is now reported that up to 70% of all
corrosion in water systems is caused or accelerated by microbes.
6
4. Biooxidation
By Deborah Mc Auliffe
Many biotechnology-derived processes use microorganisms to help ease the usage of
harmful chemicals in various industrial processes. The mining industry uses
microorganisms and their natural ability to digest, absorb, and change the quality of
different chemicals and metals, to refine ores.
Biooxidation also uses microorganisms, not to extract metals, but to make the metals
ready for extraction. Oxidation is the chemical reaction in which an element is changed
by the addition of oxygen. Rust is an example of the oxidization of iron.
Biooxidation is mainly used in gold mining. Gold is often found in ores with gold
particles scattered throughout, called refractory ores, and the small particles of gold are
covered by insoluble minerals. These minerals make the extraction difficult. Therefore,
microorganisms that can "eat away" at the mineral coating are used to pre-treat the gold
ores before they can be extracted.
Bioleaching of copper, and biooxidation of refractory gold ores are the only wellestablished large scale processes that are commercially carried out today.
Currently, 25 percent of all copper worldwide is produced through biomining. The
process is used on a variety of other metals such as gold and uranium. Biomining is not
yet a proven or profitable technology to apply to other metals such as zinc, nickel and
cobalt.
7
4. Bioleaching
By Marian Cummins
4.1 History of Bioleaching
Although mining is one of the oldest technologies known it has succeeded in escaping the
major technological advances seen in that of agriculture and medicine. Many minerals
and metals are mined today in exactly the same manner, as they were hundreds of years
previous. The crude ores are dug from the earth, crushed and the mineral is extracted by
either by extreme heat or due to the addition of toxic chemicals. But due to the
environmentally unfriendly aspect of these mining techniques new methods, which are
kinder and more environmentally friendly, are being used which uses microorganisms,
which leach out the metals- that of Bioleaching
One of the earliest recordings of bioleaching comes from Cyprus, reported by Galen, a
naturalist and physician AD166 who reported on the in situ leaching of copper. Surface
water was allowed to flow through permeable rock and as it percolated through the rock,
the copper minerals dissolved so the result was a high concentration of copper sulphate in
solution. This solution was allowed to evaporate with the resultant crystallation of copper
sulphate. Pliny (23-79 AD) reported the similar practice of copper extraction as copper
sulphate was widely used in Spain.
Prior to electrolysis, the recovery of the copper from copper sulphate was by
cementation (precipitation). It is thought that this process was known in Pliny time but no
written records of this have survived. Its is known that the Romans used to place scrap
iron into the river and over a period of a few months the copper precipated around the
iron. The pure copper was then recovered by smelting, but what the Romans didn’t
realize was microorganisms played a major biological contribution to this process by
generating the copper in the water. The Chinese were also aware of the process
(cementation) as documented by King Lui- An (177-122 BC). The Chinese implemented
the commercial production of copper from copper sulphate when the Chiangshan
cementation plant started operation in 1096 with an annual production of 190ton
8
Cu/annum. Bioleaching and cementation were also described by Paracelsus the Great
(1493-1541). He noted the copper deposition onto iron at a spring in the Zifferbrunnen in
Hungary. Although he confused this deposition with that of transmutation, he assisted in
the use of bioleaching and by 1750 approx 200t/annum Cu were obtained in the
Zifferbrunnen area of Hungary using this process of bioleaching.
Even though these earlier bioleaching operations were difficult to document, it is
known that copper leaching was well established at the Rio Tinto mine in Spain by the
18th century. Rio Tinto literally means “coloured fiver”, a name given to the acidified
fiver that issues from the Sierra San Cristobol mountains on the fiver bed and on the
abundant microbial mats, the dense floating masses made up of different microorganisms
(reference 1). At Rio Tinto the process of heap leaching of copper sulphides was carried
out on an industrial scale in 1752. In this process the ore is heaped and crushed onto
open-air pads. The layers of ore were altered with beds of wood. Once the heap was
constructed the wood was ignited which resulted in the roasting of copper and iron
sulphides. Water was then added to the top of the heap. The addition of water caused the
copper and iron to dissolve which formed copper and iron sulphates. But due to the
significant environmental damage caused by the production of sulphuric acid in this
process, the process was stopped in 1888. This heap leaching process minus the roasting
step continued at Rio Tinto until the 1970’s.The reason for it’s success was unknown, but
it was thought to be due to “some obscure quality either of the Rio Tinto ore or the
Spanish climate’. But it is now widely accepted and known that it was in fact the
microorganism Thiobacillus ferroxidans that contributed to the success of Rio Tinto.
In the 1940’s in America, several million tons of sulphuric acid was discovered in the
Ohio River, this discharge was attributed to the weathering of subbitumous coal.
Naturally enough this pollution incident was unacceptable and it led to widespread
investigation by universities and several US government institutions, such as the US
Bureau of Mines as to the source of the pollution. The cause of the sulphuric acid was
due to the oxidation of pyrite, which is present in the subbitumuous coal, but it was also
noted that this oxidation occurred much more rapidly than could be contributed to by that
of inorganic chemistry. Also an important observation was that of the presence of sulphur
9
oxidizing bacteria. And in 1950 a couple of years after the incident a new species was
identified that of Thiobacillus ferrooxidans. This organism is able to oxidize elemental
sulphur and ferrous ions at a much higher rate than that achieved by inorganic chemistry.
It is this catalysis of the oxidation of ferrous ions that makes Thiobacillus ferrooxidans
and other iron and sulphur oxidizing microorganisms such important catalysts in the
bioleaching process.
4.2 Why has Bioleaching become such an attractive alternative?
Bioleaching is a very attractive alternative to to the conventional mining techniques and it
is very desirable in today’s world due to the continued depletion of high grade reserves
and so it allows the more economically extraction of minerals by from low grade ores, it
also arise from the resulting tendency for mining to be extended deeper underground and
also it is a much more environmental friendly alternative to that of the conventional
mining methods to which there is a growing awareness of the environmental issues
associated with the smelting of sulphide minerals and the burning of sulphur rich fossil
fuels and of course there is the enormous energy costs that is associated with the
conventional methods. Bimining also improves recovery rates, reduces capital and
operating costs.
There has being a very widespread and rapid interest in the exploitation of biomining
especially in the copper industry, due to the fact that the copper in the low grade ore is
bound up in a sulfide matrix, it can be recovered by traditional smelting only at great
cost. In addition the world is running out of smelting capacity because of the depletion of
the high-grade ores means that more ore has to be smelted to produce the same amount of
copper. Oxidising bacteria can reduce the need for these expensive smelters. Whereas a
new smelter can cost 1 billion dollars the technology required for biomining I pretty
uncomplicated.
In order to understand the process of microbial mining or biomiining a number of
considerations must be understood and answered, such as what microorganisms are
10
involved in the extraction of the metals from the rocks and where in nature do they
occur? What biochemical functions do these microorganisms perform and what do they
require in the need of nutrient and environmental conditions in order to maintain their
activity? What are the constraints of the commercial exploitation of such biological
techniques? And what impact will the new tools of genetic engineering have on the future
of biomining?
4.3 General Properties of the Microorganisms
The bacteria involved in biomining are among the most remarkable life forms known.
They are described as chemolithotrophic, which basically means rock eating, that is they
obtain their energy from the oxidation of inorganic substances. Many of them are also
autotrophic that is they utilize carbon dioxide in the atmosphere as the carbon source.
These microorganisms live in very inhospitable environments, which other microbes
would find it impossible to survive or tolerate; for example the sulphuric acid and soluble
metals concentrations are often very high. Some thermophilic microorganisms require
temperatures above 50 degree Celsius (122 degree Fahrenheit), and a few strains have
been found at temperatures close to that of the boiling point of water.
4.4 Specific Microorganisms
For many years the general impression was that Thiobacillus ferrooxidans was the only
microorganism responsible for the leaching proceeds. As previously stated this
microorganism wasn’t discovered until 1957 in the acidic water draining coal mines,
where it was then determined the relationship between the existence of this
microorganism and the dissolution of metals in copper- leaching operations. Since its
discovery in the Rio Tinto Mine in Spain a wealth of information has be collected
regarding its characteristics and also more importantly on the role it plays in bioleaching
of the metals.
T. ferrooxidans is rod shaped (usually single or in pairs), non- spore forming, gram
negative, and single pole flagellated ( HORAN, 1999;KELLY and HARRISON, 1984;
11
LEDUC and FERRONI, 1994; MURR, 1980). T. ferrooxidans is also acidophilic; it tends
to be found in hot springs, volcanic fissures and in sulfide ores deposits that have high
sulphuric acid concentrations. It is also moderately thermophilic, thriving in temperatures
between 20 and 35 degree C. It obtains its energy for growth from the oxidation of either
iron or sulphur. The iron must be in the ferrous or bivalent form (Fe2+), and it is
converted by the action of T. ferrooxidans to the ferric or trivalent form (Fe3+). The
nitrogen source utilized is that of ammonium. T. ferrooxidans obtains carbon
autotrophically from the atmosphere as carbon dioxide. Although T. ferrooxidans has
been characterized as being a strictly aerobic organism, it can also grow on elemental
sulphur or metal sulphides under anoxic conditions using ferric iron as an electron
acceptor. (Donti et al., 1997; Pronk et al., 1992). It is generally found in environment
with a Ph OF 2.0.
As important and all T. ferrooxidans is in the leaching process another important
microorganism taking part ii that of T. thioxidans, this is also a rod shaped bacteria, very
similar to T. ferrooxidans but it can’t oxidized Fe3+ it is also gram negative Its maximum
growth rate is at 35 degrees C, and it is the dominant microbe found at low Ph
environments. It has being found that mixed cultures of bacteria are responsible for the
extraction of metals from their ores such as is the case with the combined effects of T
ferrooxidans and T. thiooxidans are more effective in leaching certain ores together than
as an individual organism. Also Leptospirillium ferrooxidans and T. organaparus can
degrade pyrite (FeS2) and chalopyrite (CuFeS2), a feat, which neither species can do
alone.
4.5 Bioleaching Processes
The process of bioleaching falls under 2 methods that of direct leaching and indirect
leaching. Direct leaching is the process where the bacteria attack the minerals which are
susceptible to leaching by enzymes. By obtaining the energy from the inorganic material
the bacteria aid in the transferring of electrons from iron or sulphur to oxygen. The more
oxidized product is generally the more soluble the product. The inorganic material never
12
enter the bacterial cell, the electrons released by the oxidation reaction are transported
through the cell membrane (and in aerobic organisms) to oxygen atoms forming water.
ATP (adenosine triphosphate) is produced when the transferred electrons give up their
energy.
Indirect leaching, in cons tract does not occur by the bacteria attacking the minerals.
The bacteria produce ferric iron (Fe3+) by oxidizing soluble ferrous iron (Fe2+) which is a
powerful oxidizing agent that reacts with the other metals, and transforms them into a
soluble oxidisable form in a sulphuric acid solution. In this way the ferrous iron is
produced again and is rapidly oxidized by the bacteria thus it is a continuous cycle. This
indirect leaching is generally known as bacterial assisted leaching. T. ferrooxidans can
speed up the oxidation of iron by a factor of more than a million than without the bacteria
being present in the solution.
4.6 The Process
In the case of the extraction of copper from its ore the aforementioned bacteria
T.ferrooxidans and T. thiooxidans are involved in this process, which is a 2-stage process
that of direct and indirect as previously discussed.
In stage 1, the bacteria break down the mineral arsenopyrite (FeAsS) by oxidizing the
sulphur ant the metal (arsenic ions) to a higher oxidation state whilst reducing dioxygen
by H2 and Fe3+ This allows the soluble products to dissolve as such
FeAsS(s) -> Fe2+(aq) + As3+(aq) + S6+(aq)
This process of direct leaching as described previously 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.
In stage 2, that of indirect leaching the bacteria oxidise Fe2+ to Fe3+ (whilst reducing
O2).
13
Fe2+ -> Fe3+
They then oxidise the metal to a higher positive oxidation state. With the electrons gained
from that, they reduce Fe3+ to Fe2+ to continue the cycle. This stage involves both ditect
and indirect leaching.
M3+ -> M5+
The gold is now separated from the ore and in solution.
The process for copper is very similar. The mineral chalcopyrite (CuFeS 2) follows the
two stages of being dissolved and then further oxidised, with Cu2+ ions being left.
In the process of extracting copper (Cu2+) from a mixture, the copper ions are removed by
solvent extraction, which leaves the other ions in solution. The copper is removed by
bonding to a ligand, which is essentially a large molecule consisting of a number of
smaller groups each processing a lone pair. The ligand is then dissolved in kerosene
(organic solvent) and shaken with the resultant reaction:
Cu2+(aq) + 2LH(organic) -> CuL2(organic) + 2H+(aq)
Electrons are donated to the copper, producing a complex, copper bonded to 2 molecules
of the ligand. As this complex has no charge as as it is no longer attracted to the polar
water molecules it dissolves in the kerosene and is then seperated from solution.This
initail reaction is reversible as so is pH dependent. The copper ions go back into an
aqueoeus solution by adding concentrated acid.
To increase the purity of the copper an electric current is added to the copper ions as it
passes through an electro-winning process. The copper ions which have a 2+ charge are
attracted to the negative electrode and thus collected.
The copper can also be concentarted and recovered by using scrap iron which replaces
the copper in the reaction as thus:
14
Cu2+(aq) + Fe(s) -> Cu(s) + Fe2+(aq)
As described biomining has being extremely successful in the case of copper.But gold
can also be obtained in a similar manner. Up until recently the gold mining industry
depended on high grade ores near the surface og the earth.But by the 1980 and the
depletion of these ores forced miners to rely on the lower grade ores which were located
deeper in the mines. These low grade ores were more difficult to process in comparsion
to the high grade ores at the surface as they were naturally oxidized by bacteria, sunlight
and water. But the low grade ores are generally encased in sulphide minerals a and so
processing of these ores requires roasting or pressure oxidation and then treatment with
cyanide.Biomining means that the costly procedures of roasting and pressure oxidation
can be surpasssed by usinf T. ferrooxidans for the pretreatment of the gold ores. The first
mine to take advantage of this was Fairview mine in South Africa (owned by Gencor
(Pty) Ltd. )where most of the ore was the refractory sulphide type. By using biomining at
Fairview the recovery rate of the gold increased from 70 % to 95%.And due to this
success rate Gencor opened 4 more biomining sites, Harbour Lights, Tonkin Springs,
Wiluna and Younmi in Australia, San Bento in South America and the huge Ashanti
plant in Ghana which started in 1994 and by 1998 it was producing 800t/ day of gold
concentrate.
Although gold and copper are probably the most important and valuable metals and
undoubtedly this is what has pushed the huge interest there now is in biomining. But
biomining has also played a big part in the phosphates industry. Phosphates are definitely
not as valuable as the metals but their extraction is definitely plays a part in big time
mining. Phosphates for fertilisers is the world’s second largest agricultural chemical
(after nitrogen); about 5 .5 million tons are produced every year in the US alone. Another
1.1 million tons of higher quality phosphates are used as an additive in soft drinks and in
the manufacture of detergents, rubber, and industrial chemicals.
The traditional method of extracting phosphates from ores was by burning at high
temperatures with the resultant of solid phosphorus, or else by treatment with sulphuric
15
acid with phosphoric acid and huge amounts of useless low-grade gypsum being the
result. But with the process of biomining a much milder technique was available. This
new technique used two bacteria that of Pseudomonas cepacia E-37 and Erwinia
herbicola, these bacteria were chosen from hundreds of bacteria as they have the unusual
ability: a direct oxidative pathway of converting glucose into gluconic and 2 ketogluconic
acids, which means that sulfuric acid doesn’t have to be used in the process and also this
milder technique it performed at room temperature and so it is a much more
environmentally friendly process.
4.7 Methods to increase biomining efficiencies and the impacts of Genetic
Engineering on Biomining
As biomining is now at an all time high it the next challenge is to increase its efficiency.
At the present time it is only indigenous microorganisms that naturally occur in dumps or
mine run off that are used in the bioleaching process. So now the focus is on finding
microbial strains that are better suited to large scale industrial processing. One draw back
is that the bioleaching process releases large amounts of heat and
Can raise the temperature so much that the bacteria that are being in use are killed or
slowed down. To combat this work has being and is still currently being done on using
Archaebacteria for use in biomining. These primitive thermophiles, or heat loving
bacteria are so far poorly studied and they are found in deep-sea vents and in hot springs
such as in Yellowstone National Park, Iceland and in New Zealand. They thrive in
temperatures of up to 100 C or higher. They are currently being put to test at the
Younami mine in Western Australia.
Another challenge is to find or engineer strains that can stand up to the presence of heavy
metals such as mercury, arsenic, cadmium, these metals poison the microbes currently
being used in biomining and thus slow down biomining. Some steps have being taken
toward finding resistant strains to these poisons by showing that some microbes have
enzymes that can work in 2 ways that of protecting their basic activities from heavy
metals or by pumping the metals out of the bacteria. Also some work but not a lot has
16
being done on identifying genes that help the microbes deal with the heavy metals and
these genes may be used to genetically engineer resistant strains. The genetically
engineering of bacteria to resist heavy metal poisoning is not an easy achievement.
As much less is known about the Thiobacillus species and the other microbes used in
biomining than is known for E. coli, which is of course a lab favourite? But hopefully this
genetically engineering of these microorganisms will take place at a much quicker pace
than the two millennia is took the Roman miners at Rio Tinto to become a major
improvement in biomining, but it is fairly safe to say that these developments will take
place sooner rather than later as biomining has become a worldwide accepted process
4.8 Metal extraction operations
Insitu leaching is a promising alternative for the recovery of metals from low-grade ores,
which are in inaccessible places. Also this has the advantages as this technology has
minimal impact on the environment and it is currently used to extract residual minerals
from abandoned mines. The way this is performed is the leaching solution is applied
directly to the walls and the roof of the intact stope (an underground excavation from
which the ore has being removed) or else to the rubble of the fractured workings. Insitu
leaching has been successful to the recovery of copper and uranium,
Dump leaching is also a method employed for the extraction of metals but as in the case
for copper it is not a very fast or efficient process. The dumps often contain boulders and
large rocks which have a very low surface- to – volume ratio for the action of bacteria.
Also the interior of a large dump is low in oxygen, which is a requirement for the
oxidation of iron and sulphur compounds, and the temperature can also rise to over 50
degree C. because the oxidation process are exothermic. Also there is a significant
channeling of the acidified water as it percolates through the rocks, so the copper
solubiislation is restricted to only a minor portion of the dump. Despite these
disadvantages dump leaching is a low cost and a low-tech method or recovery.
17
Heap leaching is the most popular metal extraction method used, in particular used for
copper. In this method the ore is heaped onto open air leach pads with a base of asphalt or
impervious plastic sheeting. The heaps are no more than a few meters high by a few
meters wide so as to allow the oxygen to diffuse to all parts of the heap and reduce the
build- up of heat from the leaching process. The heaps are sprayed with sulphuric acid
(for copper extraction) and with cyanide (for gold extraction) which contain a fraction of
the bacterial population, the rest being attached to the mineral, in a controlled manner and
the run off is collected on the plastic shheting.When the desired metal concentration is
obtained, the rich liquor is pumped to the solvent extraction section and then sent to the
electro winning, where the fine metal is recovered or where the purity can also be
increased as described earlier in the bioleaching process. The finely ground copper
concentrate provides a large surface to volume ratio and so promote bioleaching.
Nutrients such as phosphates can be added to promote growth if necessary. Heap leaching
is a more environmentally friendly option and is also more economic and it is especially
attractive for mines in remote areas or for small operations where only a small body of
ore is to be extracted. Although heap operation is simple and adequate to handle large
volumes of minerals, but their productivity and yields are limited due to the severe
difficult in maintaining an adequate process control.
Heap and dump leaching present a number of advantages such as simple operation,
low investment and operation costs and acceptable yields. On the other hand the
processes suffer from some serious limitations such as the piled material is very
heterogeneous and practically no close process control can be exerted, except for
intermittent pH adjustment and the addition of some nutrients. The rates of oxygen and
carbon dioxide transfer that can be obtained are low, and extended periods of operation
are required in order to achieve sufficient conversions (Acevedo and Gentina, 1989).
Heap leaching can also be used for the recovery of gold. Most of the world’s gold
reserves contain the metal bound up in the small particles in the rocks. After grinding up
the rocks the gold is then recovered by gravity separation or by treatment with cyanide.
But more often theses techniques are proving to be ineffective in the recovery of the gold.
For example if the gold is found associated with pyrite, usually arsenopyrite, it can’t be
18
recovered by gravity, while the cyanide reacts with the pyrite before it can complex with
the gold, making the process too expensive and environmentally hazardous due to the
large releases of cyanide. The gold in this case can be recovered by oxidizing the pyrite at
high pressure in an autoclave or by roasting, followed by recovery with cyanide. Both
techniques are very expensive and also pose a serious environmental risk as the liberated
gases contain arsenic.
Sometimes the gold can also be found as fine particles in carbonaceous sulphide
ores. By grinding the gold is liberating but it has a tendency to stick to the carbonaceous
compounds making it difficult to recover by conventional techniques.
It was discovered that microorganisms could oxidize the gold bearing pyrite and
arsenopyrite ores and also the carbonaceous ones. Also this process of using
microorganism’s means that the cyanide quantities needed is sufficiently reduced.
Commercial bacterial oxidation of refractory gold ores (those that were difficult to
recover by conventional methods) was first used at Gencor’s Fairview plant in South
Africa in 1986 (as previously mentioned). At that time the process used at Fairview was
that of oxidizing the gold by roasting, but wanted to expand its capacity by using the
bioleaching process and if improved successful to replace the traditional method with that
of bioleaching. By 1997 it was producing 40t/day of gold and the roasters had been
removed.
The technology used at Fairview is very different to that have the dump and heap
bioleaching processes used for copper. The finely ground gold arsenopyrite concentrate is
suspended and stirred in large tanks or bioreactors. Missing bacterial nutrients are added
and the pH is adjusted to 2. Oxygen is supplied and after about 5 days about 1/5 of the
arsenopyrite has been oxidized by the microorganisms and thus recovering up to 90% of
the gold. As previously stated the Fairview mine in South Africa was the first mine to
take advantage of the bioleaching process with recovery rates increasing from 70% to
95% and due to this success rate other mines followed suit.
Bioreactors also have their own drawbacks associated with their operation. The
choice of material for their construction is important and also the costs involved at
maintaining them at their correct temperature. The temperature inside the reactors can
rise rapidly to 50 degree C or higher, whereas the microorganisms predominantly prefer
19
temperatures of 20-40 degree C, so the reactors have d to be cooled to keep the
microorganisms alive. Although some plants are currently using extremely thermophilic
microorganisms which can grow at higher temperatures as is the case with the Youanmi
plant in Australia. This plant operates at 50 degree C. In all cases the bioreactors operate
at a pH of about 2 as previously stated and so associated with this is the problem of acid
corrosion.Severeal plants initially built rubber- lined metal bioreactors where this wasn’t
a problem but the more favored choice is that of stainless steel.
4.9 Examples of current Industrial Bioleaching Operations
■ Acid Mine Drainage
■ Rio Tinto, Spain
■ Dump Leaching
■ Bagdad, USA
■ Pinto Valley, USA
■ Sierrita, USA
■ Morenci, USA
■Heap Leaching
■ Cerro Colorado, Chile
■ Cananea, Mexico
■
Chuquicamata SBL, Chile
■ Collahuasi, Chile
■
Giilambone, Australia
■
Ivan Zar Chile
■ Morenci, USA
■ Punta del Cobre, Chile
■ Bioleaching of Gold Concentrates
■Ashanti, Ghana
■ Fairview, Zambia
■ Harbour Lights, Australia
20
■ Mount Leyshon, Australia
■ Sao Bento, Brazil
■ Wiluna, Australia
■ Youanmi, Australia
21
5. Case Studies
By Deborah Mc Auliffe
Microbes 'to tackle mine waste'
Toxic waste sign
Pollution left at industrial sites is an ongoing issue
Scientists are using microbes to clean up the problem of corrosive acid pollution left over
as mining waste.
Microbes are micro-organisms, especially bacteria which cause disease or fermentation.
Dr Barrie Johnson, from the University of Wales, Bangor, is leading research into their
use for cleaning up mine effluents.
Some of the microbes being used were found in the Caribbean and America.
Dr Johnson outlined his work at a conference of the Society for General Microbiology at
Heriot-Watt University, Edinburgh on Wednesday.
Microbes which break down minerals are already being used by miners to extract gold,
copper and other metals from their ores.
The challenge has been to find the strains which can be used to carry out this work
Bill Keevil, University of Southampton
By discovering microbes which can survive in this environment, Dr Johnson aims to
build on these developments to address serious environmental hazards at abandoned
mines and spoil heaps.
22
"We work with the mining industry to get metals from ores in more environmentallyfriendly ways," he said.
"We tend to work with micro-organisms which can clean up liquid wastes in mines,
which tend to be acidic."
Some of the microbes discovered have come from sites in Wales, America and the
Caribbean island of Montserrat. "We are using organisms that no-one has seen or worked
with before."
He said their techniques were different from others, because their microbes could
produce metals ready to be recycled, rather than metal-rich sludges, which he described
as "effectively toxic waste".
"Our ongoing research is focussing on extending the applications of biomining
technology, and on using newly-discovered extremophile bacteria to simultaneously
recover metals and clean up mine effluents from abandoned mines, streams that pass
through them and their waste tips," he said.
'Ideal'
Bill Keevil, professor of Environmental Healthcare at the University of Southampton,
said the potential for microbes to be used in this way had been known for some time.
"The challenge has been to find the strains which can be used to carry out this work," he
said.
He said the need was to find microbes which could survive at very high or very low pH
values (which express its acidity or alkalinity), and often high temperatures as well.
23
"The ideal would be a thermo tolerant bug that can survive at a low pH - you can then put
it in mine workings where it doesn't mind being...and clean up as they go." (Ref: 1)
Iniciativa Genoma Chile
The "Iniciativa Genoma Chile" (Chilean Genoma Initiative) was created in order to
integrate the country widely and systematically in the worldwide development of
genomics, proteomics and bioinformatics. It is focused on relevant areas of the national
economy, thus helping to trigger new developments and set up some efficient and
effective strategies for identifying and resolving problems as well as for keeping and
improving competitivity.
This initiative is part of the Chilean government's Program of Development and
Technological Innovation (2001-2004). Through three sub-programs : Information
Technology, Biotechnology in forestry, agriculture and aquaculture, and clean
technologies. It is partly financed by the IADB, and directed by a comitee whose
members are representatives of: the Ministery of Economy, Corfo (FDI), the Ministery of
Agriculture and CONICYT who manages the program.
The Iniciativa Genoma Chile was born in 2001 to improve and increase human and
scientific capabilities already existing in the national system of science. The orientation is
towards the improvement of competitivity in relevant areas of the chilean economy such
as the ones whose production can gain value through state-of-the-art technologies.
The scientific relevance and the formation of scientists.
This program is relevant since it will allow us to enter the top scientific achievements and
then apply these innovations in the mid term, finally creating economic rewards. The
program first considers agriculture and biomining, since they are key areas of the national
economy.
The program is considering, in these two areas already mentioned, the formation and
specialization of young scientists who are members of the projects who belongs to the
program. It will train in the use of scientific strategies and techniques which were not
available before in our country.
24
The offer
The Genoma Initiative will finance public contests and research projects through its two
main programs : Biomining and Renewable natural ressources.
a. Genoma program in renewable natural ressources
The goal is to get solutions to social and economical problems in the forestry area,
agriculture, aquaculture and the other ones related to natural ressources.
The first call for proposals in vegetal health and post-harvest was closed on May 2002.
This joint project, has as one of its goals not only to generate new links between
institutions and companies but also to integrate scientists, entrepreneurs and technologists
through its development.
The winning initiatives of the First Convocatory were granted with M US$3.5, and they
form the first Chilean network of Vegetal Genomics working on functional genomics of
nectarines and studying the viral infection and development of diagnostics systems, as
well as post-harvesting problems in grapes.
The total budget for this first call for proposals reach M US$ 6.3 adding the institutional
and private contributions. The projects were selected according to their impact, the
economical benefits and the potential improvement of the international positionning of
the products thanks to the developments financed by the initiative.
The Network in vegetal Genomics is promoting collaborative work at two different
levels. The first one at the management of the Genome Program in Renewable Natural
Resources through its board conformed bymembers of the Ministry of Economy, the
Agrarian Innovation Funds (Ministry of Agriculture), CORFO and CONICY.The second
level is conformed for the three groups of scientists participating in the network.
With this effort, this national initiative takes shape putting together the most important
national academic institutions and scientists in the country aiming to develop projects
which will study relevant problems on nectarines and grapes, which are of social and
economical importance to Chile.
25
Approved projects
Scientific Director: Dr. Ariel Orellana Lpez
Title: Functional Genomics in nectarines : platform to strenghten Chilean competitivity in
fruit exportation.
Main institution: Universidad de Chile.
Asociated institutions: INIA, Fundacin Chile, Asociacin de Exportadores de Chile,
Fundacin para el desarrollo Frutcola.
** Total budget: M$ 1.227.905
Scientific Director: Dr. Hugo Pea Corts
Title: Scientific and technological platform for the development of the Vegetal Genomics
in Chile. 1st stage : Functionnal genomics in grapevine.
Main institution: Universidad Tcnica Federico Santa Mara.
Asociated Institutions: Universidades: de Chile, Santiago y de Talca, INIA, Asociacin de
Exportadores de Chile, Fundacin para el Desarrollo Frutcola, Fundacin Chile. .
** Total budget: M$1.751.796
Scientific Director: Dr. Patricio Arce Johnson
Title : Genomic studies and genetic expression in grapes : answer to viral infection and
development of diagnostic systems.
Main Institution: Pontificia Universidad Catlica de Chile.
Asociated Institutions: Universidad de Chile, Fundacin de Ciencia para la Vida, BiosChile Ingeniera Gentica S.A.
** Total Budget: M$ 1.096.396
**Including Institutional and Private Funds.
Institutional Elegibility .
To the funds of the Program can apply Chilean citizens, among others, public or private
universities, technological companies with profit aims, technological institutes,
26
foundations, corporations and others, that fulfill the requirements. These institutions can
apply associated or forming a legal partnership with Chilean citizens as well as associated
to foreign citizens or institutions.
b . Biomining program
The Biomining Program of the Genoma Initiative started in 2001, in order to improve the
bacterial lixiviation process and the development of new mining technologies thanks to
genomics, bioinformatics and proteomics.
The chilean government (Ministery of Economy, CORFO and CONICYT) and
CODELCO (National Corporation of Copper) agreed on the constitution of a consortium
made by investors such as mining and technological companies who bring ressources and
themes of research and development.
BioSigma SA is a consortium formed by CODELCO-Chile and Nippon Mining & Metal
Co. Ltda in July 2002. With a first capital of 3 M US$, it will be focused on technological
development in biomining. CODELCO holds 66.6% of the capital, while the Japanese
firm holds 33.3%. Besides its own capital, the firm will manage M US$ 2 from the R&D
oriented funds from CORFO and CONICYT. In the R&D activities of BioSigma
international research centres, companies and university laboratorieswill be participating.
The goal is to develop biotechnologies for mining using genomics, proteomics and
bioinformatics. By working with national and international scientists, the improvement of
the competitivity in the national mining ressources and the opening of new opportunities
for industrial development will be achieved. The products will range from the
improvement of processes such as bacterial lixiviation to genes technology, in order to
get microorganisms to be used in the present and future natural ressources. They will be
especially focused on the comercial application and the environmental sustainability.
This program finance its projects through a public call for proposals. Due to the
importance for the national economy and the degree of knowledge existing in our country
in this area, we chose to improve the processes of bacterial lixiviation of minerals, thanks
to new technologies using bioinformatics and genomics.
Necessary conditions for applying :
For applicants with Chilean legal personality
27

Institutional capability for R&D.

Institutional capability for project management.
For applicants with Foreign legal personality

Institutional capability for R&D.

Institutional capability for project management.
It is compulsory to involve a Chilean entity or to be settle in Chile.
Groups of people can apply, if they engage themselves in forming an enterprise once they
are selected.
For groups of people which are applying, they must have:

Team capability for R&D.

Team capability for project management. (Ref. 5)
Biomining: There's Gold In Them Thar Plants
April 19, 2005 09:37 AM Gold rush miners might have been better off using plants to find gold rather than panning
streams for the precious metal. Early prospectors in Europe used certain weeds as
indicator plants that signaled the presence of metal ore. These weeds are the only plants
that can thrive on soils with a high content of heavy metals. One such plant is alpine
pennycress, Thlaspi caerulescens, a wild perennial herb found on zinc- and nickel-rich
soils in many countries. This plant occurs in alpine areas of Central Europe as well as in
the Rocky Mountains. Most varieties grow only 8 to 12 inches high and have small, white
flowers.
Biomining is the use of plants to mine valuable heavy metal minerals from contaminated
or mineralized soils. In fact, 25% of all copper is mined this way, amounting to $1 billion
in revenue annually. This ranks it as one of the most important applications of
biotechnology today. Bioprocessing is also being used to economically extract gold from
very low grade, sulfidic gold ores, once thought to be worthless.
To increase the efficiency of biomining, the search is on for bacterial strains that are
better suited to large-scale operations. Bioprocessing releases a great deal of heat, and
this can slow down or kill the bacteria currently being used. Researchers are turning to
28
heat-loving thermophilic bacteria found in hot springs and around oceanic vents to solve
this problem. These bacteria thrive in temperatures up to 100 degrees Celsius or higher
and could function in a high temperature oxidative environment.
More about biomining from the Canadian government.
[by Justin Thomas] (Ref. 6)
29
6. Economics of Biomining
By Deborah Mc Auliffe
Biomining is a form of mining (mineral processing) that utilises microorganisms to
degrade metal sulfides for the enhanced recovery of metals with economic value.
Biomining has developed into one of the most successful and important areas of
biotechnology; the estimated 1999 global value of the process was about $10 billion.
There are many advantages to using bioleaching for the extraction of metals in terms of
cost-efficiency, simplicity, robustness, high performance and environmentally friendly
alternative to conventional mineral processing methods.
1) Bioleaching of pyrite by defined mixed cultures of moderately thermophilic
acidophiles
Leaching of pyrite (FeS2) concentrate and ground rock pyrite has been investigated using
defined pure cultures and consortia of four moderately thermophilic bacteria: (i) a
thermotolerant Leptospirillum isolate (strain MT6); (ii) Acidithiobacillus caldus (strain
KU); (iii) a novel Gram-positive bacterium `Caldibacillus ferrivorus' (strain GSM); (iv) a
Sulfobacillus isolate (strain NC). Parameters measured included total iron released from
pyrite, Fe2+ and Fe3+ concentrations, dissolved organic carbon , pH, Eh and numbers of
different bacterial species. Pure cultures of both strain MT6 andstrain KU did not
accelerate the pyrite concentrate dissolution, while both strain GSM and strain NC were
able to do so, albeit at relatively slow rates and at low redox potentials. The most
effective dissolution of pyrite was observed in mixed cultures that included strain MT6,
all of which maintained high redox potentials. The data indicate that strain MT6 was the
most significant in the consortia and that At. caldus, although active in generating acidity
and numerically the dominant acidophile present in mixed cultures, contributed nothing
either directly or indirectly to pyrite oxidation.
30
2) Exploitation of important iron-metabolising microorganisms and development of
RFLP method for their differentiation
Research on the biooxidation of sulfide minerals has tended to be heavily biased towards
Gram-negative bacteria, such as Leptospirillum ferrooxidans and Acidithiobacillus
ferrooxidans. However, the research team at the UWB has been finding significant
biodiversity which has potential important role in biomining. We have isolated and
characterised a number of phylogenetically distinct Gram-positive iron-metabolising
bacteria, some of which are novel genus. Also, we have isolated gram-negative bacteria,
such as L. ferrooxidnas and At. ferrooxidans, which, in contrast to other recognised
species, have unique characteristics. Development of a rapid, simple and convenient
method to differentiate such microbes would have significant importance in the quick
examination of biodiversity in industrial samples. To this end, a RFLP (Restriction
Fragment Length Polymorphism) protocol is being currently developed.
European Topic Centre on Terrestrial Environment
Topic Centre of European Environment Agency
Local soil contamination
Contaminated sites are the legacy of a long period of industrialisation involving
unconsidered production and handling of hazardous substances and unregulated dumping
of wastes. The expansion of industry and subsequent increase in the amounts of industrial
wastes have led to considerable environmental problems in all industrialised countries.
Additionally, mining activities and former military sites, the latter resulting mainly from
the former Soviet army presence in Central and Eastern European countries, are giving
rise to severe contamination problems.
seriously considerably endanger human health and the environment. Pollution of drinking
water, uptake of pollutants in plants, exposure to contaminated soil due to direct contact,
inhalation and ingestion are major threats. Provision of public and private money for
remediation, as well as restrictions onn land use and the use of groundwater and surface
water for waste-related activities, are particularly important responses.
The foundation for dealing with local soil contamination was laid by the former European
Topic Centre on Soil (ETC/S), which began its work in 1996. ETC/Soil addressed this
31
issue by developing a relevant network and initiating a data collection process.
Development of policy relevant indicators has been of major interest for the EEA within
the Topic Centre. The Centres first steps were to provide a basis for future work by
reviewing land management practices and the state-of-play in various countries. The
problems which have to be dealt with were discovered to be the following:
different definitions of "contaminated site"
So far, three indicators for soil contamination have been developed and published in
several reports:
-up contaminated sites
in the management of contaminates sites
The main objective within the European Topic Centre on Terrestrial Environment is to
contribute to the further development of policy-relevant indicators on local soil
contamination, the collection and assessment of data related to those indicators that have
been developed, and the provision of aggregated data in published reports, proceedings
and electronic form. The Centre seeks to ensure the close involvement of EEA country
representatives, for example,in the form of workshops with a strong focus on the
integration of new member States. Work on local soil contamination is also intended to
develop into close consideration of EU regulations (recent and future policy aspects, link
with reporting obligations, ...). (Ref: 3)
32
7. Remediation of Metal-Contaminated Sites
By Lisa Smith
It is now widely recognised that contaminated soil is a potential treat to human health,
and its continual discovery over recent years as led to international efforts to remedy
many of these sites, either as a response to the risk of adverse health effects of
environmental effects caused by contamination or to enable a site to be redeveloped for
use.
Soil Flushing; Soil flushing is a developing insitu technology where a solution is injected
in the ground in order to move contaminants to an area where they may be extracted from
the ground and treated.
Soil Washing; Soil washing is an exsitu remediation process where the contaminated soil
is excavated and washed with water to remove contaminants. Additives may be added to
the water to enhance removal and the soil may have to go through several remediation
cycles to remove the contaminants.
Stabilization/Solidification; Can be an insitu or exsitu remediation technique using
cement, concrete, chemical fixation to stabilize or physically bind contaminants. The
solid mass limits the solubility of mobility of the contaminants but does not destroy them.
Bioremediation is an option that offers the possibility to destroy or render harmless
various contaminants using natural biological activity.
Phytostabilization; Phytostabilization is the immobilisation of a contaminant in soil
through absorption and accumulation by roots, adsorption onto roots, of precipitation
within the root zone of plants and the use of plants to prevent contaminant migration via
wind and water erosion, leaching and soil dispersion.
33
Phytostabilization occurs through contaminants accumulation in plant tissue and in the
soil around the roots, changes in chemistry of the contaminant cause it become insoluble
and/or immobile in the soil (i.e. less toxic). After investigating the contaminant chemistry
in soil, soil is farmed, fertilisers or other products might be used to improve soil
conditions for plant growth, to reduce chemical mobility and plant toxicity of the
contaminant. Plant species are selected based on local conditions, native flora, soil
composition and the plants tolerance to the contaminants in question. Irrigation is
provided if necessary, as well as supplement fertilisation and/or soil amendment.
Plants immobilise metals and radionuclide in the soil minimising their mobility in water
or wind. Success achieved when a stable vegetation cover develops and contaminants and
portions of metals decrease to non-toxic or background levels.
Phytoremediation; Phytoremediation is an emerging bioremediation technology that uses
plants to remove contaminants from soil. “Phytoremediation is cost-effective “green”
technology whereby plants vacuum heavy metals from the soil through their roots”
(www.agclassroom.org). Certain plant species known as metal hyperaccumulators, have
the ability to extract elements from the soil and concentrate them in their stems, shoots
and leaves. The plants possess genes that regulate the amount of metals taken up from the
soil by the roots, the metals enter the plant’s vascular system and are transported to other
parts of the plant finally deposited in the leaf cells. The metals are removed from soil by
harvesting the plant’s shoot and extracting the metal preventing soil recontamination.
The plant Thlaspi caerulescens, commonly known as alpine pennycress, is a member of
the broccoli and cabbage family and thrives on soils having high levels of zinc and
cadmium.
34
8. Conclusion
Traditional extraction caused environmental hazards and degradation, biomining offers
many advantages including;
 It is carried out insitu,
 Less energy output,
 No toxic or noxious gases produced, SO2 is produced from traditional mining
methods,
 No noise or dust problems,
 Process is self generating,
 Can be carried out in large or small scale operations,
 Can be used for a wide variety of metals, Cu, Ag, Ni, Co, Pb, Se, Au, Zn,
 Is used to remove impurities of mixtures
 Works on low grade ores
The main disadvantage of biomining is that it is a slow process.
Biomining contributes to sustainable development in the same way all microorganismmediated process do: it uses existing organisms and mechanisms in nature.
Due to the fact that the over that the overall process of biomining is a more
environmentally friendly alternative than that of conventional mining methods, it also
improves recovery rates, reduces capital and operating costs and probably one of the most
significant factors that has lead to it’s universally accepted acceptance is the fact that it
permits economical extraction of minerals from low grade ores, which are being used
more and more as highgrade ores are being depleted. Due to these advantages of
biomining it is a realistic safe bet that genetically engineering a bacterium to resist heavy
metal poisoning, which may not be an easy task, but that it will occur sooner rather than
later and it is for definite that it will not take the two millennia that it took for the curious
35
phenomenon noticed by the Roman miners at Rio Tinto to become a major improvement
in copper mining.
Biomining is an environmentally friendly alternative to conventional mining processes.
36
References
Acevedo, Fernando. "The use of reactors in biomining processes." Electronic Journal
of Biotechnology, Nature Biotechnology. Vol.3 No. 3, Issue of December 15, 2000.
Barrett, Jack & Hughes, Martin. A Golden Opportunity - Chemistry in Britain, June
1997
Beech, B. Iwona. (2003). Sulfate-reducing bacteria in biofilms on metallic materials
and corrosion, Microbiology Today, 30, 115-117.
Beech, B. Iwona, Sunner, Jan. (2004). Biocorrosion: towards understanding
interactions between biofilms and metals. Current opinion in Biotechnology, 15, 181186.
Biomining. Access Excellence at the National Health Museum.
www.accessexcellence.org/AB/BA/biomining.html
Biotechnology Applications in the Mining Industry: Bioleaching. NRCan
Biotechnology, Factsheets. www.nrcan.gc.ca/cfs/bio/fact2.shtml
Biotechnology in gold extraction. The Hindu.
www.hinuonnet.com/thehindu...02/21/stories/20020221000060300.htm
Brock - Biology of Micro-organisms
Canada's Biotechnology Regulations: Who's mining the store? NRCan
Biotechnology, Factsheets. www.nrcan.gc.ca/cfs/bio/fact9.shtml
Environment Consultation Document. CBS Online. www.strategis.gc.ca/cgibin/...%20(product%20contains%20)%20 5 June 2002. (Ref: 2)
37
Harrison, R. - Nuffield Advanced Science Book of Data
Hill, G.C. & Holman, J.S. - Chemistry in Context, Pages 316-317
http://www.agclassroom.org/teen/ars_pdf/9earth/2000/06phytoremedation.pdf
http://www.biobasics.gc.ca
http://www.copper.org/innovations/2004/May
http://www.ejbiotehnology.info
http://en.wikipedia.org/wiki/Bioleaching
http://www.evvirotools.org/factsheet/remeditech.shtml
http://www.ireland.com/newspaper/ireland/2000/0628/archive.00062800012.html
http://
www.ireland.com/newspaper/ireland/2005/1116/3458522606HM2TIPPERARY.html
http://www._mining-technology.com
http://www.pamp.com
http://www.spaceship-earth.org/REM/BRIERLEY.htm
http://web.tiscali.it/biomining/history.htm
Marx, Jean L. A Revolution in Biotechnology, Pages 83-92
38
Metals and minerals. The Biotechnology Gateway. www.strategis.gc.ca/bio
Minerals & Metallurgical Processing - Biotechnology Special Issue,
Commercialisation of Bioleaching for Base-Metal Extraction
Minerals and Metals Sector. NRCan Biotechnology, FAQ.
www.nrcan.gc.ca/cfs/bio/faq3.shtml
Sector Overviews: Mining and Energy. CBS Online.
www.strategis.ic.gc.ca/ssg/bh00175e.html 11 June 2002
Shriver & Atkins - Inorganic Chemistry
Taylor, Jane. Micro-organisms and Biotechnology, Pages 113-115
Winter, Mark. - d-Block Chemistry
39
Glossary
By Deborah Mc Auliffe
* Acidophilic autotrophs - Organisms that are able to live solely on sulphides and in acid
conditions
* Biohydrometallurgy, biomining, bioleaching - A method of mining and extracting
metals from ores by using micro-organisms
* Centrifugal extractor - A method of solvent extraction that uses the principle of
centrifugal forces
* Electrowinning - The final method of extracting the metal, by using an
electrochemical cell
* Extract - The organic liquid that holds the useful product after solvent extraction
* Leaching solution - A solution that is used for solubilisation and removal of metals
from an ore by microbes attack
* Ligand exchange solvent extraction - A method of extracting a mtal from a solution
by using ligands
* Raffinate - The aqueous solution that is taken off after solvent extraction
* Thiobacillus ferroxidans - Micro-organisms that they can get all their energy from
oxidising Fe2+ to Fe3+ and are able to live solely on sulphides and in acid conditions
40