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| '''Bioleaching''' is the extraction of [[metal]]s from their [[ore]]s through the use of [[living organism]]s. This is much cleaner than the traditional [[heap leaching]] using cyanide.<ref>{{cite web|url=http://ngm.nationalgeographic.com/2009/01/gold/larmer-text/5 |title=Flotation technique cleaner than heap leaching |publisher=Ngm.nationalgeographic.com |date=2012-05-15 |accessdate=2012-10-04}}</ref> Bioleaching is one of several applications within [[biohydrometallurgy]] and several methods are used to recover [[copper]], [[zinc]], [[lead]], [[arsenic]], [[antimony]], [[nickel]], [[molybdenum]], [[gold]], [[silver]], and [[cobalt]].
| | Do you need to lower the BMI (Body Mass Index)? Do we want to become slimmer? Do we want to have more lean muscle than fat? Follow these easy suggestions.<br><br>Tuna is the featured protein found on the 3 day Cardiac diet. 1/2 cup of tuna is prescribed found on the initial two days, and found on the final day, you'll grow which to 1 cup. Variety plus nutrition is provided with tiny to medium sized portions of cheese, eggs, crackers, greens, grapefruit, banana, and toast. Coffee, tea, or diet soda could accompany food however water ought to be the drink of choice outside of mealtime.<br><br>He really had kind 1.5 diabetes or Latent autoimmune diabetes of adults (LADA). Here is what Wikipedia states about LADA. Officially it will still be said to be kind 1 diabetes. This is a shorter article of mine, however, you can watch the 2 videos below and you are able to also purchase Dr. Cousen's book on curing diabetes.<br><br>Here is a [http://safedietplans.com/bmi-calculator bmi calculator females] within the CDC (Centers for Disease Control plus Prevention). Below is a 2 part movie that follows 6 folks with diabetes which goes to Dr. Cousen's center in Arizona for 30 days. The major change the people made was to consume a raw plant-based diet.<br><br>BMI is utilized worldwide to determine if an individual is obese. Since BMI is utilized just for a screening tool, anybody that claims you are at health risk before operating any different tests is lying. Doctors can screen people for health dangers after seeing that their BMI is above normal.<br><br>Another limitation is that age is not considered when calculating BMI. So for elderly people, even if the BMI indication is usual, the truth remains that many muscles have been lost considering of age.<br><br>These formulas aren't exact, yet they provide very accurate approximations. This usually provide we the ability to measure the body fat plus have a greater idea of how healthy you are. Use this info perfectly, plus keep up the advantageous work! |
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| == Process ==
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| Bioleaching can involve numerous ferrous iron and sulfur oxidizing bacteria, including ''[[Acidithiobacillus]] ferrooxidans'' and ''Acidithiobacillus '' (formerly known as ''Thiobacillus''). As a general principle, Fe<sup>3+</sup> ions are used to oxidize the ore. This step is entirely independent of microbes. The role of the bacteria is the further oxidation of the ore, but also the regeneration of the chemical oxidant Fe<sup>3+</sup> from Fe<sup>2+</sup>. For example, bacteria [[catalyst|catalyse]] the breakdown of the mineral [[pyrite]] (FeS<sub>2</sub>) by oxidising the [[sulfur]] and metal (in this case ferrous iron, (Fe<sup>2+</sup>)) using [[oxygen]]. This yields [[soluble]] [[product (chemistry)|products]] that can be further purified and refined to yield the desired metal.
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| '''[[Pyrite]] leaching''' (FeS<sub>2</sub>): | |
| In the first step, disulfide is spontaneously oxidized to [[thiosulfate]] by ferric ion (Fe<sup>3+</sup>), which in turn is reduced to give ferrous ion (Fe<sup>2+</sup>):
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| :(1) <math>\mathrm{FeS_2 + 6 \ Fe^{\,3+} + 3 \ H_2O \longrightarrow 7 \ Fe^{\,2+} + S_2O_3^{\,2-} + 6 \ H^+}</math> spontaneous
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| The ferrous ion is then oxidized by bacteria using oxygen:
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| :(2) <math>\mathrm{4 \ Fe^{\,2+} + \ O_2 + 4 \ H^+ \longrightarrow 4 \ Fe^{\,3+} + 2 \ H_2O}</math> (iron oxidizers)
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| Thiosulfate is also oxidized by bacteria to give sulfate:
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| :(3) <math>\mathrm{S_2O_3^{\,2-} + 2 \ O_2 + H_2O \longrightarrow 2 \ SO_4^{\,2-} + 2 \ H^+}</math> (sulfur oxidizers)
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| The ferric ion produced in reaction (2) oxidized more sulfide as in reaction (1), closing the cycle and given the net reaction:
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| :(4) <math>\mathrm{2 \ FeS_2 + 7 \ O_2 + 2 \ H_2O \longrightarrow 2 \ Fe^{\,2+} + 4 \ SO_4^{\,2-} + 4 \ H^+}</math>
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| The net products of the reaction are soluble [[ferrous sulfate]] and [[sulfuric acid]].
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| The microbial oxidation process occurs at the [[cell membrane]] of the bacteria. The [[electron]]s pass into the [[cell (biology)|cell]]s and are used in [[biochemical]] processes to produce energy for the bacteria while reducing oxygen to [[water]]. The critical reaction is the oxidation of sulfide by ferric iron. The main role of the bacterial step is the regeneration of this reactant.
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| The process for copper is very similar, but the efficiency and kinetics depend on the copper mineralogy. The most efficient minerals are supergene minerals such as [[chalcocite]], Cu<sub>2</sub>S and [[covellite]], CuS. The main copper mineral [[chalcopyrite]] (CuFeS<sub>2</sub>) is not leached very efficiently, which is why the dominant copper-producing technology remains flotation, followed by smelting and refining. The leaching of CuFeS<sub>2</sub> follows the two stages of being dissolved and then further oxidised, with Cu<sup>2+</sup> ions being left in solution.
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| '''[[Chalcopyrite]] leaching''':
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| :(1) <math>\mathrm{CuFeS_2 + 4 \ Fe^{\,3+} \longrightarrow Cu^{\,2+} + 5 \ Fe^{\,2+} + 2 \ S_0}</math> spontaneous
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| :(2) <math>\mathrm{4 \ Fe^{\,2+} + O_2 + 4 \ H^+ \longrightarrow 4 \ Fe^{\,3+} + 2 \ H_2O}</math> (iron oxidizers)
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| :(3) <math>\mathrm{2 \ S^0 + 3 \ O_2 + 2 \ H_2O \longrightarrow 2 \ SO_4^{\,2-} + 4 \ H^+}</math> (sulfur oxidizers)
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| net reaction:
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| :(4) <math>\mathrm{CuFeS_2 + 4 \ O_2 \longrightarrow Cu^{\,2+} + Fe^{\,2+} + 2 \ SO_4^{\,2-}}</math>
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| In general, [[sulfide]]s are first oxidized to elemental sulfur, whereas [[disulfide]]s are oxidized to give [[thiosulfate]], and the processes above can be applied to other sulfidic ores. Bioleaching of non-sulfidic ores such as [[pitchblende]] also uses ferric iron as an oxidant (e.g., UO<sub>2</sub> + 2 Fe<sup>3+</sup> ==> UO<sub>2</sub><sup>2+</sup> + 2 Fe<sup>2+</sup>). In this case, the sole purpose of the bacterial step is the regeneration of Fe<sup>3+</sup>. Sulfidic [[iron ore]]s can be added to speed up the process and provide a source of iron. Bioleaching of non-sulfidic ores by layering of waste sulfides and elemental sulfur, colonized by ''Acidithiobacillus'' spp., has been accomplished, which provides a strategy for accelerated leaching of materials that do not contain sulfide minerals.<ref>Power, I.M., Dipple, G.M., and Southam, G. (2010) ''Bioleaching of ultramafic tailings by Acidithiobacillus spp. for CO<sub>2</sub> sequestration'', http://pubs.acs.org/doi/abs/10.1021/es900986n Environmental Science & Technology. 44: 456-462.</ref>
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| == Further processing ==
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| The dissolved copper (Cu<sup>2+</sup>) 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 [[functional group|groups]], each possessing a [[lone electron pair]]. The ligand-copper complex is extracted from the solution using an [[organic compound|organic]] solvent such as [[kerosene]]:
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| :Cu<sup>2+</sup><sub>(aq)</sub> + 2LH(organic) → CuL<sub>2</sub>(organic) + 2H<sup>+</sup><sub>(aq)</sub>
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| The ligand donates electrons to the copper, producing a [[complex (chemistry)|complex]] - a central metal [[atom]] (copper) bonded to the ligand. Because this complex has no [[electric charge|charge]], it is no longer attracted to [[polar molecule|polar]] water molecules and dissolves in the kerosene, which is then easily separated from the solution. Because the initial [[chemical reaction|reaction]] is [[reversible reaction|reversible]], it is determined by pH. Adding concentrated acid reverses the equation, and the copper ions go back into an aqueous solution.
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| Then the copper is passed through an electro-winning process to increase its purity: An electric [[Electric current|current]] is passed through the resulting solution of copper ions. Because copper ions have a 2+ charge, they are attracted to the negative [[cathode]]s and collect there.
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| The copper can also be concentrated and separated by [[single displacement reaction|displacing]] the copper with Fe from scrap iron:
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| :Cu<sup>2+</sup><sub>(aq)</sub> + Fe<sub>(s)</sub> → Cu<sub>(s)</sub> + Fe<sup>2+</sup><sub>(aq)</sub>
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| 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).
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| 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 [[adsorption|adsorbing]] (taking it up on the surface) to [[charcoal]].
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| ==Bioleaching with fungi==
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| Several species of [[fungi]] can be used for bioleaching. Fungi can be grown on many different substrates, such as [[e-waste|electronic scrap]], [[catalytic converter]]s, and [[fly ash]] from municipal waste [[incineration]]. Experiments have shown that two fungal [[strain (biology)|strains]] (''Aspergillus niger, Penicillium simplicissimum'') were able to mobilize Cu and Sn by 65%, and Al, Ni, Pb, and Zn by more than 95%.''Aspergillus niger'' can produce some organic acids such as [[citric acid]]. This form of leaching does not rely on microbial oxidation of metal but rather uses microbial metabolism as source of acids that directly dissolve the metal.
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| ==Compared with other extraction techniques==
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| Extractions involve many expensive steps such as [[Roasting (metallurgy)|roasting]] and [[smelting]], which require sufficient concentrations of [[chemical element|elements]] in ores and are environmentally unfriendly. Low concentrations are not a problem for bacteria because they simply ignore the waste that surrounds the metals, attaining extraction yields of over 90% in some cases. These [[microorganism]]s actually gain [[energy]] by breaking down minerals into their constituent elements. The company simply collects the [[ion]]s out of the [[solution]] after the bacteria have finished. There is a limited amount of ores.
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| ===Advantages of bioleaching===
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| *[[Economics|economical]]: bioleaching is in general simpler and, therefore, cheaper to operate and maintain than traditional processes, since fewer specialists are needed to operate complex [[chemical]] [[factory|plants]].
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| *[[pollution|environmental]]: The process is more environmentally friendly than traditional extraction methods.{{citation needed|date=October 2012}} For the company this can translate into profit, since the necessary limiting of [[sulfur dioxide]] [[air pollution|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 [[biological reproduction|breed]] in the conditions of the mine, they are easily cultivated and [[recycling|recycled]].
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| *ore concentration: Bioleaching can extract metals from ores that are too poor for other technologies. It can be used to partially replace the extensive crushing and grinding that translates to prohibitive cost and energy consumption in a conventional process.
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| ===Disadvantages of bioleaching===
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| *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.
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| *environmental: [[Toxicity|Toxic]] chemicals are sometimes produced in the process. [[Sulfuric acid]] and H<sup>+</sup> ions that have been formed can leak into the [[groundwater|ground]] and surface water turning it acidic, causing environmental damage. [[Heavy ion]]s such as [[iron]], zinc, and arsenic leak during [[acid mine drainage]]. When the [[pH]] of this solution rises, as a result of [[concentration|dilution]] by fresh water, these ions [[precipitation (chemistry)|precipitate]], forming [[Acid mine drainage#Yellow boy|"Yellow Boy"]] pollution. For these reasons, a setup of bioleaching must be carefully planned, since the process can lead to a [[biosafety]] failure. Unlike other methods, once started, bioheap leaching cannot be quickly stopped, because leaching would still continue with rainwater and natural bacteria.
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| At the current time, it is more economical to smelt copper ore rather than to use bioleaching, since the concentration of copper in its ore is in general quite high. The profit obtained from the speed and yield of smelting justifies its cost. Nonetheless, at the largest copper mine of the world, [[Escondida]] in [[Chile]] the process seems to be favorable. However, the concentration of gold in its ore is in general very low. The lower cost of bacterial leaching in this case outweighs the time it takes to extract the metal.
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| Economically it is also very expensive and many companies once started can not keep up with the demand and end up in debt. Projects like Finnish [[Talvivaara]] proved to be environmentally and economically disasterous
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| == See also ==
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| * [[BHP Billiton]]
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| * [[Talvivaara]]
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| * [http://www.bactechgreen.com BacTech Environmental]
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| == References ==
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| {{reflist}}
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| == Further reading ==
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| * ''T. A. Fowler and F. K. Crundwell'' - 'Leaching of zinc sulfide with Thiobacillus ferrooxidans'
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| * ''Brandl H.'' (2001) Microbial leaching of metals. In: Rehm H.J. (ed.) Biotechnology, Vol. 10. Wiley-VCH, Weinheim, pp. 191–224
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| *{{cite journal | doi = 10.1016/j.hydromet.2006.05.001 | title = The bioleaching of sulphide minerals with emphasis on copper sulphides — A review | year = 2006 | last1 = Watling | first1 = H.R. | journal = Hydrometallurgy | volume = 84 | page = 81}}
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| *{{cite journal | doi = 10.1007/s00253-003-1404-6 | title = Bioleaching review part B: | year = 2003 | last1 = Olson | first1 = G. J. | last2 = Brierley | first2 = J. A. | last3 = Brierley | first3 = C. L. | journal = Applied Microbiology and Biotechnology | volume = 63 | issue = 3 | pages = 249–57 | pmid = 14566430}}
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| *{{cite journal | doi = 10.1007/s00253-003-1448-7 | title = Bioleaching review part A: | year = 2003 | last1 = Rohwerder | first1 = T. | last2 = Gehrke | first2 = T. | last3 = Kinzler | first3 = K. | last4 = Sand | first4 = W. | journal = Applied Microbiology and Biotechnology | volume = 63 | issue = 3 | pages = 239–48 | pmid = 14566432}}
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| [[Category:Biotechnology]]
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| [[Category:Economic geology]]
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| [[Category:Metallurgical processes]]
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Do you need to lower the BMI (Body Mass Index)? Do we want to become slimmer? Do we want to have more lean muscle than fat? Follow these easy suggestions.
Tuna is the featured protein found on the 3 day Cardiac diet. 1/2 cup of tuna is prescribed found on the initial two days, and found on the final day, you'll grow which to 1 cup. Variety plus nutrition is provided with tiny to medium sized portions of cheese, eggs, crackers, greens, grapefruit, banana, and toast. Coffee, tea, or diet soda could accompany food however water ought to be the drink of choice outside of mealtime.
He really had kind 1.5 diabetes or Latent autoimmune diabetes of adults (LADA). Here is what Wikipedia states about LADA. Officially it will still be said to be kind 1 diabetes. This is a shorter article of mine, however, you can watch the 2 videos below and you are able to also purchase Dr. Cousen's book on curing diabetes.
Here is a bmi calculator females within the CDC (Centers for Disease Control plus Prevention). Below is a 2 part movie that follows 6 folks with diabetes which goes to Dr. Cousen's center in Arizona for 30 days. The major change the people made was to consume a raw plant-based diet.
BMI is utilized worldwide to determine if an individual is obese. Since BMI is utilized just for a screening tool, anybody that claims you are at health risk before operating any different tests is lying. Doctors can screen people for health dangers after seeing that their BMI is above normal.
Another limitation is that age is not considered when calculating BMI. So for elderly people, even if the BMI indication is usual, the truth remains that many muscles have been lost considering of age.
These formulas aren't exact, yet they provide very accurate approximations. This usually provide we the ability to measure the body fat plus have a greater idea of how healthy you are. Use this info perfectly, plus keep up the advantageous work!